How to protect the inner cowl surfaces?

[Bill Wightman]

I've been told that over time, engine oil will penetrate the inner cowl surfaces and soak into the honeycomb core. The pre-preg glass used here does look like it could be porous to me, so this looks like a valid concern.

So, do any of you here know what might be a good choice for finishing/protecting the inner surfaces of the engine cowl? Something that will seal the surface, stand up to high heat, and remain impervious to fuel/oil etc?

I was thinking about epoxy paint, and just roll it on with a thin nap roller...

[Mike S]

Yes, straight epoxy, also reflective foil from Vans.

Try a search, this was covered more than once in the fairly recent past.

[f1rocket]

I took some spare epoxy paint and applied it until all the pin holes were filled.

[Rick6a]

Originally Posted by Bill Wightman

....do any of you here know what might be a good choice for finishing/protecting the inner surfaces of the engine cowl? Something that will seal the surface, stand up to high heat, and remain impervious to fuel/oil etc?

I was thinking about epoxy paint, and just roll it on with a thin nap roller...

This topic along with dozens of other very helpful tips is covered in Van's "27 Years of the RVator." Typically the builder brushes in West System epoxy, some builders thin it down with up to 50% acetone. I applied it in stages using leftover resin after other projects were done. Sealing the inner cowl will not only keep liquids from soaking through the honeycomb but also provides a good base for the reflective foil tape to adhere to.

[rv72004]

I dont really agree with the oil soak. Mine is bare plus foil and still looks new. 100hrs. I have a new xp360 that does not leak oil . I guess if youre using a old engine with lotsa leaks then paint/epoxy will help. Otherwise leave as is . Then again if I had one of them "pink" ones I might be persuaded to paint inside.....Luckily mine is the older green type cowl.

[lostpilot28]

Sorry to hijack this thread, but is the reflective foil required? This is the first mention of it that I've heard. Where is it applied?

[Mike S]

Sonny, the foil is to keep the heat from the exhaust system from damaging the cowl.

Damage can range from none, to paint blistering, to actually charring the inside of the glass.

Depends on lots of things, engine, exhaust system, etc.

I would suspect a 4 to be more prone to heat damage than a 9, just due to being cowled much tighter.

Hope this helps.

[lostpilot28]

Hi Mike,
Thanks, that helps. Is there a rule as to how far away the exhaust should be before needing to use the foil? My pipes are very close down at the bottom by the nose gear leg.

[rv72004]

Originally Posted by lostpilot28

Sorry to hijack this thread, but is the reflective foil required? This is the first mention of it that I've heard. Where is it applied?

Most definitely. Mine was slightly damaged by heat before applying the foil.