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Old 06-07-2019, 08:37 AM
7DeltaLima 7DeltaLima is offline
Join Date: May 2005
Location: Senoia, GA
Posts: 160
Default Delamination on engine cowl

Hi All,

RV 10 with about 1000 hours. I noticed the inside skin of the cowling had buckled and came loose, away from the honeycomb.

It does look like the heat shield that I put inside worked as the delam stopped where it was applied. Not sure why I didn't go higher up the wall of the cowling...

My question --- Is there anything special about laying a new piece of "skin" over the honeycomb?

Obviously need to clean up the area, make sure to get back to solid edge, etc. but just wanted to check on laying over the top of the honeycomb.

I'm don't recall any instance of the engine running hot, etc. so not really sure what caused this but I'll also take the heat shield up higher on the walls when it goes back.

RV-7A N277DL flying 4-15-2004
RV10 N277CK flying 5-28-2010
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Old 06-07-2019, 03:41 PM
Jpm757 Jpm757 is offline
Join Date: May 2013
Location: Sherman, CT
Posts: 793

That didn't happen overnight, something's been going on for quite some time. How often do you removed the cowlings for inspection? Appears you may have a serious exhaust leak.
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Old 06-07-2019, 05:24 PM
David Paule David Paule is online now
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435

I doubt if you'll be able to laminate a new bit of skin on that successfully. Problems will include cleaning the existing honeycomb surface and ensuring a fair laminate, not one that's pocketed at each honeycomb space. Even if you manage to do it, you'd probably want to use a high-temp epoxy there.

If you succeed, please tell us how you did it!

Perhaps Van's can make you a cowling section that you can splice in.

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Old 06-07-2019, 06:44 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 5,516

See how that core is butted together . . . I believe if the exterior is not damaged, you can simply grind down the inside and core to the exterior, then install replacement core (butt like the photo) and layup a cover like the rest of the cowl. Prewetting the cloth is needed.

Sourcing the materials may require some research.

Its just basic, but I was reminded with a recent project that the core becomes an insulator, so radiant heating of one side must be aggressively addressed as it has no avenue to cool itself.

The vertical section of the exhaust pipes of the 10 come pretty close to the walls.

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Old 06-07-2019, 07:24 PM
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9GT 9GT is offline
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966

Thats an EZ fix. Clean the area several times with lacquer thinned and flush out any oil in the honeycomb. Do this several times and thoroughly dry with light compressed air or better yet, a hair dryer. It will have to be COMPLETELY oil free and dry. Rough up the exiting perimeter of the missing fiberglass about 2" wide with 60 grit zircon paper. There can be no "shine" in the sanded glass when you wipe it clean of dust. Mix up some pure mixed epoxy and paint the edge you prepared with it and wet out 2-3 layers of fiberglass you have already cut to size as the patch. 8 mill clear clear visqueen works well for this. Mark the size and shape on the underside with a black sharpie. You will be able to see the line through the wet out glass to use as a cutting line. Use BID fiberglass. I like the Rutan Composite AS&S carries primarily because that is what I used building the Cozy MKIV. Now pour a little of the pure epoxy in a mixing cup and add just a little bit of micro in it to create a paint able slurry. Paint and stipple the slurry in the honeycomb and when you got it good and wet, lay the whetted and prepared cut out fiberglass patch on top. Stipple and paint it down so you have good contact with the honeycomb and the fiberglass edge. Check it with a light to ensure you have no air bubbles trapped under the fiberglass mating surfaces. Cover the repair with peel ply overlapping the edge of the patch by an inch and wet that down also and use a rubber squeegee to smooth everything out. Let cure fully and then peel off the peel ply. You will have a structurally sound repair that looks good. Make sure you extend the replacement reflective aluminum shield high enough to avoid another de lamination for the exhaust heat.
David C.
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Old 06-08-2019, 04:23 AM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 9,494

I'm with David, assuming the honeycomb isn't contaminated with oil. There is really nothing to lose by giving it a shot.

Suggested methods are good. Only detail I'd add is to grind or sand the existing inner skin to a feather edge where it transitions to the open core.
Dan Horton
Barrett IO-390
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Old 06-08-2019, 05:46 AM
7DeltaLima 7DeltaLima is offline
Join Date: May 2005
Location: Senoia, GA
Posts: 160
Default Thanks

Thanks for describing the method to repair. The inner skin wasn't punctured so the honeycomb wasn't exposed to oil and it appears to be in pretty good shape. Blackened a bit by the heat in a couple areas but still seems sound. The method to fix described above seems to add more strength to those areas.

I was headed down the recommended path based upon past advise here on a couple other fiberglass opportunities. I have cleaned / degreased / sanded, etc. and ready to go back with the fix (not reflected in the pictures). I hadn't had the pleasure to work with the honeycomb before so thought I'd validate with some that had actual experience rather than like my speculation.

Thanks for sharing your expertise / experience.

RV-7A N277DL flying 4-15-2004
RV10 N277CK flying 5-28-2010
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