as glassing fins with epoxy seems to go so cloudy through so many layers of cloth and a yellowy tint in the resin, is it possible to glass fins with polyester resin and then glass on to epoxy board? will it stick or fall off and sink to the bottom of the ocean. never to be seen again?
i often see cloudy rovings at the base of fins. should i just avoid them all together and use cloth? so many questions
Hey shifty,
Epoxy can be put on clear, it just requires different techniques. The single most effective thing you can do to improve the clarity of epoxy is add heat to thin it down. When epoxy is heated, it becomes less viscous, and bubbles that are worked in by brushes/squeegees/rollers rise and break much more easily.
There are 2 ways to do this: heat the epoxy, or heat the substrate (fin/board/whatever you are trying to glass). If you heat the epoxy, as soon as it touches the colder substrate, it gets thicker, and you only have a few moments to make sure everything is right. This is great for people who are fast hotcoaters, as the resin is very thin/runny while spreading it around, but at final walkout, it becomes thicker and is less likely to drip off the rails so much that the resin thickness at the rail is easy to sand through. You can then get any bubbles worked in from the walkout (no matter how slow you go, you’ll get some if the epoxy is thick) with a heat gun or by misting a solvent over the surface. I prefer the heat gun; I have never tried the solvent spray, although here is a link that shows it…
Here’s another:
http://s75.photobucket.com/albums/i293/ebayPCI/MAX CLR HP CARBON FIBER PANEL/?action=view¤t=MAXCLRHPCARBONFIBERCOATING_0001-3.flv
Just paste the entire second link into the address line of you browser, it will work.
The second way is to heat the substrate. This means that the warm substrate will heat & thin the epoxy as the epoxy touches it. This would be a technique better suited for something like a lamination, where you would want some time to work with the thinned resin, letting it soak in everywhere it needs to (as well as getting excess off) without generating as many bubbles. Again, any leftover bubbles you can get rid of with the heat gun or spray, if they aren’t too deep in the fiberglass…
Needless to say, you may need to use a slower hardener working with all of this heat. You can also thin epoxy with solvent, but then you affect it’s physical properties; it won’t be as strong. Here’s a white paper written on the subject:
http://www.westsystem.com/ewmag/14/ThinningEpoxy.html
Here’s a general manual on using epoxies:
http://www.westsystem.com/webpages/userinfo/manual/index.htm
And here’s how a boatbuilder uses epoxy to minimize the cloudiness:
http://www.epoxyworks.com/16/index16.html Click on “fiberglassing a wood strip hull”
Bottom line, epoxy can be made as clear as poly, but you have to prepare more in order to do so.
JSS
I can’t see this being a problem myself. Just so long as you’re aware of the fact that polyester eats polystyrene for breakfast then I’d say you’ll be fine.
cheers mate. i could not have asked for a more usefull and informative answer than the one you just gave.
ive been scared shitless to glass this board ive put so many hours into, but with the info ive been provided i feel a heaps more confident. first board gitters i guess…