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  #1  
Old 05-12-2014, 07:17 PM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
Posts: 2,349
Default RV-7 cowling exit bump

Seeing other posts on VAF has motivated me do do some smoothing on my RV7 O-360 cowling outlet.

I can make it two ways, first is more of a bump on the bottom of the firewall. Screws/ nutplates on the bottom of the firewall and riveted to the firewall.
Poster board mock-up:



Choice #2 is more of a ramp directing air into the exit. Screws/nutplates for the bottom and adel clamps to the engine mount for the top.



#1 is more permanent leaving less room for experimentation than option #2. Hoping to start cutting some metal tomorrow and appreciate any input.
Thanks!
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  #2  
Old 05-12-2014, 08:11 PM
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lostpilot28 lostpilot28 is offline
 
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Looks a lot like mine! Just be glad you don't have the -A model! It was a pain to get the curved aluminum in there without looking horrible. It ended up looking pretty good and has held up well over the past year.

Make sure to report back with your results after a test flight.
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  #3  
Old 05-12-2014, 08:57 PM
crabandy crabandy is offline
 
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What were your results? Did you make the bump or the ramp?
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  #4  
Old 05-12-2014, 09:34 PM
BillL BillL is offline
 
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Location: Central IL
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Here is what I am doing. Ready for some screws so it can be removed. I just installed it before mounting the engine so riveting would be easier. I hope it will work

I made a hole template to make it easier to construct air management radius when the time comes.

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  #5  
Old 05-12-2014, 09:47 PM
glenn654 glenn654 is offline
 
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All of the exit ramps I have seen have open ends, do any of you think the ramp would be any more efficient if the ends were closed as much as possible?

Glenn Wilkinson
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  #6  
Old 05-13-2014, 06:43 AM
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DanH DanH is offline
 
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Andy, choice 1 or 2 is probably a matter of convenience. Either way, I'd suggest that you fabricate from stainless sheet and extend it 12 inches aft of the firewall, over the aluminum belly skin.

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  #7  
Old 05-13-2014, 08:00 AM
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airmel airmel is offline
 
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Location: SC
Posts: 156
Default My "firewall fairing" -



It is .025 aluminum and the nut plates are on the fairing instead of the firewall.

FWIW: My husband has been flying with one similar to your option 2 on his 6 for many years and has not had any issues with the skin just aft of this area. He recently changed to one like option 1...
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  #8  
Old 05-13-2014, 09:20 AM
krw5927 krw5927 is offline
 
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I've been considering this mod. Does anyone have actual before and after data on temps and/or speeds?
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  #9  
Old 05-13-2014, 09:46 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by airmel View Post
[IMG] My husband has been flying with one similar to your option 2 on his 6 for many years and has not had any issues with the skin just aft of this area. He recently changed to one like option 1...
Extending the fairing, in stainless, is a fire protection measure.
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  #10  
Old 05-13-2014, 10:31 AM
crabandy crabandy is offline
 
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Thanks for the replies, I made the drive to airparts and picked up some .017 stainless from their scrap bin. I like the fire protection.
Melinda, is your fairing only attached at the bottom? The tension in the curve keeps it from rubbing on anything...
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