fiberglass resin and gelcoat (very long)

[Florin {VACATIONER}]

The real truth about fiberglass resin (Polyester), Kevlar cloth and gelcoats.

I am writing this in hope to help the next victim who may decide to go this way.

Don

[Frank Hagan]

What a nightmare! You definately have my sympathies ... I have learned "lessons" that way too, and while the knowledge isn't bad, it sure is bad learning it that way.

Can I use your post as part of our FAQ on Resins? I think it would make it a bit more permanent (or at least more accessible) for others.

[Florin {VACATIONER}]

Go right ahead Frank, that's why I posted it to begin with....

Hopefully it'll help someone out (or keep them from doing the same things) we've done.

I've just checked the status of the gelcoat. It seems like we may be able to do some sanding. I tried it last night on a spot where it was as hard as glass using open coat 120 grit. It still plugged it up quite quickly. If it goes at this rate I'll be going thru a lot of sandpaper. I'm not sure why it clogs up, the stuff comes out like powder, I'm not applying too much pressure and I'm not going too fast either.

I wonder if they make wet/dry paper in such coarse grit...

I was looking at some boat paint (Interlux) the other day... this stuff is prohibitively expensive here. They want 45 bucks for a liter. Can you guys recommend some good bottom and to paint that is a bit more reasonable in cost, for I think we may be going that route.

Thanks

Florin

[captjack]

Florin,

thanks for posting all your woes. I am starting to epoxie the hull of the Diane G now. Sorry to hear about the problems that you had ...but am glad to know this can be a problem.

hope all is well now.

[MikeStevenson]

Wow, it sounds like Florin had a tough time of it. I'm sorry no one asked these questions before. I thought we covered this in the plans and/or tape, but I'll have to check to make sure we did. Having grown up in SoCal, and been deep in the surfboard and boat building communities, the resin details have become second nature to us.

First off: There are very valid reasons why we specify "boat resin". This is the generic term for a pre-promoted, self-curing (waxed) resin. It doesn't need any help to work right, but you DO need to sand before applying a second coat to get a good bond (or at the very least wipe with MEK, Acetone, or better yet Styrene Monomer. That said, be careful of both the MEK and the Styrene Monomer; both are nasty and the Styrene can become unstable after a period of time (becoming like a low-grade nitroglycerine.) Can you begin to see why we tell people to use Boat Resin and just sand between coats? This is simple, safe, and works great.

The reason for the un-waxed stuff is to keep it from going off on the surface. This is allows subsequent layers of resin to form a good secondary bond without having to do any sanding or wiping with solvents/styrene. When the next later is applied, it kicks the first off as well and a new sticky surface is created. This first type of resin (unwaxed) is generally called Surfboard Laminating resin. Surfboards are made this way. It's a critical part of the process for them. The process is brought to a close by applying a layer of Surfacing Resin which does have wax. Then this is sanded smooth and Finishing Resin is applied to give the boards a super-glossy clear finish (this resin is buffed to get the polished look). Someone who's done a board in the last decade or so might be able to correct any of these steps, as it's been nearly twenty years since I last went through the process with anyone. It might have changed in the meantime, though the last time I went to a board supply place about a year ago it looked like the same stuff was still being carried.

Gel-Coat is really supposed to be used inside a well prepared mold. This is why you only see it on production fiberglass boats. It can be patched if damaged, but this is usually done with a sheet of Mylar or similar to form a smooth surface (like the inside of the mold). This is why we NEVER have mentioned gel-coat as a potential surface finish. This is also why so many good boat paints have been developed: To come up with an externally applied finish which looks like gel-coat and stands up well to weather. Buy the LPU boat finishes (which cost about $100 for the Weekender) and you'll end up with a great looking finish which will last a very long time.

Overall, the fiberglassing and finishing process should work OK if you stick to the boat stuff. This can be tough if you don't have a boat community around to draw from. Happily, one can get supplies by mail from West Marine. Also: West's full catalog is a huge source of information about all sorts of boating processes and equipment. If you don't have one, you should go to their site and get one.

Once again, our condolences to Florin for his agonising fiberglassing experience. I'm afraid even the most experienced can get caught in the soup though: A member of our extended family who is one of the most able plastics men anyone will find (the creator of the fiberglass tennis racket, designer of very high-tech cored composite boats from dinghys to 120', etc.) got sold a drum (yes, 55 Gal) of bad resin. It was old, which makes it go off too fast. He didn't check it and got way into a layup over a male mold. It started to go off way too soon and he had to pull all the glass off and trash everything! I can't remember what he did to save the mold; I think it had to have what resin was still stuck to it sanded off and the whole thing rechecked to get back to the shape he wanted. Bad. This does address the shelf-life question: about a year to a year-and-a-half is usually what we've seen over the decades. Old drums of resin will start to get "growths" in them as the plastic begins to polymerise/crystalise on its own. At this point most would toss the resin, but we've been known to use the stuff even after the point at which we have to strain out chunks (mostly because it was al the resin we had at the time...) It will work, but it's super-sensitive to catalyst at that point and I have no idea how strong it is. This is not recommended.

Mike