Fibreglass repair over osmosis hull

[andrew-b]

Hi all,

I was wondering if you could give me some advice.

My boat (Colvic Sailer 29) has a few hairline cracks in the gelcoat around the keel/hull "join" on the starboard side. Actually, there is no keel/hull join, because it is an encapsulated keel, but the "join" is a good way to describe it, as it's where the two meet.

Last year I ground off a few "sample" patches along the crack and determined that it is only gelcoat and not into the glass so was happy sticking to the plan that year and putting her back into the water. This year I would like to grind out the entire crack and repair, however I have been told to be careful, as new resin won't stick to a hull which has osmosis (it does). How far is this true?

At the moment the plan would be to:
1. grind out all of the cracking and 30cm each side back to nice glass
2. put a few layers of woven matt and resin (epoxy or polyester?) over the area
3. gelcoat it
4. prime it
5. antifoul it

I'm not a racer so doesn't need to be perfectly flat, and if the repair was in any other location I would just get on with it and see what happens - but it's a fairly sensitive area so wanted to see what you guys think first.

Thanks!
Andrew

 

[Tranona]

You are basically right. Don't think osmosis has anything to do with it unless you find damp in the laminate once you grind back. Epoxy is best to bond in with cured polyester resin but make sure your glass is compatible with epoxy. No need to gel coat underwater - just fill and fair with epoxy filler, Primocon and antifoul.

You will find useful information on doing such repairs using West epoxy (although equally applicable to other epoxies) on the Wessex Resins site.

 

[wotayottie]

For once I agree completely with Tranona. So I must be right!

 

[William_H]

I would not imagine there could be any concern re compatibility of glass with epoxy. Yes new chopped strand mat is stuck together with a binder which is dissolved by polyester (as you want) but not by epoxy (so a problem) but I have not heard of a problem of old CSM in a grp hull. Possibly also made with chopper gun so no binder anyway. olewill

 

[Tranona]

I would not imagine there could be any concern re compatibility of glass with epoxy. Yes new chopped strand mat is stuck together with a binder which is dissolved by polyester (as you want) but not by epoxy (so a problem) but I have not heard of a problem of old CSM in a grp hull. Possibly also made with chopper gun so no binder anyway. olewill

It was the new glass I was referring to, not the old. Would not be chopper gun layup from that builder.

 

[andrew-b]

Thanks all for your replies, definitely put my mind at rest. Time to get to work I guess!