Introduction: Sawfish, an Unsinkable, Lightweight, Foam Kayak (23 Lbs). Free DIY Kayak Plans, the Hardware Store Boat

Picture of  Sawfish, an Unsinkable, Lightweight, Foam Kayak (23 Lbs). Free DIY Kayak Plans, the Hardware Store Boat

Do you really want a kayak? Want one so bad you can taste it, but can't afford one, or think you don't have the skills to build one? Then I have a few questions for you.

Can you cut a crusty bagel with a knife, stack blocks, stick a sandwich together with mayo, skewer meat and veggies for kabobs, grate cheese, cut thin fabric with scissors, stretch wrinkles out of bed sheets, and roll paint onto a wall? Then you can build this boat!

Unlike most boat plans that require you to do a whole bunch of reading and learning, require you to buy or own lots of tools and learn what seems like a whole new language devoted to boat building. I designed this boat, and wrote this I'ble, to be as simple as possible. You don't need any boat building books, or much in the way of tools. You can find everything you need to build this boat at hardware stores, the internet, and discount stores. When you are done, you will be a real boat builder, and have an excellent boat to show for it.

While I have built many plywood kayaks, from a simple free design called a mouseboat, to a fast capable tandem kayak called a Larsboat, they all have a few problems. They are made of plywood, and since I am cheap, and don't buy the expensive marine plywood, the cheap plywood must be taken care of or it fails after a few years. I designed this boat to use as little wood as possible, and to be nearly indestructable, It won't rot, and even if you punch a hole in it, it won't sink.

I am on FB pages dedicated to kayaking like "kayak DIY projects and tutorials", "church of the double bladed paddle", "look at the front of my kayak", "Duckworks", "plywood pirates", "skinny hull canoe and kayak sailing", "kayak building", and love to see the pictures of people on the water, I believe this boat could get more people out on the water for less than any other plan out there.

On top of how easy this boat will be for the first time builder, it is also lighter than just about any other type of boat out there. If you struggle to get a kayak onto roof racks, or hate to carry your boat any distance because of how much it weights, Sawfish is what you want. Weighing under 30 lbs, it is easy to carry any distance and to lift onto a roof rack. I designed it for my parents who are both retired, and find themselves unwilling or unable to deal with the weight of their current SOT (sit on top) kayaks.

In spite of the simple build, and low tech materials, Sawfish is not slow, I normally cruise at 4 MPH on my GPS, and can sprint to just over 5 MPH. I can also stand up in Sawfish, though I don't recommend this, unless you have excellent balance, and don't mind getting wet.

Thanks to the unusual building materials, Sawfish will not cost very much compared to just about any kayak you can buy or build. I have built six Sawfish so far, my best estimate on cost of materials comes to $125 to $150 US. One builder (floater and Sawgundo) said he built both kayaks for $175. Depending on what you can scrounge or have lying around, you might do even better.

One of the most common questions I get about Sawfish is "how strong/durable is it?" That last picture shows Sawfish holding my 180 lbs (81kg) suspended between two sawhorses. I did this two years ago, and am still using Sawfish without any issues. Last summer I took Sawfish surfing on York Beach in Maine. The surf was up, and the crests of the waves were over my head, Sawfish came through without any problems. This summer I plan on taking Sawfish on some mild whitewater on the Sacco river, I'll let you know how that goes.

Step 1: None of This Comes From an Expen$ive Boat Builder$ $upply $hop or Catalog!

Picture of None of This Comes From an Expen$ive Boat Builder$ $upply $hop or Catalog!

this boat is built with stuff I found only in Home Depot, Walmart, and Harbor Freight here in the US, it can all be found in a Lowe's and most likely a Menard's. I'm not sure what you have to shop at in other countries, but if you have a hardware store nearby, most of this can be found there, though probably not at the costs I can get it for here. (except for the people's republic of kalifoynya, no foam there, the fire retardant added to it causes instant death or something like that, just another reason to flee the state before the big one hits!)

first you need foam, I build these boats out of XPS foam (extruded polystyrene), while the beaded white foam is cheaper and sometimes easier to get, it is not as strong, and will soak up water. XPS is a closed cell foam, even if cut or gouged, it will absorb no water. You can ask your store about ordering some 2" XPS for you, however most people seem to find the store will expect you to buy the whole pallet, at $33 a sheet, times 24 or so sheets, you would be looking at close to $1,000! That would be enough for 12 Sawfish kayaks!!! {Asking around full time insulation installers has gotten some people luck, others have found asking around construction sites. turns out many times most of a panel is tossed just because they used one corner of the sheet}

To build a sawfish you will need:

-two sheets of 4x8 foot 2" thick foam. (1.21 x 2.43 m 50.8 mm)

-the largest bottle of gorilla glue you can get, I find an 18oz bottle will be more than enough for one boat. If you are building a few boats, get a second bottle. I order gorilla glue in a 72 oz pack (four 18 oz bottles) from home depot, they ship it to the closest store or my house for free. Be aware that the glue will thicken and cure in the bottle from humidity, so don't buy too much, only what you can use in a few months.

-old bed sheets, fabric remnants, or canvas drop cloth. (the more synthetic in the fabric the harder to get glue to bond to it, and the harder to get paint into the fibers) asking around at hospitals, nursing homes, or hotel laundries may get you some free, torn or stained sheets. I buy mine at charity thrift stores, look for queen or king size, flat (not the fitted one with elastic edges) and thicker and less stretchy. Some people use muslin or even linen, just remember the thicker it is the heavier it will be.

-bamboo skewers, (sold in kitchen and food stores)

-gallon jug of titebond II

-1 gallon exterior house paint, check the oops paint rack in the paint department every time you visit, they might have the color you want for a much cheaper price.

-two (or three) gama seal bucket lids the paint department of Home depot stocks them in black around here. I found them in white at a lowes,

-plastic packing tape 2" or wider. duct tape, masking tape, etc will also work


-plastic cutting board,

-a tube or two of PLpremium construction adhesive, the 3x is best and cheaper (you can skip this to save money by using gorilla glue instead)

-1" strips of 1/4" plywood, cheap wooden yard sticks, etc. you need a bit over eight feet of them though. (every time you visit the paint department ask for a 5 gallon paint bucket stirring stick or two, in a few visits you will have enough to make the anti-dent rails)

-a few feet of nylon webbing 3/4" to 1" wide, for making handles

-about a foot of PEX plastic plumbing, or PVC tubing, for making the handles much more comfortable

-four or five feet of 1.25 or 1.5 inch PVC pipe. (this is to make the tool for installing rod holders, and to build 4 fishing rod holders into your boat. Even if you don't fish, like me, they are handy places to install an umbrella for sun, or a battery operated light for paddling at night. I've heard that most fishing rods fit into 1.25 inch pipe, but a few brands need 1.5" pipe)


-safety glasses

-dust mask

-warner 250 wallpaper removal tool

-hand drywall saw


-flush cut pliers

-bricks, paint cans, old free weights, or a bunch of 5 pound rocks, ( I call them gravity clamps)

-paint roller handle, tray and rollers

-power hand plane while you can build a Sawfish without this, just using the shureform, it will be much harder to make a smooth hull, and take much longer.

-jig saw you can do all your cutting with the drywall saw, but not as easily or quickly, with less mess.

-tape measure

-10 foot long 3/4" pvc pipe

-carpenters pencil, sharpie marker, ink pen

- measuring stick

-chalk line

-mixing board for folding great stuff

-plastic spreader

-aluminum ice cream scoop (for carving those inside corners, a large metal spoon would also work)

-caulking gun


-razor knife

-wood rasp

-1/2" spade or drill bit

-power drill

-phillips and regular screwdriver set

Step 2: Getting Your Ducks in a Row (Sawfish 1.0, the Old Way to Do This)

Picture of Getting Your Ducks in a Row (Sawfish 1.0, the Old Way to Do This)

you need one 4' by 8' panel and one 2' by 8' panel of 2" foam, or three 2' by 8' foam panels. The further north you live (cold) the easier it is to find 2" foam panels in 4x8', only one store near me has them, and it isn't any of the 6 home depot's or lowe's I pass in my 40 min. drive to work. if you can't find 4x8 2" foam, 2x8' panels will work just fine, splice them together along the long edge using the butterfly scarph joint directions.

If you live so far south your stores only stock 1" foam, don't give up, you can easily create 2" foam using gorilla glue, in fact this will make stronger (but more expensive) panels. read up on how to do this in the butterfly scarph joint step.

once you have your foam panels ready to go:

draw a center line 14" from the edge of the 4x8 panel, and another center line right up the middle (12") of the 2x8 panel, align these center lines so that there is a 2" step where the 2' and 4' panels meet. the 2' wide panel will be the bow end. measure 12 feet from the end of the 4x8 panel, and mark that point on the centerline, that will be the base of the bow. From the bow measure and mark each foot, these are called stations. Once you have the stations marked and numbered, measure from each station mark toward each side with the dimensions given.

starting at the very end of the 14" centerline at what will be the stern of the boat, measure 2 inches out to either side of the end of the centerline and mark these dimensions on the edge of the foam. at the very point where the centerline meets the edge of the foam, write the number 12, for station twelve.

Now measure six feet from station twelve and mark that point, write the number 6 next to the mark. This will be the midpoint of the boat. Measure 14" out to either side of the midpoint, this will be the widest part of the boat.

With your centerlines lined up, measure twelve feet from station twelve, and mark this point on the centerline. This will be the bow, write a zero next to the mark on the centerline. measure one inch to either side and mark. You do not want a pointy bow on a foam boat, it will be easily damaged, instead, a nice rounded bow will do just as well cutting through the water.

Now take your PVC pipe (batten) and use the bricks (ducks) to line up the pipe along the points you just marked. Make sure you stage the ducks (bricks) at the same place when drawing each side, this keeps both sides with the same curve (fair), stack up bricks as needed to keep them from being moved by the resistance of the PVC pipe to bending. hold the pencil vertically as you trace the batten onto the foam.

Since the hull is 12 feet long and the PVC pipe is only 10 feet, I find it best to start with the stern end, with one end of the pipe on station twelve, bricks holding it at the midpoint to the 14 inch mark, and then bringing the other end in to 12" from the centerline. Trace the outside of the batten, so that the marks for the midpoint, bow or stern are all outside of the batten. Do the other side of the boats stern, then move on to the bow.

Start with one end of the batten on the zero station mark 1" from the centerline, once again have the batten run around the midpoint mark, and then bring the other end of the batten in to line up with the line you already traced. Make sure the line does not leave a gap where the 12" and 14" centerline panels meet.

Each side rib is 3" wide, measure 3" over at each station along the left hand side of the bottom, from the line you traced it, then trace the points with the batten. measure and trace another line 3" from the last one until you have six side ribs marked out. number them so you get the right amount.

you will notice that the bow panel only has one section marked out to be cut, cut it out and use that triangular section to trace your cut lines.
with the remaining bow section lying on the table or floor, place the triangular bow section on top of it, slide it forward until the two "legs" sticking out behind it are three inches wide at the aft end of the triangle. If you are like me, you will not be able to get both to be three inches wide, and have your centerlines lined up. In that case, keep going forward until the second leg is 3" wide with the centerlines straight.

Trace the two sides of the triangle that run back from the point on the center line.

Repeat the steps above. the last time you copy the triangle, the point will be hanging off the end of the bow panel. this is fine, the two triangles you have left when you cut off the last flattened V will make up that missing point.

Step 3: Roadblocks

Picture of Roadblocks

The internet is a great tool for spreading the word about building boats out of foam. But this also causes some problems due to the fact that everyone doesn't have the same stores that I do near them.

Even if you can buy XPS foam where you live, you may not have the same glues in your stores. The glues I use are formulations that are not sold in every country, I know that some cannot be shipped, or have crazy charges added to them if they were.

