Solid 8’4" balsa mini-mal
epoxy -vs-poly.
Any thoughts out there by the epoxy masters?
Thanks in advance
Drew
Epoxy: handles residual moisture and off-gassing from the wood very well, and makes an excellent bond with the wood.
Poly: UV resin will handle the moisture very well, and makes a fair bond with the wood.
Both will yield great results if you have good quality balsa. Good Luck!
I am no expert but I would search for polishing epoxy. I have seen threads that people do not get the same polishing finish as polyester. So it might be a question of what finish you want for your board.
Epoxy polishes fine if you use Additive F in the gloss. Without Add F it’s challenging. And epoxy is widely known to be the best resin for use with wood.
Greg,
Having never glassed a balsa before I did some initial searching and discovered that you need to seal the board with a coat or two of lam resin before glassing.
Would this be necessary with your epoxy?
And as far as hot coat and gloss I, probably jsut stick with polyester…I think that you can put that over epoxy no problem right?
thanks all for your input
Drew
use whichever one you’re most comfortable with, both should work but you don’t want to screw up a balsa board, too expensive!
I’d glass and hot coat with epoxy and gloss with poly if your more comfortable in finshing with poly. Generally you don’t have to seal with epoxy although if there are knots or gaps, these need to be filled first.
Drew,
look for a June 30, 2004 thread entitled “polyester or epoxy for balsa”. You may find the answers you’re looking for.
Drew. This morning I glassed the the bottom of my 10’ balsa. Sitting here waiting to cut the laps.
I’m using Vinylester resin. Far better than poly, but not as good as epoxy. Some manufactures call it epoxy vinylester. You need to use a slow reaction MEKP. It gasses a bit with regular catalyst. Other than that it is just like using poly.Totally compatable with poly. I’m going to hotcoat and gloss with poly. It is not clear. It has a brownish tint. But over balsa it is barely noticable. I did a sealer coat last night.platty.
The main reason you need to put a sealing coat on before glassing, whether epoxy or polyester, is that if you apply the glass without this sealing layer, the resin will soak into the wood and may ‘starve’ the fiberglass of adequate resin. There won’t be enough resin in the glass layer, you will have to apply another coat, the glass job probably won’t be as strong and the board will be that much heavier!
On the other hand, with a sealing layer, you control for this problem as well as outgassing, which is almost inevitable with balsa. Even if you stand guard while the resin cures you will end up with a few bubbles here and there in the sealing layer but the fix is quite simple. Let it cure and then sand them out. Now when you laminate with glass the only bubbles you have to worry about are those you might accidentally stir into the resin and/or trap under the glass. If the board outgasses under the glass job it will not be a pretty picture!
Another advantage of applying a sealing layer is that balsa ‘case hardens’, especially if it sits around a while exposed to the atmosphere. The outer layer gets kinda dry, pithy, and funky and easily peals away from the underlying wood layer. A sealing coat prevents this from happening and makes for a stronger, better bond between the glass and the wood.
Once a good sealing coat has benn applied, if for some reason you can’t finish glassing it right away, the board can sit around for a while and the wood will not case harden. When you finally get back to it just sand it down and the glass will bond just fine to the sealing layer.