Polyester is cheaper but it is a greatly different proposition to using epoxy/ply.

Cost vs Strength

Polyester doesnt grip ply nearly as well, where as we know the epoxy bond is greater than the internal strength of the wood itself. Eventually polyester will let go and of course if not caught in time lots of damage ensues. And it can be hard to spot, for the damage is most likely within the plies and cant be seen from the outside because the paint system is preserving the hull.

Weight vs Strength

The other thing is pound for pound ultimately foam glass structures strength exceeds that of ply or ply glass, and as structures get larger this effect becomes more pronounced. So conversely while the larger boats seem to have the weight tolerance to enable ply they are strength deficient, whereas the lighter designs can afford weight less but strengths are closer to comparable.Therefore if there is a case for a epoxy/ply HP it is with the smaller designs.

Skin vs Weight

A less strong skin needs more framing to guarantee its form which adds to weight and cost. Unsupported distances between frames and intercostals translates better to smaller structures and therefore preferences smaller boats. Failing to attend to that eats into the load carrying budget.

So is there a case for Ply skins

So whats the case for ply? You dont have to make the materials to build the boat, you simply have to have the facility to scarf and bond sheets of ply together, mark and cut the skin. Hull sides might nearly mirror their opposite sides speeding things up.

You would skin it with glass if you wanted more durability, if the ply thickness you selected was light but not so strong, and if you wanted to fair the hulls with added peel ply afterwards. Otherwise resin coating could have been as simple as flow coat which will definitely add to the parts rigidity anyway.

It makes for a tight strong and fair structure resistant to weather during the remaining build process which will go on far longer than you might like.

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