Costs

I kept fairly good records for the sea kayaks. I estimate total cost of materials and supplies to be about $700 for each boat, plus various tools like the palm sander. It's interesting that Kevlar doesn't actually add much to the final cost of the boat: 3 or 4 oz. fiberglass is about $5-10 per yard, and 5 oz Kevlar is about $20-30 a yard (prices vary widely depending on where you get it), but you use less than 3 yards in covering the hull, and if you want to be clever you can probably use an offcut from the last 2 yards of the bow to cover the stern, but then you'd have to deal with a Kevlar seam. Either way the difference in price is only about $60.

Here in Northern California we have the luxury of some of the highest sales taxes to be found and some of the highest prices on stuff in general. 4mm Okoume marine ply is about $35 per sheet and things like cheap bristle brushes and disposable resin rollers really start to add up.

It might also be worth while to use the 1.8 oz. Kevlar covered with a 1.8 to 3 oz. fiberglass. This would give both strength and workability.

I used about 4 gallons of resin for the two Kayaks, which varied in price from about $32 per gallon for USCI to $77 per gallon for WEST. I also used Tap Plastics($63/gal.) and Raka ($46/gal.). I purchased mostly single-gallon quantities; the more you buy the more you save! The more fiberglassing you do, the less resin you will use because you will figure out new and creative ways to apply just the right amount, and you will measure just the right amount and not have to rush another batch or watch your excess as it melts through a plastic cup.

I can't say whether any of the different resins is stronger than the others. The strength properties the manufacturers quote (if you can dig them up) don't readily apply to the plastics when they're in a composite, although supposedly strength should be proportional. I will be doing some testing later on each of these different resins to see which one is the strongest for my application. Raka is probably the easiest to use and, along with USCI, dries somewhat flexible. USCI is the least viscous by far. Gougeon (WEST) have the best support system. They've built many boats with their own products and have inexpensive books on boatbuilding, laminating, and vacuum bagging.