I have a few balsa boards that are ready for glassing and I have never done it. I was told that they need to be sealed prior to laminating. What is the best way to do this? Lam resin or a poly sealer? Brushed or sprayed? Mahalo!
lam resin. search for the rest
noooooooooooooooooooooooooooooooooo NEVER put poly straight on balsa…epoxy onto balsa …either epoxy sealer sand then some poly or epoxy all the way through to gloss coat …epoxy all the way is best option …heat the board before you glass it to avoid blow outs… regards BERT
Hmm I’ve put lam resin cheater coat straight onto balsa w/ no problem, other than having to be careful laying down the glass cloth later because it doesn’t want to slide around much… What’s the theory that makes it bad, Bert? balsa master Jim Phillips, what’s your opinion on this?
poly delams off balsa real easy in comparison to epoxy…sure use poly …but for a truly superior finish and better quality epoxy has got it regards BERT
ps ive only made about 3000 balsa boards maybe i got it wrong??? regards BERT
No harm in asking for a second opinion, is there?
Polyester is known to have problems binding with wood… I’ve build only one balsa board and sealed it with a water based floor sealant prior to lam with polyester. I do have delam problems with that board. Balsa is porous and with changes in air temperature, the air inside the wood will expand and tend to create delams (even worse if the board is chambered or has a styrofoam core). Now, any boat builder will tell you to alway use epoxy on wood. I tried epoxy on styrofoam and had found out you really have to keep your board away from high temps as the resin seems to soften at lower temp than polyester (I’m talking about the kind of epoxy that doesn’t go through a baking curing process). Therefore, unless you never ever leave your board in the sun, I would use a polyester lam with a primer coat of polyester or even better G4 (a primer specifically for binding polyester with wood – although I don’t know if you find it elsewhere than in europe). That’s what I would do, but as I said i’m not very experienced. Pierre
If you plan on doing extra steps on a board, plan ahead. If laying down balsa on polyurethane foam, use polyester laminating for a cheater coat, put it on thin and not too fast a gel time, a sure fire way to get yellowing from over catylization on the foam. As Bert says, polyester ISN’T the best finish for wooden boards, but prior to the Silamar’s and other kinder and gentler resins, Dion and PPG resins stuck to wood boards like resin is supposed to. I certantly haven’t done 3000 balsa boards, but have more than a few under my belt and don’t seem to be having those delam by cheater coating them once if not twice before glassing
also the delaming isnt the biggest issue in my opinion either what is ,is small cracks and dings …because poly fractures way easier you get grey stains anywhere where it seeps in ,where as epoxy is way more flexible and doesnt crack and shatter as easily so your board still looks goood for years even if your a little rough …you have to bend epoxy to extreme places before it cracks …the board will keep its value better… regards BERT