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Inside the cowl paint

maniago

Well Known Member
What are you guys using for primer/paint for the inside of the fiberglass cowl and cowl atch strips?? Logic dictates that it has to be some kind of high temp paint, but the James instructions just say epoxy, so I'm torn. I really have no idea how hot it'll get under the cowl - I'm also running a plenum.

I still have a bunch of Akzo 463-12-8 and I love the stuff, but its not high temp. In fact I cant get a data sheet that says what its temp tolerance is. I bought some rattle can high temp engine paint, but its enamel and I vaguely rem that enamel cant take flexing.

Thoughts?
 
What I did...

Thin epoxy brushed on to fill, Vans reflective stick on foil over that.
 
I just did this - used epoxy primer to stick to the resin and urethane 2k top coat (white). Areas with hot parts near are getting vans reflective material and some 1/16" fiberfrax under the foil where the really hot parts are within 2". That cowl won't take a lot of heat and don't expect it to get that hot. Tg of the resin considered.

I can not say how well it works, but followed DanH's technique and he says his works well.

So one thing, definitely use the neat epoxy and squeegee it on to fill any and all pin holes and seal the weave. What ever you use won't look very good if you don't. If you want it really smooth, then finish (squeegee)with some micro, but it will take a lot of sanding to look smooth.

I know Will James was experimenting with some fine weave for the inside to facilitate a smooth surface. I got an early model with no core material and raw weave was easily visible. Maybe yours will be easier :D
 
I used West Systems epoxy with white pigment (Aircraft Spruce). I did not thin the epoxy but used a heat gun to warm the cowl a bit as I applied it.
Stewart Willoughby, 6 wiring/panel.
 
I just did this - used epoxy primer to stick to the resin and urethane 2k top coat (white). Areas with hot parts near are getting vans reflective material and some 1/16" fiberfrax under the foil where the really hot parts are within 2". That cowl won't take a lot of heat and don't expect it to get that hot. Tg of the resin considered.

I can not say how well it works, but followed DanH's technique and he says his works well.

So one thing, definitely use the neat epoxy and squeegee it on to fill any and all pin holes and seal the weave. What ever you use won't look very good if you don't. If you want it really smooth, then finish (squeegee)with some micro, but it will take a lot of sanding to look smooth.

I know Will James was experimenting with some fine weave for the inside to facilitate a smooth surface. I got an early model with no core material and raw weave was easily visible. Maybe yours will be easier :D

My cowl is only a few months old, I have the core material. Not worried at all about the inside being smooth - is there something I dont know here? (my cowl outside is as smooth as glass - no pin holes etc, not sure if that was what you were referring to - its smooth enough to go straight to primer).

What is "neat epoxy"? Not heard that term before.

I like the idea of reflective and even fibrax in the obvious hot spots.....
 
My cowl is only a few months old, I have the core material. Not worried at all about the inside being smooth - is there something I dont know here? (my cowl outside is as smooth as glass - no pin holes etc, not sure if that was what you were referring to - its smooth enough to go straight to primer).

What is "neat epoxy"? Not heard that term before.

I like the idea of reflective and even fibrax in the obvious hot spots.....

If your interior is smooth, and no pinholes, HURRAY!!! You are way ahead. Maybe all you want is a scuff, prime, top coat. I am wishing I had swapped with Will for a new one when he offered :eek:

Neat epoxy, no additives or dilution. I sounds like you won't need this.

The fiberfrax will go directly on the spots to be protected, and covered with the self adhering Vans reflective material. Other areas I am just using the reflective material direct to the paint.
 
Neat epoxy, meaning unthinined. Vans says to thin with some acetone to help fill pin holes, but if you work it around well with a squeegee it will fill without thinning and avoid potential weakening of the fiberglass from the acetone

E
 
Ok thanks guys. Neat as in scotch neat. Not heard it allied to epoxy, but I get it now.

For sure you should have traded yours Bill. My top side cowl is smooth enough to see my face in it (not a pretty sight, but you get the idea!) The inside is a bit like an absorbent dish cloth in texture. Smooth in that way and also shiny, but not smooth enough for reflections. Both are devoid of pin holes - very much better than any fiberglass part with gelcoat Ive ever seen.

I'll scuff and prime with Akzo then and relieve Vans of some of that a reflective foil. Does it have a proper name and number, or just search Vans for reflective foil?
 
Three coats of white tinted epoxy (West Systems) with a tiny bit of acetone to thin looks like this after being rolled/brushed on.
Nice hard shell coating. Good visibility of any drips/leaks. Easy to wipe clean with some soapy solution.
This is before laying down the reflective aluminum and heat shielding from Van's.

IMG_3720-M.jpg


More photos here.
 
I envy you guys with no pinholes to fill. My cowl (green glass) resembled a window screen in spots. The inside was actually less porous than the exterior, though I can't say the same for the texture. Took two applications of epoxy to kill almost all of the holes.

I squeegeed a portion of the inside of the cowl each time I had a little epoxy resin left over from another task. Most of it was coated while glassing in the windscreen. Thinking about a coat of paint for the interior but not convinced that the pros outweigh the conns. It's sealed, and that was my primary concern.
 
....

I squeegeed a portion of the inside of the cowl each time I had a little epoxy resin left over from another task. Most of it was coated while glassing in the windscreen. Thinking about a coat of paint for the interior but not convinced that the pros outweigh the conns. It's sealed, and that was my primary concern.

One of the "pros" is that a coat of white paint would make it brighter in there and easier to inspect stuff and look for leaks.
 
Three coats of white tinted epoxy (West Systems) with a tiny bit of acetone to thin looks like this after being rolled/brushed on.
Nice hard shell coating. Good visibility of any drips/leaks. Easy to wipe clean with some soapy solution.
This is before laying down the reflective aluminum and heat shielding from Van's.

I'm doing mine this way!
 
I also use west systems epoxy to close and seal the cowling.
After that, I paint on a couple coats of Diamond Brite aluminum paint.
It creates a nice oil and fuel proof surface and since it has a high aluminum pigment content, it also acts as a heat shield.
On my last RV8, I didn?t install the foil heat shield and saw no adverse effects due to heat inside the cowling.
YMMV
 
Just finish it like the outside...seal, prime, paint. Maximum adhesion of the reflective aluminum foil depends on surface quality.
 
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