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Old Mar 17, 2006, 05:15 AM
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Notched leading edges

Anyone have any comments about the notched leading edge article in the April issue of Quiet Flyer? Done by the Seleig team, noted for their wind tunnel work on model airfoils. The tests they ran both in the wind tunnel and in the air indicate a reduced (softer) stall and elimination or reduction of wing rock in harrier.

Azarr
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Old Mar 17, 2006, 12:27 PM
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I haven't seen that yet, but it is probably some form of turbulator. There is actually some discussion about this in the indoor/F3P forum.

At really low reynolds numbers it can be best to introduce a turbulent flow, as at these really low speeds a laminar flow may have a seperation bubble form between it and the surface. Since a turbulent flow is actually easy to control and manipulate, and it actually sticks to the surface then this is the best way to handle this. So, people started experimenting probably twenty or thirty years ago with turbulators. Full scale competion glider pilots will sometimes put just a strip or sometimes a zigzag pattern of tape on the top of the wing to turbulate the flow. It takes some trial and error to figure out the ideal placement.

So, I'd guess these notches are somehow related to this.
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Old Mar 17, 2006, 08:15 PM
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i've used strips of nyrod taped to the top near the LE outer half span.. and it worked,.. but now i just fly planes that dont wing rock
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Old Mar 19, 2006, 05:34 AM
The God in God-mantooth.
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Sounds like a better mousetrap, I think it may be the only way to go for any serious indoor/outdoor 3d pattern pilot... Plus it looks pretty menacing to see the serrated leading edges, im sure someone will encorperate that fact into a design that looks pretty less strange...

for those of you who havent seen or read it, the leading edge of the wing normally looks like this => ________________ (flat. Normal.) but the leading edge of the new and improved foamy wind looks like this => __/\/\/\/\/\/\/\/\/\/\/\__
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Old Mar 19, 2006, 09:05 AM
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I messed around with that "zig-zag" sewing tape on some of my slope gliders many years back. It realy helped on the calm wind days. I used to put it just ahead of the thickest point on the airfoil. Everybody thought I was nuts... But then we could all realy see the difference in how long I could stretch a calm wind glide. Cool idea... Maybe I should cut out some "saw tooth" 3DX wings and see what it does.

Actually, I've been thinking of making some little depron "chuck gliders" to test some of these leading edge configurations. Every time I think about it though, It's blowing at 30kts outside... No good for chuckies...

Tim H.
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Old Mar 19, 2006, 10:46 AM
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Quote:
Originally Posted by Tim H.
I messed around with that "zig-zag" sewing tape on some of my slope gliders many years back. It realy helped on the calm wind days. I used to put it just ahead of the thickest point on the airfoil. Everybody thought I was nuts... But then we could all realy see the difference in how long I could stretch a calm wind glide. Cool idea... Maybe I should cut out some "saw tooth" 3DX wings and see what it does.

Actually, I've been thinking of making some little depron "chuck gliders" to test some of these leading edge configurations. Every time I think about it though, It's blowing at 30kts outside... No good for chuckies...

Tim H.
The 3DX would be a great test bed for this, I may just modify mine. It's basically the same principle and has the same affect as putting a turbulator at or just in front of the high point on a traditional "airfoiled" wing, however it moves the turbulator to the leading edge. Here's a quote from the article:

"Well, small scale turbulence at the very front of the wing causes exactly that. It flattens the lift peak just before the stall and fills in the valley after the stall. This means you don't play the throttle and elevator so much as you move between cruise, stall, and harrier"

Azarr
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Old Mar 20, 2006, 11:23 AM
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I had to go out this weekend just to buy this issue to see the photos firsthand. Cool stuff.
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Old Mar 20, 2006, 01:41 PM
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Hmmm.... Very interesting. I will have to check my collection of QF to see if I have this on or not. I would like to know more about this.
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Old Mar 20, 2006, 01:54 PM
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It's the newest one.
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Old Mar 20, 2006, 02:56 PM
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Nope, don't have it yet, the latest one I have is March. Will have to go and pick it up. Maybe tonight...
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Old Mar 20, 2006, 06:50 PM
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any pics??
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Old Mar 20, 2006, 06:56 PM
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Yes, pics please!!

I think I understand what is going on, but not sure of where on the wing. I see that you should place it just before the thickest part of the airfoil, but how far in front, and how much of the length of the wing?.
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Old Mar 20, 2006, 09:08 PM
The God in God-mantooth.
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Like this
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Old Mar 20, 2006, 09:39 PM
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That I understand, but do you put it on the leading edge of an airfoiled wing too? or just infront of the thickest part of the airfoil?
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Old Mar 20, 2006, 09:58 PM
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You put it on the LE of a flat plate wing.
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