Bubblehead

Bubblehead

Well Known Member
My 450 hr 7 year old -8 came complete with some delaminations of the inside surface of the lower cowling. I just changed to a AWI 4-into-1 exhaust and want to reapir these areas and then protect the lower cowl from heat. I've read some other threads on the forum about reflective tape, etc., but I'm more concerned about the F/G repair.

I didn't build this plane, but I have a lot of experience with Epoxy and glass, having built most of the airframe on a Long-EZ. (That's another story for another time) I started repairing the cowl last night by cutting away the bubbled up fabric and then using a sanding disk to feather back the edges to where the skin is still bonded to the honey comb core.

I then lightly sanded the entire interior surface and wiped it down with thinner, which I will follow up with alcohol. This morning I mixed up some Aeropoxy and dabbed it in various places to test compatibility with the existing skin and core.

My question has to do with the new layup over the core. I think core usually is laminated with prepreg and vacuum bagged and I won't be able to do that here. I think they also use some thickened epoxy rolled on the core before the skin is put into place.

Can anyone offer some suggestions for good technique dealing with the honey comb core?
 
<<I think they also use some thickened epoxy rolled on the core before the skin is put into place. Can anyone offer some suggestions for good technique dealing with the honey comb core?>>

I've not seen epoxy rolled on honeycomb prior to prepreg. Maybe sometimes, can't be sure. It is common to fill the honeycomb in the area of attachment hard points.

Why not treat it like filling foam surface on the EZ? Wipe dry micro in the comb and do the layups. Very little weight, and it would really stiffen up the honeycomb if it has suffered any heat damage.
 
AC 43.13-1B

Has good instructions on how to repair honeycomb core, Page 3-2 and 3-3. Good enough for the Feds good enough for me.
 
DanH - good idea on filling the honeycomb. I especially like the idea of stiffening up the areas that may have some heat damage.

I think the thickened epoxy was used so fillets were formed around the thin walls of the honeycomb, but that would require the layup to be done upside down. Fabric/epoxy first, then honeycomb. In this case I have to do the layup with fabic on top of the honeycomb.

AMURRAY - I'll check AC 43.13 Great suggestion.
 
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