Boatbuilding Tips and Tricks Blog Post

Monday, June 1, 2020

Finishing the Inside of Ply-on-Frame Boats

I'd like to spend some time and discuss how to finish the insides of boats, ones you built of plywood over framing and have covered the outside with epoxy and fiberglass cloth. In my Ply-on-Frame Construction manual I suggest that you coat the inside with epoxy resin. Well, since I live in a very arid environment, actually a desert, and use my boats in saltwater, this has been my preferred method. I suggest it not to seal water from entering the boat, but to strengthen the inside surface of the wood so that it is less apt to become damaged, in case you might drop something on it, to prevent scarring.

I would also not recommend fiberglassing the inside of the boat because, it will be extremely difficult to get over, under and around the internal framing. It will be a mess, even if you are a skilled fiberglasser, let alone a first timer. Glassing the Outside is easy since you can reach it and if you've prepared the surface adequately, it consists of smooth, broad surfaces. Dealing with all of the Inside, corners and small spaces is just the opposite.

Where you live, this is probably not a good idea though. You cannot seal the wood from water entry, all you do by sealing the inside is to prevent the water from escaping. Epoxying or glassing the inside will make sure that the water will always be wet with fresh water, not saltwater. And wood that is wet rots. It is called "dry rot" but it is not dry - it is really fresh water that starts rot, and no matter how many layers of epoxy you use to cover the inside it will not stop water from getting through.

The secret to these boats is giving the wood a change to dry out. This is especially true in the Eastern Half of the US, or anywhere tropical. You cannot allow rainwater to sit in the bilges, you must get it out, and just pumping it out won't get there unless you live in a desert. You should drain the water out of your boat after use with appropriate drain plugs, store your unused boat nose high so that any collected water can drain, and keep your boat covered or at least stored under a roof when kept out of the water.

I would also recommend using something like Thompson's water seal, or "boat soup" oil on the wood, and finish it with either a finish oil, like Tung Oil, or polyurethane varnish, if you want to maintain that woody appearance, or something like a Latex enamel primer and paint or epoxy paint, if not. This will allow moisture in the wood to get out, and through the paint or oil, when it is warm and dry. Storing under a roof (like in a garage) and uncovered is even preferred to under a roof and covered with a canvas top, again, unless you live in a low humidity environment like I do. If you live in a humid place, and store the hull outside and covered, uncovering the hull on warm sunny days and letting it air out is also a good idea.

Wood Boat Plans Inside

Wooden Boat Plans Inside

More information and free downloadable study prints for all of my boats may be found at: Wooden Boats You Can Build

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YouTube Channel: Easy To Build Boats YouTube Channel

Jeff Spira, Naval Architect, marine engineer and boat designer

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