: Don't forget that more epoxy doesn't mean more strength. The strongest layup
: is when you have just enough epoxy in the weave to wet it out clear. The
: cloth should lie flat with the strands in contact with one another, hence
: the need to squeegee the heck out of it. Fill coats are used to simply
: fill the weave and, aside from minor scratch resistance, don't add any
: strength to the boat. 1.5 gallons is plenty for a 17' kayak glassed inside
: and out, that's the amount that Pygmy supplies with their kits.

Jim,

Good point, but we need to be careful here. For a given reinforcement, "more epoxy" really means "more weight". Obviously, you are familiar with plots of strength vs fiber volume fraction or weight fraction, that show a drop in strength with an increase in the matrix (epoxy) content. But keep in mind that those strength values really show us that the cross sectional area of a sample is increasing faster than the load carrying ability of the sample. If we were to make all our samples 2 cm wide strips from the same roll of cloth, having the same orientation, use different amounts of epoxy for each sample, then plot load to failure for each sample, the failure loads would show a small increase with increased epoxy content. But the failure stress values would drop because stress is load divided by cross sectional area, and the area (thickness) was increasing faster than the failure load. So when we use extra epoxy in our boats, we are really making them a little stronger, but a lot heavier.

Those strength/fiber fraction plots have important implications when doing calculations, and for demonstrating how to optimize strength to weight ratios.

Sam