The BO-AT Single Sheet Plywood Boat

Step 4 Sanding, Sealing & Painting

Once assembled, the next step is to sand the boat to a nice smooth finish.  We tried to round out all the edges somewhat to keep from scraping any body parts while on the water.

After we had a nicely sanded boat, we went a bit wild with the Silicone Sealant.  This is not a bad thing as this is basically what keeps the water outside your boat and you dry.  I gave the Silicone a good 24 hours to dry before I applied any paint.

After the Silicone has dried, you are ready to paint the boat.  I used a Valspar Latex Enamel paint.  We applied three coats to the outside surfaces of the boat (green in pictures) and two coats to the inside surfaces (tan in pictures).  between each coat I waited the recommended time for drying and sanded lightly.

Now that I have had it in the water, I will put another coat on at the water level for some added protection.

One thing to note is that paint does not adhere well to Silicone so where ever your sealant is, your paint will not look very good.  This is more cosmetic than a problem. 

Comments

[charlessenf-gm]

Prime (oil-based exterior primer) "finish cut" boards first. Then paint two coats of finish paint color. Then assemble and caulk with Silicone sealer or, better yet DuPont 5200 (comes in white only as far as I know). Sealer will adhere to paint, paint does not adhere readily to most silicone sealers.

Seal exterior of seams first and foremost - sealer is to keep water out. Sealing interior joints can't hurt, of course.

If you add sealer (esp DuPont 5200) to joints before assembling (use as a "glue" as well as a sealer, you will seal exterior and interior simultaneously.

[solarbipolar]

Those were very good suggestions except that there seems to be no such thing as Dupont 5200. If I do a search on it, all I come up with is stone counter sealers, which don't seem like the right kind needed here.

[ArtisanEclectic]

That's because 5200 is made by 3M. It's used a lot in the marine industry and can be used under the waterline. It's an extremely tenacious sealer/adhesive that should only be used on things that you would rather throw away that have to take apart.

[ArtisanEclectic]

It's also very expensive, About $20 a tube. PL Premium would be a better choice than even silcone. I saw Deek's video on building this boat and I wondered why he would use silicone. Then I remembered, He is a Tiny house builder.

Silicone is for doors and windows, Not boats. It's a sealer, not an adhesive.
Wooden Boat magazine used to sponsor an annual family boat building event where the contestants (A parent/ child team) had to take a bunch of precut pieces and build a boat then put it in the water and hopefully not sink.

They were not allowed any fasteners. Only PL Premium.

It's available at the Big Orange Place for less than 5 bucks a tube. But read the labels and test for your self since there are different formulations. I'm pretty sure this is the one I used to glue the skin to the frame of my Hollow Wooden Surfboard (Instructable coming soon.)

http://tinyurl.com/7rqgzbh

Ok. It's less than 6 bucks a tube.

[rwilliams22]

I had a buddy who built boats for a living. He made his hulls out of thin strips of wood, nailed and glued to the spars. After sanding, and before covering the boat with fiberglass, he would rub the entire hull down with a mixture of flour and sawdust, making sure to work it into any cracks or defects. He explained that if there was any moisture at all in the wood or leaking through the fiberglass coating, the bits of flour and sawdust would soak it up and swell to keep the boat from leaking. Not sure how much value that would add to a plywood joint, but it's worth considering

[PaleoDan]

I appreciate the idea - I will try that next time. Mine is still holding but this sounds a bit more stable

[hilojohn]

Hey guys, You can use sandable paintable silicone caulking or paintable bathroom caulking from the hardware store. It is a little more expensive but whats a dollar or two when making a masterpiece.

Good job on the boat.

[PaleoDan]

I will try that on the larger one. I was not sure if it had the same strength and flexability as the one I used.

Thanks

[hilojohn]

It does dry a little firmer, but I have used it to seal boat seams before and never had any trouble. The other thing to use and which will also seal the ends of the plywood boards is fiberglass resin, when mixed and applied it makes a flexible waterproof seal as long as you don't introduce any fibers or cloth.

[ac-dc]

Sandable caulking is not nearly as flexible. Paintable usually isn't either but I confess to not having tried every possible type.