polyester over epoxy can it be done

[dunkelly]

Ok so i keow when i filled the cracks with epoxy filler i shouldnt have ! but it was all i had available at the time - now i want to, finally, do the job and gel coat the repair properly . i know the polyster wont normally cure over epoxy so my question is , can i do anything other than dig it all out and start again , ie is there anything i can use as a barrier to allow the gel coat to set off allowing proper finishing . any ideas anyone ??

 

[Tradewinds]

See this link

Gelcoat can be successfully applied over Epoxy repairs - Cruisers & Sailing Forums

He recommends a tie coat of Awlgrip 545 primer.

I don't know if it works or not but it was in my bookmarks - the chap suggesting it is a 'marine professional'.

Javelin of this forum is the person you need to ask. I suspect the answer will be the one you don't want to hear.

HTH

 

[dunkelly]

thats what i thought but i live in hope .

 

[TernVI]

It's quite common to put polyester gelcoat over an epoxy repair.
I've had no trouble.
Let the epoxy cure.
Clean with solvent.
Abrade.
Apply gel coat and cover.

There are thousands of dinghies out there with polyester gelcoat and Epoxy structure. Most scratches etc are simply repaired with gel coat.

 

[dunkelly]

i am genuinely surprised , i always though it would not cure . i did epoxy the repair last year so hopefully it has hardened enough . that will be very good news . thanks

 

[dankilb]

Andy/BoatWorksToday on YouTube did a test and basically found it stuck fine with proper prep:

 

[DownWest]

Once they have gone off, it is a mechanical bond, so, as above, preparation of the surface.

 

[De.windhoos]

why not use epoxy gelcoat?

 

[dunkelly]

spent weeks colouring my new pot of white gel coat to match my 40 year old cockpit ........ took ages to get it right .

 

[William_H]

Epoxy when hard will be no different to polyester when hard. (and old) The gel coat or flow coat of polyester will as said only make a mechanical bond. Polyester as gel coat or flow coat are not very good adhesive to make the mechanical bond. Epoxy or polyurethane is better at mechanical bond. Having said that the gel coat will probably be fine at adhering just not the best. Far better to my mind is polyurethane (2 pack) paint. I wonder if DeWindhoos above is calling polyurethane "epoxy" paint. Epoxy paint is not to my knowledge used as it is susceptible to UV damage. ol'will

 

[DownWest]

Just remembered that they put a bit of wax in gelcoat that is to dry in air. When one coats a mould prior to laying up glass and resin, the gel mix is designed not to go off quickly, so the bond with the layup is good. Useing that mix of gel coat for repairs needs a bit of cling film cover to go off.

 

[dunkelly]

Thanks all for the advice . happy to go ahead with it .

 

[Praxinoscope]

'Topcoat' sometimes known as Flowcoat, is a gelcoat premixed with wax which means it cures in air unlike gelcoat.
It saves the uncertainty of how much wax to add to gelcoat to get it to cure.