Foredeck Skin puncture (a la harness hook) repair help

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EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Foredeck Skin puncture (a la harness hook) repair help

Post by EdS » Sun Apr 07, 2013 9:02 pm

Evening all,

As above, last time i sailed my crew climbed on board forward of the shrouds and put is weight on his stomach, unfortunately straight through the skin.

I dont know how to upload images, but on the link you can see the area above the pocket, forward of the shrouds but aft of the jib track, this is the area that got damaged.
http://theboatyardatbeer.com/images/14g.htm


The boat is a nomex sandwich and it appears to have a single thickness laminate in this area.
The hole is the size of a biro (ball point pen) and there is a small flap of carbon still there.

So how do i go about repairing this to seal the hull and not make a mess?

The boat has been dried out all winter in the garage so the moisture should be out.

any input would be appreciated, thanks.
Roaring Forties GBR1524

selsbowbitch
Posts: 25
Joined: Tue Dec 04, 2012 8:58 am
Boat Number: GBR 1525

Re: Foredeck Skin puncture (a la harness hook) repair help

Post by selsbowbitch » Mon Apr 08, 2013 10:08 am

Hi

Have just done several of these on 1522, same issue, nomex with thin skin of carbon. Asked a friendly boatbuilder and he told me that the best way is to make sure that there is strength below the repair and recommended filling the honeycomb with epoxy then allowing it to set, then gelcoat over it. Worked a treat. Few tips...

Tip 1 - Mask over the hole and cut round it accurately with a scalpel or alike before applying epoxy, keeps the edges nice and clean for gelcoat. Don't fill the hole right to the top with epoxy, allow for 3-5mm of gelcoat so it makes it easier to sand & less brittle

Tip 2 - Use neat epoxy with a tiny bit of high density filler, still allows the mix to flow but takes the brittleness away from epoxy

Tip 3 - once the epoxy is dry, mask off as before and apply gelcoat, use a scraper to scratch off the excess, by having the tape there it will prevent too much excess which will make sanding easier.

Tip 4 - make sure you get the correct colour gelcoat from the manufacturer of the boat

Tip 5 - When sanding to a finish be careful and take your time as the gelcoat tends to be really thin and its easy to get through to carbon underneath.

Tip 6 - Sack your crew (I can say that as I did exactly the same thing at Itchenor the other weekend and I wanted to sack myself!)

Hope this helps

Graeme

EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Re: Foredeck Skin puncture (a la harness hook) repair help

Post by EdS » Mon Apr 08, 2013 4:24 pm

Graeme,

These things are just unfortunate, does make you wince though.

The boat doesn't have gel coat so that isn't an issue, it is painted white.
I was expecting to have to patch the hole with carbon.
I haven't opened it up to see the damage to the honeycomb, but thanks for the tips of reinforcing it if it is damaged.

Thanks,

Ed
Roaring Forties GBR1524

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Shu
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Boat Number: USA 1183
Location: San Diego (sort of)

Re: Foredeck Skin puncture (a la harness hook) repair help

Post by Shu » Mon Apr 08, 2013 7:13 pm

Ed,
If the puncture is in a location where you are concerned about stresses in the laminate, you can do the following after filling the hole with thickened epoxy:
1. Sand out a very shallow dish shape, centered on the puncture. The depth of this very shallow dish should be the thickness of the carbon skin. The edges of the dish should show about 1" of exposed carbon skin (if it's only one layer of 200gm, it will be hard to get this gradual of a taper, but do your best. If it is several layers, you will want a longer taper; I try to do about 1/2" of taper for every 200gm layer of carbon).
2. Cover the dish shape with the number of layers of carbon that are present in the skin (the carbon is wet out with epoxy). Cover out to the extreme edges of the exposed carbon taper. If you have multiple layers, alternate the orientation of the fabric by 45 degrees between layers and increase the overlap of each layer by about 1/2" to match the underlying taper. Only the topmost layer needs to extend to the extreme edges of your taper. Use peel ply and a dab at it with the end of a stiff disposable brush to force out all the air bubbles. You can vacuum bag it instead, but that is overkill for this type of repair.
3. After curing, sand the repair flush with the surrounding surface. Use a sanding block to keep it flat with the surrounding surface. Finish with matching paint. If it's in a place that can benefit from non-skid, you can skip the paint; just seal the sanded surface with liquid epoxy, and apply non-skid foam or tape once the epoxy is cured.
-Steve
Steve Shumaker
USA 1183

EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Re: Foredeck Skin puncture (a la harness hook) repair help

Post by EdS » Mon Apr 08, 2013 7:46 pm

Steve,

Thanks for the input, I think it would probably be best to do a repair as you suggest.

How do i work out the layers are present in the current laminate.
I looks pretty thin, other than calling the yard who built here, is there another way?
I cant see that it is a particularly highly stressed area, having sail that its proximity to the shrouds and jib track probably mean a patch would be smart.

Thanks,

Ed
Roaring Forties GBR1524

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Shu
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Boat Number: USA 1183
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Re: Foredeck Skin puncture (a la harness hook) repair help

Post by Shu » Tue Apr 09, 2013 1:01 am

Someone very smart with laminates (Hendo? Bieker? I forget) told me to use 1000gm of vacuum-bagged carbon cloth to acheive 1mm of thickness, or one 200gm layer = 0.2mm. Try measuring that carbon flap you mentioned with a pair of calipers and go from there (sand the boogered-up edges first or your caliper reading will be messed up). My guess is that the general layup for your deck is probably 2 layers of 200gm. It will be more in reinforced areas. But this is just a guess.
Steve Shumaker
USA 1183

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