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The Jupiter Point series of kayak designs are intended as easy-to-build, fun-to-paddle, versatile collection of kayaks. With a simple 3-panel hull and unique 3-panel deck, the boats are quick to assemble, have a lot of character and perform very well. Plans are currently available for Ganymede a 13' recreational kayak that uses 3 sheets of plywood. You can download free plans from my website: http://bit.ly/xde8Bz. I've also drawn it up as a 7' childs boat I call "Io" that can be made out of a single sheet of plywood. The free plans for this are also available. Chesapeake Light Craft makes high quality boat kits they offer a complete kit for Ganymede if you don't want to scrounge materials on your own. I have blog post on Makezine.com that discusses the Io design specifically.
The construction is done with a technique called “stitch-and-glue” and is built from thin plywood. The stitch-and-glue (S&G) method use plywood panels cut to shape that are temporarily wired together with copper wire. This wire is the “stitches”. With the panels held in their intended shape with the wire the plywood is permanently glued together. The wires are removed and the whole thing is covered in a layer of fiberglass cloth and the cloth is saturated with epoxy resin to make it strong and waterproof.
The preferred material for this construction is 4 mm thick okoume marine plywood, covered with a 6-ounce per square yard fiberglass cloth coated with an epoxy resin. This will provide the strongest, longest lasting construction, but if you are strapped for cash, you can substitute lauan “door-skin” for the okoume and polyester resin for the epoxy. Lauan is apt to have gaps in the interior veneers that make the plywood. These gaps can weaken the material and may accumulate condensation leading to rot, but with a little care in building and storage when you are done lauan can make a nice boat. The description of techniques in these instructions assume epoxy resin, you may need to adjust your technique if you opt to use polyester.

Step 1: Prepare the Plywood Sheets

Plywood usually comes in 8 foot long sheets. Most of the Jupiter Point designs use panels that are longer than 8 feet. As a result, you will often need to make longer pieces of plywood. The standard way of doing this is by creating a “scarf” joint. All this means is the ends of two pieces of wood are shaped to a sharp knife-like angle, and two matching angles are over lapped and glued together. The glue used is the same epoxy you use to coat the fiberglass cloth with a little bit of powder used to thicken it up. Colloidal silica or cellulose are typical powders used, but bread flour works also.
First you need to form the scarf shape. Your plans will provide guidance on how to cut the plywood, you can just go ahead and scarf 2 full sheets, but these can be hard to handle. You may want to cut the plywood down into smaller sizes so it is easier to move around.
Stack the plywood with the edges you want to scarf aligned on one side. Plywood often has one “better” side. Flip over one of the pieces so on one the better side is up and on the other the better side is down. This way you can the better side up on both pieces when you glue up the scarf. It will help get the scarfs even if you have a piece of scrap plywood the same thickness on top and bottom. Stagger the edges back 1 inch each to make a shallow stair case. Clamp this down the edge of your workbench so the bottom layer hangs of the edge by a small amount.
One of the best tools for cutting the scarf is a sharp block plane, but you could do this with about as easily with a belt sander. If your plane has not been sharpened in the past 24 hours is probably needs to be touched up. If you have never sharpened it, you definitely need to give it a through sharpening.
Use the slope of the stair steps as a guide as you plane down the stairs. Cut into each step evenly, trying to keep the amount of material you have sliced off each layer even and consistent. The goal is to make a smooth, flat, wedge all the way from the top to the bottom. If you that the planed area on on one layer is getting wider than the other layers, adjust your planing to make them even again. As you plane deeper into the plywood you will start to see dark stripes and then the wood may change color a bit. The dark lines are the layers of glue between the plies of the plywood. Use these glue lines as guides to help assure a straight flat surface. Work to keep the glue lines straight and parallel. If you see part of the line curving up higher than on either side, plane down the sides to bring the rest of the line up even and straight.
You are done cutting the scarf when the side of the plywood has sharp edge and there is no step down from one layer of plywood to the next. Give the surface a quick sanding with 80 grit sandpaper to promote a good glue bond. Take one sheet of the plywood and flip around to the sharp edge is facing the other way and the bevel is facing down. Put a strip of wax paper under the joint. Mix up some epoxy and then add your powder to make a mayonnaise consistency glue. Spread this on the planed surface. Line up the joint so the two wedges overlap 1” such that the thickness is consistent throughout. Place a layer of wax paper on top of the joint and pile some weights to clamp the scarf tightly.
When the epoxy has cured, peel off the wax paper and scrape and sand off any rough spots. Don’t sand into the wood around the joint.

