Gelcoat - chips and scratches. Major repair work or fill the worst ones?

[Robert Wilson]

During scraping off the antifouling (many years worth) I have found chips and small gouges and have caused a number of scratches with the scraper. some of the scratches are through the gelcoat into the GRP.
Must ALL damage be filled with gelcoat filler or can some of the minor scratches be left to be covered/protected by the primer and antifouling coats?
I am about to smooth down the result with an orbital sander and then I fill the required chips and scrapes before a final sand and then prime-coat.

Any tips on the process?

Thanks in anticipation of a "non-drift" response!

P.S. I scraped-off the starboard side which took 4 hours (in short sessions). Hard and squeeky :nightmare: work.
I applied Strippit to the port side which was messy and caused a couple of caustic burns to my skin although I thought I was totally covered with waterproofs, goggles etc. The whole application and stripping took six and a half hour hours; it was messy and nasty work but did make for a slightly easier scrape. Getting rid of the resultant "caustic goo" on the ground was a big worry and nasty task.
I hope I never have to do the job again.

 

[Nicholas123]

Clean up the surface of the chips with a LIDL multi-grinder & fill with Wicks wood filler which is effectively fibreglass paste.Smooth back with a surform shaver.Job done with a minimum of fuss & expense.
I'm sure someone much more 'expert' will be along shortly to tell you that that is all wrong

 

[Avocet]

If it were my boat, I'd definitely fill any that were through the gelcoat to the laminate. I don't think antifouling paint has any water-resisting properties. I'd use one of the many "below waterline" epoxy fillers that are available (they stick better and are more waterproof than polyester).

 

[Ian_Edwards]

Having done all the hard work, I'd be applying several coats of epoxy primer after filling the major chips and scratches with epoxy filler. The epoxy will provide much better protection and help prevent water ingress into the structural GRP, especially if the gelcoat is thin in places.

 

[maby]

I would agree - don't leave gelcoat damage that has penetrated to the underlying GRP unfilled - particularly below the waterline. If you are going to slap antifouling over it, you really don't need to do a particularly pretty job - grind back a bit to get a good, clean surface and fill out with epoxy. Use a Dremel type tool with a ball grind stone to clean out the damage - that will avoid opening it out more than necessary, then fill it out with a suitable paste. If it is going to be covered with antifouling, you should be able to get a good enough finish just spreading it on without having to do any sanding after it has set.

Not sure I would use wood filler - the "correct" stuff for boats is not particularly expensive, so why use something not rated for the job?

 

[oldsaltoz]

You can save some time and effort by first making sure the areas to be treated are clen a dry, a wipe with a white cloth and some Acetone is good.

Then mix a smal batch of epoxy resin and hardener and give each area a light coat of epoxy, just enough to wet the damaged area and perhaps a few mm beyond.

Next mix a bit more resin and hardener and add some Micro-spheres to the mix till it's like toothpaste, apply this to the damaged areas and slighly overfill each one.

Wait 24 hours for this fully cure and sand smooth, wipe with Acetone and apply another layer or 3 or mixed resin and hardener. Job done.

Note Micro-spheres are nice and easy to sand but a very good below the waterline sealer.

Good luck and fair winds.

 

[Robert Wilson]

Having done all the hard work, I'd be applying several coats of epoxy primer after filling the major chips and scratches with epoxy filler. The epoxy will provide much better protection and help prevent water ingress into the structural GRP, especially if the gelcoat is thin in places.

Thank you, one and all.

With regard to "epoxy primer", do you mean several coats (of e.g Jotun Penguard ) all over the hull or just over the repaired areas?
I have already bought some multi-purpose metalic primer which I intended to use first before two coats of antifouling. Would the multi-purpose primer be ok or should I first "epoxy prime" then the metallic primer?

The scrratches caused by my scraping really are very minor with a few exceptions. Not wishing to sound lazy, but to go round the whole hull bottom filling and epoxying sounds like overkill.

As you can see, this is my first attempt at GRP work.

 

[maby]

Don't worry about anything cosmetic - it's going to be smothered with AF. It is worth checking it reasonably carefully for anything deep enough to penetrate the gelcoat and fixing them - the underlying GRP may not be so waterproof and you don't want to leave any defects that could encourage osmosis.

 

[TQA]

Important ! Fill all the gouges that are through the gel coat.

I would use an epoxy based filler. A couple of tubes of Marine Tex go a long away.

 

[Ian_Edwards]

I've been down this route twice in my boat owning career, both times I've completely covered the under water part of the hull with epoxy primer, to protect the hull from osmosis. I guess it depends on the value of the boat and how long you intend to keep it and whether you think that an epoxy barrier coat will enhance the re-sale value. I used International InterProtect, but only because I had a trade contact and could get it at a reduced price, I guess other brands are just as good.

My logic was to take advantage of all the hard work in cleaning off the old antifouling and do a "proper job", I really didn't want to have to do it again!

I wouldn't bother filling the minor scratches, but on the deeper ones I'd use epoxy filler and if you don't cover the whole area with epoxy primer, I'd be sure to cover any areas where the gelcoat is thin with either epoxy primer or a thin coat of straight epoxy as suggested in post #6.

