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. 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…
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.
My, now favorite board, was glassed with RR. I had heard how it rubs out glossy, so I put it to the test. Now, I’m a clear, sand only type of guy, so my friends were surprised to see me show up with a “glossed” board. The RR works really well. http://www.hdxsurfboards.com
Is there a site for Resin Research? This is Greg L.'s company correct? Thanks for all the information.
Xylene and parafin wax plus some secret “solids”… Are you sure about that? Just a guess, but I would think that parafin might be a bummer when building up coats. Greg Loehr says to use it (Additive F) at every stage including lamination. Here is his post - Resin Research epoxies are available by calling 321-223-5276 or 321-779-2369. 1. Mix ratio must be adhered to. Deviation from the mix ratio will keep the resin from attaining a full cure. Also the material must be THOROUGHLY mixed. If not there can be soft spots. We use metered buckets (I’m sending you one which we get at the local hardware store) to assure proper mix. We use large paint stir sticks (like the ones hardware stores give you to stir paint). All our resins are 2 to 1 mix ratio by volume. The metered buckets work unreal, actually better than pumps and we laminate right out of those buckets. 2. Additive F. We use it in every batch we shoot, including laminates. It eliminates blush which is the biggest problem in building epoxy boards. It only takes 1cc per ounce of hardener in the mix. We put it in after pouring the resin and hardener into the bucket and then mix them all at once. It makes the resin a bit cloudy but clears out when the resin cures. 3. When laminating, the first thing to do is to pour all the resin out and spread it over the glass. You then wet the rails and tuck them. This gives the resin time to soak into the cloth on the flats. Polyester must be pushed through the cloth. Epoxy just soaks in and it does that in its own good time. It can’t and shouldn’t be forced. Additive F actually helps with this quite a bit. After it soaks in, squeegee out any air and remove any excess. We use plastic, “spreader,” type squeegees. We’ve found that they move epoxy better than rubber squeegees do. They take a couple boards to get wired but after the initial learning curve laminating is much easier. 4. We use VERY little resin. Below is an example of our use levels for different size boards. As there is no “gel” time, any resin left over can be used on the next board. If you run short you can easily mix up additional resin to finish with. Usually we just work out of one bucket and simply keep mixing more material as needed. It isn’t the same, “this bucket for this board,” as polyester. These are estimates for total mixed material. 6’ and under - 9 -12 oz. bottom 12-15oz. deck 7’ and under - 12 -15oz bottom 15-18 oz. deck 8’ and under - 18 - 21 oz bottom 21- 24 oz. deck 9’ and under - 24 - 27 oz bottom 27- 33 oz deck Hot coats run just a bit more than an ounce per foot. For instance a 6’ board would take about 7 oz. per side. Longboards, 9’, take about 12-15 oz. per side. If your glossing use a bit less than a hot coat. We use 3" disposable white bristle brushes for hot coating. We don’t clean them. We use them for one batch and pitch em. Not only do we feel that their not worth cleaning but we’ve also had problems in the past with contamination from cleaned brushes which manifested itself in bad hot coats. New brushes always make for clean hot coats. 5. Do not use acetone for clean up and never let contaminated acetone touch the skin. Any toxicity problems we’ve seen in the past always included contaminated acetone. Not only that but acetone doesn’t work that well with epoxy anyway. Leaves everything sticky. For your hands use disposable vinyl gloves. Clean gloves between boards with scrap fiberglass. I usually cut scrap and pile it neatly on the table so I have plenty ready. Clean your squeegee with scrap glass. Anytime the squeegee gets slick I just wipe it and my gloves down. When the gloves get funky, peel em off and put on a new pair. 10 cents a pair is cheaper than acetone. With so little resin being used very little goes anywhere except on the board so things tend to stay much cleaner. We don’t ever get more than a drop or two on us. If you do get some on you, use Go-Jo or Fast Orange or some other waterless cleaner with water to get it off. These clean epoxy more effectively and are much safer to use than acetone. I think that’s it. You shouldn’t have any problems but if you do my phone number is on the bottle. I also have a cell # 321-223-5276 which I usually have with me always.
I use Additive F in every batch to varying degrees and successive bonds are no problem in spite of having parafin present. Appears that the epoxy molecule seeks binding sites readily (and aggressively) rather than the catalysis of polysester (which does not penetrate the repulsing layer of floated wax of a previous HC batch).
I’ve been working with epoxy for quite a few years and every time I read something from Greg L. I learn something new. I’d like to try RR epoxy but we don’t have it here. Do any of you use a paint finish? I use epoxy primer and linear polyurethane top coat. ( I have have this done by a paint shop now - super toxic stuff) They don’t look like “regular” surfboards but I’ve found them to be very durable.
back to the original question. you can get a good bond with polyester to epoxy on the hot coat. unfortuneately, a sharp rap will pop the polyester away from the lamination causing chipping mentioned above. stay with epoxy, use additive f, it is especially helpful when applying sanding coats w/ epoxy. no fisheyes in the “hotcoat” sands like a dream. just keep your ratios right and you’re good to go.
Thanks again for all the information. I think I’ll be working with the Resin Research/Additive F epoxy in the future. Best site in the world. Damon
I would add something if I could. Thanks guys.
david platt made some valid comments about epoxy …so did a few others ,the best results ive had is epoxy all the way to sanding stage ,then after sanding ,polyester gloss coat, the polyester dries way harder and scratch resistent gives a way better shine ,because youve cut it right back to a real thin layer ,its very flexible and will bend with the epoxy ,im now using an automotive 2 pak instead of polyester and getting better results but it takes another day in the system, greg will your additive f work with any epoxy??? i really have to get some ,sounds to good to be true… if not im gonna have to get some rr down here … i got some basalt coming from the states so i will either contact you or get my supplier to chase it up… regards BERT