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  #1  
Old 11-08-2015, 05:48 PM
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hlangebro hlangebro is offline
 
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Location: San Diego, CA
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Default Zig zag strip etc

Has anyone tried zig zag or dimple strips on their gear leg fairings?
It seems to me, with the relative thickness of the leg fairings, that a certain amount of separation can be expected... which to a certain extent can be overcome with zig zag or dimple strips...
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RV-7A, slider
Lycoming O-320 D1A, 160hp C/S
First flight 6-11-13

Re-engineering a Lancair 320..!


http://www.youtube.com/watch?v=AJuQ68tccTQ
http://www.mykitlog.com/hlangebro/
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  #2  
Old 11-08-2015, 06:08 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
Posts: 4,435
Default

You can tuft the fairings (or use an oil film) and check out your hypothesis. If it holds true, then you'll probably see that separation occurs near the trailing edge. If so, change their shape so that it has a reflexed trailing edge, like Van's wheel pants, that should cure the problem.

The reflex will aid both with a more favorable pressure recovery and an increase in Reynolds number.

I think this might be more efficient than forcing it to go turbulent at the leading edge - but you can try that and see.

Please report back. Thanks!

Dave

Last edited by David Paule : 11-09-2015 at 06:56 AM.
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  #3  
Old 11-08-2015, 06:17 PM
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hlangebro hlangebro is offline
 
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Location: San Diego, CA
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I did some tufting, however mostly of the wheel pants and fillet, which showed separation in 2 areas. I did see some separation from the leg fairing as well though.

https://www.facebook.com/photo.php?f...9&l=2914d98f39

CFD analysis shows that there is some separation..

https://www.facebook.com/photo.php?f...9&l=1fe55feca4

I am currently working on various mods to the fairings and fillets.

https://scontent-lax3-1.xx.fbcdn.net...29&oe=56B01531


I have ordered some zig zag tape and will try it on eventually!
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H?kan Langebro
San Diego, CA

RV-7A, slider
Lycoming O-320 D1A, 160hp C/S
First flight 6-11-13

Re-engineering a Lancair 320..!


http://www.youtube.com/watch?v=AJuQ68tccTQ
http://www.mykitlog.com/hlangebro/
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  #4  
Old 11-08-2015, 07:03 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by hlangebro View Post
I did some tufting, however mostly of the wheel pants and fillet, which showed separation in 2 areas. I did see some separation from the leg fairing as well though.

https://www.facebook.com/photo.php?f...9&l=2914d98f39

CFD analysis shows that there is some separation..

https://www.facebook.com/photo.php?f...9&l=1fe55feca4

I am currently working on various mods to the fairings and fillets.

https://scontent-lax3-1.xx.fbcdn.net...29&oe=56B01531


I have ordered some zig zag tape and will try it on eventually!
Are the Facebook pictures viewable by anyone? I get an error.

Edit/update: Nope - still not working for me.
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 11-09-2015 at 06:02 AM. Reason: Still no joy.
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  #5  
Old 11-08-2015, 08:35 PM
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hlangebro hlangebro is offline
 
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Location: San Diego, CA
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They are all posted as "public", so they should all be available....
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H?kan Langebro
San Diego, CA

RV-7A, slider
Lycoming O-320 D1A, 160hp C/S
First flight 6-11-13

Re-engineering a Lancair 320..!


http://www.youtube.com/watch?v=AJuQ68tccTQ
http://www.mykitlog.com/hlangebro/
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  #6  
Old 11-09-2015, 06:25 AM
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blueflyer blueflyer is offline
 
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Location: Shreveport, LA
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I get "Sorry, this content isn't available right now" when i click the links
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  #7  
Old 11-09-2015, 06:52 AM
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flyboy1963 flyboy1963 is offline
 
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Location: Lake Country, B.C. Canada
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Default turbulator stips....where and why?

I find it amazing that these aren't more widely used.

I recently saw a Stemme motorglider, had them EVERYWHERE, I was surprised that they were 1 to 2 mm thick; I guess that's a function of the boundary layer on that particular airfoil or some such thing. they were mostly in front of control surfaces, on both sides of the wing, stab, rudder etc.
apparently they felt they were worth the slight drag penalty to keep the flow attached...on something as drag sensitive as a glider.
I can imagine a dozen dirty airflow places on our aircraft that would benefit.
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  #8  
Old 11-09-2015, 11:59 AM
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hlangebro hlangebro is offline
 
Join Date: Mar 2012
Location: San Diego, CA
Posts: 133
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The reason is two-fold, keep the boundary layer attached and reduce drag. If you have separation and use a zig zag to keep it attached, it will result in a drag reduction. I dont think anyone would use them if the drag went up... unless it was for controllability/crosswind performance and such.
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H?kan Langebro
San Diego, CA

RV-7A, slider
Lycoming O-320 D1A, 160hp C/S
First flight 6-11-13

Re-engineering a Lancair 320..!


http://www.youtube.com/watch?v=AJuQ68tccTQ
http://www.mykitlog.com/hlangebro/
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