Glassing a chambered balsa board; Going for an epoxy lamination as I don’t want to take any delam chances. I have already done epoxy lams and epoxy hot-coats on EPS boards but I can’t say that I like the stuff. Here’s my question for all you epoxy fans: is a PE hot-coat over epoxy lam a no-no? Since most of it is going to be sanded, I think that it should not pose any problem; In case any PE would go through the lam (which I strongly doubt) it would not affect the balsa core as it would on EPS. I don’t see the benefit of using expensive epoxy for a sanding coat, especially since epoxy doesn’t sand as easily as PE. Any thoughts on this?
PE and epoxy do not bond well together. I would just stick to epoxy HC unless you want pieces of PE hotcoat to flake off your board.
Balsa, I’ll have to respectfully disagree. The resin research epoxy I use sands just fine, isn’t expensive if you minimize waste, and is the perfect companion to an epoxy lam. I haven’t used poly resin for my last 25 boards, and havent missed it.
Have never used PE over an epoxy lamination coat.
Years ago, I some posts on a boat building/repair forum saying that PE over epoxy does not bond well. That was good enough for me.
There is a hot coat / gloss coat PE resin that some sways members use , cant think of the name of it right now perhaps someone will speak up , that looks good and shines up very nice , the only problem is if you get a ding the PE coat flakes away around the ding and you must repair with the same PE resin .
Balsa, the epoxy we have here sand just fine. I think resin research sands just as easy as poly resin. As for putting Poly over epoxy, … I wouldn’t do it. It’s only going to be as good as the mechanical bond, which means you have to scuff up the lam coat… Which means cosmetic no no. Either keep it all epoxy or all Poly.
If you mix a epoxy lam with a poly hot coat, it will last for a few months, but then it will peal and flake. Also. An epoxy lam on wood is going to be suspect cosmetically. When you pour the epoxy on the wood it will saturate differently than when you pour and pull. I don’t care how hard you,try it will always be cosmetically inferior to a poly wet out…the cosmetic inferior is when you look at the glassing on an angle, it makes a wonky halo effect with the cloth. So if you are looking for a beautiful clear board…best to do poly.
I do it on near all the boards i make for about 20 years. For sur it’s not the best strengh, but if you use a phénol free époxy, let it Fully cure, then sand/scuff it go. Better to use iso resin, and even better a réal poly “top coat” with same flexibility as epoxy.
The main problème is poly lam resin break at 1.5% while epoxy lam resin at 3% so on a ding you can have spider in poly coat but lam still good and if you well prép lam it don’t “flake of”.
A l’époque tout le monde faisait comme ça, Dabbadie, Roro, Panvern etc ont toujours fait comme ça. L’epoxy s est améliorée, plus facile à finir et moins chère, mais pour cette étape le poly est plus facile faut juste pas faire une strat papier à cigarette sur un support mou du genre les planches epoxy ultra light que tu vois fleurir dans les shops. Fais une strat un peu riche, laisse bien sécher au chaud, ponçage en surface gros grain, tu cherches pas à niveler mais à rayer toute la surface.
Guilhem,
We’ve done it a bunch with Jérôme over the years - on full balsas, hollows, compsands…
Just make sure that your lam and hotcoat are fully cured, I mean really and fully cured. Sand as usual, then hand sand lightly with a rougher grade like 120 to scratch the surface and help the bond. Clean it perfectly and gloss. The flex is minimal on a balsa, so you won’t have real flex incompatibility issues between the two resins. Ding repair has to be done gently, as stated above. This is only my experience, but the boards I was shaping in the around 2006/7/8 with that combo still look great.
That being said, a nice epoxy gloss can be easily laid down and sanded. I like the Enthropy resin for this (Atua Cores) with the “fastest” hardener (which is still a bit slow), mixed with about 5% alcohol. MIx it really well but slowly to avoid bubbles, and once it is really dry, it’ll sand and polish out beautifully though with a bit more elbow grease in the beginning as the surface is harder. Once the board is uniformly surfaced you run through the grits as usual. Result is temperature and humidity sensitive, like epoxy often seems to be.
