Author Topic: GRP composition  (Read 2900 times)

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GRP composition
« on: April 08, 2014, 07:17:19 AM »
Adrian Evans
   
Posted on Tuesday, December 04, 2007 - 01:26 pm:      
living about as far away from the sea as is possible, I'm not mowed out with sensible boat repairers, and I think I am going to undertake my repair to Peg myself. It is essentially a tear in the deck about 14" long, levered up by the bowsprit. (Arrgh!the bobstay shackle popped when the top of the mast made contact with a tree I thought I was well clear of - the branch no more than an inch in diameter, less than a foot from the top of the mast. Thus the mast pulled the forestay and the forestay pulled the bowsprit and the bowsprit pulled the deck...)

I plan to get her indoors to allow proper curing. My question is a)can anyone confirm that the grp matrix is epoxy resin,as I expect, and not polyester?
b)I have assumed that resin compatability is critical, but is this the case with repairing old, long cured grp?

Many thanks for your thoughts

Adrian

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Re: GRP composition
« Reply #1 on: April 08, 2014, 07:17:41 AM »
Roger Parish
   
Posted on Tuesday, December 04, 2007 - 05:45 pm:      
Poor Peggotty! I would expect the boat to have been made from polyester and choppped strand matting however it is probably better to undertake small repairs using epoxy and glass tape or glass matting. Do not use epoxy with CSM as it will not wet out properly. I am not aware of any incompatibilty between two systems other than already stated. I would go for epoxy which does not shrink like polyester. If using epoxy follow instructions carefully.

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Re: GRP composition
« Reply #2 on: April 08, 2014, 07:17:56 AM »
Julian Swindell
Username: Julian_swindell

Registered: 03-2007
   
Posted on Wednesday, December 05, 2007 - 10:25 am:      
I think Roger is certainly right that the orginal hull GRP will have been polyester based. I think I read somewhwere that the deck is strengthened with "coremat". Not sure what that is or if it was used on the foredeck.

Where has the deck been damaged? Is it around the cleat that the bowsprit fits under?

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Re: GRP composition
« Reply #3 on: April 08, 2014, 07:18:12 AM »
Adrian Evans
   
Posted on Wednesday, December 05, 2007 - 02:24 pm:      
Roger, Julian,thankyou. It certainly was a sickening moment! Especially as I was trying to make space in the yard for others, after pulling Peg out at a busy time.
The second, real lesson learned was that I knew I flustered by the prang, so I took great care to carefully tie down the damaged parts, and pack away carefully and methodicly, making sure I had done everything correctly,not left anything lying on the tarmac, double checking the hitch, trailer etc., and drove home very slowly and carefully.
Which was just as well. Despite my methodical approach, when I finished my unpacking the next day, I found the tie-down straps lying in the bottom of the boot, underneath the rest of the gear! I feel very, very lucky, and happy that I didn't excede 45 on the way back!

I shall probably go for Epoxy. Just hoping I can get her undercover, because I know the low temperature will be a problem with curing.

Julian, the principle damage is a split in the deck from the port bow about 7 inches back from the stem, running across to the sampon post at the back of the bowsprit. The Bowsprit pivoted about this point.There is a small nick, an inch or so long, in the starboard bow as well. The starboard bulwark was spectacularly shattered, but my friendly local joiners have already sorted me out a replacement which is a very good match, and nice and flexible.

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Re: GRP composition
« Reply #4 on: April 08, 2014, 07:18:28 AM »
David Cawston
   
Posted on Thursday, December 06, 2007 - 12:37 am:      
Certainly on Markie the construction is polyester. Coremat is like very thick blotting paper which absorbs the resin, very good at thickening/stiffening up panels without too much weight. When I reattached the bilge plate housings to the hull I used West epoxy with woven rovings and many years later it is still holding up. If you use polyester or epoxy it is essential to thoroughly clean/abrade/rough up the old grp as a waxy layer forms on the surface as part of the curing process and you must remove this before laminating onto it. http://www.wessex-resins.com/pdf/English.pdf is an excellent source of information. Good luck with the repair.