Gelcoat cracks. What causes this and how do i repair

[geardownthreegreens]

Hi guys

I've noticed a few small areas, on my Rinker, of cracks to the gel coat. There could be several concentrated in one small spot. Of course,i'm talking hair line cracks and nothing major.

My question is, what causes this and can it be repaired, or should i just leave it.

Whilst i'm here, Gelcoat scratches from mooring. The green gelcoat in places is quite scuffed, is there a product that can buff this out or tone down the obvious look of scratches.

Cheers guys
Simon

 

[Nick_H]

Its called "crazing" and you eventually get some on most old GRP boats. It can't be polished out, it would mean grinding off the old gel coat and applying new. Unless you're very practical its a professional job and not cheap. Most people just live with it.

The scuffs on the other hand can be polished out, start with a course grit polish and finish with something finer. If they're deeper you can start with wet and dry paper, and ridges in the gel coat can be filled with a gel coat filler, but if you want perfect colour match, then again it may be a professional job.

 

[Deleted User YDKXO]

Gilly1, all boats will exhibit hairline cracks in stressed areas eventually, for example around guardrail stanchion bases, cleats, at window frame surrounds or sharp edges. All boats flex to some degree only that grp is not a particularly flexible material, particularly the top gel coat. A few hairline cracks in the gelcoat is nothing to worry about although a cluster in one particular area should be ground down and repaired. These kinds of repairs are usually quite cheap
More worrying would be larger cracks. For example, the bonding between bulkheads and the hull is a high stress area and these areas should be regularly inspected and immediately repaired if necessary. Worse than that, sometimes you see cracks on the outside of a hull or the deck where the bulkheads butt up. This could be a sign of inadequate or poor grp lay up or driving the boat too hard in a rough sea. If you see something like this, get a surveyor to look at it
Re the scuffs, it sounds like you've got a coloured gel coat. If the scuffs are deep enough to show the white grp below, then the only solution is a repair which will be more expensive as the colour match may be tricky. If the scuffs are on the surface, then you could try some gel coat restorer. 3M are considered a good make. Website HERE

 

[geardownthreegreens]

Houghn and Mike.

Appreciate your full explanations and descriptions there. very useful information there.
I had an idea it was called crazing but i didn't want to say in case i made a fool of myself and no-one understand what i meant /forums/images/graemlins/grin.gif

Only small cracks at present so i'm not concerned right now and she is a 98 model,so not doing too bad i guess.

your right Mike, a coloured gelcoat, green band around the boat that shows in certain spots where she's been moored. Not particularly nice to look at so will definately take a look at 3m.

Thanks again guys.
Regards
Si

 

[gjgm]

well, you can have impact fractures, which as the name suggest, radiate out from a single point. Also, you have stress fractures, the minor ones, being around where the grp has been cut-cleats for example,. These might need grp repair under the gelcoat. As mentioned elsewhere, rather more serious cracks are where the various parts of the boat are "joinded" together. The ones knows as hairline(ie REALLY fine, like hair), you can try dripping in some coloured superglue.. it will temporarily bond it, and show the extent the crack runs.
What you want to grind out and repair is anything more "crack" like.. You can buy a tube of gelcoat repair for £6-7, and try that. If it cracks again, the fibreglass underneath is fractured, and you ll need to do a bit more work.
But grp and gelcoat are miracle products.. if you can make a pot of tea, you can manage a small repair, though structural work, maybe you want to get a pro.
Plenty of tips on the net, and wessex (chemicals?) do some good guides. They used to run a short course , too ....

 

[geardownthreegreens]

Thankyou very much also, for your input.

There is nothing serious at present but i will keep an eye on things to make sure they dont get any bigger.I'm glad to know that its nothing serious also.