You’ll hear lots of different views, many of the backed up with experience… in this case I would go with a poly gloss and experiment with the epoxy finshing when the weather improves.
Enjoy, amigo!
I’d go all poly on balsa. sometimes epoxy can get a bit of cloudiness in the overlapping parts of the lams no matter how careful you are which would be a shame on balsa. Poly won’t do that (at least, not at your skill level). For what it’s worth, I’ve made exactly one balsa. I was going through the same thought process as you, and decided to go all poly. Came out great and no bonding issues at all.
If you do go epoxy, I’d go all epoxy as mentioned by others. You can gloss with epoxy and get an acceptable shine. Or, you get a gloss using an automotive clear coat finish. They adhere really well to the epoxy and can be polished to a really nice shine.
Thanks guys for the answers! Let me explain: I have made maybe 8 or 10 balsa boards and all were glassed with polyester resin, never had any issue. Then two years ago I made a balsa gun for a friend, glassed with poly as usual and then, about one year later, the guy brought bthe board back (never surfed) with a bad delam UNDER the nose. he swore that the board had never been left in the sun or in a car and, since he’s a friend, i said I would re-glass it with epoxy to avoid any new delam. Then I got this order for a balsa longboard and, since I didn’t want to take any chances with possible delams, I thought I would glass with epoxy, too. Now, reading your experiences, I wonder if I am not going back to good old poly after all…
Some Wood don’t “work” with poly or need to use a primer before. You can use pu primer, the famous g4 from soloplast, or epoxy primer like the 1040 from resoltech a waterbased epoxy primer. But again poly finish on epoxy go well and is simple, let dry, sand/scuff/scratch, call it like you want et voilà.
Keep in mind that the G4 will considerably darken the balsa - to more of a honey color.
I’ve had good luck with poly overall, but will say that nothing adheres to wood like epoxy and if the board is meant to be ridden… I would still do an epoxy lam and hotcoat. The enthropy resin works reall well in terms of clarity and has acceptable drying times.
No worries with a polyester gloss in my opinion. The end user will still need to be somewhat careful about temperatures, but nothing like with a hollow or with a pre-made blank.
SystemThree SB-112 resin is designed to be a tie coat, allowing polyester resin to bond well to epoxy. I use it, not for this purpose but because it is UV resistant as well as extremely resistant to fisheyes. It is not cheap.
I’d not fill a epoxy lam’s weave with poly, I’d fillcoat it with epoxy while still fully uncured, then sand that to 120 then gloss coat with poly, If I was looking for the super glossy showroom finish.
My latest cedar board I did things differently on the glass job. Instead of first sealing the cedar with epoxy, then laminating, I lammed 1.43oz to bare wood, but used System3 clear coat epoxy, which is super slow and Super thin, in warm but dropping temperatures. It wets out cloth instantly and penetrates deeply into the wood below too.
I also did my first cut laps, but the tape was just past the rail apex rather than wrapping onto the hull/deck as one would do with foam, I assume.
1.43oz requires only a very thin fill coat, I used SB-112, I wetsanded this to 1500. Then since I pretty much have given up on an epoxy super glossy perfect finish as a dust free work area is impossible for me, I mix up a small batch of epoxy(SB-112) about 7.5ML, and using a clean car wash sponge cut into a smaller pieces, I can smear this 7.5ml across the 6’11"x22, and it dries super glossy, but is not a perfect mirror finish like one can get with poly gloss resin.
I’ve done the wetsand to 1500 then buffed epoxy, with excellent results, only to have the epoxy react with something in the final meguires mirror coat car wax polish. At first it was as good looking as any Poly gloss coat, but It turned all cloudy over a period of 2 weeks and I resanded it and did the “smear coat”.
Perhaps if I buffed it two weeks after sanding to 1500 it would not have reacted with something in the buffing/wax compounds. I know not.
