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Nomex Honeycomb Compression Fix?


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#1 TornadoCAN99

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Posted 24 May 2012 - 07:36 PM

Had an F18 ram my Tornado (him on port, me on Starboard) at low speed. Bow made a good sized compression on the side of the hull...maybe 6"x4". Location is about halfway from main shroud chainplate to transom, about 6"-8" below gunwale...not a highly stressed area. It is a bit more pliant than surrounding undamaged hull.

Hull is epoxy glass sandwiching a Nomex honeycomb core. Hull is painted, not Gelcoated. I'm thinking to make drill holes through the out glass skin at regular positions across the damaged area and inject epoxy thickened with microballons or West lightweight filler...to stiffen up the area. Then fair in the outer surface using more light weight filled epoxy.

Suggestions?

#2 bruno

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Posted 24 May 2012 - 08:19 PM

add layer of carbon on outside, try look inside to ensure the panel didn't buckle clean through, rent a fiber optic cam, and look whilst pushing against it.

#3 TornadoCAN99

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Posted 24 May 2012 - 09:10 PM

add layer of carbon on outside, try look inside to ensure the panel didn't buckle clean through, rent a fiber optic cam, and look whilst pushing against it.

Can't do carbon on/in hulls as per class rules, but glass is an option. I'll see if a camera can be had locally...

Thx.

#4 Scarecrow

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Posted 24 May 2012 - 11:39 PM

Any photos of the damage? Injecting resin into honeycomb will add weight but not fix anything. From your description is sounds like you've sheered the skin core bond. There are photos in the AC forum of oracle fixing the same problem on Bundy's boat and there is no easy fix.

1. Carefully cut away outer skin and core.
2. Patch any damage to inner skin.
3. Replace core ( use foam if you don't do a lot of composite work.
4. Replace outer skin.
5. Fair and paint.

#5 Ncik

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Posted 25 May 2012 - 01:10 AM

Any photos of the damage? Injecting resin into honeycomb will add weight but not fix anything. From your description is sounds like you've sheered the skin core bond. There are photos in the AC forum of oracle fixing the same problem on Bundy's boat and there is no easy fix.

1. Carefully cut away outer skin and core.
2. Patch any damage to inner skin.
3. Replace core ( use foam if you don't do a lot of composite work.
4. Replace outer skin.
5. Fair and paint.


+1

#6 Soley

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Posted 25 May 2012 - 03:22 AM

+2

#7 Major Tom

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Posted 25 May 2012 - 06:17 AM

The only way nomex dents is by the core failing under the localised compression, so if there if a dent, then you do not have a sandwich structure in that area. I would remove the outer skin in the damaged area, use a stanley knife or a fein multimaster, do not cut through the inner skin. Remove the patch, of outer skin, make sure there is no moisture in the damaged core area. You can then either replace the core with corecell, airex etc or simply fill the damaged cells with a resin, glass bubble mix. This weighs so little it is the option I would use most of the time. Once the core is sorted and the epoxy is cured then do your prep for the final laminate, making sure that the completed repair will not be proud of the original laminate.

#8 Johannos

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Posted 27 May 2012 - 01:04 PM

Any photos of the damage? Injecting resin into honeycomb will add weight but not fix anything. From your description is sounds like you've sheered the skin core bond. There are photos in the AC forum of oracle fixing the same problem on Bundy's boat and there is no easy fix.

1. Carefully cut away outer skin and core.
2. Patch any damage to inner skin.
3. Replace core ( use foam if you don't do a lot of composite work.
4. Replace outer skin.
5. Fair and paint.



glue the honeycomb in with some slightly thickened epoxy,
layup the outer skin on a piece of mylar, place against the core,
vac-bag it.
The piece of mylar will give you a smoother surface to begin fairing with, and will prevent the glass to be pushed in the cells too much.




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