Intro: Build a Greenland Kayak Part 7
In this Instructable, part 7 of the Build a Greenland kayak series, you will be putting the skin on your Greenland kayak and attaching the coaming to the skin.
Step 1: Materials
Measure the length of your boat along the keel line and get that length plus one foot of fabric.
8 oz nylon is available from George Dyson (360) 734-9226.
#10 canvas I don't have a source for, but art supply stores seem to handle it. Check the internet for sources.
I have lately been using mostly 8 oz nylon fabric. It is strong, easy to work with and lasts a long time. I have used heavier nylon fabric, but it is too strong and if the boat is left in the sun, the skin shrinks and warps the frame. Before you buy skin, measure your boat. It will be longer than 16 feet with the stem and stern boards in place. Width of the fabric should be sufficient to circle the boat in the cockpit area. If you can only get fabric in 48 inch width, you might have to sew some patches in the cockpit area. Buy a foot more material than the length of your boat.
In the past, I have used cotton canvas. If you use it in salt water, it can last a decade, but in fresh water, canvas starts rotting out after a few years and you either have to keep busy patching or replacing the skin within 5 years.
Thread - I use a nylon thread because it will not tear while I am sewing. With cotton canvas, I have used a cotton polyester blend string.
Varnish or Paint - On cotton canvas, I used to use house paint. With nylon, I have been using exterior polyurethane varnish. The varnish makes the skin translucent and the yellowish color of the varnish also gives the skin a natural sealskin look. Be sure to get exterior varnish. Interior varnish lacks UV protection additives and if you leave your boat in the sun, the skin will start to degrade.
Step 2: Tools
2 straight sewing needles
1 curved sewing needle
Soldering or wood burning pencil with a sharp tip - If you use nylon or other synthetic fabric, use a hot soldering pencil to cut the material. Cutting with a scissors leave lots of frayed edges since the nylon threads are so slippery.
Scissors if you're using plant fiber skin
Step 3: Drape Your Fabric Over the Inverted Boat
If you are using nylon, all the skin work should be done in a cool environment out of the sun since heat shrinks nylon. The opposite is true if you are using cotton for your skin. That should be sewn on a warm dry day since cotton shrinks with moisture and cold.
Drape the fabric over the inverted boat. Center it left to right and front to back. You should have a little overhang on each end. If the fabric is just barely long enough, don't worry, it will stretch. If not, you can always patch some on the ends.
Step 4: Sew Around the Bow
Sew a few inches around the pointed bow using a straight needle. The idea is to make a small pocket that anchors the skin at the bow so you can pull from the stern of the boat to make the skin tight in the longitudinal direction.
Step 5: Stretch the Skin Lengthwise
Position yourself at the stern and see how far you can stretch the skin lengthwise. You will have to brace yourself against a deck beam to do this. You should be able to get at least 4 inches of stretch out of the fabric. Make a mark where the fabric intersects the stern at maximum stretch.
Step 6: Sew a Pocket at the Stern
Sew a little ways down at the stern maximum stretch position. You need just enough stitches to hook over the stern. Stretch the skin and hook the pocket of skin over the stern
Step 7: Pin the Skin Down the Keelson
Use some push pins to pin the fabric to the keelson. These pins will keep the skin centered when you stretch it around the hull.
Step 8: Lace Up the Deck
Flip the boat upright so you can work on the deck. Using some strong synthetic twine, lace back and forth across the deck to pull the sides of the fabric together. Start near the bow at a point where the deck is about 6 inches across and lace up to the cockpit. Use a straight sewing needle to catch about a quarter inch of fabric for each lacing back and forth. The lacing twine should be about 18 foot long. You want enough to zigzag from the bow all the way to the cockpit. When you have reached the cockpit, tie off the end of the line or clamp it to a deck beam. Starting at the bow, tighten up the line all the way to the cockpit. You can now permanently tie it off.
Repeat this process for the back half of the boat
Step 9: Trim Excess Fabric
With the boat rightside up, trim one side of the fabric right up to the centerline of the boat. Trim the other side of the fabric so it overlaps the first side by half an inch.
For now, the cockpit will be completely covered. We will trim it up when we're done sewing the center seams.
Step 10: Install the Bow and Stern Decklines
Install the bow and stern decklines before you sew up the seam in the center. Once it is sewed up, you will no longer be able to tie off the ends of the deckline on the inside of the gunwales. The decklines around the cockpit can wait until later since you can reach them from the cockpit. And varnishing the boat is easier if they aren't installed yet.
