Plywood Boat Build

This is the story of how I built a small wooden boat.

[diagram showing rough dimensions]**

I have been wanting a one-person hard-shell kayak for a long time, but decided the perfectly suitable used examples I saw on Craigslist for less than a couple hundred bucks exceeded my arbitrary budget. I therefore decided it made sense to spend almost the same amount plus an embarrassingly large number of hours building my own out of mostly scrap plywood, because when you're building something whose sole function is to keep you floating and alive in potentially precarious situations, scrap plywood is the obvious choice.

Surprisingly, I used very little duct tape.

But first, be advised that I am neither an expert carpenter nor an experienced boat builder. This post and the corresponding video are posted for entertainment purposes only, and to fully document my foolish, wholly unwise and completely ridiculous efforts. Seriously, if you think it's a good idea to build a boat out of plywood you are probably wrong, but in any case you should obtain plans and instruction from a qualified boat builder and follow them to the letter. Also, when you are on the water be sure to wear a Personal Floatation Device.

The design is basically a flat-bottomed canoe squared-off in back.  However, I installed a seat and intend to paddle it like a kayak. I'm calling it a canuyak. [UPDATE: I recently learned that technically this is a skiff, although I'm still calling it a canuyak]

You might wonder why I didn't make it pointed at both ends. I decided that, in order to stay within my arbitrary budget and to simplify construction, the bottom of the boat would be no longer than eight feet (the length of a piece of plywood). Squaring off the back allowed the widest portion of the bottom to extend across a longer span of length, which I hoped would provide more stability in the water. Another reason for keeping it short was so that it could more easily fit in the back of my pickup truck. Also wood is heavy, so shorter means less wood and therefore less weight to lift onto a transport vehicle. The tradeoff, I suspect, is that the squared off back will create a bit more drag in the water. And while I'm not going to touch the subject of weight capacity, I'll note that I had zero chance of getting a football scholarship (i.e. I'm not a big guy).

My total cost for the project was around $125, but I had some of the materials on hand. If I had had to purchase all of the materials, here's the approximate cost:

• 1 4x8 sheet of 1/4 inch exterior grade plywood: $18 (outer skin of boat)
• 1 4x4 sheet of 1/4 inch exterior grade plywood: $12 (outer skin of boat)
• 1 sheet of 1/2 inch exterior grade or treated plywood: $35 (ribs, transom and maybe the seat)
• Wood glue: $5
• Screws & misc. hardware: $15
• Bondo: $13
• Caulk (exterior grade, paintable): $4
• 1 gallon of exterior grade latex semi-gloss paint, bright yellow: $24
• 1 quart of fiberglass resin:$15
• 3 sheets of 2'x4' fiberglass cloth: $21 (enough to cover the bottom and seams)
• 1 treated 2x4: $4 (for mounting the seat)
• 1 treated 1x4x10: $6 (I ripped off a couple of strips for the rails)

That adds up to $172. For the seat, I used one I had from a fishing boat, which otherwise would have added $30 or $40 to the cost. But it would also be possible to fashion a seat out of the 1/2 inch plywood, using excess pieces of the 2x4 and/or 1x4 as the frame. For the record, the finished product weighs about 58 pounds, which includes the seat but no additional gear.

Obviously, to have a fully functional boat it's also necessary to have a paddle, PFD, maybe 20 feet of line, and a few other odds and ends. But you would need all that even if you just bought a boat, so I didn't consider it in my costs.

Here is a description of my building process (again, not intended as a set of instructions):

Nose piece

1. Sketch out shape of bottom of boat on the 1/4 inch plywood.
2. Cut out bottom piece from the 1/4 inch plywood.
3. Cut out nose piece  (approximately 1" x 1.5" x 14" and angled at the bottom). I used a scrap piece of treated lumber.
4. Google "what's the technical name for the  nose piece of a homemade boat" so that you don't sound like an amateur when someone asks how you built your boat.
5. Attach nose piece to front tip of boat bottom with glue and screws.
6. Cut out pieces from the 1/4 inch plywood that are approximately 8' by 1'. These will form the side pieces of the hull. Cut front of side pieces at 45 degree angle. Cut so that exterior side of plywood will face toward the water.
7. Attach side pieces to nose piece with screws.
8. Cut first rib from 1/2 inch plywood. Screw and glue sides and bottom of boat to first rib.
9. Cut out second rib. Screw and glue sides and bottom to second rib.
10. Cut out third rib. Screw and glue sides and bottom to third rib.
11. Trim sides to be flush with third rib. Since the sides are curved, the length of the sides of the boat will be longer than 8 feet. Thus, I needed a second piece of 1/4 inch plywood on each side to extend all the way to the back/transom.This is why you would need the additional 4x4 piece of 1/4 inch plywood if you were foolish enough to actually try this process yourself.
12. Cut out a fourth rib identical to third and screw and glue it flush with third rib (this gave me the spot to attach the additional side pieces).
13. Cut the transom piece from 1/2 inch plywood.
14. Cut the bottom of the transom piece at an angle so that when it's attached to the bottom of the boat, it will angle out away from the boat.
15. Attach transom to bottom piece with glue and screws.
16. Cut another rib with same outer dimensions as transom. Glue and screw it to the inside of the transom (this provides a beefier attachment point to which the final side pieces are attached). 
17. Cut the additional side pieces (described in step 11) from the 4x4 piece of 1/4 inch plywood.
18. Attach the additional side pieces to complete the sides of the boat (glue and screw to the last rib and the transom).
19. Cut 4 small blocks from 1/2 inch plywood.
20. Install blocks midway between first and second rib and midway between second and third rib by gluing and screwing to bottom and side pieces. This helps pull all the hull pieces together and eliminates gaps.
21. Cut side rails by ripping a couple of 3/4 inch strips from the 1x4.
22. Attach side rails along outer top of hull with screws.
23. Sand everything thoroughly.
24. Apply caulk to all inside seams.
25. Apply bondo to cover screws and fill in gaps and holes.
26. Apply more bondo.
27. You cannot apply too much bondo.
28. Sand everything thoroughly.
29. Cover bottom and seams with fiberglass cloth and resin. In retrospect, it may have been better to use cloth on the seams only and use more coats of resin over the entire outer hull. I could have bought less cloth and a whole gallon of resin.
30. Sand everything thoroughly.
31. Paint.
32. Install seat.

Assuming it floats, I intend to use this boat solely in calm, flat, shallow waters. I also plan to store it out of the weather, in my garage. I don't believe it would hold up well stored out in the elements.

Maybe I'll see you on the water. I'll be the one waving my arms wildly yelling something semi-coherent about how scrap plywood sure is prone to leaks.

UPDATE: I added a skeg to help reduce side-to-side motion while paddling. See picture below, or here's a video.

**I left a key piece of information off the diagram, which is the vertical height from the floor to the top of the gunwales. That measurement is approximately 10 inches.