The best advice I can give you is to see if there are boat building blogs or websites for home builders in your country. See what glues are sold locally that boat builders have had good results with.

If XPS is too expensive near you, or just is not sold, you can use Styrofoam (the white stuff made out of beads of foam), but your boat may have problems from this later on. Styrofoam will absorb water, and this means it will get heavier and not float the way it did. To keep the water out you need to seal the surface of the foam hull. You can depend on the fabric skin to do this, but you will need to carefully inspect the hull before each paddle and repair any holes or tears and be sure to repair them. I would also try storing the boat bottom up where the sun can shine on it. This will help bake any water out of the hull.

The boats pictured at the top are built with styrofoam instead of XPS


Another issue I get questions about is if you can only get one 1 inch or 3/4" foam in stores. You can make thicker panels by gluing them together.

lay out both panels flat on the floor or table.

using the werner 250, score the complete faces of the foam.

drizzle on a thin, overlaping, looping line of gorilla glue in 3-4" circles on the face of one panel,

take the scored up face of the second panel and lay it into the glue on the first panel.

align the edges and pin the two layers in place with bamboo skewers in each corner.

lay boards over the glue stack of panels,

apply weights to the to of the stack until the glue cures, the boards will spread out the weight.

Step 4: Butterfly Scarph Joint

Picture of Butterfly Scarph Joint

In plywood boat building you always run into one fact, plywood comes in 8' lengths, boats that short are slow.
To make plywood long enough to have a fast shape you must join two or three panels together.

While there are many ways to do this, the best is called a scarph joint, I "invented" my own joint for making longer foam panels. In reality it is a "butt" joint, but I like to call it a scarph joint, (butt joints do not flex the same as the rest of the plywood panel, so they must be put in the middle of the boat where the least curve is happening, a scarph joint will flex just like the rest of the panel and can be put anywhere. since the butterfly joint can flex the same as the rest of the panel, I call it a scarph joint)

Start by using the wallpaper scoring tool to perforate the faces to be glued, this gives you the best glue joint possible. Rub the perforated ends with your hand to remove any little chunks of foam torn loose.

Lay the sections to be joined together along the join line as tightly as possible.

Run a strip of tape along the length of the joint and you want the tape to extend past both ends of the joint by a few inches.

Now fold one section of foam back on top of the other using the tape as a hinge.

Apply gorilla glue in a zig zag pattern from the top of one panel to the bottom of the other and back, this will get glue into as much area as possible.

Fold the top panel down again.

Flip both panels over so the tape hinge is on the bottom of the joint.

Lay the joined foam panel on a flat surface and apply weights along the joint to force the joint shut.

Fold the ends of the tape up to trap the glue that would run out of the ends of the joint.

Once the gorilla glue is cured, remove the tape, sand off the beard (glue that ran out of the joint and cured)

I made a short video to help explain this step.

Step 5: Sawfish 2.0 New Cut Pattern! (Sawfish 2.0)

Picture of Sawfish 2.0 New Cut Pattern! (Sawfish 2.0)

In the three years since I built the first Sawfish, I've built a few more, and am currently working on a stretched Sawfish for two. The bow design seemed to be the hardest to understand by many people, and I had to come up with a new way to do the cut pattern for the tandem anyway.

I ended up coming up with a better idea for making the hull and am now building a new sawfish using the new cut and build pattern. I thought I was so smart, and then I got a facebook post on my Rowerwet page from James Brown. He's building a Sawfish kayak, and came up with the same idea for making the side ribs. And then he really came up with an even better idea. I'll be modifying the instructable again to reflect the Jame's idea. I will leave the old one up for a while longer as it seems there are some people currently building Sawfish and I don't want to confuse them, but if you are planning a sawfish build, use this pattern, not the old one! It is much easier.

>>>>The best part! You can make just about any shape or length of boat with the new cut plan! short and fat, long and skinny, all it takes is a little imagination! Just figure out the length and width you want, make a foam panel long enough and wide enough for the whole bottom to fit, then copy it the same way I show for Sawfish, to make the side ribs. It doesn't get any easier.<<<<<<<

>start by finding a flat surface that you can lay both foam panels on end to end. If you don't have a 16 foot long area, cut one panel in half at four feet.

>use the wall paper perforator to prepare the foam on the two faces to be glued. (rub the surface with your hand afterwards to get the loose chunks of foam loose)

> lay out a strip of plastic or wax paper under the joint to avoid gluing it to the floor.

>follow the steps in the Butterfly scarph joint video to make a 12 foot foam panel

>fold the ends of the tape up to keep the glue from running out the ends of the joint, apply weights along the joint.

>Once the glue is cured (overnight) remove the weights

>from the 12 foot (3.6576 m) side of the foam panel, mark each end 14 inches (35.56 cm) from one side.

>snap a centerline onto the foam panel using the chalk line or a straight edge.

>Using the tape measure, mark each foot (304.8 mm) along the centerline.

>lay out the hull dimensions from the centerline.

at the bow measure and mark 1 inch (25.4 mm) to either side of the centerline

at the 6 foot (182.88 cm) station measure and mark 14" (35.56 cm) from the centerline to each side

at the stern measure and mark 2" (5.08 cm) to each side of the centerline

The bow can be either end of the centerline.

>Now take your PVC pipe (batten) and use the bricks (ducks) to line up the pipe along the points you just marked. Make sure you stage the ducks (bricks) at the same place when drawing each side, this keeps both sides with the same curve (fair), stack up bricks as needed to keep them from being moved by the resistance of the PVC pipe to bending. hold the pencil vertically as you trace the batten onto the foam.

Since the hull is 12 (3.6576 m) feet long and the PVC pipe is only 10 feet, I find it best to start with the stern end, with one end of the pipe on station twelve, bricks holding it at the midpoint to the 14 inch mark, and then bringing the other end in to 12" (30.48 cm) from the centerline. Trace the outside of the batten, so that the marks for the midpoint, bow or stern are all outside of the batten. Do the other side of the boats stern, then move on to the bow. Start with one end of the batten on the zero station mark 1" from the centerline, once again have the batten run around the midpoint mark, and then bring the other end of the batten in to line up with the line you already traced.

>Using the tape measure, measure 18" (45.72 cm) from the edge of the hull pattern you just drew onto the foam at the bow and stern. Mark each 3" (7.62 cm) from the pattern edge to 18" (45.72 cm). Do this at the bow and stern.

Step 6: Now Cut It Out (Sawfish 2.0)

Picture of Now Cut It Out (Sawfish 2.0)

>Now take the wallpaper removal tool and score up the faces of each foam panel, each of the holes left by the spikes on the tool will allow glue to penetrate into the foam deeper. I prefer to think of the holes as becoming thousands of tiny nails that pin the glued joints together. Peeling of the fabric later on for modifications to the boats has proven this to be true.

>Using the drywall saw or jig saw, cut along each line, always cut so you remove the smaller sections first, this gives you a bigger section to hold onto with your hands, feet, knees, teeth, elbows, etc. do not cut the center line! (if you did, glue it back together with another butterfly scarph joint)

Step 7: Ribs (Sawfish 2.0)

Picture of  Ribs (Sawfish 2.0)

>take the bottom blank and match it up with the 3" marks you made at each end of the panel.

>trace the edge of the bottom blank.

>Repeat for all six side ribs.

>be careful when handling the ribs, they can snap easily if grabbed from one end. Hold them in the middle when moving them, and they will not be so prone to breaking.

>take all six ribs and match them up. If you are like me, some will be a bit thicker in the middle, and others will be a little narrower. Try to put them in three matched pairs.

>The thickest set will be the bottom, and the thinnest set will be the top, the remaining two will be the middle.

Step 8: Stacking (Sawfish 2.0)

Picture of Stacking (Sawfish 2.0)

>copy the ends of the centerline on the bottom blank over to the other side of the foam.

>snap a centerline to the other side of the foam using the chalk line.

>take the two thickest ribs and lay them on top of the bottom blank so that one goes up each side of the bottom blank.

>align the stern ends of the bottom blank and side ribs to be flush.

>using the fist digit of your first finger as a measuring tool, set the overlap of the first rib at a consistent depth at the stern.

>pin the stern end of the rib in place with a bamboo skewer

>set the overlap of the side rib at the 9 foot station to the same depth, using the same finger tip.

>pin the rib in place at the 9 foot station

>repeat this for the 9 foot station and the bow. Using the same finger tip dimension

>trace the inner edge of the first rib onto the bottom blank.

>Cut the inner tip of the first rib to match the centerline.

>using the same finger tip as a measurement, pin the other side rib in place at the stern first, then the 9 foot and 3 foot stations

>remove the skewer from the bow end of the first rib

>align the bow end of the other first rib, and cut it along the centerline

>push the joint closed between rib bow tips, and pin it in place.

>save the sections you cut off, they will be used later.

>go along the top of the first layer ribs and snip off the skewers so that they are flush with the foam. Save the ends as you will use them for the next layers. Use the flush cut pliers to snip away at the ends of the skewers at an angle to make new points on them. you should be able to reuse each skewer a few times.

Second and third layer ribs.

>continue to line up the ends of the ribs so that they are all flush with the stern end of the bottom blank. This gives you a flat stern for mounting a rudder or motor mount on, or just gives extra volume for carrying a load of gear in the stern of the boat for camping trips, etc.

>to give the hull extra volume in the ends, use your fingertip to set the same overlap dimension at the stern and pin it in place with a skewer

>now go to the 6 foot station and line up the outside of the rib so that it is even with the first layer.

>go to the bow and set the overlap with your fingertip dimension again.

>don't worry about how much the foam overlaps at the front of the bottom blank and first rib, this is done on purpose.

>trim the second rib at the bow so that it is cut off even with the centerline at the bow. (just like you did on the first layer).

>repeat this for the other side of the second layer, and again on the third layer.

>the hull should have steps leaning further and further out at the bow and stern, but have no flare in the middle. This makes it easy to paddle, but gives it extra volume in the ends to help it rise over waves and wakes.


Step 9: Waste Not, Want Not

Picture of Waste Not, Want Not

If you are building a kayak the way I show, you will want a forward bulkhead to support the end of the front deck, and and aft bulkhead to support the front of the rear deck. Decks give you dry places to store things, and a good way to keep stuff from being lost if the kayak flips, or from everything being soaked in rain, spray or waves. The bulkheads also make the kayak much stronger and not so flexible.

Some people have made an open area behind the rear bulkhead to haul oversized gear, or give easier access to stuff like fishing gear. One guy incorporated a bungee cord system to retain everything, (he is a hunter, and wanted easy silent access) This would also allow a place for a dog or child to ride.

Forward bulkhead

>to make the forward bulkhead we need to know how wide it needs to be.

>start by finding the 6 foot station. Measure and mark 6 inches behind it. this will be the front of the aft bulkhead.

>from the mark you just made measure toward the bow 4 feet (I like to add a few inches on top of that, like 4 feet four inches, for extra room for boots. If you have longer than average legs, this will help) and mark the centerline. This will be the aft face of the front bulkhead.

(I make all of my kayaks with a gama seal bucket hatch in the bow. this is the perfect spot to store your car keys, wallet, and anything else you want to keep with you and dry, but don't need access to while paddling. In order to make sure that a hatch will fit, I test fit one as far as it can sit into the bow of the kayak. This lets me know how far forward my bulkhead can be. Water bottles, lunch, camera, binoculars, phone, GPS, jacket, sun screen, sun glasses, etc all go in the hatch right behind the cockpit so I can grab them quickly while sitting in the boat.)

>measure across the top rails at the front bulkhead mark and remember this dimension. (write it down after you measure it twice!)

>measure the depth of the hull from the base of the ribs to the top of the ribs.

