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  #11  
Old 06-14-2018, 12:35 AM
crabandy crabandy is offline
 
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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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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
 
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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
 
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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
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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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  #17  
Old 06-24-2018, 08:36 PM
crabandy crabandy is offline
 
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Not exactly a hot day today with an OAT OF 82* F, but I had the time finishing an oil change and did a couple quick flights. I did a cold start and Flight to stabilize oil at 190ish and cylinders at 350ish followed by a taxi back and sit for 5 minutes. I then remove the oil door and did a similar flight, no consideration to CHT’s in the climb as I am mostly interested in ground/taxi cooling.

Oil door installed .3 Flight time.
Preflight initial lower cowling Temp: 84* (I suspect the temp probe reads 2 degrees hotter)
Pre-takeoff after taxi and runup: 150*
Stabilized temp in cruise: 170*
After landing/taxi/shutdown: 178*
5 minutes after shutdown: 162*

Oil door removed and heat soaked quick turn .3 flight time.
At engine start: 150*
Pre-takeoff after taxi and runup: 165*
Stabilized temp in cruise: 177*
After landing/taxi/shutdown: 174*
5 minutes after shutdown: 168*

I’m a little befuddled by the “5 minutes after shutdown” temps higher with the oil door off, but I did pull it into the hangar at the end of the flight whereas the oil door on sat outside in 15 knt winds.
The “after landing/taxi/shutdown” temps are promising; without the oil door temps went down instead of up after landing. More flights needed especially in 95*+ quick turn and long taxi senarios.
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  #18  
Old 06-24-2018, 08:42 PM
crabandy crabandy is offline
 
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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
Great read Dan! My large round inlets and plenum take up all the room on the front top of the cowling though! And he is cooling at high AOA in Flight, I’m aiming to cool better on the ground.

I have a really neat upper cowl flap idea (in theory) but not sure I shouldn’t just keep it simple by modifying the oil door that is already there.
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  #19  
Old 06-25-2018, 05:08 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
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Default -7 side cowl flap

I have seen a recent -7 build done by a local friend that is on the forums. He had some heating issues on his, which sounds to be a similar set-up. He installed one of the electric cowl flap doors on the left side of the lower cowling, and did a beautiful job of making it look "as designed". I believe his temp drops from that system where significant. Perhaps he may chime in, or I can contact him directly for more intel.
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  #20  
Old 06-25-2018, 05:54 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by crabandy View Post
Great read Dan! My large round inlets and plenum take up all the room on the front top of the cowling though! And he is cooling at high AOA in Flight, I’m aiming to cool better on the ground.

I have a really neat upper cowl flap idea (in theory) but not sure I shouldn’t just keep it simple by modifying the oil door that is already there.
Or just forget about it. The oil temps are great, with the oil door closed. CHTs apparently not an issue. The best cure for poor idle due to temperature is generally twofold; higher energy ignition, and reduce heating of the carb and fuel lines. I suspect most of that heating is radiant, so just blowing more air through the cowl is not gonna to get 'er done.
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