Repairing heat-blistered paint on cowling?

alfadog

alfadog

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alfadog
I need to do minor repairs and repaint the fiberglass cowlings of my Arrow.
  • Crazing on the top cowling.
  • Deep scratches on top from letting the wind catch it when I had it off.
  • Heat blistering or paint separation on the lower cowling(s).
I am very familiar with fiberglass as I used to do it for a living many years ago, first building cars for Glassic Motors and then as foreman of a fiberglass shop that did mostly high-end government contract work (Pratt & Whitney, NOAA, NASA, USN, USCG, etc.) That was over 30 years ago but I can still work with the crap when I want to :D

I also used to paint my own cars as part of the restoration process and have painted with Imron, which is what is on the Arrow.

So I am good with the repairs and the paint but not so sure of how to handle the heat damage. Obviously neither was the fellow who last painted it.

Any suggestions?

Oh, work will be signed off by A&P/IA as needed.
 
Are you sure that all of the original heat shields are still in place? The little offset mountings that were installed by OEM were flimsy at best and many have simply fallen off over the years.

alfadog said:
I need to do minor repairs and repaint the fiberglass cowlings of my Arrow.
  • Crazing on the top cowling.
  • Deep scratches on top from letting the wind catch it when I had it off.
  • Heat blistering or paint separation on the lower cowling(s).
I am very familiar with fiberglass as I used to do it for a living many years ago, first building cars for Glassic Motors and then as foreman of a fiberglass shop that did mostly high-end government contract work (Pratt & Whitney, NOAA, NASA, USN, USCG, etc.) That was over 30 years ago but I can still work with the crap when I want to :D

I also used to paint my own cars as part of the restoration process and have painted with Imron, which is what is on the Arrow.

So I am good with the repairs and the paint but not so sure of how to handle the heat damage. Obviously neither was the fellow who last painted it.

Any suggestions?

Oh, work will be signed off by A&P/IA as needed.
Click to expand...
 
You can do this with out any A&P to return to service.

CFR 43. A. (c) (9) Refinishing decorative coating of fuselage, balloon baskets, wings tail group surfaces (excluding balanced control surfaces), fairings, cowlings, landing gear, cabin, or cockpit interior when removal or disassembly of any primary structure or operating system is not required.
 
wabower said:
Are you sure that all of the original heat shields are still in place? The little offset mountings that were installed by OEM were flimsy at best and many have simply fallen off over the years.
Click to expand...

Good idea. I will check the parts manual and then the airplane. Assuming they are in place, any ideas on improving them or ??
 
Tom-D said:
You can do this with out any A&P to return to service.

CFR 43. A. (c) (9) Refinishing decorative coating of fuselage, balloon baskets, wings tail group surfaces (excluding balanced control surfaces), fairings, cowlings, landing gear, cabin, or cockpit interior when removal or disassembly of any primary structure or operating system is not required.
Click to expand...

Thanks.
 
I don't have the answers, but recently saw a similar problem on an Arrow. Then I found a problem-in-the-making on my Cessna 180 due to one end of the offset having failed at a bend. Can you can isolate the surface areas of the cowling that appear to be most-affected and then work backwards to determine the specific source of the problem?

alfadog said:
Good idea. I will check the parts manual and then the airplane. Assuming they are in place, any ideas on improving them or ??
Click to expand...
 
wabower said:
Are you sure that all of the original heat shields are still in place? The little offset mountings that were installed by OEM were flimsy at best and many have simply fallen off over the years.
Click to expand...
That's my thought -- if the heat is blistering the paint, there's an underlying problem needing correction or you're just going to have to do this again.
 
Strip, fill, sand, primer, paint...


You know what you are doing.
 
Skylane81E said:
Strip, fill, sand, primer, paint...


You know what you are doing.
Click to expand...

Yes, thanks, that part I know. The heat thing, not so much.

I know when I used to paint cars with acrylic enamel we would add a "rubberizing agent" (don't recall the better term) to paint flexible bumpers, etc. So I was wondering if there is a high-temp polyurethane paint or additive for this heat thing?

edit: it is called a "flex additive". GIYF.
 
I have found that well applied Imron should hold up to a LOT of heat.

We had an exhaust pipe slip and burn a hole through a cowling, the paint was fine all the way up to where it burned.
 
Ron Levy said:
That's my thought -- if the heat is blistering the paint, there's an underlying problem needing correction or you're just going to have to do this again.
Click to expand...

It's a chronic problem with the arrowIII they simply don't have enough airflow thru the cowl.
 
I've seen aluminum tape applied inside Arrow, Aztec, etc.
cowlings in areas showing heat distress. I've recently seen some
paper thick composite heat shield material. Maybe source some
from your old contacts.
Dave
 
d.grimm said:
I've seen aluminum tape applied inside Arrow, Aztec, etc.
cowlings in areas showing heat distress. I've recently seen some
paper thick composite heat shield material. Maybe source some
from your old contacts.
Dave
Click to expand...

Yes, I was thinking of something like that. Thanks.
 
If you know the process, then fair and fill as normal and repaint. The plasic is going to be heat damaged, but there's nothing to do about that really and since it's not structural it doesn't matter. When it's all fixed head to one of the yacht exhaust shops and get a piece of sheet lagging that will cover the hot spot. On the inside of the cowl, take a few flat head screws and stick them through a tab of fiberglass down to the head. Now take those and bond them inside the cowl in a pattern around, over the hot spot. Put the lagging down over the screws and pushing it through and secure in place with some nuts. Since very likely that hot spot is caused by an exhaust pipe, you can go get some exhaust insulation wrap tape around the pipe there and it may be enough.
 
Henning said:
If you know the process, then fair and fill as normal and repaint. The plasic is going to be heat damaged, but there's nothing to do about that really and since it's not structural it doesn't matter. When it's all fixed head to one of the yacht exhaust shops and get a piece of sheet lagging that will cover the hot spot. On the inside of the cowl, take a few flat head screws and stick them through a tab of fiberglass down to the head. Now take those and bond them inside the cowl in a pattern around, over the hot spot. Put the lagging down over the screws and pushing it through and secure in place with some nuts. Since very likely that hot spot is caused by an exhaust pipe, you can go get some exhaust insulation wrap tape around the pipe there and it may be enough.
Click to expand...

Thanks.
 
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