>find a section of corner waste that you can cut a square out of that is deep and wide enough.

>cut the panel out and mark it "forward bulkhead".

Rear bulkhead

While the forward bulkhead is a vertical section, the aft bulkhead is made up of a stack of blocks. This is to give you a good place to install fishing rod holders, and tow rope anchors.

>measure the width between the first layer ribs at the aft bulkhead mark.

>do the same for each layer and add up all of the lengths.

>using the waste panel left after the ribs were cut, measure 4 inches from the straight side of the waste at each end.

>snap a line between the two marks you just made,

>measure from one end to the dimension you added up to get before, add a few inches (cm) to the sum and mark on the chalk line.

>cut the along the chalk line, stopping at the mark you just made.

>cut the 4" section off at the mark.

>measure the dimension between the first ribs at the aft bulkhead and cut a section of the 4" beam off.

>use the sureform to shape it to a tight fit against the ribs.

>do the same for the next two layers of ribs. (if you cut too much off, fit a section to fill the gap and glue it on during the glue step)

Bow and stern

the bow and stern have gaps at the ends of the ribs if you flared the ends like I do, use sections of the waste to trace the triangles you need to fill these gaps and make the ends solid. This is important as the ends get the most bumps and bangs, and they give you solid foam to anchor your handles and rope anchor loops into.

>for the bow, use the waste sections you trimmed from where the ends of the first two layers of ribs meet. I use the ends of the second layer to fill the corner of the first, and the ends of the first layer to fill the tip of the second.

>you will probably need to unpin each layer to trace the ends of the ribs onto the bottom of the waste panel. Save the cut off skewers for reassembly during the glue stage.

>lay the waste section over the ribs, try to line up one side of the waste with the inside of one of the ribs. I like to have my end blocks extend into the boat at least 6 inches.

>use the tip of the drywall saw to trace the inside edge of the other rib onto the bottom of the waste section.

.>cut the end block out and use the sureform to shape it to a close fit.

>repeat this for all of the layers of ribs at bow and stern

Step 10: Like Stacking Blocks, Really Big Blocks... (1.0)

Picture of Like Stacking Blocks, Really Big Blocks... (1.0)

glue the bow triangle to the boat bottom main panel using the butterfly scarph joint now. once the glue has cured, remove the tape.

Examine the side ribs you cut out, if you are like me, some are thicker than others. select the thickest two ribs and label them bottom. the thinnest two ribs will be the top. the remaining two will be the middle layer.

take the bottom ribs and place one on top of the boat bottom. align the stern end so the rib is flush with the stern of the bottom, now slide the rib outboard so it over hangs by a half inch, pin it in place using a bamboo skewer every few feet starting at the stern, keeping the same half inch overhang the whole length.

now select a bow V that is whole and using sections of "waste" foam, space it over the bow of the boat and the one bottom rib as shown in the picture. you want the point of the bow V to overlap the bow by a half inch to and inch. (this will give the bow "rake" )

trace the leg of the V onto the forward end of the bottom rib, cut away the part of the rib that was overlaped, the bow V should fit nicely in the "birdsmouth" made in the rib. (if you cut too much, trim off some of the removed foam and slide it in the gap to keep it fairly tight.

now place the second rib over the bow V and the first rib. with a half inch side overlap, the stern end of the second rib should overlap the first rib. trim the second rib to have a tight joint against the first rib at the stern.

Now pin the second rib in place, with a half inch overlap along the sides, but flush at the stern, and trace the other leg of the V onto the rib. cut the traced section out, and check for alignment between the V and the centerline.

once the first layer is pinned in place, trace along the inside edge to ensure you get everything back where you want it later on.

for the middle level of ribs, start with the opposite side from what you did for the first level, keep the stern flush, and cut your stern overlap on the opposite side from the first overlap, this way the stern has staggered operlaps, giving more strength to the whole assembly.

when you get to the top layer, the outside edge should of the ribs should be set in from the last by a half inch to get that tumble home. this will make it much easier to paddle the boat after it is done. don't do this with the point of the bow, it should still overlap forward, take the waste sections left over from the bow section and use them to make the point of the top V, trim them to shape as needed.

pin the foam in place after you are happy with the symetry of each side.

Step 11: Carving It Out (1.0 and 2.0)

Picture of Carving It Out (1.0 and 2.0)

yes there is a boat inside all that foam! just like an ancient canoe builder could look at a tree and see the dugout canoe locked inside it, there is a functional foam boat inside all that rough ugly looking foam layer cake.
start by taking the edges of the steps in the hull off, tapering the hull up from the bottom layer to the top layer of the side ribs. (easier to do and see if the hull is upside down)

the sureform or harbor freight knock off can do this ok, but not as quickly or easily as the power plane.

step back often and sight along the hull to see where the high spots are and avoid making a low spot.

on the bow make the taper go all the way to the top of the deck from the bottom. I also did this at the stern to help the stern lift over any following waves. Don't make the tip of the bow very sharp, since foam isn't very strong, in thin sections and sharp edges it tends to crush easily. Instead give the bow a blunt round shape. It will spend 99% of it's life out of the water anyway.

make a nice radius from the flat bottom to the sides, and the sides to the top deck, this will make the transitions easier to lay fabric over and the hull go through the water easier. smooth off the inside edges of the cockpit and bulkheads,

I found the ice cream scoop best for carving out the very inside corners. if you make a divot or have a crack you want to fill, use the light weight spackle to fill them, then sand it off smooth.

Step 12: Putting a Lid on It (1.0 and 2.0)

Picture of Putting a Lid on It (1.0 and 2.0)

To make the ends into usable dry storage spaces, we need to put a top on the boat hull, and add some access hatches. Since we are using the remaining half of the 4x8 panel we cut off in the first step, these decks will be strong enough to stand or sit on.

See if there is enough of the waste left after cutting the ribs to make the bow deck, if not use the extra panel from the first step.

Take the foam panel and lay it on the bow. Since we also want to get the stern deck out of this section, trace the hull onto the underside of the foam panel, and try fitting the stern deck onto the panel as well, You may need a small filler piece to make part of a deck, this will not be a problem if you use the butterfly scarph joint.

Save any large sections of foam for the next boat!

Since the forward hatch has no margin of error if it will fit a gama seal lid, I cut a small hole through the forward deck roughly in the middle of the hole location. With the deck held in place with bamboo skewers, I reached in and traced the hull sides onto the bottom of the forward deck. Then removed the skewers, flipped the deck over, and using the traced lines as locators, traced the gama seal lid ring. Then cut the hole out and ensured a good fit on the deck ring.

The aft hatches aren't so critical on location so I left them for later.

Pin the decks in place with skewers, and weight them down with bricks for a good bond. fill any gaps along the deck edges with scraps and glue in place.

Since the decks stick up above the sides through the cockpit area, use sections and scraps of foam to make the cockpit rails the same height as the bow and stern decks. glue the fillers in with GG and pin and weight them as needed to get a good bond.

trim the rough edges of the decks to match the contours of the hull.

Step 13: Gama Seal Deck Hatches

Picture of Gama Seal Deck Hatches

Since you do not want to waste all that space in the ends (where else are you gonna put your car keys, wallet, camera, lunch, nice cold drink, dry towel, etc.) you will want to add some gama seal boat hatches to the boat. Follow the instructions I give in this album to make water tight hatches for your boat that cost much less than any boat hatch you will find in a marine supply catalog or store.

Gama seal lids are designed to snap onto the standard five gallon plastic bucket, making it into a resealable water and air tight storage container. I get them at my local Home Depot in black for $8, I have also found them at some Lowe's in white for about the same amount. You can also find them on, and plastic container web sites in 7 colors.

>>>The Gama Seal bucket lids allow you to do one more trick for expedition paddling, in the last picture at the top notice the 5 gallon pails in the deck holes. Pack the cargo tanks, then drop the buckets in. We use the buckets instead of expensive dry bags, though dry bags would also work in the holes. (like the 5 gallon water jug in the mouseboat ring) With the gama seal rings in Sawfish the buckets are held securely, unless the hull turned upside down they will not fall out, and even then the buckets would float.

- to make a gama seal lid into a deck hatch: trim off the outer flange that locks the rim to the five gallon bucket, remove the giant O ring that seals the rim to the bucket lip. leave a tab or two of the outer flange to help lock the rim to the hull of the boat. find the correct dimension from the bulkhead to install the hatch as close to the cockpit as possible using the tape measure, also use the tape measure to mark the center of the deck panel, take the rim of the gama seal lid and find where it will be centered on the deck panel and clear of the bulkhead. Now take the gama seal ring, and use it to trace hole for the deck hatch. trace as tightly as possible around the smaller end of the ring. cut along the line with the drywall saw. trim away areas as needed to make a nice fit on the gama seal rim, small gaps will help with getting the glue in between the ring and the foam deck. DO NOT GLUE THE RIM INTO THE DECK YET! Set the completed hatches aside, they will go on after the fabric skin is on

Step 14: Some Positive Reinforcement

Picture of Some Positive Reinforcement

Foam will get small dents in narrow areas like the cockpit rails if the kayak is strapped down to roof top carrier bars with the force on the narrow areas. to avoid these dents I added strips of 1/4" plywood to the insde edge of the cockpit rails.

The boat does flex when pounding into waves, the wood rails in the cockpit rim are needed to keep the hull from flexing too much. I made my rails from scraps of plywood, there is a break in each rail about a foot from the front of the cockpit. The force of the hull flexing caused the fabric skin to tear right at each break in the rails.

If you go with sectioned cockpit rails (stir sticks, etc), you need to have another layer of wood bridging each break in the rails. Another section of plywood, stir stick, etc that is 6 inches long (three inches on each side of the break) will take care of any stresses.

for extra strength run your rails into each bulkhead, you can do this by gluing them in first, or by cutting a gap into the bulkhead and using GG to seal the rail into the bulkhead.

5 gallon bucket stir sticks from home improvement store paint counters can be had for free, just ask for one every time you visit (I had one worker give one to each of my kids to use as mock swords) those cheap wood yard sticks would also work, but they aren't free. (I noticed that Home Depot now sells wood stir sticks near the paint counter, I wonder if all of you asking made them suspicious)

You want to make sure the wood is flush with the upper edge of the rail so it will protect it, I install my strips a bit high and then sand them smooth with the rail for perfect match.

pin each end of the rail and the middle with drywall screws screwed into the foam, so the rails won't slide while clamped.

I like to use gorilla glue to attach the rails to the foam, I have used PLp, both work, GG is just easier.

I have a bucket full of those cheap spring clamps from harbor freight, but don't use them anymore as one or two break and parts go flying every time I use them. To replaced them with some 4 inch PVC pipe cut into 1.5 inch slices with my sawzall. They are much cheaper and more reliable.

place some more paint stir sticks on the outside of the hull where the clamps will land to keep from denting the foam.

<<< If you are going to install rod holders made of PVC pipe embedded in the aft bulkhead, cut the holes now using the instructions in the rod holders step>>>

Step 15: Its a Wrap!

Picture of Its a Wrap!

Now on to the step that makes all those foam layers into one solid boat.

lay out your fabric sections out to get the best coverage of the hull, you want the bottom section to wrap up each side above the water line.

I chose bed sheets to cover the hull as they make a lighter layer as the fabric is thinner. The bed sheets are not as strong and from time to time rocks punch tears in the fabric and dent the foam. You can just live with the dents, as they don't hurt anything, or use some lightweight spackle to fill the dent, sand the spackle smooth when dry, and sand a few inches around the spackle, then use more exterior paint to glue a patch over the dent. Or use heavier fabric.

Using canvas like the canvas drop cloths from Home Depot will make a tougher skin, it will also end up using more paint and weighing more.

once you have your layout figured, use a pen or marker to mark the way the fabric should be. this will come in very handy as you are trying to smooth the fabric into the glue.