Drawing the Panels
If you down load the free plans you will need to graph out the dimensions at full size. These dimensions are sometimes called "offsets" This will take a large sheet of paper such as Rosin Paper you can get at hardware store or home center. Mark out the dimensions for each panel on the paper with little "x"s. Push some "T"-pins into the x and bend a narrow, flexible wood strips or fairly stiff wire around the pins to create a long smooth curve. Mark along this spline to draw the edge shape. You can fold the paper in half to cut out the symmetrical parts.

Layout the Panels
Cut out your paper patterns from the plans. Lay the patterns on the plywood as suggested by the plans. If you find a more efficient layout of the patterns, feel free to use it, but on the long panels you want the grain of the plywood running down the length of the long axis as much as possible. With the parts that require you cut two, such as the hull sides and front deck, lightly mark out the location with a pencil of both sides before doing any cutting. You want to make sure you arranged the parts correctly to get both pieces. Plywood generally has one better side, flip the pattern over when you layout the other side so you will have the better plywood side showing on both sides of the boat.
Once you have determined exactly where each part will come from, tape down the patterns so they don’t move. Make sure the paper is smooth and flat, without wrinkles or bumps or lifted areas.
Use an awl or sharpened nail to punch holes through the paper along the edges of each part into the plywood. Make the marks deep enough so you will be able to see them later. Make the marks as close together as necessary to assure you will be able to reproduce the curve accurately. This may be every 3 or 4 inches in straight areas, or ever 1/2 to 1 inch in places with tight curves. The patterns have little “+” marks with circles that indicate wire stitch holes. Use a 1/16” drill to drill out all these holes right at the crossing point of the lines.
Use a pencil and flexible strip of wood to connect the awl marks. Make a dark line that will be easy to see when it comes time to do the actual cutting.
Before you do the final cutting loosely cut out the parts where you will be making to matching pieces. Use a power jig saw to do the cutting. Install a new, fine tooth, smooth cutting blade in the tool. Cut outside the line but pretty close. Be aware of where you will be cutting the other side so you don’t cut into the area you will need for that other side. If you roughly cut out the marked piece first you can use it as a pattern to trace for the other side. With the two pieces cut out lay the marked on on top with the marking showing. Drill through the stitch holes of the first side into the other side. Push a small finish nail or brad through the holes as you drill them to keep the panels from shifting. Now, use your jig saw to cut out the final shape. Cut just on the outside of the leaving half the line. If you are uncomfortable cutting that close, leave more of the line and then come back with a block plane or sanding block to even out the edge and remove half the line.
Cut all the pieces in a similar manner. Work slowly and carefully. While the Jupiter Point boats are more tolerant of a little inaccuracy than other S&G designs, good, accurate cuts will make assembly easier and assure the finished boat is the desired shape.
<p>Shouldn't it be named a &quot;Plyak&quot;?</p>
<p>I just wrote an article for the Makezine.com blog that discusses the Io childs kayak specifically, it may offer some tips for anyone interested in that boat particularly. http://makezine.com/2016/02/26/building-child-sized-kayak-single-sheet-plywood/</p>
Brilliant! Thank you for sharing your expertise. Someone below was asking about the cost of this build. What do you think would be the feasibility of building this from coroplast? The glassing could conceivably be eliminated entirely.
could anybody if you can use polyurethane glue or any other glue in the step 4 (filling the plywood)? <br>thanks for the plans, the instructions (and the books)
Could you give an idea of what this would cost to build? I'm afraid the f/g would be too expensive for me. Thanks though,