I’ve had no issues with this ‘smear coat’ flaking off the epoxy that was wetsanded to 1500.
I really prefer to use all one product rather than using a varnish or spray on clear coat, as dings are inevitable and the edges of those dings always seem to be visible when such products are used, and I make my boards for myself.
That settles it. Epoxy lam and HC, poly gloss. And prayers, lots of…
I’ve done plenty of poly gloss over epoxy hot coat. Just make sure it’s cured, clean, freshly sanded to 80 grit. No worries.
Which is a stronger bond, epoxy to balsa, or poly to epoxy?
You could seal the balsa with epoxy, then glass with poly.
I definitely would not hot coat with poly over epoxy. Little impacts chip it off.
The first foam boards I ever saw, circa `1958, were made by Hobie. The foam was Styrofoam, which was coated with epoxy resin and sanded, prior to glassing with polyester resin in the then ‘‘normal’’ way. I saw several shaped blanks that one of the ‘‘regulars’’ at WindanSea, had obtained, so that he could do the glassing himself. By the following year, both Walker and Clark were producing PU Foam, that was compatible with polyester resin.
Again, I have never tried it.
According to that same boat forum, you can use epoxy over PE but not PE over epoxy.
Supposedly, compounds found in the surface of the epoxy resin affect PE bonding over it.
Milage may vary, but the only real delam issue that I have ever had on a balsa was using epoxy to laminate over a poly cheater coat. My suspicion has always been that the cheater wasn’t fully cured before the board was lammed - otherwise there is no good way to explain it. Since then (I had to strip the board down to the wood, clean up the shape, and reglass) I have only gone epoxy filler/epoxy lam/epoxy hotcoat. Glossing either way works for me.
I while back I was working on a boat and we were using both polyester and Epoxy on some different parts.
I had a drip of PE resin drop onto Epoxy that had cured. I noticed it only after the tools were clean as well as my hands. I decided to let it be an adhesion test and let it cure overnight, and see how hard it was to pry off the weave of the epoxy lam.
When i returned the next morning the PE resin drip had not even tried to cure on top of the epoxy and I wiped it up with a paper towell, while the PE resin that had not touched epoxy was ready for sanding. This was DMC epoxy and Silmar PE resin, and this little experiment saved many headaches that would have arisen, had it not been realized PE resin would not cure atop this specific epoxy.
I regularly repair my older PU/PE surfboard with epoxy, and have sometimes been disappointed in the mechanical tooth bond, but I had used worn sand paper merely to remove the shine. Good enough to remove the shine but likely the valleys and mountain peaks were flat topped and bottomed instead of sharp.
Now, for maximum mechanical tooth, I use only sharp new paper scraps/ offcuts, 80 to 120 grit, pulled in one direction, in a cross hatch pattern, mindful of keeping sharp mountain peaks and valley floors. Also I insure the older well cured PE resin is devoid of any contaminates before sandpaper touches it, usually with DNA and green scrubbie, then paper towell, as I rarely keep acetone around.
No issues with epoxy bondng to ancient PE resin with this technique, but simply skuffing shiny PE resin to dull with dull paper, has left the bond lacking 1 too many times, and fixing this is more than 2x the work compared to having done it right in the first place with new sharp paper.
While i do not use PE resin anymore, I will insure mechanical tooth with epoxy to epoxy, is contaminate free before sanding begins, using only sharp new sandpaper under a finger or two, and once that area of paper is somewhat dull( it sounds and feels different) , I move my fingers on the paper to fresh sharp paper. Time consuming, and uses more sandpaper, but the paper is still more than adequate for tasks that do not require maximum mechanical tooth.
If I were doing Poly gloss over epoxy I’d test to see if the PE gloss would even cure properly on the specific epoxy used, and then use a lot of paper and time digging deep sharp valleys leaving sharp peaks with fresh sharp paper in a cross harch pattern, pulling the paper under a finger or two.
Perhaps not necessary to go this far, but why use half one’s ass when the other butt cheek is right there, and failure would be more than twice as much time and material cost consumed.