RV-7 cowling issues - anyone else seen this?

Hi everyone,

I bought my RV-7 a year ago and have been enjoying it. On my flight today, I noticed that air is flowing out of the top of the cowling and warping the cowling. See attached photo of the cowling both in flight and on the ground.

I'm concerned that this may eventually pull out the screw locks that hold the cowling in place there. I'm also concerned that this airflow may introduce additional drag.

Has anyone else seen this? Is it a known problem? Are there any fixes?

Thanks,

Stephane

Cowl fasteners

Without seeing the aircraft in person, it appears your cowling fasteners are too far apart. What is the measured distance between them?

That is sometimes called "pillowing". It can be addressed by adding more fasteners or stiffening the cowling. If you're connected to any builders in your area, they could probably look at the installation and tell you how much work will be required to correct the issue. At worst, it probably wouldn't be more than a few hours work for an experienced builder.

A picture or two showing the upper firewall flange with the top cowl removed would be a starting point if you'd like more detailed, specific advise.

Fastener spacing too large and the cowl was not pulled down tight when they were drilled. This yields a static pillow on the ground and aggravated with internal pressure in flight.

IMO, it would take reinstallation of upper cowl, and closer spaced fasteners. The interface between the upper and lower cowl will be affected. It is not a quick fix.

BTW - I had to relocate some fasteners on my cowl during the build process. The holes were filled with layers of reinforcement (fiberglass cloth) and epoxy, then sanded down from both sides. The repair was invisible from either side when done.

It can be done with some work and repainting, it is not rocket science just some labor and attention to detail.

Steph,
I have the same effect on my 7A (I built it). Yep, it gets my attention, but after 1200 hobbs hours it has not been an issue. I may apply an underlying strip of aluminum to reinforce it at some point.

Here is the visual explanation.

akmeesan said:

... Has anyone else seen this? Is it a known problem? Are there any fixes? ...

Click to expand...

I experienced this in cruise on my newly-finished RV-8A using Skybolt quarter-turn fasteners at the high end of the manufacturer's spacing recommendation.

The fix was to lay down two layers of carbon fiber on the inside of the cowl along the line of fasteners. End of problem -- hadn't thought about it since.

--
Joe

Thank you to everyone for your responses, very helpful. I will live with it for now, but I'm looking to do some other body work in the near future and will add this in.

If anyone knows a pro builder in the Phoenix area, that would be great.

Thanks again,

Stephane