I have a ding to repair for a kid on his skimboard, but he doesn’t know if the board was made out of epoxy or polyester. I know Victoria makes boards out of both.
So, I don’t want to polyester over epoxy, because I’m 100% sure it doesn’t work that way, but what about the other way around?
If not are there any test you guys know to determin which resin it is made out of?
you’re correct, polyester will NOT bond to epoxy, but epoxy WILL bond to polyester.
I just poured a heavy layer of some “bartop” system three mirrorcoat 2-1 epoxy over the top of some wood boxes over the top of some “untouched” UV poly laminating resin that I used to “seal” the wood from outgassing into the bartop layer…
even though I didn’t physically touch the surface of the UV laminating resin the Epoxy did not stick in about 60% of the surface area… It just poured right off the flat surface leaving huge puddles of “uncovered” UV resin…
I now have a big mess to sand down smooth to get ride of the epoxy… but not have to wait for the epoxy to harden up enough not to gum up on my paper…
So there may be some prep requirements to think about…
I regret I didn’t use poly finishing resin with Kokua’s formula over the UV and used UV sanding resin instead of laminatng resin…
Soulstice, On the advice of some experienced guys here I did a polyester gloss coat over an epoxy hotcoat and it came out looking great, and seemed to bond just fine. I pre-sanded the hotcoat to 100 grit. Have you had another experience with it? Doug
This is what I’ve heard
One of the former pro glassers for Fiberglass Hawaii who my brother surfs with does it on all his boards and advised us to do the same…
Polyester finishing resin (kokua’s recipe) over an epoxy glassed and hotcoated board just sand up to 100-150 and wash multiple times with soap and water…
He said epoxy emits a gas that is a contaminate which is the cause for the pitting on all finish coats epoxy or poly…
Poly is easier to buff out and the end product looks more like a normal board…
Washing vigorously with soap and water then using clean cotton gloves reduces the pitting and pinholes…
Alot of pros wash their board like this before glossing to get the best results…
2 types of bonds: chemical and mechanical.
i’m of the understanding that epoxy will bond on a chemical level to polyester, but that poly will only bond mechanically to epoxy. that is to say that in sanding the epoxy hotcoat, and then painting on your poly gloss, the poly only grips because it’s able to grab onto the scratches you put in it when you sanded, whereas epoxy will have total adhesion. over time, poly over epoxy is more likely to chip and peel…especially with the different flex characteristics of the two resins.
the only experience i’ve ever had was on a board a friend of a friend did. used poly to glass on fins over epoxy. board is strapped on the roof as we’re cruisin’ across I-10 to jacksonville (probably goin’ about 75mph), and the fins fly right off the board. i’ll admit it…i laughed.
Neither will chemically bond to the other.
In either case, roughsand the surface, clean with an appropriate cleaning agent, and go for it.
Cleaning agent for using new epoxy is rubbing alcohol.
Cleaning agent for using new polyester is acetone.
I’ve used epoxy for fixing Pu/Pe dings with no problem, and vice versa (only for epoxy over Pu, of course).
Hi Dave -
Hope all is well in the new digs.
I read somewhere (airplane construction site?) that with epoxy you should wipe with solvent first to avoid digging any surface grunge into the sandpaper grooves.
The SFoam website also recommends doing in that order when sealing the EPS blanks with epoxy slurry.
Yeah, thanks. I hope I can pick up enough repair to get something going. Eitherway can’t hurt.
Thank all you guys for the info.
soulstice Merry Christmas from one S.Fla guy to another. Incomming high tide on those swell days has been tons of fun behind the Gulfstream Golf Club’s clubhouse. Delrey is a little bigger, but 5 guys vers 105…
Howzit Oneula, Was talking to one of my shapers last night about poly gloss over epoxy and he said that if he does any epoxies he wants me to do poly gloss on them. Might be a good thing to get into for me, so just how did the gloss work for the boxes.Aloha,Kokua
Aloha Kokua
Well first of all since I just spent the last 2+ hours grinding off the UV lam resin/Mirror coat epoxy or UPOL/Mirror coat epoxy from my Koa lammed boxes I’m a little prejudiced…
But by coating the boxes first with a good coat of UV sanding resin them sanding them down lightly to get a good clean flat surface I got some unrela results putting the FH finish resin with your styrene/SA formula…
All I had to do was light sand with my rotex starting with 320 then 400 them switch to a buffing pad with marine fiberglass restorer and wax them a light touch with the foam pad. The look is really nice. It’s a like glass gloss but with depth to it. The dark the wood the more depth you get…
Mirror coat is an excellent finish but it don’t settle perfectly smooth and it don’t sand at all so you can level things out…
I did the same to my new 9’2 balsa lam glassed and hot coated with epoxy them used the same poly finish coat… I didn’t get ot perfectly smooth but nothing a few scrapings with a cabinet scaper couldn’t take care of…
I’ll try and post a photo later…
Raw Material… $5.99 Balsa Box from Ben Franklin Crafts
Box after disassaembled, aromatic cedar wood vacuumed, UV coated, sanded, poly finish coating buffef and hardware re-attached
blakestah… i was wondering about that. everyone always spoke of the epoxy-to-polyester bond as if it were chemical, but if the base was fully-cured, that just didn’t sound right to me. i think, though, that epoxy makes a better mechanical bond to poly than poly to epoxy because of it’s flex characteristics…making it less likely to chip and peel.
I read alot of that about West Syestems epoxy for repairing polyester boats.
It isn’t a chemical bond, but a mech.bond after the resin dries. Went on to say that epoxy has a better mech.bond to polyester than polyester does to it’s self. It also went on to explain the propper prep for using jelcoat over epoxy.
Howzit oneula, That's some beautiful craftsmanship there and glad to hear the gloss worked for you. You now have an alternative product to carry you through the rough times of surfboard building. One thing I do is but small aloha shirts from Wal-Mart and resin them and put them in frames, They look pretty cool but instead of selling them I give them to frieds for presents.Aloha,Kokua
I hope so because I used UV on my little football patches covering the fin boxes over an epoxy board. No problems,yet.Mike
Howzit rooster, Probably one of the safest places to use poly over epoxy since that area won’t flex very much if at all. The flexing of the epoxy is the problem since the poly will pop off because the poly doesn’t flex as much as epoxy.Aloha,Kokua
That’s good to know, Kokua, because the patches are over futures boxes and the boxes hold big ol keel fins. My best fish, yet.Mike
Aloha Doug,
Have always used poly to get that gloss look on my balsa boards, but a while back we too tried epoxy sanded up to 80gt. under a polly gloss. Looks exactly the same as all poly. However, if it’s an everyday rider getting lots of flex, heat, and sun, I don’t know that I’d go that way. What say you?
Richard
Howzit rooster, Probably one of the safest places to use poly over epoxy since that area won’t flex very much if at all. The flexing of the epoxy is the problem since the poly will pop off because the poly doesn’t flex as much as epoxy.Aloha,Kokua
Is epoxy more flexible than ploy???
I always thought it was the other way!
Richard, I’m not sure what’s going to happen to the new board I just made. It has a polyester gloss over epoxy hotcoat, and so far everything looks ok. The board has been surfed in 2 ft. overhead surf, a few wipeouts as in Over the Falls. I haven’t seen any separation of the resins, so I’m hoping for the best.
I haven’t tried to polish out an RR epoxy gloss coat to see if it shines up as good as poly. Greg Loehr says it will, so I’ll try it in the future. This is all new territory for me, so I’m trying to absorb all the info I can. Thanks for your input. Doug