Gel coat cracks??

BabySharkDooDooDooDooDoo

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These have manifested themselves on the side decks around the cockpit. Any ideas what might have caused these and how they could be economically fixed? They look quite different from the usual 'stress' cracking.

We suspect the blue stuff is deck paint but not sure about the rest. Boat was built in the 1970s

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TQA

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My 40 year old boat has multiple gel coat faults on the deck moulding including one small non stress area where there is alligator flaking like yours. When I had it surveyed 10 ears ago the surveyor bought in a fibreglass expert to look at it and his opinion was the gel coat had been too thick.

Generally the faults have not worsened in 10 years.

Every now and then I feel I should do something about them but lie down and play with the cat until the feeling goes.
 

rogerthebodger

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That look exactly the same as the cracking on the deck of my motor boat which is cracking in the painted surface.

Remove the paint and inspect the gelcoat for cracking which needs to be opened up then filled and repainting.
 

KAM

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Over thick gel coat coupled with dry lay up underneath. Same as my 1978 boat. It needs to be fixed as water gets in and freeze thaw opens up the cracks.
 

BabySharkDooDooDooDooDoo

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Thanks for the replies, it looks like the next step is to try and determine if this is paint of gel coat.

As the side decks are unaffected hopefully it is a localised problem.
 

Yorkshire Exile

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When I saw these photos I thought thank God that's one problem I don't have. But today we removed the canvas rope bags which are mounted on the bulkhead at the forward end of the cockpit and underneath them was what looks to be the same issue. These bags have probably been in that position for at least ten years and this is the only place on the boat where this exists. Anyone know why?
 

Concerto

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When I saw these photos I thought thank God that's one problem I don't have. But today we removed the canvas rope bags which are mounted on the bulkhead at the forward end of the cockpit and underneath them was what looks to be the same issue. These bags have probably been in that position for at least ten years and this is the only place on the boat where this exists. Anyone know why?

I suspect that moisture is getting trapped by the rope bags and has penetrated the gel coat. Then during the year the temperature changes are continually drying the gel coat and then wetting it again, finally when wet the moisture in the gel coat then freezes. All of this breaks the gel coat down.

On my boat I found water trapped under some Treadmaster that caused osmosis. The Treadmaster should have been fully bonded but obviously it was not and allowed water to become trapped.
 

BabySharkDooDooDooDooDoo

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A search on Google images did suggest Osmosis as a possible cause but (in our case) without anything holding moisture against the affected section it was difficult to understand why that would have happened.
 

Yorkshire Exile

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I suspect that moisture is getting trapped by the rope bags and has penetrated the gel coat. Then during the year the temperature changes are continually drying the gel coat and then wetting it again, finally when wet the moisture in the gel coat then freezes. All of this breaks the gel coat down.

On my boat I found water trapped under some Treadmaster that caused osmosis. The Treadmaster should have been fully bonded but obviously it was not and allowed water to become trapped.

Thanks Concerto. Sounds quite likely.
 

KAM

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I think its due to the dry layup. Exactly the same thing happens to me if a rope bag is left against the surface, moisture wicks through the gel coat and forms a series of cracks possibly exacerbated by frost action. I think cockpit areas are maybe more prone to dry layup due to the probability of tight curves and vertical surfaces when moulded.
 

doug748

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I suspect that moisture is getting trapped by the rope bags and has penetrated the gel coat........


I once viewed a boat which had been ashore for a couple of years it was not very old, maybe 7 or 8 years. It had developed osmotic patches in the four places on the hull where the cradle supports had been.
 

CAPTAIN FANTASTIC

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I suspect that moisture is getting trapped by the rope bags and has penetrated the gel coat. Then during the year the temperature changes are continually drying the gel coat and then wetting it again, finally when wet the moisture in the gel coat then freezes. All of this breaks the gel coat down.

On my boat I found water trapped under some Treadmaster that caused osmosis. The Treadmaster should have been fully bonded but obviously it was not and allowed water to become trapped.

It is difficult to see how you can have osmosis under Treadmaster; most likely to be gelcoat blisters.
 

Concerto

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It is difficult to see how you can have osmosis under Treadmaster; most likely to be gelcoat blisters.

The Treadmaster on the cockpit seats was badly bonded and water had become trapped. There were some small blisters from air bubbles in the gel coat that were 1 to 2 mm in diameter. The osmosis blisters were 20 to 25 mm diameter and went right through the gel coat (about 3 to 4 mm thick) to the fiberglass. When these were burst they had a vinegar smell when burst. These were ground out and thoroughly washed and allowed to dry naturally in early summer for 10 days before heat was applied. The holes were then filled with a gel coat filler. Finally new teak panels were fitted and particular attention was paid the ensure all the edges were fully sealed to stop the problem recurring.
 
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