Fiberglass runs from about $5 to $7 per yard. You need about 18 yards. If you keep your eye out on ebay you can find off cuts quite cheap.<br><br>Another option if you are willing to go with alternatives is: just about any cloth can be wet out with resin and bonded to wood to provide reinforcement. So old cotton sheets or muslin could conceivably be used. Historically boats have been covered with canvas to good effect.<br><br>If you are looking to go really alternative, consider using tri-wall cardboard instead of wood then reinforced with fiberglass or muslin. You would want to make sure that all the edges of the corrugation were well sealed. But if you are willing to think &quot;outside the box&quot; a bit, there are many alternatives.<br><br>Lastly, the epoxy resin could be substituted with polyester resin, or going further afield diluting a polyvinyl acetate glue such as titebond or titebond III could be create a workable alternative with a little experimentation.
Guillemot, <br> <br>thank you for this generous instructable! <br>The offsets are very clear and logical. <br> <br>Can you tell us what the beautiful red plywood was used on the child's kayak? <br>Or is it a red stain over a light-coloured ply? <br>I think it's just delicious! <br> <br>Shas
Congrats on being a finalist, and good luck!
I tried to download the .pdf file but it indicates it to be corrupted. <br>
I just tried downloading and it came through without any problem.
The plans at http://www.guillemot-kayaks.com/guillemot/files/Ganymede_Offsets.pdf are also showing corrupt for me.
I tried again by copying and pasting the above URL and it still worked, but I have opened the PDF in Acrobat Pro 10 and re-saved and uploaded the new file. Please let me know if there are still problems
Okay, it seems to work in Chrome. I was trying to download it and open it with Acrobat 9 and Foxit and it didn't work. Thank you. And sorry for the hassle
Awesome Instructable!<br>Is the 7' child's kayak plan also free on your website?<br>I could not locate it.<br>I've dreamed of building one of the Chesapeake Light Craft kits for years.<br>Your Instructable may be the inspiration I need to actually do it.
I just posted the <a href="http://www.guillemot-kayaks.com/guillemot/blog/admin/free_plans_kids_kayak" rel="nofollow">free plans for the kid's kayak</a>. I <a href="http://www.guillemot-kayaks.com/guillemot/kayak/jupiter_point_series/io_childs_kayak" rel="nofollow">call the design Io</a> after another moon of Jupiter. Chesapeake Light Craft has the files to cut an Io kit as well.
Hi and thanks fore this instructablues.<br> I am going to make the Io fore my yongest son.<br> How much fiberglas and epoxy you think I need fore Io?<br> <br> I have made 2 boats: Ponnt Bennet 17,5 fore&nbsp; and Chesapeake 14 fore my 11 year old son.<br> <br> Now this winter I am going to make the 14 Foot Great Auk (got the plans from CLC) fore my 8 year old son but after seeing this instructabule I am first going to make Io for my 5 year old son<br> <br> <strong>Bulding kayaks is realy fun...</strong> <strong>:)</strong>
Thanks!<br>Io makes sense now that you point it out (I thought it was Lo.) <br>Io and Ganymede are now bringing back memories of Astronomy 101.<br>
That is an awesome and well documented build! Great inspiration!
I think I can do this! Thanks! Can you tell me the load limit on one of these? I myself am 240 lbs. WOuld it hold me?
I designed Ganymede to hold up to about 300 lbs. It won't be the most spritely boat with that much weight, but it will float with some room to spare. If you are a really top-heavy body-builder type it might be a little unstable.
Nice job but I prefer to call the stuff &quot;ookie pucky&quot;. Dookie Schmutz would be a little thicker.
great boat and awesome instructable<br><br>Thanks
Brilliant instructable. It's a terrific primer and we've learned about &quot;dookie schmutz&quot;. Thanks a million.
Excellent job, I have studied your designs in the past, we're talking 20 years ago. For those who don't know, Guillemont is a bit of a celebrity in the wood kayak building world. It's an honor to see your work once again.
Lovely instructables, thanks a lot for sharing!<br>I will use some of your techniques for my next project :)
Amazing work!

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Bio: I've been designing and making my own kayaks for over 25 years
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