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  #11  
Old 06-14-2018, 12:35 AM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
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Thanks for all the other upper cowl flap suggestions, if I make an upper cowl flap I would like it to be controlled from the cockpit. Still thinking and waiting.

Pretty sure a couple flights without the oil door will tell me what the extra exit area on the upper cowl will or won’t do.
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  #12  
Old 06-14-2018, 12:40 AM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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Quote:
Originally Posted by PerfTech View Post
….We have had many customers mount our cowl flaps on the sides of the lower cowl as well as on the top. They report back many advantages, Lower ground operations temperature being one. Another is even lower climb out temperatures, due to the fact that the pressure in this configuration is much lower on top than on the bottom. We have seen most everything possible with flaps on top, sides, bottom and all of the above in one installation. The top mounted location is very popular in Brazil on the RV-10s. Its all good!
Thanks, Allan..
Allan,
Not sure what is meant by “pressure in this configuration is much lower on top than the bottom?” Can you please explain?
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  #13  
Old 06-14-2018, 04:45 AM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
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Quote:
Originally Posted by crabandy View Post
Allan,
Not sure what is meant by “pressure in this configuration is much lower on top than the bottom?” Can you please explain?
When you're climbing, you're at a fairly high angle of attack. The pressure gradient around the airplane in that attitude creates a high(er) pressure area on the bottom of the cowling than in a normal flight attitude. This reduces cooling flow.

In that climb attitude, the top of the cowling sees a lower than normal dynamic pressure, and the sides are largely unchanged, at least in theory.

So, you may see more cooling airflow from equivalent sized vents on the sides or top of the cowling in a climb attitude compared to the same vents on the bottom cowl.

You'd need to test on your particular aircraft to definitively prove this.
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  #14  
Old 06-14-2018, 06:14 AM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
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Andy, the optimum top outlet location is not back by the oil door. Think of airfoil pressure plots at high AOA.

Peter Garrison's Melmoth 2 used updraft cooling and top exits. Here, read the first section: http://www.melmoth2.com/texts/CoolingFlow.htm
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  #15  
Old 06-14-2018, 08:34 AM
EXflyer EXflyer is offline
 
Join Date: Jan 2016
Location: Chiloquin OR
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Quote:
Originally Posted by DanH View Post
Andy, the optimum top outlet location is not back by the oil door. Think of airfoil pressure plots at high AOA.

Peter Garrison's Melmoth 2 used updraft cooling and top exits. Here, read the first section: http://www.melmoth2.com/texts/CoolingFlow.htm
Had forgotten about him quite a fellow loved reading his exploits.
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  #16  
Old 06-14-2018, 10:07 AM
Gliderguy89 Gliderguy89 is offline
 
Join Date: Nov 2006
Location: Dansville, NY
Posts: 4
Default Fuel perking?

I'm in the habit of opening the oil access door after lending. Amazing amount of hot air exits and I suspect goes a long way to keeping fuel lines and the carb cooler for departure. 5psi pressure from the aux pump on the fuel lines also helps delay any perking.
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