Cowl inlet baffling

[Dugaru]

So my RV-9A, which I did not build, has baffling strips at the top and bottom of each cowl inlet. The baffling material is held on with aluminum clamping strips secured with screws and nutplates.

Today the top right assembly decided it did not want to go flying, and tried to exit the aircraft while I was taxiing! The aluminum clamping strip dropped on top of the alternator pulley, making a scraping noise that alerted me to some sort of problem. After decowling we quickly found the strip, with damage from contact with the pulley:

Two questions:

1. Is this a Vans part, or did my builder likely fabricate it? I can only find a strip for the bottom of the cowl opening, but I’m not good searching the Vans store.

2. What’s the best way to secure these assemblies? I don’t have a lot of confidence in screws/nutplates, since the screws apparently just worked their way loose.

Thanks for any suggestions!

 

[BobTurner]

I think, but am not positive, that on the 10 this part came from Vans. However, a do-it-yourself replacement should not be difficult.
I think having a screw back out of a nut plate is near impossible (unless the nut plate was too large/screw too small). Much more likely is that during re-assembly of the cowling, the top right cowl was momentarily placed too low/too left, and the aluminum go caught under the pulley (or more likely imho, the engine flywheel). The aluminum is so soft you may not have noticed it bending as you wrested the cowl into place. But you heard it on subsequent start up.

 

[PhatRV]

The builder has to fab this part to clamp the baffle material at the inlet. Here is a snapshot for the instructions for the baffle kit shipped from Vans. It is something you build with scrap aluminum

 

[Dugaru]

I think, but am not positive, that on the 10 this part came from Vans. However, a do-it-yourself replacement should not be difficult.
I think having a screw back out of a nut plate is near impossible (unless the nut plate was too large/screw too small). Much more likely is that during re-assembly of the cowling, the top right cowl was momentarily placed too low/too left, and the aluminum go caught under the pulley (or more likely imho, the engine flywheel). The aluminum is so soft you may not have noticed it bending as you wrested the cowl into place. But you heard it on subsequent start up.

This is certainly possible. But the screws on the other one were very loose. Perhaps it was a mismatch, as you suggest.

 

[BobTurner]

This is certainly possible. But the screws on the other one were very loose. Perhaps it was a mismatch, as you suggest.

Or, because nut plates tend to be quite tight, the builder ran a tap thru it and over did it. screws in a nut plate should be impossible to turn by hand.

 

[Dugaru]

The builder has to fab this part to clamp the baffle material at the inlet. Here is a snapshot for the instructions for the baffle kit shipped from Vans. It is something you build with scrap aluminum

Thanks, that’s very helpful!

 

[Dugaru]

Or, because nut plates tend to be quite tight, the builder ran a tap thru it and over did it. screws in a nut plate should be impossible to turn by hand.

This is an extremely persuasive theory. Time to fab some new clamping strips!