GRP repair

[saltyanchor]

Hi, I am working on a small project. I've bought a 17 foot catamaran with a damaged port hull. It was hit by another dinghy. The hull is grp, woven not chopped mat. The hull is split, about a foot long. Deck ok and the split does not run right to the keel. The way I am thinking of repairing is outlined below, but I 'd appreciate any other ideas:
Remove some of deck so I can to inside of split. Cut away all jagged bits etc so I can get side of hull in line / fair. Epoxy a recatangle of woven mat inside the hull to hold the slit together, then another larger rectangle over that (still on inside). Then simply fill the cavity / split from the outside with epoxy and glass spheres / filler stuff - sand etc and paint. BUT IS THAT STRONG ENOUGH? I'd prefer a slab of mat on the outside too, but it would look awful obviously.
Also, any ideas on getting in through the deck? I do not want to remove the whole deck and tape back on, so I'm suggesting cutting a section out - but do I make the cut in at an angle to make replacing the deck a better job - and I will cut the deck all the way out to the gunwhale, thereby making one edge to simply tape.
Ta
Merry Christmas.

 

[ShipsWoofy]

I have a GRP repair manual for download

http://www.topcatsail.co.uk/GRP-REPAIR-MANUAL.pdf


Or go to the this page

This might be some help to you.

 

[Keith]

personally i would put three or possibly four patches on the inside, use epoxy preferably west, yes its expensive but its very temperature stable and easy to use, round all the corners of patch's, it cuts down on localised stress points and cuts down on the chance of the patch popping off, don't forget to thoroughly abrade the glass on the inside and degrease, i would probably look to fit a water proof inspection cover where you are going to enter the deck to do the repair, (easiest way out depending on curve of deck) if you can locate an inflatable bladder of some kind that you can use it will help put pressure on the patch when inflated inside hull and drive out air etc in the repair, don't forget mock up your repair first make sure each peice is the right shape and large enough to do the job and it should be fairly straigh forward.........keith

 

[saltyanchor]

Thank guys

Thanks guys - I am going out now to start.

 

[William_H]

When getting to the outside part. cut a shamfer in the existing F/G edge out to about 2 cms so that a patch the size of the hole is first fitted followed by a patch slightly larger to fit into the shamfered area followed by another patch of cloth coming out to near the outside edge of the shamfewred area. This gives you patches onj the outside which do not rotrude beyond the F/G level.
Hope that makes sense regards will

 

[saltyanchor]

good idea - thanks - nm

nm

 

[snowleopard]

just a few small points

1. there is no benefit to using epoxy rather than polyester. it's more expensive, harder to use, more toxic and does not give a better bond

2. the key to success is a clean, dry, well-abraded surface.

3. make up your patch on a piece of heavy-guage polythene, wet thoroughly with resin then slap on like a plaster and squeegee out bubbles. the polythene will come off easily once the resin is cured. (this works for both types of resin)

4. a layer of chopped strand mat between the woven material and the hull will give a sounder bond. regular chopped strand should not be used with epoxy.