Step 16: Poor Man's Fiberglass

Picture of Poor Man's Fiberglass

take some time to read the whole Poor man's Fiberglass instructable, we will be using the TBII method, as we are working with foam.

dump a generous amout of thinned TBII into the paint roller tray, using an economy paint roller, roll a coat of TBII onto the foam, start with the bottom of the hull near the bow, as it is flat and easiest to learn on. you have the right amount of glue rolled on when you can see that every score in the foam the werner 250 made has a dot of glue in it.

start with a stripe of glue the width of the roller, lay the fabric into the glue using your alignment marks, then use your gloved hands to press and pull the fabric smooth, working any bubbles or wrinkles out from the middle to the edges.

pull back the last inch or two laying in the glue and roll on another two to three feet of glue, lay the fabric into the glue and work from the anchored end of the fabric already in the glue, up the middle of the fabric and out to the edges. where the fabric goes over the edge of the bottom you can leave it hanging and glue it afterwards.

If your fabric was to short to cover the whole panel , overlap the next section by two or three inches and start the next section .

I went and covered the stern of the boat with a separate section of fabric before finishing the bottom, that way the edge of the stern fabric was under the bottom fabric.

Once the bottom is on, start on one side. Due to the curves of the hull the fabric will end up with wrinkles after it is pulled and pressed into the glue. use a sharp razor knife to cut the center or one side of the wrinkle, then use a small brush to glue one edge of the cut over the other so that the wrinkle is now flat.

roll glue onto the fabric where it will overlap another section, do this by folding back the overlap and rolling glue onto the folded back section.

Avoid having glue on top of the fabric as much as possible, as this will keep the paint from sticking to and filling the weave of the fabric.

trim off the over hanging fabric where needed with a pair of scissors.

The one place I used heavy canvas drop cloth on this kayak was the cockpit floor, I wanted the most strength and protection for the floor, and an anti skid treatment as well.

I cut the floor canvas an inch or two wider than the cockpit so it would overlap the bed sheets used to cover the sides of the cockpit. this overlap is how different sections of fabric become one skin when glued together.

once the floor was glued in, I did the upper decks draping the fabric down over the sides to create a strong overlap with the bottom skin.

once the top deck fabric glue cured I used a razor knife to cut the fabric out of the deck holes, then fit the gama seal deck hatches in place. I cut slits into the deck to lock the tabs on the rims into the deck.

Using PLp glue the rings into the deck, lay a bead of PLp around the rim near the top, then press the rim into the deck aligning the locking tab in the deck slots. screw the deck hatch into the rim to maintain shape as the PLp cures, and lay bricks on top for a good seal.

Step 17: Add Some Color to Your Cheeks

Picture of Add Some Color to Your Cheeks

unlike the thick canvas I used on the teardrop in the PMF I'ble to cover plywood, thin bed sheet cotton will not hold much paint, at most you will only need two layers of paint, paint it with the color you want from the start.

use a paint roller and tray and roll on the color paint you want.

Once you paint the thin fabric, you can change colors, but it won't ever stick as well as the first coat does.

I originally had a red, white and blue hull, now it is blue and yellow, my favorite combination.

Step 18: Keep It Straight!

Picture of Keep It Straight!

I found Sawfish tended to wander from side to side just a bit when paddling, I needed a way for the kayak to go in a straight line, so I came up with a plastic skeg. This skeg was a bit undersized, while I could make the kayak go where I needed with a bit of extra muscle, It is just to small for safety. (My wife was caught in a strong wind in Sawfish recently and ended up on the downwind shore, she just couldn't get the bow to turn into the wind, no matter how hard she paddled) At the same time some friends of ours were also out on the same pond and were able to make it back thanks in part to the long strake I added to their Sawfish kayaks.

In their case this strake runs all the way from under the forward bulkhead, to almost the end of the stern. This seems to be a good length, without causing problems with getting in and out of the boat with the bow just resting on the beach. However their foam strake caused another problem, the stern of the kayak was out of the water because the extra foam pushed it up. This causes the bow to be down in the water, making them slower.

I tried a strake made of foam on sawfish, but found it made the boat slower. You may have noticed the foam strakes on the outer edge that some people have added to replicate the designs found on plastic kayaks. It turns out that those extra edges molded into plastic hulls are not for stability or tracking, but instead to keep the thin plastic hull from deforming in the water.

The foam strakes make the boat slower, which makes sense, because they cause drag.

Look at the way fish were designed, they have smooth bodies and thin fins to reduce drag. Plastic fins recreate this better than any other way.


You need a plastic cutting board the longer the better. The set from Harbor freight is perfect for me, it costs roughly $9 for the set.

>>> on my sons boat I had to find another source for cutting boards, as my local harbor freight hasn't restocked the cutting boards in a while. I found smaller cutting boards at the dollar store. I was able to make three fins from each cutting board, making them cheaper than the harbor freight fins. For a 12 foot sawfish I only needed three of the $1 cutting boards.<<<

Start by measuring 2" from the long edge of the cutting board, this will be your total fin height.

draw another line 1" from the long edge of the cutting board.

measure 3" from each end of the cutting board and draw a line that goes between the 2" and 1" lines.

Measure 3" from that line and mark another line between the two long lines. Repeat for the opposite end.

Use a 1/2" wood boring bit to make a hole on the center of each of the 3 inch lines, also bore holes into the ends of the panels (see pictures above) firmly pressing the plastic onto a piece of wood you don't care about will allow you to make these holes in the ends.

Now cut along the 2" line and the lines that run through the holes you just bored. Remove the plastic between these holes so that you create "legs" for the fin. These legs will set the correct depth for the fin in the hull.

Make as many fins as you can from the set of cutting boards.

Bore holes every inch or so in the legs, (see pictures) these will be the only real way that the fin will be anchored in the hull. the plastic that cutting boards are made from is nearly impossible to glue to.

trim the ends of the cutting board fins so that they will slide over rocks and sticks easier.

Snap a chalk line onto the center of the hull.

Lay out the fins along the center line, you want the stern most one to end where the stern of the boat is two inches across on the bottom.

Set the next fin 2 inches, minimum, forward of the aft most fin, (I like to have them 4 inches apart, all the way up the center line) you don't want them to be too close together, as the fabric glued to the foam in between each fin keeps the hull strong. Use longer fins toward the back of the boat, and shorter fins (from the shorter cutting board) toward the front.

You want to have a fin under the bow, with the forward end just where the foam is two inches across the bottom. This fin will be what hits the ground when you beach your boat, and will help you slide off the beach when launching.

I find this design for the fins works best under every condition.

Set the legs of the fin on the hull and trace around them (see picture).

Using the razor knife cut along the lines, bury the blade all the way into the foam. You want each leg pocket to be 1" deep into the foam.

Use a straight bladed screw driver to dig the foam out of the pockets.

>>I used a scrap of the thinner cutting boards to dig out the foam on my sons boat, my screw driver blade is too wide, his boat is the orange one<<

Test that the fin sits flush with the hull, with the legs fully inserted into the hull. Dig out any foam that blocks them.

Lay the fin on its side next to the pockets, and mark where each hole through the legs is.

Dig small pockets off to the side that taper away from the skin, in line with each hole mark. Do this off to both sides. (see pictures)

Using the tip of the adhesive tube, pump PLpremium adhesive into each pocket.

Fill each pocket about half way with more PLpremium adhesive.

Fill each hole in the cutting board fin with PLpremium ahesive.

Press the cutting board legs all the way into the pockets, use a bondo spatula to remove the excess glue around the edges.

As the adhesive cures it swells, this will lock the fin into the hull, and will try to push the fin back out of the holes unless you hold it in until cured. Lay bricks on each end of the fin to keep it fully inserted

Excess glue will push out around the fins, I use a flush cut saw to cut the glue and then rip it off.

The row of fins reminds me of the plates on the back of a dinosaur, or the "saw blade" nose of a real saw fish.

Step 19: Get a Handle on It!

Picture of Get a Handle on It!

I took my standard (CHEAP!) boat handles and modified them slightly for use on a foam kayak

handles are an important part of securing and carrying your boat around, I didn't like my original idea, and have come up with a better one.

find a place on the end of the boat that you know has two layers of solid foam underneath it.

lay your hand, palm down on the hull and draw two marks on either side of your hand spaced a little bit away from the edge. make sure the marks are lined up with the centerline of the hull.

I like to use the bit holder on my screw gun to make the strap mounting holes it is about 3/8" diameter and 2.5 inches long. Drill vertically into the foam until the bit holder is buried, repeat for the second mark. You might be able to use the phillips screw driver for this also.

push the tip of the PLp tube into the hole and pump adhesive into the hole, allow the tip of the nozzle to push back out as the hole fills.

take one end of the nylon webbing strap and lay it across the top of the hole, have the end go a half inch beyond the hole.

put the tip of the flat head screw driver onto the hole and push in until the screw driver hits bottom.

pull the screw driver out, hold the strap to make sure it stays in the hole.

hold a section of plastic pipe in you hand, with the thumb and fingers wrapped around the pipe. make sure some pipe extends beyond each end of your hand. squeeze the pipe loosely.

using the tubing cutter cut the pipe to length, ensure that this leaves a little beyond your hand.

thread the the pipe onto the strap

wrap your hand around the pipe handle again, lay the back of your hand on the top of the hull and lift it off slightly

take the remaining end of the strap and figure how long it needs to be to reach the hull deck again at the remaining hole.

add 3 inches of webbing to that dimension, cut the end of the webbing,

pack the remaining hole with PLp

lay the end of the strap over the hole like you did the first time

push the end of the strap into the hole

Then make sure the strap has enough free length to not trap your knuckes against the hull. you can still pull a little bit back out at this point

use the tip of the nozzle to pump glue into any voids in the strap holes. smooth off the excess glue, and keep checking as more will ooze out until cured.

repeat the same process for a stern handle.

I use the same idea to make small loops right behind the cockpit to use as tow points for ropes to other boats, and as gear leash anchors for fishing rods, etc. I also like to add one to the bow for the bow line for securing to the car.

just make sure the strap is well bedded into the foam with adhesive, you might even try using gorilla glue instead of PLp, I haven't tried that yet on Sawfish, but it works well on Seafoam,

Step 20: Hatches

Picture of Hatches

Now that the paint is dry, you still need to add the hatch covers.

Use a razor knife to cut away the fabric over the holes you made for hatches earlier.

test the hatch rings for a slip fit in the hole. You want them to be easy to slide in, with just a little friction. Sand or cut away any fabric or foam that interferes.

Use the thin edge of the straight blade screw driver to cut a small groove all the way around the hole, about a quarter of an inch from the top skin.

fill this groove with RTV, silicone sealant (exterior grade for houses is the best), then lay a bead of RTV around the lower lip of the hatch ring.

insert the hatch ring into the hole in the deck, wipe up any excess RTV,

place weights on the hatches to ensure they sit all the way in the hole while the RTV cures.

Step 21: Gearing Up

Picture of Gearing Up

As soon as you start planning to build a boat, you also need to keep an eye out for the gear to use it safely.
three things are an absolute must:

-a life jacket, while there are many cheap ones, a life jacket meant for paddling is worth the money. the arm holes will be bigger to avoid chafing, it should have pockets for your whistle, and there should be more areas open for ventilation, as paddling is work that warms you up. Try some on at a walmart or boating store, if the prices scare you off, or they don't have paddling ones, Amazon and Ebay, even Craigslist are good options.

Remember: the kayak is unsinkable, YOU are not!

-a paddle, you can make your own, here are a few different ideas, an inexpensive one, a greenland style, or an eskimo style, there are plenty of DIY paddle plans for free on the web also. I have a variety of paddles, mostly from discount stores, my favorites have a graphite shaft so they weigh very little. the difference in weight isn't really noticeable at first, but over a few hours you notice that your arms don't feel as tired.

