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03-12-2014, 05:48 PM
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Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,357
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With a subsonic aircraft, the air ahead of the aircraft starts to move a bit before the aircraft gets to it. The air pressure above the wing is lower than the atmospheric pressure - that is a big part of why the wing develops lift. As the wing approaches the air mass, the air ahead of wing starts to rise a bit, as it is "sucked" towards the low pressure area above the wing - this rising air ahead of the wing is called "up wash".
The up wash ahead of the wing causes the angle of attack to be a bit higher than it would be if the air stayed completely still until the wing hit it. With a constant chord wing, the upwash is greatest at the wing root, and lowest at the wing tip. This means the local angle of attack is highest at the wing root, and the stall should start there and progress outboard.
All the above is true for constant chord wings with zero washout. The story changes a bit if the wing is tapered.
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03-12-2014, 06:16 PM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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RV-7A stall test with wing tufts
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
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03-12-2014, 06:39 PM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,614
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You did a lot of work to set up that test and video and I want to thank you. I understand my 9A wing better now. Any plans for a VG test?
__________________
"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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03-12-2014, 07:11 PM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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This makes sense to me.
Quote:
Originally Posted by Kevin Horton
With a subsonic aircraft, the air ahead of the aircraft starts to move a bit before the aircraft gets to it. The air pressure above the wing is lower than the atmospheric pressure - that is a big part of why the wing develops lift. As the wing approaches the air mass, the air ahead of wing starts to rise a bit, as it is "sucked" towards the low pressure area above the wing - this rising air ahead of the wing is called "up wash".
The up wash ahead of the wing causes the angle of attack to be a bit higher than it would be if the air stayed completely still until the wing hit it. With a constant chord wing, the upwash is greatest at the wing root, and lowest at the wing tip. This means the local angle of attack is highest at the wing root, and the stall should start there and progress outboard.
All the above is true for constant chord wings with zero washout. The story changes a bit if the wing is tapered.
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The above statement makes sense to me.
No plans for VG testing for me. Like my wife says to me about herself, don't mess with a good thing.
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
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03-12-2014, 10:11 PM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,614
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Confession: had VG's on two certified high wing planes. They performed as physics said they should. Pain in the butt though...
The RV9 has such pretty wings. Mine will have no more than paint on them. Not even a gopro.
But I really do like your efforts to make the invisible come alive for all of us..
Smart wife BTW.
__________________
"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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03-12-2014, 11:24 PM
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Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
Posts: 2,645
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Very interesting
Steve,
What a great teaching video. Not only for stall info, but it helped me explain to my wife why frost on the wings can cause so much trouble. I found it very interesting watching the strings flutter as you increased the angle. Thanks for posting it for us to look at.
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rockwoodrv9a
Williamston MI
O-320 D2A
Awaiting DAR Inspection
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03-13-2014, 04:27 AM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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science shows
I did this primarily because I thought it would be beneficial to add it to my "show" for kids to explain how a wing works. Plus, I thought I could learn something more about my aircraft. I will add it to my Bernoulli Ball and miniature wind tunnel demo for kid science shows. I am that goofy guy that arrives to kids science shows with fans, wind tunnels and wing diagrams your mother warned you about. The first science fair this year is this Friday at a local junior high school. My youngest daughter is helping me this year. I appreciate the input from guys on this forum.
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
Last edited by Steve Melton : 03-13-2014 at 05:01 AM.
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03-13-2014, 06:35 AM
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Join Date: Jan 2011
Location: SoCal
Posts: 391
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Kudos!
Steve:
Your thoughtful preparation for, and execution of, stall and recovery cycles is very evident; I'll work to be that smooth.
We're planning our 2nd Science, Technology, Engineering, and Math (STEM) event for middle school students; with this as a great example, I'll apply a little rudder input  to the curriculum.
__________________
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VAF dues paid though exempt
RV-9A sold (I miss that bird!)
RV10 sold (miss that one too!)
RV-14A build underway
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03-13-2014, 06:54 AM
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Join Date: Jan 2007
Location: Orem, UT
Posts: 213
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RV-12 Flaperons
Wonderful video!
It gives a nice feeling to to know that there is still some aileron control in a stall for the RV-9. I couldn't help wondering about the RV-12 wing with flaperons. I wonder if that wing has similar stall behavior, and if there is any control from the continued air flow on the outboard end of the flaperon.
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Finishing -12 tail cone
-9A Empennage done, in storage
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03-13-2014, 09:06 AM
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Join Date: Dec 2005
Location: Mahomet, Illinois
Posts: 2,195
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Quote:
Originally Posted by flightlogic
You did a lot of work to set up that test and video and I want to thank you. I understand my 9A wing better now ...
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I echo Flightlogics note of appreciation. Thanks much!
__________________
Terry Ruprecht
RV-9A Tip-up; IO-320 D2A
S. James cowl/plenum
(Dues paid thru Nov '18)
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