Polyester or Epoxy onto exposed fibres

[Major Tom]

Slightly over optimistic berthing using the tender outboard when the inboard failed, resulting in a small area of exposed fibres on the bow of my 2018 Bavaria.
Have a pot of white polyester gelcoat repair, but concerned about it reaching the foam core. Would modern cores be immune to polyester? I could go out and buy Epoxy, but it would be much easier to use the polyester I have. Or seal the fibres with Epoxy, then the repair polyester on top?
Thoughts please?

 

[HughClayton]

It depends …. If it’s just a cosmetic scratch then a colour-matched polyester repair will restore the gel coat and stop moisture ingress. If the ding is deeper or the repair needs to provide structural strength then you’ll need to fill the hole with thickened epoxy and then, once it’s set, use polyester to build up the gel coat.

As long as you take the time and use good quality resins, wet and dry sandpaper, compounding polish and wax these type of repairs are often straightforward on the hard but can be tricky afloat.

Good luck fixing the ding

 

[Refueler]

Thin epoxy first ... then the polyester gel on top.

 

[Major Tom]

Thank you both. That sounds sensible. Never tried bonding polyester to epoxy, but nicely keyed, it should be fine. No exposed foam that I saw, probably several layers down. Not deep damage at all, but as the gelcoat is quite thick at the bow, a card sized slab cracked off the surface. Local professionals don't seem interested, so like all the other boat jobs these days, it looks like muggins will have to do it.

 

[Refueler]

If the damage is not deep .... then maybe you can use Gel alone.

If you do - then I suggest getting a bent nail and then using sharp end .. digging a little under the edges of good around ... so you create a lock to the new Gel you apply. Making sure that when you apply the Gel - that it gets into that area you've created.

 

[Yngmar]

The hull is made of polyester resin, so the foam core is definitely not having a problem with that

That said, if it's down to the fibres, I'd epoxy first, sand down to the thickness of the gelcoat, then fill with polyester gelcoat. It'll be easier work with the gelcoat and a better result.

 

[waynes world]

MMM i may be wrong ere but i am 100% sure poly resin does not stick to epoxy, other way around yes but not poly to epoxy.

But yes Poly will be fine to use, epoxy is the best but not needed.