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  #1  
Old 12-27-2020, 01:55 PM
KayS KayS is offline
 
Join Date: Jul 2009
Location: lake constance
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Default low pressure area at the lower rudder fairing?

Hi All,

hope everybody survived excess caloric intake and exhausting family members at christmas. here comes a question to the guys with some knowledge on aerodynamics:

is the tail end of the rudder's lower fiberglass fairing on an RV7 (where most RV's have their tail light) a low pressure area? where the pressure is lower than... let's say the cabin?

so if one runs a tube from the cabin to the tail that sticks out directly at the tail light, any fluid that enters the tube in the cabin gets sucked out in the air. without painting parts of the aircraft yellow for example.

Cheers
Kay
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  #2  
Old 12-27-2020, 01:59 PM
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rolivi rolivi is offline
 
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I'm just imagining all the ways this thread can go seriously wrong.
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  #3  
Old 12-27-2020, 02:21 PM
KayS KayS is offline
 
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Quote:
Originally Posted by rolivi View Post
I'm just imagining all the ways this thread can go seriously wrong.
it probably will, but that's ok. let's focus on the scientific part of the question.
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  #4  
Old 12-27-2020, 02:54 PM
terrye terrye is offline
 
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Default low pressure area at the lower rudder fairing?

If you run the tube down the pilot side gear leg and exit out of the trailing edge of the wheel pant, the run is shorter and gravity helps
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  #5  
Old 12-27-2020, 04:26 PM
KayS KayS is offline
 
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Terry: had that in mind but i'm afraid that the propellers slipstream is still effective in that area and the yellow stuff will be all over the place.
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  #6  
Old 12-27-2020, 05:28 PM
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avrojockey avrojockey is offline
 
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Location: Appleton, WI
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Most relief tubes I've seen have a Venturi at the exit to facilitate the suck. Also long runs of tubing would certainly be harder to maintain
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Last edited by avrojockey : 12-27-2020 at 05:31 PM.
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  #7  
Old 12-27-2020, 05:49 PM
Cumulo Cumulo is offline
 
Join Date: Apr 2015
Location: KHMT
Posts: 97
Default aerodynamics

Humm, a bottom mounted antenna that would serve that function could easily be designed. The gear leg is mentioned. Possible.

All of the trainer aircraft of WW2 that I am familiar with such as PT-19's, BT-13's, etc had that comfort feature. The exit was a small venturi device.

The cockpit of a low wing a/c typically has a quite low pressure, so the boys long ago made sure the flow would be in the right direction by the use of the little venturi. It might be necessary in an RV as well. There is no generally low pressure area below or behind an RV that comes to mind. Pressure on the fuselage surface more or less increases as you go aft from the wing.

I speculate that the exit would need be well away from any following surface and would need an augmenting feature to lower the pressure.
Ron
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  #8  
Old 12-27-2020, 06:32 PM
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Bill Boyd Bill Boyd is offline
 
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Quote:
Originally Posted by rolivi View Post
I'm just imagining all the ways this thread can go seriously wrong.
"...glider guys... have a 12" tube that can be extended down through the belly..."

And it begins
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  #9  
Old 12-27-2020, 06:52 PM
moosepileit moosepileit is offline
 
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A glider gear up/belly landing at this most inopportune time is now the thing I fear most in aviation.

#nogrommet
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  #10  
Old 12-28-2020, 02:11 AM
KayS KayS is offline
 
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Location: lake constance
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thanks for the hints about freezing. a tube blocked by frozen liquid is probably not so cool when you wanna use it. solution could be to flush the system with a small amount of antifreeze, the stuff we use in our cars, prior actual use. pee entering the tube has around 98 F, that temperature should do the job then.

as some mentioned, the trailing edge of the rudder or rudder fairing is not optimal. i'm going to try to exit the tube somewhere at the tail wheel. what could be an augmenting feature at the exit?
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