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Repairs to stress cracks 
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Post Repairs to stress cracks
Can anyone tell me how to fix the Coupes body where there appears to be stress cracks or crazy cracking, not that well up on fibreglass repairs


Mon Dec 15, 2008 11:21 am
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Post Re: Repairs to stress cracks
Dino][quote="Andy wrote:
Can anyone tell me how to fix the Coupes body where there appears to be stress cracks or crazy cracking, not that well up on fibreglass repairs

Yes! :D
PM me your email and I'll send you a set of scans I have of a very good book, sadly long out of print.[/quote]


Last edited by Dino on Mon Dec 15, 2008 10:12 pm, edited 2 times in total.

Mon Dec 15, 2008 3:51 pm
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Post Re: Repairs to stress cracks
Ok to send me a copy too? Sure I'll be needing those sort of skills at some point! :D

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Mon Dec 15, 2008 6:27 pm
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Post Re: Repairs to stress cracks
No problem, they're on the way :D


Mon Dec 15, 2008 7:50 pm
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Post Re: Repairs to stress cracks
To some it up in a nut shell patience


You have to grind out completely the cracks, gelcoat, even the fibres if the crack goes that far :roll: , then taper this out

then reglass, gelcoat, fill to bring back the surface to the right level, the reglass adds a little strength rather than just filling/gelcoating as these are very brittle on their own.

GTM altho a cunning plan to offer the bodies in gelcoat to save painting, does mean the gel coat is that little thicker meaning it is more likely to crack :x

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Mon Dec 15, 2008 8:30 pm
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Post Re: Repairs to stress cracks
Dino wrote:
Dino][quote="Andy wrote:
Can anyone tell me how to fix the Coupes body where there appears to be stress cracks or crazy cracking, not that well up on fibreglass repairs

Yes! :D
PM me your email and I'll send you a set of scans I have of a very good book, sadly long out of print.

OK emailing wasn't a great success, due to the size of the pics so here's a link to them instead:
http://s26.photobucket.com/albums/c149/Dino422/GTM/Glass%20fibre%20repairs/?start=all


Mon Dec 15, 2008 10:18 pm
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Post Re: Repairs to stress cracks
You also need to reinforce the rear of the panel. Gel coat cracks are usually a sign of undue flexing in the underlying GRP.

You can get an extra thick version of Gelcoat resin especially for filling the finished repair. You tint it to the correct colour then add the catalyst and use it like filler.

http://www.ecfibreglasssupplies.co.uk/s ... 9_174.html

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Tue Dec 16, 2008 10:38 am
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Post Re: Repairs to stress cracks
gtmdriver wrote:
...Gel coat cracks are usually a sign of undue flexing in the underlying GRP....

Or as in my case, people smacking the car into things :roll: :roll:


Tue Dec 16, 2008 12:45 pm
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Post Re: Repairs to stress cracks
Guys,

I have read the article that Dino sent a link to how how to repair fibreglass cracks but I'm confused on the repair method as all my cracks seem to be very small and are all in the most ackward of places to get at ,i.e. door opening/jams and around the windscreen opening, they all look to be just gelcoat cracks. If I grind out the crack and fill it with resin is this satisfactory, it seems crazy to make the crack or repair big enough to get mat in. I have also noticed when rubbing down the car that there are a number of imperfections, can these be filled?? and what should I use.

Any help would be appreciated.


Andrew


Fri Jul 17, 2009 7:47 pm
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Post Re: Repairs to stress cracks
Andy wrote:
Guys,

.... If I grind out the crack and fill it with resin is this satisfactory, ...

Seriously, I wouldn't do that.
I had loads of small cracks, well crazing really all over my bonnet - this is the result of 'painting' resin over them.
Image
The rest of the bonnet I covered with very fine tissue with resin stippled into it, then sanded flat afterwards, this has worked...so far!

Quote:
I have also noticed when rubbing down the car that there are a number of imperfections, can these be filled?? and what should I use.

An ordinary polyester body filler is fine .


Fri Jul 17, 2009 8:29 pm
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Post Re: Repairs to stress cracks
Dino,

What about a fibreglass inpregnated filler, would that give the same effect, I would still sand/grind out the cracks but maybe use this instead, I've read a couple of more modern articles and they say that reinforced filler is as good as a fine mat in small circumstances. Anything big would be filled with mat and resin as per your book. Did the paint not take to the resin or did the cracks just reapear.

Andrew


Sat Jul 18, 2009 8:32 pm
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Post Re: Repairs to stress cracks
Personally I've never had much luck with the resin / fibre mixes, they seem very thick...but I guess it should work for your small cracks.
The advantage of what I did is that you can apply the tissue and resin very thinly - I would recommend it.
The cracking you see in the pic is, I think. a result of the panel flexing as it changes temperature - the paint is still bonded fine.
They appeared during the winter when the temperature cycled from quite cold (sub zero) to ~ +10c during the day and in the sunlight.
It's only over a small area - I got bored doing the tissue/resin thing and thought I'd try just resin..........won't do that again!

Once you get used to working with it, you can jiggle the tissue into very small patches, then apply a thin skim of filler if needed to finish it off.


Sat Jul 18, 2009 11:14 pm
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Post Re: Repairs to stress cracks
Dino,

That was my dealings too with fibre fillers until I got my hands on the tin I'm using now, it's fantastic very easy to spread and resembles fibreglass both on application and then on drying. I used it on a number of areas on the car so far and it seems to work well. Thanks for the adivse though, whats your car doing being exposed to sub zero temps, you don't have it in a garage with central heating :lol: :lol:


Sun Jul 19, 2009 11:12 am
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Post Re: Repairs to stress cracks
The sub zero was a bit of a surprise actually, we've lived here 14 years and that's only the second time it's snowed!
Bit of a shocker - only about an inch or so but of course no-one could get up the road :evil:

Interesting about your filler - what's it called?


Sun Jul 19, 2009 1:35 pm
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Post Re: Repairs to stress cracks
Can't remember off hand but will look next time I'm in the garage and post it up.


Sun Jul 19, 2009 10:18 pm
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