RV-7 Lower Cowl Modification

[yahugh]

Prior to beginning the conversion from a Subaru engine to an O-360, the previous owner had installed a variable cowl flap. I've removed the flap and am now evaluating the situation. As shown in the pictures, the clearance between the new exhaust system and the cowling appears inadequate. I plan to enlarge the existing opening to accommodate the new exhaust system. Basically, I want to restore the cowling to its "stock" configuration with a fixed exhaust ramp (or whatever the proper term is for that bump in the lower, aft cowling). Does Van's sell a separate fiberglass piece that I can bond on or will I need to fabricate something? If the latter, then I guess I would need to make some sort of mold and layup the part. Any pointers on how to do that would be appreciated!

(Don't get me started about the reverse NACA ducts! They're going to be removed as well.)

 

[johnbright]

... I want to restore the cowling to its "stock" configuration with a fixed exhaust ramp (or whatever the proper term is for that bump in the lower, aft cowling). Does Van's sell a separate fiberglass piece that I can bond on...

Sounds like you want what the Van's store calls "FAB-6-SCOOP-360-1". It’s for vertical induction.

BTW VAFers commonly refer to the aft part of the scoop that accommodates the exhaust pipes as the "coal shovel".

 

[yahugh]

Sounds like you want what the Van's store calls "FAB-6-SCOOP-360-1". It’s for vertical induction.

BTW VAFers commonly refer to the aft part of the scoop that accommodates the exhaust pipes as the "coal shovel".

Thanks for the suggestion! It seems like this also addresses some issues I have with the induction system, which is probably a topic for a separate thread.

 

[johnbright]

Thanks for the suggestion! It seems like this also addresses some issues I have with the induction system, which is probably a topic for a separate thread.

The link you shared is to "FAB-6-SCOOP-360-1" at the Van's store so we are saying the same thing.

 

[bjdecker]

Those subbie-folks did some interesting things....

There looks to be enough clearance laterally. Adjust the right (copilot side) exhaust stack to be parallel to the longitudinal axis of the aircraft -- it appears to be toe'd out a bit to the right side.

Movement left/right at start-up & shut down is about 1" at that location.

Personally, I'd remove all of the material that forms "the coal shovel" -- about 8" forward of the current terminus. Then layup a flat transition with two "humps" for the exhaust stacks, and add a cowl flap in between the humps.

Worth a couple of additional knots...

 

[wirejock]

I would find another 7 builder at the airport and ask if you can layup that part using their cowl as a mold. Protected of course.
Apply a section of protection film. Apply several coats of wax or pva. Layup a couple layers. Pop it off. Remove the film. Buy them some beverages and glass it onto your cowl.
Modifications easily done from that point.

 

[yahugh]

I would find another 7 builder at the airport and ask if you can layup that part using their cowl as a mold. Protected of course.
Apply a section of protection film. Apply several coats of wax or pva. Layup a couple layers. Pop it off. Remove the film. Buy them some beverages and glass it onto your cowl.
Modifications easily done from that point.

Genius!

 

[johnbright]

Oh, I think I see now, you already have the induction intake snout, just you need the coal shovel or to two humps like the latest RV-14 for the tail pipes.