I prefer blades that are brightly colored, as they tend to flash in the sun, increasing your safety on the water through better visibility.

I keep all of my paddles in one paddle quiver bag to protect them and keep them organized. (this way I don't show up at the river with missing paddle halves)

-a seat. the Oniva seat is the best I've found, I have done many two hour paddles without my seat going numb. every other seat I've tried left me sore and numb. amazon and ebay are the best source for them, unless you live near an ocean state job lots store, as they sell them for much less money, without the Oniva name.

a large car wash sponge works best to remove water in the boat. look for a sponge with a cloth cover as this keeps the sponge from being filled with dirt and sand.

I always carry my phone in the boat for safety. I also use the here app for data free, off line, GPS positioning and maps. I keep the phone in a phone dry bag that allows me to hear music, and take pictures through it. it will float if dropped into the water.

get a good paddling hat, bring sun glasses, sun screen, bug repellent, bandages (great for blisters), and a waterproof camera on a floating strap.

never forget a water bottle!

Step 22: OUCH!

Picture of OUCH!

It won't take you long on a kayaking blog or page to find out that most paddlers, find their kayak seats to be uncomfortable. I agree.

I started with just sitting on a square throwable boat cushion, after a while this feels like concrete...

I've tried the seats out of motorboats, for $40 you would think they would be comfortable... but no. My rear end gets numb and painfull before too long.

I have a folding stadium that has a thin hard foam seat and a fabric back. I guess it beats a hard cement, steel, wood, or aluminum bench, but not by much...

I bought foam to make what many claim is the nicest foam seat for kayaking ever, however I haven't had time to make the seats yet.

Finally, I tried out what I think is the cheap, easy answer, a stadium seat that actually doesn't hurt my rear. Searching around on the web I discovered it seems to be usually sold under the name "Oniva seat", however the one I have does not have that name anywhere on it, I got mine at Ocean State Job Lots, a discount store that is based in Rhode Island, but has stores all over the norhteast US. At Ocean State they sell for $15 in red, blue or green, searching on google for Oniva the prices seem to start at $29.99. Either way the seat is worth the money! It has nice soft supportive padding inside for people like me with a boney rear end, and the seat back has adjustments for six different positions. Even at $40 you are getting a good seat at a good price. The seat most often recomended on paddling sites as a comfortable folding seat costs costs about that much, (GCI sitbacker)

The Oniva seat folds flat and has a carry strap, I can also see it being used as a camping seat, and even a cushion for a quick nap in the sun.

>>>this is my current option, I have another idea floating around in my head, stay tuned<<<

Step 23: Fishing Kayaks

Picture of Fishing Kayaks

Fishing from a kayak has become a very popular activity in the past few years. Just about any kayak can be outfitted for fishing, at a cost that is much less than that of a motorboat and trailer. Not to mention how much healthier it is to paddle in and out.

AF_Caveman (instructables screen name) has taken this design idea and created a great fishing kayak. By widening the hull to 36" in the middle he made his boat wide enough to stand up in. He also added foot pedal steering connected to a trolling motor. you can see his battleyak build album here. For about $400 he has a fishing kayak similar to those 3-5 thousand dollar ones. He also made a nice video showing the details of his kayak, and a full build video that explains how he put it all together.

I haven't gone fishing since high school, so don't ask me for tips on how to rig your boat, I would recommend that you head on over to Kayak diy projects and tutorials and do some research on the mods most kayak fishermen find useful. From what I see, anchor travelers, power poles, and fish finder mounts are the most popular, and the guys there love the foam kayak idea, so don't be afraid to post up what you are building.

I had a friend ask me for two Sawfish kayaks so he could take his wife fishing. He liked the idea of build in rod holders, and his wife asked me to make the sides a little higher. I started with the basic Sawfish design, but made the aft bulkhead wider to allow rod holders to be embedded in the foam, I also made the decks higher so that the whole boat was able to go through bigger waves without getting water over the sides. (this is the current sawfish design)

I'm currently doing a complete remake Sawfish hull #1, giving her the higher sides, thicker decks, correct cockpit location, rod holder bulkhead, and an open well behind the cockpit bulkhead for hauling a fishing crate (the biggest mod you see on the kayak DIY pages) or in my case, a child, stay tuned.

Many of these fishing modded sawfish end up getting a battery and motor, be aware that this means you must register your boat in every place I know of, save your receipts for all of the materials used! many places will try to charge you tax on a boat, but the materials will already have been taxed, don't get taxed twice!

Some other ideas for a modifying your kayak:

-PMF the inside of the bow or stern tank, and add ice for an integrated cooler.

-PMF a tank in the stern to make a live bait well, add a pump to bring in fresh water.

-the flat stern was done on purpose, to allow a rudder to be added, anchor some dowels into the foam by boring holes slightly larger than the dowel into the hull, glueing them in with PLp to attach the rudder to.

- or attach a motor bracket to the dowels, then you can add an electric trolling motor, like this idea. AF_Caveman used this idea to make attachments for his motor mount. I was at the Old Town factory store recently and noticed that the latest design they have, has the motor fixed in place, and the steering is done with a rudder. This could be done with the motor mounted anywhere, even off to one side.

- you may need to add a larger hatch to the bow for the battery. I have an idea for a larger hatch you could use here

-if you add a battery, how about some lights (If you haven't already, check out the pictures of Ryan Swift's awesome kayak. He might get reported as a UFO from a distance, but no one will be able to miss him on the water!)

-If you don't have a built in battery, save your empty gorilla glue bottles, they fit perfectly over those cheap aluminum 9 LED flashlights. Use a little five minute epoxy to glue the bottle over the lens end of the flashlight, fabricate a PVC pipe to hold the flashlight higher than your head behind the seat, and you have an excellent light for after dark.


Just be aware, if you add a motor to your kayak the regulations for lighting get much tougher. Any light you have on a motor boat has to be visible for two miles in the dark, there are only a few lights with this rating.

If you don't have a motor, a flashlight you can wave is good enough (your cell phone probably has one you could use in an emergency) I prefer those cheap Energizer LED headlamps, if a boat approaches I stare at them and shake my head, making the light appear to flash.

Step 24: Rod Holders

Picture of Rod Holders

I tried a few different things to bore the holes for the rod holders, and ultimately created a new tool to do the job. Since the cockpit floor is 7.5" from the lip of the rail, I cut off a section of PVC 12" long. Using a saw, I cut teeth into one end of the pipe.

Then I used a 1/2" boring bit to make two holes, one on either side of the pipe, near the top. finally I marked the depth I wanted to cut the foam to all the way around the cutting pipe I had created.

By inserting two screwdrivers into the holes in the top, I could lean on them and turn, boring a perfect hole into the foam. When I hit the depth I wanted, I gave it a few turns then pulled the tool out. The plug came out in the cutting pipe, leaving a perfect hole.

I asked for which sizes to use on the best kayak fishing facebook page and was told that 1.5" and 1.25" inch were both good sizes to use based on the brand of rod used. I made a tool in both sizes, and put two of each size in each kayak, bored into the aft bulkhead. I angled the outboard pipes so that they would hold a rod at a good angle for trolling, and put the center two vertically for out of the way storage. I could have probably added five or six holders, but four seemed the standard number seen on most DIY kayak mods.

To keep the end of the PVC pipes from tearing up the rod handles, I flared the ends of the pipes with heat, using an incandescent light bulb as the heat source, then holding the pipes under the faucet while flared by a glass bottle until they took the new shape.

After the whole hull was wrapped in fabric, I sanded the outside of the PVC pipe with 60 grit, then glued the pipes in with gorilla glue.

I also added loops of nylon strap with the ends glued into the foam with PLp, to anchor rod leashes too, with one anchor between each set of rod holders.

Even if you don't ever plan on fishing from your kayak, adding the rod holders will make it that much more useful for you, the rod holders are handy spots to install an umbrella for sun protection, or anchor a light in for night time paddling. It will also make it that much easier to sell, and for more money if you can call it a fishing kayak.

The gear anchor loops are also a great place to tie off another kayak when you end up towing another boat.

Step 25: Sawfish Gets a Makeover

Picture of Sawfish Gets a Makeover

Since I first launched Sawfish, I have been using her hard, and testing different ideas on her. I tried two handle anchoring ideas before I was happy.

Then we had the day my wife got blown away in Sawfish and ended up on a beach far from the car, because she couldn't control the boat in a strong wind.

I added a foam strake to the bottom of the boat to see if it would help with control. This strake made the boat slower, and got hung up on many rocks when we did a family trip on some mild whitewater in North Conway, NH. I hacked the foam strake back off the bottom of the boat, but that left a bare section of foam right down the middle.

The wood cockpit rails had a break in them, and this caused the foam to crack right at the break, and tore the fabric there. The damage was only in the top layer, and it didn't weaken the boat when it was floating, so I just lived with the damage.

The cockpit location was about a foot too far aft, and this made sawfish slow, and hard to handle in a cross wind, moving the seat up as far as possible helped, but didn't fix all of the problem.

Finally I took sawfish on an exploring mission, ending up in thick reeds and shallow water. I split my kayak paddle in half and used each half like ski poles to push through the reeds, until our way was finally blocked by a stone wall. There were rocks and logs in the water, and Sawfish was being bent and beaten harder than any time before.

The flexing caused the score line running right down the middle of the foam used in the hull to split, and sawfish began to leak into the cockpit.

After we got back to the shore and were carrying her to the next pond, we found a stick embedded in the foam of the hull. it hadn't gone all the way through, and even with the split seam, sawfish wouldn't have sunk, instead she let in some water, but that was it.

It's been a few years of hard use and no repairs on purpose, to see if the boat would be safe over long term. The design passed and met all of my expectations, but now it was time to make sawfish over into a boat that would look as great as the sawfish I'm building now.

First I removed the fabric, this was easy, I cut it all the way around with a razor knife, then peeled the fabric off.

Then I used the power plane to reshape some of her bottom curves and bow shape to be less square, and flow through the water easier.

I removed the cockpit rails, decks, bulkheads and top rails.

I used the ice cream scoop to remove all that extra foam from her bow and stern, and created more useful space for bow and stern cargo tanks. .

I added a new aft bulkhead a foot forward of where her old one was, a new forward bulkhead, added new decks, and higher cockpit rails with no inward curve to them. (they didn't keep waves out the way they should have)

I also added a third bulkhead in the stern, this will enclose a small cargo tank in the very stern, but leave an open area behind the cockpit for fishing gear or a small child to ride.

There were a few deeply damaged areas in the foam on the bottom of the hull, I cut them out and glued in new sections of foam to give the hull a smooth surface again.

I used the power plane to remove the plastic cutting board skeg, as it would get in the way of putting on new fabric.

Stay tuned for the latest on the New, Improved, Original Sawfish!

Step 26: Repairs

Picture of Repairs

your boat will be damaged from time to time, some of this will go away on it's own as the foam will swell back into place with a little time and heat from the sun, but some of the damage will need more attention.

The steam Iron trick,

lay a thin towel you don't care about over the damaged area, apply the steaming iron to the towel and work it back and forth slowly, the foam will shape itself back to the original if it can, and the TBII will stick to the foam and fabric again.

If this doesn't work, go to the next two repairs.

For damage to the foam,
use the razor to cut around the damage, don't go deeper than an inch. use the screw driver to dig out the damaged foam. cut a plug of foam that fits tightly into the hole. glue the plug in with GG. sand or plane smooth, then patch the fabric

for tears and holes in the fabric,

cut away the damaged area, repair the foam as needed.

then cut a patch that overlaps the cut away section all the way around.

sand the edges of the fabric around the removed section.

apply titebond II glue to the bare foam and glue the patch to the foam.

