Hi,
So I’m a Grad stedunt at the University of Florida in Aero engineering, and a few years ago I became greatly enamored of sailing. I became so interested in it that I decided to build a boat: I found free plans online for the all-plywood Minicup.
I started building my Minicup in the livingroom of my studio-apt at the beginning of last summer. By mid-summer it was epoxy time.
I chose US Composites epoxy because it was very inexpensive and had cheap shipping. Here’s my thoughts:
I’ve used both the thick and thin epoxies with medium hardeners. The thick is great as a wood glue. I used it greatly to glue stringers to the ply. I did many peel tests with ply pieces and also drilled through it a lot: it machines nicely. I took a cured billet and was able to machine it on a milling machine rather well also. It isn’t as stinky as many epoxies can be but doesn’t work too well with the mixing pumps. It’s thick and it takes a while for the pumps to recenter. I asked USC for a material data sheet and they sent me one. If anyone is interested I can post the data if it’s legal.
The thin epoxy: I love this stuff. Those pumps are great! It is very thin and wets out even thick laminates fairly quickly. I did most of my epoxy work w/ this stuff outside(during the summer) so I can tell you how it cures in high humidity and heat. Heat can set the medium speed stuff off very quickly. It gets 88+ most days here in the summer and that gives you about 15 minutes before a single 4 oz serving gels. However, the daily rains bring the temps down to about 75, and that gave me problems. First, at 75 deg it may be overnight before the thin becomes hard. However it has almost always cured within 2 days. The humidity causes an amine blush that can cause little dimples in the surface. Indoors this cures nicely but stinks to high heaven. Finally, do not get this epoxy wet anytime before a 90% cure. Some part of this epoxy must be water soluble because my deck got rained on after a coating. The epoxy never cured even after 4 days of hot sun. It had the consistency of gooey rubber, and I had to sand and scrape the whole thing off, a real pain.
After sunlight exposure this epoxy yellows considerably. However that doesn’t seem to affect it’s properties too much, at least in the short run. I left my rudder outside for over a year(pine ply coated with USC thin 3x) and it didn’t seem ill affected. I coated every single surface of my boat generously with USC thin, and then I applied all kinds of fiberglass. I have the idea my little minicup will now live till I’m an old man…
Anyway, I give it my recommendations,
Whenever I do work at school I alwaus plug USC products because of my positive experiences. My girlfriend uses USC thick in her lab to attach PVC to itself and other plastics because it doesn’t stink like pipe glue, cures over time, may be thickened, and overall is less expensive.
I’ve also purchased many of USC’s fabrics and urethanes and thickeners so ask me questions
