Epoxy coating

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I've built a few boats from plywood stitch and glue.

I used epoxy for the  connections but did not coat the plywood surfaces with epoxy and glass because of the increase in weight.  I painted and clear finished the plywood.  I have owned and used the boats for many years and I've not once regretted leaving out the epoxy coating.The hulls get the odd dent and scratch but are easily fixed with filler and paint at the end of the year.  The boats seem to be strong enough without epoxy and glass coating

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I've built several small plywood stitch and glue boats during the last 12 years.

I've never coated the plywood with epoxy and glass because it makes the boat much heavier.  I use paint and varnish. I use the boats on lakes and they frequently contact sharp rocks.  I have not encountered a situation  where I regretted not having the extra strength.  The boats are strong enough without coating and the inevitable dents and scratches are easily repaired. They're also cheaper and quicker to build

Why do  designers specify epoxy and glass coating?

 

 

 

 

                         and much easier to carry.

 

 

2

Daffyd,

If the boat is designed to take advantage of composite construction, it will end up stronger & lighter than an unglassed boat. This is because true composite construction is stiffer and allows the use of thinner wood.

For example, I have a 14 ft pirogue made from 1/4" wood with glass only on the bottom. It weighs more than my WD12, in spite if the fact that the Wood Duck is fully decked and the pirogue is completely undecked. The WD12 is also less flexible than the pirogue, even though the hull and deck are substantially thinner than the pirogue's hull.

So in this case the glassed boat is lighter and stronger than the unglassed one made with heavier wood.

Now if you just cover a plywood on frame boat with glass, it will get heavier with little increase in strength.

Hope this helps,

Laszlo