This may be dumb, or spoken of before, and if there is a link in the archives please let me know so I don't waste your time. I'm thinking about glassing my next board in epoxy but I am confused about the hotcoat. Is it done in polyester resin or with epoxy? Fiberglass Supply's technical sheet states that their epoxy works well with polyester resin and I almost feel like they are hinting at a p.e. resin hotcoat and gloss. Am I reading to much into it? Also, does the length of setting time make it difficult to use epoxy? Paranoid... Pieri
Pieri, I am pretty sure that I have this right - hopefully a pro will chime in and elaborate: Some epoxy boards are sold with a polyester hotcoat, which I read is in efforts to reduce costs to the builder. If making your own epoxy board, I am not sure why you would want this combination. To me it would seem inferior and or complex to an epoxy/epoxy glassing. Herb bean
You can use polyester for hot coating but the board comes out stronger if you use epoxy. Many companies suggest using polyester for hot coats because they lack an effective surfacing agent that makes epoxy sand right. Also many systems are very slow to set. Resin Research does have surfacing agent, Additive F, and a faster hardener which hot coats and sands almost the same as poly.
OK the responses help, but a few more questions: 1)Would there be any difference in mixing the hotcoat of polyester for an epoxy lamination? That is are there any strange chemical properties that will react? 2)If you did not use Resin Research Epoxy, in your personal opinion would you still use an epoxy hotcoat (and at what sort of mix) or would you then resort back to polyester? Thanks Damon
Correct me if I'm wrong, but the hotcoat serves one main purpose, to seal off the weave from water and create a smooth surface. Ideally, you want to sand your hotcoat as close to the weave as possible, without hitting it. Strength comes from the resinated hotcoat and sandwich design. So if poly resin is cheaper and sands better, why not use it for hotcoat on epoxy boards? No covalent bond with epoxy to poly?
A poly hotcoat will work on an epoxy lam, BUT, I think, it's a mechanical bond. Have you ever seen an epoxy board that is chipping? I have and I think it's due to a poly hotcoat. I've heard this numerous times, epoxy bonds to everything, but NOT everything bonds to epoxy. If you're using EPS foam and getting little pinholes after laminating the board, email me and I'll give you a trick that I use. eval(unescape('%64%6f%63%75%6d%65%6e%74%2e%77%72%69%74%65%28%27%3c%61%20%68%72%65%66%3d%22%6d%61%69%6c%74%6f%3a%4a%65%66%72%6f%35%39%39%40%61%6f%6c%2e%63%6f%6d%22%3e%4a%65%66%72%6f%35%39%39%40%61%6f%6c%2e%63%6f%6d%3c%2f%61%3e%27%29%3b')) http://www.hdxsurfboards.com
Jeff is right. I would not attempt to hotcoat with poly over epoxy. You will not get a phyical bond and the mechanical bond is questonable. In some cases i've seen poly not even gell when applied to epoxy. I work in the composite boatbuilding industry,have done for over 20 years and we never lam poly over epoxy. Epoxy over poly is ok, but why would you bother.If you start with epoxy finish with epoxy.David.
In my opinion, the reasoning behind a polyester hotcoat over epoxy is an attempt to protect epoxy from UV and to get a glossier finish. Pierre
I've used a half dozen different epoxies on surfboards. Hysol, Saf-T-Poxy, West, SB-112 (System3), Resin Research, and some others. Long ago we had to use polyurethane as the "tie coat" to allow a bond between the Poly HC and the Epoxy Lam. In all cases but one it has been either a nightmare to sand OR a failure in the water. The one case that has been successful has been Resin Research; I am very impressed with the use of this stuff as a hotcoat mostly because of Additive F. This epoxy HC applies like poly, sands like butter and stays stuck to the Lam, unlike the Poly hotcoats "applied" to epoxy. This is just my own experience, your mileage may vary...
what form does the additive f come in? http://www.feraldave.com
liquid... looks/behaves like surfacing agent. Xylene and parafin wax plus some secret "solids". Makes all the difference in the epoxy's behavior and puts a smile on your face.
Pages