Use paint to glue the edges of the patch to the fabric that overlaps around the foam, then paint the new fabric patch to match the rest of the hull.

Step 27: Make It a Double!?

Picture of Make It a Double!?

The builder of the first sawfish in the Ukraine turned his 12 foot sawfish into a tandem by stretching the cockpit, I like the idea, but the seats seem a bit high in the hull to me. He says the boat is fast and stable, which is all that matters. His daughter has helped with the construction, which is an excellent learning experience and should create some memories.

You can make a tandem out of your 12 foot kayak, but if you want a capable boat that can carry two and gear for camping, I'm currently building a 16 foot Sawfish. All I did was lay out the bow and stern dimensions the same measuring 6 feet from each end, then added four feet in the middle. I'll post pictures as I go.

Most couples find they each prefer to steer their own boat. However if you have a child, large pet, friend, or spouse who you want to take along, this hull would be very easy to make into a double. I made my tandem kayak so I wouldn't have to wait for my wife, over the years this has proven to be a great way for her to be with me even if she wasn't as into the paddling as I was. ( tandem kayaks are referred to as "divorce boats" by most, you've been warned)

Duet is my 16' Larsboat, the Larsboat is a Jim Michelak design, that is a simple stretch of his most popular design, the Toto double paddle canoe. The Toto is 13' long, adding three feet to the hull makes it into a fast tandem.For comparison I have a picture of Sawfish next to Duet at the top, while Duet is a fast seaworthy boat, she is also rather heavy, weighing 65 lbs, not much fun to move on and off of the van, or pick up after a long days paddle.

Here is a teaser video of our new tandem sawfish in action, Tango, this was the first time we tried having three in the cockpit, while we all fit, the boat was a little nose down and hard to steer. looking at the video though, it is easy to see that we had a good headway going in spite of the trim issue. Once we had tried this for a few minutes, we had our six year old ride in back instead. Since it was hot she rode on the aft deck instead of inside of it. Before long she was standing up as we paddled along, only grabbing my head when we turned hard or slid onto the bank.

interesting idea for paddling with your feet



I'v gotten a few questions about the strength of the boat, will it handle rocks and moving water, etc. To prove it to myself and the rest of you I took it to the most extreme conditions I know of, the surf zone on my favorite beach.

I tried it out in the surf on two different days, one was very windy with good surf conditions, I'm not sure what the wave heights were, but I know the waves were covered with surfers and they got plenty of rides. I punched out through the surf, the boat went through just fine, though many waves came over the bow and filled the cockpit. With a cockpit full of water the boat got harder to handle, but still made good progress and rode over most of the wave.

Once I got past the break I rolled out of the kayak and then rolled it up on one side to dump out the water. Thanks to the foam it floated high on its side, so all of the water came out. I was able to climb back in with some effort, without filling it up again. This will only work for stronger more agile people as it takes some strong swimming with your legs to get up enough to straddle the hull with your body, then swing your legs around into the hull. I did all of this in water too deep to touch bottom. (NOTE- if you fall out of this boat with any wind, it will sail away quickly, faster than you can swim, keep a rope tied to it to give you something to grab)

I tried to surf the waves back in , but the hull is too long, the skeg too far back, the bow too pointy, and the stern to narrow, for this hull to be able to surf in the big stuff. The bow dug in, the stern came around and I got dumped!

Part of the problem was the lack of a good way to brace my feet in the cockpit, mostly the hull shape is wrong. I do plenty of surfing in a Yakboard, so I know how to surf, but I also know a normal kayak will be swamped, rolled, and handle like a pig in the surf. I see people try to surf in regular kayaks all the time, it is entertaining for me, but not fun for them. Even white water "squirt boats" do not last long, they fill up fast even with a skirt.

Since the boat was no match for the surf, and I really wanted to surf, I launched back through the surf, then paddled over a mile down the beach to get as close to my parents beach cottage as I could, so I could swap Sawfish for a surf kayak. The seas were very rough thanks to the wind, and most of the rollers (this is the north atlantic ocean, gulf of Maine) were over my head as they approached, then I would be launched off the top, to smack down on the other side. if the hull was going to fail it would have then.

It made the trip just fine. To make it out without another trip through the washing machine surf, I hopped out of the kayak where I could just touch bottom, then holding onto the bow handle and the paddle in the other hand, I bobbed and walked out of the surf.

Two days later the surf was much lower, the waves were perfect for kids on boogie boards, so I tried the surf in Sawfish again. This is the day I have pictures for, the surf is small, and the surfers were only getting a few good waves.

Before I launched I made a scupper in the cockpit. I used the shaft of the double paddle to punch a hole through the cockpit floor fabric, the foam bottom, and the bottom fabric. SInce the hull is foam, it floats even with a 1" hole in the cockpit floor. however I discoverd the hole was too small, I had to wait a few min. for the water to run out, sitting out beyond the break. I am currently working on a foam surf kayak, check out my Rowerwet facebook page Sandshark album

I was able to surf a few small waves this way, but the boat is not for surfing! I just did this to prove how strong it is, if it will handle being smashed around in the surf, a hole drilled through the bottom, and a couple good wipeouts in the surf, you do not need to worry about how strong it is. It tood a lot of force on the kayak paddle, and a twisting motion like a drill to make the hole through the fabric skin, you will probably not punch a hole in your kayak unless you drop it from a height or run white water/surf with it. stick to rivers, lakes, and streams, anywhere you would take a regular canoe on and you will be fine.

Step 29: Getting There

Picture of Getting There

Most of us are not fortunate enough to live on the water, even if I did, I would want variety. New waters mean new scenery, and place to explore and discover. One lake I paddled recently, has almost no undeveloped shore line. I spotted ducks, cormarants, and Canada geese, then was amazed to get a fly by from a Bald Eagle! a bit later I spotted a pair of loons. More bird types on this very urban pond than I've found on remote Adirondack ponds, or secluded spots in the river.

Getting your boat to these spots couldn't be easier. Unlike plastic or wood kayaks, Sawfish is super light, easy enough for almost anyone to toss up on roof racks. Thanks to being light weight Sawfish can be carried a good distance without becoming a strain. While exploring the Adirondacks I carried Sawfish nearly a quarter mile from one pond to another. This was a marked canoe carry with a smooth enough path through the woods. Unlike most people who carry the boat across, then return and carry their gear, I simply put Sawfish over one shoulder, hung the seat strap over the other and carried the paddle with my free hand. It took me longer to answer questions about the boat, than the portage took!

Thanks to the light weight, I've also been able to park and walk a distance to the water, much further than most kayakers or canoers would want to deal with. Another way to carry Sawfish is resting on the top of my head like a hat, thanks to the softness of the foam, it doesn't hurt like a plywood boat does.

A simpler, cheaper option than a roof rack, would be canoe blocks, foam blocks with a groove cut into them to lock over the rails of the boat. Either way, you need a good way to secure the boat to the car.

In the above pictures you will notice the bow rope is tied to a strap coming up next to the hood. I've added these anchor points to every car I've owned. there is no lying on the ground to reach tie off points, and no chafed paint from vibrating tie down straps or ropes.

To make it easier to carry my paddles around I carry them in a bag, this way they are protected, and aren't all trying to slide out and fall when I carry them.

Step 30: Conclusion

Picture of Conclusion

Sawfish was the first boat I designed, my 10th or so boat build. It is light weight, fast (relative term), inexpensive, unsinkable, and stable. best of all it can be built without one expensive "marine" component. The foam in the hull will keep a 200+ lb adult afloat with no problems (like a Boston Whaler) yet it weighs only 25lbs.

my total cost comes to just over $100 dollars US, compare to the cheap, tipy, 8 or 10 foot kayaks sold at discount stores for $150 to $250 and up!

the hull is cut out and assembled in very little time. I really only had time to build this boat starting in April of 2015, and even then only spent one or two hours two or three days a week to not only complete this hull, but cut out the parts for three more, and partially assemble another. I cannot put a time to build with the boat because of this, but it won't really take that much longer than a plywood boat.

It will never rot, it will never sink, it is stable enough to trust your kids in, can be built for cheap money, with stuff found at home stores and discount retailers. most people sitting on the shore will be amazed that you built it yourself, even more amazed when you tell them what it is made of, and show off how strong you are/how light it is.

Even real snobbish kayakers will not know you have a home built boat until they take a close look at it.

-If you damage the fabric, just use some more paint to glue a patch over the damage.

-If the foam gets gouged, use some GS or light weight spackle to fill the gouge, then sand smooth and glue a patch over it with paint.

-If the foam gets "pin striped" by a rock or log and it bothers you, get a thin towel you don't care about and a steam iron, apply the steaming hot iron to the towel over the crease or dent in the foam, heat will activate the foam and TBII and the dent should pop right out.

-Leaving the hull out in the hot sun will also heat the dents and creases out of the hull.

Step 31: Registration

Picture of Registration

I live in a state where human and sail powered craft do not need any registration, however there are states and countries that require a registration, and that requires a hull number. I'm using the same idea Gavin Atkin uses for the mouseboats, and shorty pen uses for the Puddle duck racer. When you get your hull to the 3D stage (glued together into a boat shape, doesn't have to be sculpted yet even) send me a message here on instructables, I'll give you a hull number and will keep a list on the next page. click the "I built this" tab on the page also, and include a picture of your first launch, this is the best way to get more people to want to build one themselves.

>WHEN you build a Sawfish, email a picture of it to , let chuck know what the design is (Sawfish), what you named it, when (where) it was first launched, a bit about how it was to build (how long did it take you) and how it was to paddle. they will put your picture on the splash! page at the best boat building site on the web. The splash! page comes out about once a month.

That is the only payment I ask for answering your questions and sharing my plans and ideas for free. does that sound like a deal? thank you, Josh, (Rowerwet on Facebook, and everywhere else)

I built this kayak to learn about building with foam, on the best teardrop forum on the web this is called a foamie, there are more of us every day.

Step 32: Hull Number List

Picture of Hull Number List

this is the list of hulls as far as I know.

1. Sawfish (the original boat), MA (pantherworks)
2. ?, Pantherworks (my mom's boat) MA
3. ?, Pantherworks (my dad's boat) MA
4. ?,Pantherworks (my aunt's boat)

5. battleyak, AF_Caveman, hull widened to 36", foot pedal steering trolling motor (the blue one) VA

6. Tydra, ffernandez indiano, the Czech Republic

7. ?, Pantherworks (built for my friend sam)

8. ?, Pantherworks (sam's wife's boat)

9. floater, jim bayes, MI

10. Talon, FernandoA89, NM

11. Saw-gundo, jim bayes, MI.

12. Bountiful harvest, bionic randy, he has the build record at 10 days!

13. ?, kkid

14. Myanos, Jim Wright, RI

15. Golden Sawfish, EddieR33, PA

16. ?, John Henson, the Azores

17. ?, Mikael Larson, Denmark

18. ?, Don Kirkley

19. ?, Gary Schepers, GA

20. ?, Gennady Kedrovsky, Ukraine, First person to make sawfish 12 into a double.

