Stupid question...

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#1

Anyone here ever try a polyester gel coat with an epoxy infusion? How were the results? Did you use a production gel coat or a waxed version? Any problems with it adhering?

I ask because I have been asked by a client to produce a mould with a high polished gel coat. Since we deal in epoxy and my choice being Endura or DT I thought I would run a test.

We did both a non wax and waxed polyester gel coat, sprayed to 18 thickness on a ES gauge, on the waxed poly we sanded it with 80 grit after cure. Wiped it out and proceeded to the lay-up. The non-wax version was straight to lay-up.

I won’t know much till tomorrow when we can demould but I thought of asking here since someone may have already tried it. I can’t stand anticipation so curiosity got the best of me…

#2

Tried it, did not work for me. At least not without surface prep.

I do have a customer who rolls polyester gelcoat in a mould, let it cure thoroughly, then sand it by hand, as not to pull it from the mould, then infuse epoxy behind. This seems to work.

We did a lot of testing, in order to produce a mould for a 42 ft boat, and this was the outcome:

-polyester gelcoat (or in the case of the mould, VE tooling gelcoat)
-vinylester + csm
-peelply
After a couple of days, remove the peelply. (carefully, you do not want to prerelease the gelcoat). Now infuse epoxy behind.

We also tested:
-no prep
-sanding
-sprinkle sand
-sprinkle glass fibers
but all failed in some more destructive testing. The only survivor was peelply. (we ran chisels into the bondline between VE and epoxy)

Oh, there also is epoxy compatible polyester gelcoat, but the use is somewhat limited. (not for moulds, not for humid environments)
And I believe Ferro makes (made) a very good ty-coat, which made it possible to use polyester gelcoat and epoxy laminate.

#3

I’ve used polyester gelcoats with a csm/vinylester skin on different boats. They seem so hold up well, but it was no infusion though, wet layup and bagging. 6-12 meter boats. It adds a lot of weight. Never used a coating for adhesion, but there are several.

#4

I plan to pull the part late this aft to check it out, see if it is do-able. The next option is to put a tie-coat between the polyester gel coat and epoxy. I normally would not bother attempting this but it is a good client and he is stuck on having a super duper glossy mould.

#5

You can have a super duper glossy mold with an epoxy surface coat. You start with super glossy plug and then use a gloss semi-permanent as the reslease. I always do it this way because I despise polishing molds. :smiley: