Builders' Forum Archives
Re: Fiberglass this Weeke
Posted by Robert N Pruden on Sep 23, 2004
All of the above comments are right on, especially the one about being careful to fill in "ALL" voids. It's well worth while to fill 'em before glassing.
If you end up with large air bubbles under the glass or along the joints, you can use a syringe with needle, poke the needle in one end of the bubble as an air escape, then inject epoxy into the other end. You will see the epoxy fill the void. This is readily visible because the white glass will disappear as it should. This type of corrective action is as good as doing it right the first time.
Make sure there is no dust on the boat before you start, you want the epoxy to soak as well as possible into the wood if you haven't done a seal coat first. Make sure all edges (chines and keel) are well rounded or you run the risk of elongated air spaces because the glass will have a tendency to lift off sharp edges. I've found that epoxy thickened with Cabisol (really thick, like thicker than peanut butter) is really good for filling voids that I have found immediately prior to glassing. The Cabisol thickened epoxy won't flow or run and you can glass over it and expect it to stay in place.
I always slather on tons of epoxy over the glass then use either a squeegee or brush to quickly spread it around. Bear in mind that I always use slow-curing epoxy. I try to spread the epoxy along the keel first, then stroke it down the sides being careful not to cause the glass to get creases.
One solution I have for getting glass to lay out on sharp curves around the bow and stern where it is prone to lifting is to go back and add the epoxy that has thickened a little in my mixing cup. The partially thickened epoxy (thick from beginning to set in the mixing cup) holds the glass down a little better.
I always do the fill coats as soon as the glued glass is tacky, for me that is usually after a 3-6 hour wait depending on ambient room temperatures. I apply the fill coats until the surface gets fairly smooth, usually two fill coats.
Once the epoxy has become smooth and non-tacky to the touch, I use 40 grit sandpaper to get rid of any really rough bumps, usually around the stern and bow. Once done, I can add more coats of epoxy to get the finish smoother (filling in teh weave).
Using this method of glassing and filling, I generally have to attend to the kayak for a 48-hr period. That means all I think about is kayak and gluing for two days. The nice thing about this level of dedication is that I won't have to worry about the formation of amines and the rough epoxy work is done very quickly. If you are using a non-blush epoxy, then you don't have to dedicate so much time with glassing and fill-coats in such a short period of time.
Once the major epoxy work is done, you can focus on the fine finishing to attain that ever-so-smooth finish that people ooh and ahh about, yeah, the one that you will see only before your first launch. ;)
I've worked with both blush and non-blush epoxies. Never had a problem with either using the method descibed above. I far prefer non-blush epoxy because if I get delayed between fill coats then I don't have to worry about washing the amines out before the next coat.
Keep your work smooth to reduce sanding later on. Make sure not to starve the glass of epoxy, don't be afraid to use enough to soak it good, enough epoxy is when it doesn't run and if it's going to run you'll see it run within a half-hour. You can still squeegee those runs even after and hour. Any roughnes caused by squeegeeing can be scraped off as soon as the glue stops being tacky. Use the squeegee to smooth out the excess epoxy after you get the glass on. Once the glass is on, go back after a few hours and scrape off any runs with a sharp scraper. The scraper can be a cabinet scraper (I have no experience with this) or a simple sharp plastering knife (that's what I use).
There's plenty of excellent advice at this site so read as much as you can, form a picture of what needs to be done in your mind until you know it inside and out, then get to work. Worry not, if you screw it up you can remove any errors, get more advice and still end up with a pretty boat.
Hope this helps!
Robert N Pruden
In Response to: Re: Fiberglass this Weeke by Homer on Sep 23, 2004