21. ?, James brown, TN, currently being created (a really bright guy who figured out the new cut pattern for Sawfish on his own at about the same time I figured it out. He also figured out the better way to do the decks on Sawfish) He wrote about his build experience in Duckworks Magazine

22. ?, Ryan Swift, widened for fishing, with some awesome LED lights built in. you can search for his build on the Kayak DIY and tutorial facebook page

23. ?, Stephen Conrad, The bright green one

24. ?, Terry Garrett, CA, No pictures yet

25. Brickfish, BrianM351, first Sawfish 11, shortened to fit in and out of the builders apartment. (the one with the interesting rails)

26. Beta-Yak, Bruce Glassford, He tells me he is creating youtube videos of his build, I can't wait!

27. Redwall, the first Sawfish 14, in TX

28. Sunburn, sawfish 12, built by my 12 year old son, possibly the last using the old cut pattern

29. Tango, the first sawfish 16, a tandem sawfish with room for expedition paddling.


Sawfish length are based on the bottom blank length

variations on sawfish

Unnamed, Arthur Meiners, a unique boat built of 1" foam for exploring the canals in Holland. Probably more closely related to my Seafoam instructable than Sawfish. The builder is a photographer, and wanted a boat that would let him sneak through shallow water and under very short bridges. He used the green patterned fabric to help him hide, and covered it with epoxy so the pattern would show. Overall the boat is only 8 feet or so long, this allows him to store it vertically in his house, and to carry it inside of his car.

unnamed, Tim Murphy, Tim built a rather boxy foam boat using methods more like my foamie mouseboat idea, only his boat is 12 feet long and 36" wide (orange and white boat).

unnamed, Tim Murphy, His second boat is built of stacked foam, but only 10 feet long and without the fabric skin. I'll be interested to see how long the foam survives like that. (bare blue foam currently)

Step 33: Frequently Asked Questions

Picture of Frequently Asked Questions

I can't find/afford XPS foam.

A) this is the most common question I get, yes you can use EPS, the beaded foam panels, just be aware that they will absorb water unless carefully sealed. You might want to consider coating the whole bottom of the hull with marine epoxy, or some other tough, waterproof membrane. Stored dry, especially someplace hot, with any tears or holes carefully repaired after each paddle, you will probably be fine.

I can't find the glues you recommend, or they are very expensive in my country.

A) This is more of an issue than I ever imagined, my best answer is to find any boat building blogs in your country, and see if there is a local equivalent. More than one builder has found something locally made and sold that was close enough. When you do find it, and are happy with the results, please share that info here or on my facebook page, it will help others in the same situation. The more this design is built around the world, the better the support will be for those who want to build outside of North America.

Have you or anyone ever tried some other coating than the ones mentioned in the Instructable?

A) If it hasn't been mentioned, then most likely no. I have a system that works, and I'm all about low cost and simple, If you do try it, please post back here or on my facebook page in a year or two and let us know what the long term results are, you might have the next great idea.

Can I make it longer/ shorter/ wider?

A) Yes! just be aware that anything over 36 inches wide is too wide to paddle, and oars work best at 48" up to 60" wide.

Can I add a motor to it?

A) Yes, but aware that a motor makes it so that you have to register the boat, save all of your receipts for what you buy to prove you paid taxes on the materials. You also may have stricter regulations about required gear and lighting.

If you want to add a gasoline motor, be aware that gasoline eats foam, use plywood encased in fiberglass with bilges that do not drain toward the motor or tank storage. Finding a motor small enough to be safe may also be an issue, let us know what you discover.


RyanT118 (author)2017-12-03

Is it possible to use a combination of xps foam and other foams for parts that don't need to be that strong? Also, with the kayak be able to be used in bays? I'm planning to use it for fishing or crabbing.

DavidA722 (author)2017-11-27

I’m considering using Sawfish as the basis for a poor mans Hobie Adventure Island. Any thoughts/experiences with adding a small sail?

frank villegas (author)2017-11-05

my problem is i cant find titebond in my area so my option is to coat in resin but epoxy resin is not available but only the polystyrene types. so my idea is to wrap the foam with paper mache then apply the resin composite. would it be ok?

rowerwet (author)frank villegas2017-11-09

If you are in the US titebond II is easy to buy from Amazon or the home depot website.
Outside of the US you have more of a challenge.
I posted the link to the manufacturers page so you can get a rough idea of what the glue is chemically.
More than one international builder has found a suitable substitute by asking around on local boat building pages, or even carpentry pages dealing with outside projects.
The paper coating idea sounds like a lot of work.
You might look into the shellac coated paper boat building ideas from around 1900.

NiteWolfeTX (author)2017-11-09

I am not sure why my other comments are not here but ill try one last time.
Thank you for the wonderful plans and advice i got from you on facebook.
Here is my version of the sawfish.
I call it the WolfeYak!

NiteWolfeTX made it! (author)2017-11-08

I introduce you to the WolfeYak!

NiteWolfeTX (author)NiteWolfeTX2017-11-08

It is 12'4" long, 38" wide and 12" thick. It weights 64.9 pounds unloaded.
It had a rough start...I knew the foam was light so i felt my car top could carry it. What i did not take into account was lift.
5 sheets pulled my home made roof rack up and broke it in half.
My foam ended up on the hwy and got ran over some.
I did collect it all and fit all of it inside the car and some rough strapped back to the roof while we took slow side roads home.
My wife though it was dumpter time and i said hold my beer!

This is 38 wide but still paddles well. It is a slow boat with the paddles but i dont have much to compare it to other than my 10' pelican.
I am ok with the speed and plans are for motors later anyways hince the transom.
I will be adding a electric motor and a short shaft weedeater motor later.
No seats or future gear will be hard bolted to the yak. I am designing items to be movable and corded down as needed so this is a open deck design.

I did have a massive issue with the light weight spackle. It would never dry and even trying to clean it off was problematic so the upper curves of the rails are very rough instead of smooth. Nothing else would stick to the areas where the spackle was. so i just pmf over it and will live with it and a lesson learned for the next one.

jsq (author)2017-10-14

Hello - in planning stages to build a PMF boat, and I see you updated this Instructable with 2.0 material. When I try to download the updated one, I only get the older PDF! Any idea what my problem might be? Am I the only one? Thank you!

rowerwet (author)jsq2017-10-25

I'll be adding more updates some time this winter, but until then, the revised version is fine.
Mostly I plan on making a video tutorial out of each step with links to youtube

jsq (author)jsq2017-10-17

UPdating myself- I found a request to Instructable service to delete the orginal PDF, held online to reduce response time, allowed a new PDF with the 2.0 updates to be created and downloaded! Yes!

EthanC59 made it! (author)2017-07-21

First off - massive thank you to rowerwet for putting this together and giving me inspiration/a starting place to pursue building a foam kayak.

I just wanted to share a draft, I quickly threw together in PowerPoint, designed mostly from rowerwet's instructions and adjusted to more closely match a manufactured kayak design.

When designing this, the biggest question that came up was the seat location. It seems that having the back of the seat at 6" aft (towards rear) of the centre of the kayak seems too far forward, thus the design shows a seat moved further back. Any opinions on this?

PS - on the picture, each dot on the grid represents 1", and each line is spaced at 1'

rowerwet (author)EthanC592017-10-25

If the kayak is symmetrical bow to stern, the paddlers seat needs to be just behind the center of the hull for balance.
If you make the widest point immersed in the water end up further back, you can move the seat back as well.
Your center of mass when sitting, is just forward of your belly by an inch or two, because of the weight of your legs

TheTexasViking made it! (author)2017-06-19

Hi, rowerwet, thank you for your Instructable, it helped me immensely in my effort to make my kayak. I increased the length to 14 ft, added wood in several areas (strips of pine along the gunwales, 1/4" ply on the lower deck, a few 1x4's on the upper decks, and a 1x1.5 keel along the bottom), and I used canvas drop cloth on the whole thing, instead of sheets. It ended up costing me about $260 to build (I was only able to get the paint and one 2x4 free) but that's still a lot cheaper than a comparable plastic yak. It's not completely done, as I'm still waiting on some ordered things, I'll post an updated photo when it's finished.

I've decided to call it Redwall as a tribute to one of my favorite book series from back when I was a kid.

Thanks again for the detailed instructions and also for the inspiration, I'm looking forward to using my yak quite a bit.

rowerwet (author)TheTexasViking2017-06-22

Congratulations! A nice looking boat.
Soundslike you went for extra strong, on the build.
Thank you for the pictures!

ScottS451 (author)2017-05-04

Thanks so much for your work and for sharing. I was wondering if you might have an estimate for the amount of weight this design could support? What might I be able to change in the design to support more weight?

rowerwet (author)ScottS4512017-05-05

I think the original design would safely carry 300 lbs with no issues. 400 or more in very calm water, the new design will carry more , probably 4-500 lbs with no issues.
If you want to carry more weight you can easily make the hull longer, I'm finishing up a 16 foot tandem sawfish kayak right now, the extra length will carry much more weight.
For more stability under load make the hull wider. My plan gives you a boat 28" wide minus a little on the water line. Adding a few inches increases the weight capacity and stability, at the cost of a little speed.
You can go up to 36" wide before you can't paddle a kayak.
The battleyak is 36 inches wide, and Josh Bryie is a big tall guy, he easily stands and casts from it, and he takes his kids with him, along with a battery, trolling motor, fishing gear, etc. and can still almost paddle as fast as his friend in a plastic fishing kayak.

BrianM531 made it! (author)2017-04-29

Successfully took my 'Brick Fish' (due to color of the oops paint) for an hour long test in the local river yesterday!

This was the second test actually - the first time it leaked badly. Best I can tell, some of the layers of foam separated when I put accidentally applied pressure to the hull bottom piece after gluing while it was still on blocks. Additionally, I was not careful enough putting the side fabric on.

To fix this, I cut away the fabric from the sides as you can see in one of the pictures. I cut new pieces of fabric and nailed them all along one side. This way, I could fold the fabric out of the way, apply undiluted Titebond II to the foam, and then fold the fabric over the hull. This gave good seals.

Two other changes to your Instructables:

-The boat itself is smaller (11 x 2 feet at base) so it can fit out the door of my small apartment!

- I spray coated the sides and bottom of the boat after painting with Marine Varnish (Helmsman Spray Varnish) to add more water resistance. I did not want to take any chances after the first leaky test. Next time I would apply this Marine Varnish outside because the headache-inducing fumes linger for days!

The supplies were mostly purchased at a Home Depot or Lowes in CT, USA. Some things were bought on Amazon. Here is a cost summary:

- $156 for materials to make the boat

- $96 for a good life vest, Oniva seat, and paddle

Additionally, I spent $63 on new tools - and that was even skipping some of the tools, like the wallpaper perforator (instead I stabbed holes by hand with the bamboo skewers - very time intensive but cheaper).

All told, this was a $315 project that took ~2 weeks of regular effort each night. I'm quite happy with the final version and it is wonderful to be out on the water. I will likely be building a second one in the near future. Thank you for the Instructable!

rowerwet (author)BrianM5312017-05-01

Glad you made it all work out, hopefully you can enjoy many years of use without any issues.
You get hull #24, congratulations!

DavidM1392 (author)2017-04-05

I have seen pontoon stand up paddle boards and though of making them out of this. Would it be strong enough. What about a canoe? My fear is it would be to light and tippy.

rowerwet (author)DavidM13922017-04-07

You can make any shape out of foam, it may need some wood reinforcement to keep its shape.
Im not sure why you'd be afraid your foam Canoe would be light, i prefer my boats to be as light as possible :^)
As far as being tippy, that just takes a little adjustment to the design. Heavy materials are best for a hull with a V bottom that settles into the water.
Foam barely draws any depth in the water, so a flat bottom with rounded edges will give a stable footing.
Just make the bottom as wide as you want the hull, and it will be stable.
Sawfish is 28" wide, and I can stand in it easily on the water. The guys who want a design for standing to cast widen that out to 36 inches

DavidM1392 (author)rowerwet2017-04-12

How do you thin the tightbond 2. You mentioned it but must have missed the instructions. Thanks

rowerwet (author)DavidM13922017-04-26

Add water, not more than 5-10%, personally I hate the way it acts thinned.
It doesn't tack up as quickly, takes longer to dry, and runs easier

pasonguy1 (author)2017-04-25

I am using your sawfish idea to build outrigger pontoons for my canoe. Love the light weight and the fact that it is hard to sink. I will have my young son and his friends fishing out of the 16' canoe and can't wait to see how stable this baby will be with the pontoons. I have also made them adjustable so I can have them at the side of the canoe or outreached 28" on both sides. Pics coming

rowerwet (author)pasonguy12017-04-26

Awesome! I always thought it would be easy to make some this way, I just don't need any myself.
If you don't mind, i would like to add a page to the instructable showing how you did it.
I think outriggers are a great way to have a fast kayak and then also have stand up stability for fishing

srcpt (author)2017-04-03

I was able to get four 2'x8'x2" sheets of Dow XPS very cheap. I have butterfly scarfed a 12' sheet and ready to draw out my pattern. Just wondering if 24" beam is enough? If wider, should I do two halves (14" at the widest) with a joint down the center line to get a 28" beam or add two inches on each side at the widest part of the bottom?

