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Cowl paint blisters

C

cholladay

Well Known Member
Well it did it again. First long flight after paint the RV10 blistered on the lower cowl. I used Hortons method of insulating the inside along the exhaust pipes and repainted. Today it did it again. I have always thought the CHTs were to high and that I was retaining to much heat around the engine. I am considering increasing my air exit area by adding lower cowl louvers. I'm thinking this would help the CHTs and help get rid of the heat blistering the paint.
Does anyone have any experience or a educated opinion on adding cowl louvers?
 
cholladay said:
Well it did it again. First long flight after paint the RV10 blistered on the lower cowl. I used Hortons method of insulating the inside along the exhaust pipes and repainted. Today it did it again.
Click to expand...

Curious.....what paint are you using? And it blisters along the pipes or all over like a rash?
 
Way off topic but related - ish :cool:

Some time ago - ( people of my age use that a lot I find )

I flew a Cherokee 6 for skydiving.

Oh my.......

This poor thing had a hard life, however when it came under my supervision it had a better life.

We ran 3 big singles - a Cessna 206, A Cherokee 6 and a Piper Lance (low tail) at the skydiving centre I was Chief Pilot at.

The Cherokee 6 was dubbed 'the nail'.

Poor thing.

6 big blisters (here's the topic ) on the cowling.

Bless her - at 10 grand the oil temp was red, the oil pressure was red, but that motor went to 3500 hours before overhaul !!!

Anyhow - what were you talking about ?

:D
 
Dan
It's acro Glo. The blisters range anywhere from 1/16 to 1/4". In your methods defense the part I insulated did well. It blistered away from the muffler this time. Maybe I should have insulated the entire bottom cowl.
 
cholladay said:
Dan
It's acro Glo. The blisters range anywhere from 1/16 to 1/4". In your methods defense the part I insulated did well. It blistered away from the muffler this time. Maybe I should have insulated the entire bottom cowl.
Click to expand...

Sherwin Williams Acry Glo? What filler, primer, etc is under it?

We had a Bucker here which blistered cowl paint near pipes, but I don't know what filler, primer, and topcoat was used.

FWIW I'm running pipes very close to cowl surfaces (as little as a 1/4" in places) and not burning or blistering straight epoxy fill followed by PPG DPLF, K36, and Deltron or Shopline protected with 1/16" fiberfrax under an aluminum foil reflector.

It's a radiant heat problem. Your in-cowl air temperatures are unlikely to be above the 200F ballpark.
 
I had the exact same problem with blistering paint on the lower cowl on both sides. I installed louvers on the bottom of the cowl, one on each side, and that took care of the problem. Also, my cht's now run approx. 30 degrees cooler.

Bob
 
Dan
It is sherwin Williams acro glo with a high build epoxy primer. I used the fiberfrax and aluminum after the first round of blisters around the pipe area. The new blisters are mostly around that area, minimal in the treated area, so I know the insulation helped.

Bob
Thanks for the input.

I've decided that I'm going to go with the louvers and fiberfrax all of the lower cowl instead of just around the pipes. I sure don't want to paint it a fourth time.

Now I just need to decide if I'm going to make the louvers removable or build them in.
 
Sitting in front of the rv10 at Oshkosh enjoying the airshow. I am glad to report the louvers I just added brought my CHT temps down by >30 degrees. I never once saw 400 even with a hard climb out from hot SanAntonio. I also had no paint blisters. Heat problem resolved.
 
cholladay said:
Sitting in front of the rv10 at Oshkosh enjoying the airshow. I am glad to report the louvers I just added brought my CHT temps down by >30 degrees. I never once saw 400 even with a hard climb out from hot SanAntonio. I also had no paint blisters. Heat problem resolved.
Click to expand...

How about some photos of your new louvers?
 
cholladay said:
Sitting in front of the rv10 at Oshkosh enjoying the airshow. I am glad to report the louvers I just added brought my CHT temps down by >30 degrees. I never once saw 400 even with a hard climb out from hot SanAntonio. I also had no paint blisters. Heat problem resolved.
Click to expand...
How and where did you end up installing them Chad?
 
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