 

[Robert Wilson]

I've been down this route twice in my boat owning career, both times I've completely covered the under water part of the hull with epoxy primer, to protect the hull from osmosis. I guess it depends on the value of the boat and how long you intend to keep it and whether you think that an epoxy barrier coat will enhance the re-sale value. I used International InterProtect, but only because I had a trade contact and could get it at a reduced price, I guess other brands are just as good.

My logic was to take advantage of all the hard work in cleaning off the old antifouling and do a "proper job", I really didn't want to have to do it again!

I wouldn't bother filling the minor scratches, but on the deeper ones I'd use epoxy filler and if you don't cover the whole area with epoxy primer, I'd be sure to cover any areas where the gelcoat is thin with either epoxy primer or a thin coat of straight epoxy as suggested in post #6.

Good advice, and the way I was thinking after nearly exhausting myself!
I have no experience of epoxy primer, seems expensive stuff and a long process for two/three coats. Soi I'm wondering if just covering the damaged/repaired areas with epoxy primer, then totally priming with the metallic multi-purpose primer.
The damaged areas are not extensive and the very greatest area of the hull is absolutely sound.

Interprotect sounds good, but 750ml covering not a large area could mean two or three tins for three coats. OUCH!

What is straight epoxy as in #6?

 

[Ian_Edwards]

By straight epoxy, I meant mixed as it comes out of the tin, no fillers added or use one of the brushing epoxy like Gurit SP320, it's just formulated to be thinner and can be used like varnish.

 

[longjohnsilver]

I have literally just finished preparing my hull for coppercoating. It was blasted which left a multitude of pin pricks in the gelcoat which i then expanded with a grinder. I then painted the eposed areas with a solvent free epoxy and then filled them with an epoxy filler (I used International Water Tite). All fairly easy to do, and sanding the filled areas was easy.
Certainly worth doing on your areas of exposed grp, easy and inexpensive.

 

[Robert Wilson]

I have literally just finished preparing my hull for coppercoating. It was blasted which left a multitude of pin pricks in the gelcoat which i then expanded with a grinder. I then painted the eposed areas with a solvent free epoxy and then filled them with an epoxy filler (I used International Water Tite). All fairly easy to do, and sanding the filled areas was easy.
Certainly worth doing on your areas of exposed grp, easy and inexpensive.

Thanks. I'll investigate. More work!!

By straight epoxy, I meant mixed as it comes out of the tin, no fillers added or use one of the brushing epoxy like Gurit SP320, it's just formulated to be thinner and can be used like varnish.

OK, gotcha. Thanks.

 

[longjohnsilver]

Thanks. I'll investigate. More work!!

Yes but not much. Certainly worth doing. Lets say you've got a dozen areas where you've gone down to the grp, then it should all take a couple of hours at the most.

And if you've taken off all the antifoul and the hull is dry, and you expect to keep the boat for some time, I'd also consider epoxy coating the whole hull.

 

[Robert Wilson]

Yes but not much. Certainly worth doing. Lets say you've got a dozen areas where you've gone down to the grp, then it should all take a couple of hours at the most.

And if you've taken off all the antifoul and the hull is dry, and you expect to keep the boat for some time, I'd also consider epoxy coating the whole hull.

WHAT, MORE work?........... Sheeesh!

Latest thinking is:-
Repair with Gelcoat filler. Primer coat. 1 coat Water-Tite. Primer coat. 2 coats antifouling. Relaunch mid May.

I'm running out of energy, money and time - October's haul-out approaching all too quickly!

 

[oldsaltoz]

The exposed epoxy repairs will need an epoxy primer over them, almost nothing will stick to epoxy, so a primer is a must, or you may well see spots with no anti-foul on you next haul out.

If you epoxy coat the entire area it will be expensive.

PS. when using an Epoxy primer look for "High Build" it goes on a bit thicker but lasts and works much better.

 

[Robert Wilson]

WHAT, MORE work?........... Sheeesh!

OK, revision:-
Repair with Gelcoat filler. 1 coat Jotun Penguard HB or Hempel Epoxy primer. 1 coat Water-Tite (on order). Primer coat (already bought). 2 coats antifouling (already bought). Relaunch late 2014 !!

What does that sound like to you?
Thanks for your patience, time and advice. Much appreciated.

 

[longjohnsilver]

WHAT, MORE work?........... Sheeesh!

Latest thinking is:-
Repair with Gelcoat filler. Primer coat. 1 coat Water-Tite. Primer coat. 2 coats antifouling. Relaunch mid May.

I'm running out of energy, money and time - October's haul-out approaching all too quickly!

I'd just use Watertite. Quicker and more effective, especially below the water line. If it's going to have antifoul over it, the blue colour won't matter.

 

[Robert Wilson]

I'd just use Watertite. Quicker and more effective, especially below the water line. If it's going to have antifoul over it, the blue colour won't matter.

Encouraging, verrrry encouraging. Thanks.
Blue no problem because a/f is pale blue

So, if I understand you:- Repair - Water Tite - Primer - a/f. Or is that:- Repair - Water Tite - a/f?