FYI, I tried cutting the first cut (8 feet down to four feet) with a jigsaw using a Bosch soft materials blade. Clean cut with no dust, but I was unable to keep the blade from bending and thus cutting straight. I then tried the same blade in a Rockwell Bladerunner, but 2" thick was just a hair too much to slide under the control arm, so no luck there, either. If I were using thinner stock, I think either would have worked beautifully.

rowerwet (author)srcpt2017-04-05

24" is a bit narrow, i tried it on one hull and don't recommend it.
You would have an easier time by glueing onto the edge of the section you have now.
I use a very coarse demolition blade in my skillsaw, they tend to be longer and thicker and resist bending better.

srcpt (author)rowerwet2017-04-05

Thanks. I'll use the "waste" from the corners to build out a short section on each side.

jimbayes (author)2017-03-21

The missus just gave me permission to build a tandem. This weekend I will start on Sawfish #3.

rowerwet (author)jimbayes2017-03-22

And don't forget to share pictures!

bill_randolph (author)2017-03-22

I'm going to start the final sanding before skinning my kayak. I was thinking of using folded GS instead of the light weight spackle to fill in some low spots, dents, etc. Is there any reason I shouldn't use GS for this ?

rowerwet (author)bill_randolph2017-03-22

GS tends to foam up as it cures, and it tends to leave pockets underneath. You may have to repeat the process a few times to get it all solid.
On the teardrop site, many builders use the vinyl spackle, it comes in a tub that feels empty compared to regular patching plaster.

BruceG45 (author)2016-12-04

First off, thank you for this kayak and all the info and details; much appreciated. Where I live (Cali) I only have access to the expanded polystyrene but I can get it in 2" thick sheets. I'm wanting to build a kayak that closely imitates Bass Pro's Ascend 128T model. To add rigidity, I plan on adding a thin sheet of plywood or similar between the two bottom sheets. Also thinking of making a ply "drop-in" cockpit. This would allow me adjustable seat heights and foot braces.

A concern is the "skin". I'm actually considering a shell made of paper mache consisting of wood glue and heavy paper - the brown wrapping paper.

I do plan to make a smaller scale model to test some of these theories.

I would really appreciate and input, suggestions, and feedback prior. Thanks much!!!

rowerwet (author)BruceG452016-12-05

I really don't think you need the layer of plywood in the hull, as the picture on the first page shows, the hull held me just fine, straddling two sawhorses about 9 feet apart.

wood is weight, I use as little as needed. Sawfish has now survived two summers with regular use, and I am hard on my toys.

48224 (author)rowerwet2017-03-13

I was thinking I would add a luan floor in my foam yak. Would a little added weight be helpful for standing up in the yak? Some of those fishing yaks that you can stand in are 12 feet and 95 pounds. A guy posted a vid on youtube and calls the vid "the battle yak"'s a fishing yak, I think he said it weighs 55 pounds. That's not bad for a fishing yak.

rowerwet (author)482242017-03-15

Josh added the wood to the battleyak because it has a motor on the back, i don't think any wood is needed for the floor at all.
Remember the fabric skin is the real strength of the hull.
I stand in my kayak all the time, it doesn't even dent the foam under my feet.
I use thick canvas for the cockpit floor and that is all the reinforcement it needs, unless you are wearing spike heels

BruceG45 (author)482242017-03-14

Hi 48224 - here's what I can tell you; I've seen all the vids on "Battleyak". Some things I like...some I don't but those are personal preferences. It is well executed. I think a luan floor is a great idea for rigidity, especially if you, like myself, are using open-cell foam. My yak is under construction as we speak and overall dimensions are 13' at 33" wide - laid out in a more traditional SOT fishing kayak. Front and rear compartment floors will have luan glued in and cockpit floor will be 7/16 OSB - most of the weight / sitting...standing. Littlle likelihood of flexing and breaking the glue bond. Willing to sacrifice more weight for integrity. Should still weigh at least 20 lbs. less than anything commercial in its class.

BruceG45 (author)rowerwet2016-12-06

Thank you - was thinking of luan or similar; something very light. Knowing polystyrene doesn't have the same integrity as expanded foam, thought this may be a solution. Gladly omit it if it isn't needed.

rowerwet (author)BruceG452016-12-07

You might look for 1/8" door skin plywood for the cockpit floor, once glued to the foam, it becomes many times stronger, and the foam is much harder to puncture as well

rowerwet (author)BruceG452016-12-05

The biggest problem with EPS (beaded foam) is that the little voids between the beads will suck up and then hold water.

The sawfish that was just launched in the Azores is made of EPS, as he had no way to get XPS there. He used a waterseal product to seal the foam, then wrapped it with fabric. I don't know what the long term condition of the boat will be, but if water gets in, it will get heavier and ride lower over time.

Obviously this type of foam is usable though, as Snark sailboats as well as many fishing gear floats, and even dock floats are made of it. The trick is getting it well sealed.

Your paper mache idea could work if the paper layer is waterproof. I don't know what kinds of paste there are that would remain waterproof, you may know better than I do, or an art supply place or artist blog could help.

Historically, there was a paper canoe fad back around 1900 or so. it involved paper layers glued into a boat shape with varnish I believe. Polyuerathane might be a more modern material to try.

Whatever you try, I would suggest getting a tub or bucket of water that you can let sit for a few days. cut out some foam circles or squares just small enough to fit in the bottom of the container, after being sealed or wrapped with whatever materials you come up with.

Once you have your test panel sealed, wrapped and painted, weigh it and record the weight on the panel so you don't forget.

Now submerge the test panel in the water, place enough weight on it to make sure it is submerged.

After two or three days, get the test panel out, shake off the water and weight it. This should let you know if the seal will work in roughly the same conditions it will when you are paddling your Sawfish Kayak.

Unless you plan on an epic paddle with many hours on the water every day (in which case you really should invest in a better boat, IMO) Your test of a few days should be longer than the average paddle, W

BruceG45 (author)rowerwet2016-12-06

Thank you again for all the feedback and input. This will have to be left open ended for now as I haven't yet done any proofing / testing. The paper mache will be done with waterproof glue. I will be testing the strength of 1-2-3 and more layers if needed. Just for my own knowledge and experience if nothing else.

This would then be sanded, primed and a coat or two of latex paint applied. I do know polyurethane and likely varithane can be applied over latex; more options to test.

No epic adventures - my intention is something something somewhat and very stable; not so much concerned about speed or weight. Small waters on mild days fishing for bass and crappie, a few hours at a time at tops. Likely 4-6 times per year. I do want something that will last though.

I think the most intriguing thing though is making it myself!

rowerwet (author)BruceG452016-12-05

a few other people in the comments have run into the same issue, and atleast one has actually launched his boat. (he painted the foam, then sealed it with polyester resin)

The only other guy I know who has had a lot of success building with EPS, does a two layer skin of marine epoxy and light fiberglass. But as I said below, this is expensive, costing nearly as much as the rest of the boat.

48224 (author)2017-03-13

Is there any reason I cannot use expanding foam to glue my sheets of foam together? I know you used Gorilla Glue. I was thinking the foam would better seal the pieces together....just guessing.

rowerwet (author)482242017-03-13

there really isn't much reason you couldn't use expanding foam. I actually used it as the glue for my foam mouseboat (google "seafoam kayak")

I think it might cost you a bit more, and might not be as strong as gorilla glue unless you follow the instructions in the seafoam instructable to fold the foam before gluing with it..

i believe there is a guy in the Ukrane building one with expanding foam right now

48224 (author)rowerwet2017-03-14

Thanks again for all the info. I am a former construction and science teacher and used some spray foam to bond various materials together a few days ago. I wanted to see how the materials bond with the foam. Foam spray bonds the 2 inch thick sheet insulation VERY well. I can't pull it apart. Bonds to wood very well also but not as well as foam on foam.

Maybe I will use foam on the joints below the water line and Gorilla Glue above the water line. I am thinking the foam will seal the seams better.....we will see I guess. LOL

I was reading quickly through your directions the other day, If I read correctly, you just have 1 sheet of insulation on the hull of your boat and I saw the picture of you in the boat between two saw horses. Wow....never would have believed it.

dvanny (author)2017-02-18

I'm getting ready to build a skin on frame boat and am doing it on quite a small budget. The hardcore guys who apparently are all millionaires use kevlar-carbon fabric with some special two-part urethane to waterproof it. However, the money tree I planted still has yet to produce nice crisp $100 bills, so I'm using duck canvas and...something. I'm thinking of leaning toward Titebond 3 glue for the waterproofing, like you use on your boat. However, a whole lot of the kevlar snobs say Titebond is no good. Also, Titebond itself says it's "not for use below the waterline." I generally think they are just saying that to cover their butts because lawsuits, but I'm also a little cynical when it comes to that stuff. So after you built this boat using Titebond as your proofing medium, have you had any issues with it? And how many coats of the stuff did you put on? A gallon jug of it is enough for 2 or 3 coats on the kayak I've designed. Would you think that's enough?

dvanny (author)dvanny2017-02-18

By issues with the glue I mean has the stuff started degrading and coming apart. I know waterproofing isn't a huge deal on this boat since the thing can't really sink no matter how hard you try.

rowerwet (author)dvanny2017-02-21

Actually I use the Titebond 2 and I really only use it to attach the fabric to the foam.
I then fill the fabric with exterior house paint.
I did just read on duckworks magazine about a SOF kayak that used titebond II to waterproof the fabric.
You might want to look into the wooden canoe forum, and read up on using shellac to waterproof and protect the canvas.
That was wat the old maine builders and guides considered the best protection for their canvas skinned boats.
They claimed that the canvas just slid off of rocks and showed no damage.

dvanny (author)rowerwet2017-02-21

Thanks for the info! I've been having such a difficult time finding what is a good substance to use for proofing the skin. There are, of course, the special purpose-built 2-part epoxies and urethanes that I would use if I had the money. But then a lot of people use standard exterior spar urethane on their nylon skins, and I have yet to find the regular stuff (not marine-grade $90/gal urethane) that is labeled as "usable below the waterline." I've never used shellac in woodworking stuff, so I'm really not sure how it behaves, but I'll read up on it and look into that forum and hopefully I'll come to a conclusion on the matter

rowerwet (author)dvanny2017-02-22 this thread gives the best details I've found

rowerwet (author)dvanny2017-02-22

Another SOF builder mentioned using PLpremium construction adhesive as the waterproofing, i don't know how that works in the long term, as from what I hear, it tends to continue to harden, and eventually becomes brittle

About This Instructable




Bio: airplane nut since forever, rower since high school, airplane mechanic since '94, lay pastor, father of four
More by rowerwet:Mercury foam teardrop, how to build a foam teardrop trailer. rot proof, well insulated and super lightweightQuiver Paddle bag, keeping a bundle of paddles safe and organizedSeafoam Kayak, the Unsinkable Foam Kayak Anyone Can Build, 16 Pounds and Eight Feet of Fun
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