Polyester or epoxy for balsa

I’ve only used epoxy to laminate onto Balsa. Do many people use polyester on balsa? If so does it stick well to the balsa? any delam problems?

I have glassed five balsa boards using polyester resin exclusively and never had any trouble. While five boards isn’t that much as far as statistics are concerned, I suppose that at least one of them would have gone wrong should any incompatibility between polyester and balsa exist…

Thanks Balsa, I’d like to try polyester but bit nervous about how quick the resin goes off/gels

Why don’t you try UV curing polyester? Won’t gel until you allow sunlight upon it. Which means you may spend as much time as you like getting your lamination near-perfect. (Perfection, as you probably know by now, is something to look for but out of reach, at least in this life…). Beginners swear by it! While I never used it myself, I think it might be worth it…


unless your never gonna use your board and its a show piece,yea you can use poly… but epoxy handles the knocks and bumps and your board will be in way better shape in years to come…

ive built my share of balsa boards …polyester doesnt cut it…



heres a pic of a few outlines i started today…

had an eager customer looking for a progress report …he can relax now ive finnally started them…

Bert, we all know that epoxy is way stronger than polyester. Sure, a balsa board will ding less if glassed with epoxy as compared to polyester. Same for a foam board. But unless I missed something, I think the question was about possible delamination using polyester on balsa. Which I never witnessed.

But then again, I agree with you about balsa pumping up water and subsequently rotting and epoxy is less likely to ding and let water in. Polyester is just cheaper and is quite “usable” on balsa. Or am I wrong?

balsa, I think you are right on this one. They have used polyester on balse for years. They also just varish the balsa. My balsa is glassed with 4 oz glass and polyester. Because the balsa is so strong it does not ding as easy. Remember glass as the day starts to cool. The balsa is on its way down, and the heat of the kicking resin will not swell the balsa as bad, and you will get a better bond.

Having been around the fishing a boating industry for years I can tell you for sure that if you’re looking for durability and maximum bond strength between resin and wood. Epoxy is the choice hands down. I have seen many wooden boats that were glassed over with a poly fiberglass skin. In every cast the skin with the seal of the death for the boat.

Surfboards may not be boats, but the mix is still the sea and wood and how to keep one away from the other. Paul Jensen does his hollow boards with epoxy. There’s a good reason that he’s made this choice for these boards that are of museum quality.

Good Surfin’, Rich

I believe there is some truth in each of these posts and replies. Epoxy is going to surely be more bullet proof, if that’s your primary objective. Poly isn’t as strong a bonding “glue” as epoxy. However, I like the polished look of a high gloss poly on my boards and have only used poly. Besides I’m an old fart retro purist (and I’m stickin with it). By the time you’ve invested the money, time, and effort in a shaped balsa board, I think the extra bucks for epoxy is a relatively minor reason for not going with it if you’re planning on surfin it tough or dodging rocks (which old fart retro guys don’t do).

The main problem to look out for is delamination, especially on redwood stringers. I’ve used burled redwood for nose and tail blocks and skegs which is very difficult to seal and keep from delaming. Also used solid redwood rails on two recent boards, one rail had to be sanded back down after first layer of glass was laid due to a delam.

Bottom line is you MUST coat the board with resin first to seal it before glassing. The glasser I use applies a slow mix resin covering the entire board. I’ve brush coated as many as four coats of sealer resin to some redwood. I keep applying resin sealer until all wood has a shine (no flat spots where resin soaked on inside the wood).

I really don’t think the time of day or temp is important. The resin always shoots off hotter than any ambient temp you’ll ever encounter so the temp outside has little or no affect on the temp of the balsa relative to the resin going off. Also don’t know that it all has much to do with balsa being “strong”, as glass over balsa or glass over foam, or glass over solid oak for that matter is going to crack if hit. It’s the glass rupturing not the material under it.

I do however pay attention to moisture. I would not immediately glass a board that had been stored in an open garage or storage unit during super rainy periods. I’d put it inside the shop for a few days or until the humidity drops back for a few days (I live in a super humid area blocks from the water). I’d listen closely to the guys that have been doing this for a while like Bert. Experience is everything. Professor J. Phillips is the go to man on this whole subject of ply resin on balsa because he has the experience. what say you Jim? Enjoy the ride!

MJ, have you considered using Vinylester resin. It is far superior to poly and on a par with epoxy. It is conpatible with poly so you can do the laminating with vinyl and hotcoat and gloss with surfboard resin.The only drawback for some would be the colour. But it would be bearly noticeable over balsa. I can see problems using UV resin as far as putting it in the sun. As soon as the balsa warms up it will start breathing and you may get air coming out of the balsa into the laminate.One or two sealer coats is must when laminating with vinyl or poly over balsa.Hope this is of some help.platty.

Thanks for the feed back. I had thought about using vinylester but found out that it wasn’t clear so I didn’t pursue it any more, I might buy some and do some exepriments.

As for air coming out of the balsa When I do a wet layup of epoxy with out sealing the balsa There are no bubbles in the laminate BUT… when the boards have been vacuum bagged there are heaps of air bubbles in the laminate even when the balsa has been sealed with epoxy before bagging just a few less bubbles.

bake it…work it hot…



Jack Reeves, regarded as the the North Shore Guru glasser of all time, only glasses wood boards on a falling temperature. He wants the blanks inhaling instead of heating up and exhaling.

yep thats the way to do it …baking it means its really inhaling as your glassing…

bubbles will be an impossibility,plus your wood resin bond cannot get any better…

and by using epoxy that bond will run even deeper…

hey jim excellent comment you made the other day about how to do wooden fins with the bead around the edge… i was thinking surley that same method would work if you did rovings around the outline in that slot…??



Bert I wanted to do rope, but knew I wouldn’t be able to see if there was air inside that I couldn’t see