Gelcoat repair - explained

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Jonathan.
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Gelcoat repair - explained

Post by Jonathan. » Thu May 04, 2017 4:03 pm

I've always found the process of gelcoat repair something of a mystery so I was pleased to find this http://www.cfsnet.co.uk/acatalog/Gelcoat_Repairs.html. It seems so clear I thought it worth sharing.

It's on the site of http://www.cfsnet.co.uk who will, I believe, send catalyst by post, something some suppliers won't do.
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thesambaman
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Re: Gelcoat repair - explained

Post by thesambaman » Fri May 05, 2017 8:55 am

This is great. Thanks for posting.

I have been told that the repair should be covered with a sheet of acetate while it cures. This is not mentioned here. Can anyone advise if this is necessary or not?

One thing they never tell you (of course) is that acetone is widely/cheaply available in the form of nail varnish remover.

Ken R
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Re: Gelcoat repair - explained

Post by Ken R » Fri May 05, 2017 10:08 am

I believe the mention of wax means that you do not need to exclude air for the gel coat to go off.

It's many years since I repaired gel coat but I did not have wax in the gel coat. On small repairs I used sellotape - worked fine.

Aled
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Re: Gelcoat repair - explained

Post by Aled » Fri May 05, 2017 10:24 am

The acetate sheet method is a shortcut technique to reduce/avoid the sanding and finishing. Pressing the sheet over/onto the newly applied gelcoat will effectively create a temporary mould surface for the outer skin. It will squeeze the gelcoat flat and leave a shiny finish, which, if you're not too bothered about an 'as new' repair, would give you a 'satisfactory' repair. The acetate sheet is unlikely to contour to the curves of your boat, so will always leave a a slight flat and possibly some over-spill around the edges. It could be a useful technique out in the wild when you need to repair a boat with glass/gelcoat.

The secret I've found to successful gelcoat repairs is dealing with the unavoidable air bubbles induced while stiring. When you sand back the applied gelcoat, there will always be small pockets of air which show as pinholes. The process of tamping can remove them. Just like a chef with a chopping knife, but using a ruler... Lay the ruler edge on into the wet gelcoat, pinch one end to form a pivot and raise/lower the other end in a vibrating motion - you'll generate a rapid tapping noise. Avoid lifting the ruler out of the gel, but move it around during the process to chase out all the bubbles - you'll see them rise to the surface and pop.

Many people advocate adding 'wax in styrene' to the gelcoat to make this 'flowcoat' non-stick. It's not absolutely necessary, wait for the gelcoat to harden, and simply give it a good wipe with acetone - it will remove/dry off the sticky surface. Adding the wax to gelcoat raises the viscocity - if you're repairing a non-horizontal surface, the gelcoat may be prone to sagging or slipping.

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Robert Craig
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Re: Gelcoat repair - explained

Post by Robert Craig » Fri May 05, 2017 10:55 am

thesambaman wrote:... acetone is widely/cheaply available in the form of nail varnish remover.
Some nail varnish removers have an oil added so's to make nails look shiny. I was able to buy pure acetone from Ebay. It arrived by ordinary post, somewhat to my surprise.

Maarten Z
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Re: Gelcoat repair - explained

Post by Maarten Z » Thu May 11, 2017 3:13 pm

Aled wrote:Many people advocate adding 'wax in styrene' to the gelcoat to make this 'flowcoat' non-stick. It's not absolutely necessary, wait for the gelcoat to harden, and simply give it a good wipe with acetone - it will remove/dry off the sticky surface. Adding the wax to gelcoat raises the viscocity - if you're repairing a non-horizontal surface, the gelcoat may be prone to sagging or slipping.
Thanks for this tip! I find repairs to be rare on a flat surface when considering kayaks.

When will you write a book on all this? :-)

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Jim
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Re: Gelcoat repair - explained

Post by Jim » Thu May 11, 2017 10:38 pm

thesambaman wrote:One thing they never tell you (of course) is that acetone is widely/cheaply available in the form of nail varnish remover.
Can you seriously buy nail varnish remover more cheaply than buying acetone by the litre or 5 litres? Seems unlikely.

Hamish
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Re: Gelcoat repair - explained

Post by Hamish » Sun May 28, 2017 11:39 pm

The gelcoat on my Quest is full of star cracks. I think it's beyond my abilities and patience to repair.

Two questions:

Does it matter if I ignore the cracking for a while at least?

Does anyone know if it is possible or economic to get large areas of star cracked gelcoat repaired? If so, is it best to send it back to p&h or use a local boat builder?

Thanks

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Jim
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Re: Gelcoat repair - explained

Post by Jim » Tue May 30, 2017 12:47 am

Star cracking is from impacts, in itself it is nothing to worry about and I probably wouldn't bother to repair them, but first I would inspect the area thoroughly (inside as well if possible) and make sure there is no damage to the underlying laminate. If there is damage I would probably chip or sand the cracked gel off completely to patch the laminate, and then use gelcoat filler to finish the repair off.

Hamish
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Re: Gelcoat repair - explained

Post by Hamish » Wed May 31, 2017 11:11 pm

Thanks Jim

I guess looking at it, my boat has as much crazing as it has star cracks.

I have used it like that for a while.... But I may ask P&H if they can do large scales gelcoat repairs....

Hamish

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