The (Ply)Wooden Boat, Part IV: She's Got To Float

With the keel finished, construction of the boat was done and it was time to waterproof. When Eric made his plywood boat on GardenFork.tv, he used liberal amounts of silicone caulking as waterproofing. As a professional roofer and waterproofer, this made me cringe. Contrary to popular marketing, silicone is not the be-all and end-all of caulking. When compared to commercially available urethane and moisture curing polyether sealants, silicone is crap for most applications. I used the best caulking I've ever used, M-1, between the plywood panels & the battens. Then I sealed all of the exterior joints and the screw heads with the new M-1 Marine.
A little M-1 sealant here, a little M-1 sealant there . . .

Chem Link was kind enough to send me some M-1 Marine to try out. It's designed for applications in consistently damp marine environments. It can even be used in underwater applications (post curing). In application, the M-1 marine was just as easy to tool as standard M-1. While I can't describe my boat as consistently damp, the M-1 marine did an excellent job of sealing the joints and screws.
M-1 Marine is very good sealant.
At this point, with the boat constructed and the joints sealed, many would have called it done, put on a decorative coat of paint if desired and set out to sea.

Alas, I am the few (not the many) and knowing what I do about waterproofing and having access to the waterproofing products that I do, I had to seal the boat more. Once the M-1 Marine was dry, I then coated the entire outside of the hull with BARR waterproofing, also by Chem Link.
The now empty original tube and new bucket filled with BARR.
BARR is a liquid waterproofing. It comes it what look like giant toothpaste tubes. To apply it, I squeezed the tubes out into a plastic cup and used a cheap, disposable paint brush. First I put a coat of BARR over the joints. Then I covered the entire exterior hull with BARR, right up to the underside of the batten.
The joints coated and beginning on the bow.
Once the boat was coated, I allowed the BARR to dry overnight before dropping it in the lake.
A close up of the stern and keel after being coated with BARR.
The finished boat, ready for the lake.
Coming up in Part V, we'll take here out on the open lake.

Dyami PlotkePlywood Boat, Plywood