Step 11: Sew Up the Seam
Start at the stern and work toward the cockpit. The reason for starting at the stern is that your sewing will improve as you do it and it is better to have your best work on the front deck where you have to look at it all the time.
If you are right handed, overlap the left flap of fabric over the right hand flap. Right and left as you're facing the direction you are sewing in.
The stitch you will be using is a simple spiral like the spiral at the edge of a spiral notebook. Stick the needle in the right flap, come out at the left of the seam with the thread going under the center gap and come out on top on the left of the gap. This is easiest to do with a curved needle.
As you are sewing, try to grab enough fabric on each stitch from each side of the seam so that you are tightening up the fabric as you go. Excess fabric will roll over on itself to make a nice tight seam.
Sew from the stern up to about 3 inches into the cockpit. Tie off your thread.
Repeat the procedure for the front deck starting at the bow and sewing into the cockpit
Step 12: Trim Up the Cockpit Area
With the cockpit coaming set on deckbeams 6 and 7 and centered right and left, mark about 3 inches inside of the coaming. Trim off the fabric leaving a hole that is 3 inches less in radius than the coaming
Step 13: Sew the Coaming to the Skin
Clamp the coaming to the deckbeam in front and back of the cockpit if you can.
The best way to maintain equal tension on the skin as you are sewing is to work with two needles and start sewing in the front center of the coaming and working in both directions. Sew about 4 inches in one direction and then 4 inches with the other needle in the other direction. This way tensions will be balanced and you won't be pulling the coaming off center.
Starting on the inside of the coaming, sew through the underside of the skin flap, run the needle out the nearest hole in the coaming, run the thread through the next hole, into the top of the skin, back through the bottom of the skin and back into the next hole in the coaming. Repeat until you have gone halfwaw around the cockpit. As you are sewing, you will be pulling the flap of skin on the inside of the coaming up toward the coaming. As you are sewing you will be building up tension in the skin. To relieve some of the tension, cut slits in the skin flap up to within an inch of the coaming.
Keep sewing until you end up at the back center of the coaming with both threads.
Step 14: Trim Off Excess Skin
The flap of skin that was on the inside of the coaming is now pulled up against the inside middle of the coaming. Trim off excess on the top to within 1/2 inch of the stitches
Step 15: Sew Another Pass on the Cockpit Coaming
As you sewed around the cockpit on the first pass, the thread snaked back and forth between holes, covering the coaming alternately on the inside and on the outside.
Now sew another pass around the coaming, so that the thread will cover the gaps between the holes that weren't covered on the first pass.
As you sew, bend down the excess 1/2 inch of fabric and sew through it as you go in and out of the holes in the coaming.
As before, use two needles and work down both sides of the coaming.
When you reach the front center of the coaming, tie off the threads and trim them.
Step 16: Wet Down the Skin
If you are using nylon fabric for your skin, soak it down with water and let it dry. As it dries, it will tighten almost drum tight.
Step 17: Paint the Skin
Paint the skin using your favorite medium. I use exterior satin polyurethane varnish on nylon.
I generally find two coats to do the job. Sometimes a third coat is needed on the bottom of the boat to completely fill the weave and make the skin smooth. The first coat will soak up quite a bit more varnish than the second coat. Follow the manufacturer's suggestions on painting. For polyurethane, you want to apply subsequent coats a few hours after the previous coat so the subsequent coats will bond to the previous coats. If the previous coat is allowed to cure completely, you might want to sand before applying the next coat. Look out for drips.
Step 18: Install Deck Lines Around the Cockpit
Once the varnish is dry, install decklines on either side of the cockpit. You can reach through the cockpit to tie off lines. Toggles are pieces of wood or plastic with holes spaced 2-1/2 inches apart. As you slide them toward the gunwales, they tighten up the deck lines.
Step 19: Install Rub Strips at the Bow and Stern
Rub strips are a good idea to keep you from rubbing the paint or varnish off the bottom of the boat.
Use small dowels like bamboo barbecue skewer size or small brass screws to attach the rub strips. Pre-drill the holes. Put a dab of sealant between the rub strip and the keelson at each hole before attaching the rub strip. The sealant will prevent leakage.
Step 20: Congratulations, You're Done!
Step back and admire your boat from all angles.
If you've never paddled before, get some instruction on water safety.
Always wear a pfd (life vest)
Install floatation in the bow and stern of the boat.
Get a spray skirt for the boat to seal around the cockpit.
When paddling in cold water, wear a wet suit or a dry suit. Always dress for the temperature of the water, not the temperature of the air