It will not stick. I’ve had good results with an acetone rinse of the wood surface, letting it dry, and then applying the ‘‘cheater coat’’ of lam resin, before continuing to glass the fin.
Don’t ever, ever use polyester resin on cedar… and if you are stupid enough to do so seal the wood with de waxed shellac!
Bill’s Acetone method works.
So does a lam resin batch thinned with Styrene.
Seal it first.
Then laminate.
Good luck.
Barry
okay so i lammed it and it looks good. (used epoxy) . should i wipe with alcohol or something in between this stage and adding the cloth/resi, so oils from my hands are washed off?
Once you paint on the resin onto the wood fin do you let that dry before you lay up the fin with the glass or do you just laminate once the fin is completely coated? Also if you are laminating the fin prior to glassing it onto the board do you have to hotcoat it and then sand it before tacking it onto the board?
I scrapped using any cedar in my wood fins, too problematic, but if you must, no one mentioned solar activated resin, a super thin coat, high amount of activator, let sit for a few minutes and get into the sun. Epoxy is excellent to seal with, but in the long run the poly will not stay stuck to it, I begged a glass shop in Sorento Valley to NOT put my mini Simmons fins on with poly over epoxy, they fell off once the boards got to Japan. Stay with one system of resin, but to save the head ache, avoid cedar, it contain antioxidents, what is catalytst ? an oxidizer, there is part of the problem right there
Interesting. So that’s why the UV polyester works, if you mix in enough powder?
Epoxy over polyester works though.
Polyester resin only bonds to on thing – itself.
IMHO it’s the worst choice for fin lay-ups incorporating wood.
Certainly some wood choices are better than others.
Mahogany is a fairly good choice and so are others including bamboo and paulownia.
Choose epoxy for glue and you’ve made the best first step possible.
Stay Stoked, Rich
I searched for this topic because I had a chat with a friend today, regarding cedar. He shaped a chambered cedar board about ten years ago just for the hell of it. Never glassed it, just left it hanging in his workshop. He now wants to glass it, stick some fins on it, and take it out for a few. He asked my advice and I said his best bet was an acetone wash before lamming with epoxy. Am I on the right track? Can anyone steer him in a better direction?
Sounds right on track to me.
I used to get really into the details. Glass towards the end of the day as the board cools to avoid the inevitable tiny bubbles (thanks Don Ho) that form as the air expands… A thin sealer (again, epoxy) prior to lam the day before for the same reason. If you (he) takes the time to do it right, you can get a virtually bubble-free glass job that will never delam.
For the gloss - Poly can give great visual results but even with careful prepping can have long-term bonding issues. I suppose I got lucky since I never really had a problem. A single board had that weird lifting effect around a rail ding where a small section of gloss had to be removed, edges feathered and redone.
You can get a nice gloss from thinned epoxy, or I’ve heard of great results from automotive type finishes. Haven’t done one in a while and am not really up to date on all the options.
My next personal balsa will probably just have a thinned epoxy gloss layed on carefully and done with it. Just clean up the tape line and surf.
avoid glassing the wood in very humid or rainy conditions,a coat of laminating resin applied to the wood and let cure before actual glassing procedure will prevent a lot of problems… I do this on boards with cedar stringer , tail blocks,also some foam sprays especially dark colours,seal first then glass.