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Old 04 November 2005, 17:46   #11
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Gelcoat adds close to no strength. It is a finishing effect for the most part almost like paint but not really. The structure of a boat is the polyester and fiberglass matting under the gelcoat. When boat makers create a boat hull they spray the gelcoat into the mold first, then they lay glass and more resin over this etc etc. Once everything is cured, they pop the hull out of the mold. The gelcoat is just a thin eggshell layer of resin over the structure of the boat. The reason gelcoat cracks and develops hairline cracks is because the boat flexes. Since the gelcoat has no real structure (fiberglass) it cracks but the poly resin mixed in the fiberglass doesn't.

The only time you need to worry about gelcoat cracks on the hull is if its permanent water boat because then you can have reverse osmosis that eats into the fiberglass.

Something like that.
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Old 04 November 2005, 17:58   #12
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Quote:
Originally Posted by Biggles
Hi J,

I've read all sorts of conflicting things about Gelcoat on this forum.

If I angle grind the cracks out and then fill them with gelcoat do I need to cover them with something to make the Gelcoat harden.
No. The surface will be slightly tacky but for such a small job it's not significant. The first piece of abrasive paper will choke with it but that's only pennies. If you intend to do a substatial area, there is a wax which can be added to the resin to prevent the surface tackiness.

Quote:
Also because my hull is orange, and I couldn't find orange pigment in my local chandlers, Aladins Cave, Hamble, can I add a little bit of orange paint to colour the Gelcoat.
Dunno. For general info, there is a set of colours known as British Standard Colours. Standard pigments are made in these colours as are paints. Orange is one of them. If a laminator simply buys in standard orange pigment for the hulls, you should be able to get a good match. Likewise, you should also be able to get matching paint.

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Forgive my ignorance but what sort of consistency is Gelcoat. Is it like filler or is it like a paint ?
Neither. It's thick and sticky. It contains a thixotropic agent to prevent it slumping down vertical surfaces. You do have to add catalyst to the resin to cause it to cure.

I buy my resins from Glassplies in Southport and I know they do small quantities by mail order.
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Old 04 November 2005, 18:04   #13
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Okay so Gelcoat of the correct colour is the ideal finish.

However because it provides no strength couldn,t I just use a filler to fill out the Angle Grinded grooves. and then pint it the right colour.

This was my initial thoughts but I was worried about the filler just popping out.

As I said its an old boat and I just want to protect rather than make it look like new and protect.

To do both would be nice but I'm just learning...
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Old 04 November 2005, 19:27   #14
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There is a bloke called Stuart Hopkns at Drivers Worf, Sarfamtun he is a damn fine bloke and kwite yewsful. I know for a fact he has a tin of rescue orange pigment and some gell coat!

If you said that Portsmouth FC were crap he's probably give you the stuff!

He would probably point out to you however that you are better doing the fix with epoxy gell coat cos polyester isn't very adhesive ( not at all really!)

07774401963
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Old 05 November 2005, 04:07   #15
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Quote:
Originally Posted by boatster_sr4
Gelcoat is just polyester resin. You can use a thick celophane to keep the resin from air while it cures, this is called Vacuum bagging.
Gelcoat is gelcoat and resin is resin - different stuff but uses the same catalyst. Vacuum bagging needs a vacuum machine - covering it with celophane is just covering it with celophane! Listen to JW - he knows what he's talking about!
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Old 05 November 2005, 04:39   #16
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Quote:
Originally Posted by Cookee
Gelcoat is gelcoat and resin is resin - different stuff but uses the same catalyst. Vacuum bagging needs a vacuum machine - covering it with celophane is just covering it with celophane! Listen to JW - he knows what he's talking about!
Gelcoat can come as straight pigmented resin, so gelcoat at times is in fact resin. Vacuum bagging can also include laying celophane over a flat or curved surface that needs to be void of air contact. The term is the same in the surfboard industry for ding repair, I do it all the time. The effect is the same as literally bagging and sucking the air out. I suppose I should have suggested Biggles get a large bag to put around his boat if I were to to use the words vacuum bagging. The term is used losely but the principals are the same. But sure listen to JW - he knows what he's talking about!
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Old 05 November 2005, 04:48   #17
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http://www.cfsnet.co.uk/

Nick,

check out that link. They can supply everything you need (including pigment) and they can give very helpful advice over the phone. I have used them for all my supplies for my boat build and they are also cheap like the budgie.

Stu is right about the epoxy being more adhesive but you have to be very careful to get exactly the right ratio of resin to hardener, with polyester its not so critical.

If the cracks are as small as I think they are (ie hairline) then I would've thought that angle grinding them out may be a little drastic. Can the cracks not be filled with that stuff in a tube (name escapes me) that uses capillary action to penatrate deep into hairline cracks and seal them tight? Over to you JW....

Tim
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Old 05 November 2005, 05:21   #18
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Nick, scratch the Gelcoat repair and do what I did.

Use Loctite Plastic Padding Gelcoat repair apoxy, it's great stuff and sticks like nothing else it also air cures. One drawback though it only comes in white, but take that "Nice" Stuart Hopkins up on a little of his stain powder and your away. Aladdins cave and Port Solent Marine superstore sells it, just don't grind too bigga groove into the hull to make it go further. It's the same consisancy as car body filla and just as east to mix and sand.

Andy


http://www.loctite.com.ua/int_henkel...tenance|Marine|

Product 3024. Sorry couldn't find it on the UK website

And try this: http://www.loctite.com/int_henkel/lo...at_UK_0803.pdf

Go to Page 18
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Old 05 November 2005, 06:53   #19
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Quote:
Originally Posted by slimtim
Can the cracks not be filled with that stuff in a tube (name escapes me) that uses capillary action to penatrate deep into hairline cracks and seal them tight? Over to you JW....
I dunno.

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Old 05 November 2005, 07:12   #20
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Look what I've just found: http://cgi.ebay.co.uk/GELCOAT-FILLER...QQcmdZViewItem
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