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Diamond airfoil

Old 10-20-2004, 11:42 AM
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Default Diamond airfoil

Hello, all.
I have been experimenting with a diamond airfoil for 3D for awhile, much like the Jeff Gilbert designs for competition funfly I first started seeing in the early '90s. I have built 6 profile funfly/3D ships using this airfoil and 2 charctoristics have exsited in each plane, regardless of variables like tail moment, control surface size, etc. the transition from normal "on the wing" flying to high alpha 3D has been seamless, more so than with my traditional airfoils. Also, harriers in all the panes have been completely solid, and easy to do. I guess the SPAD design is kind of like this, but with a built up semetrical wing more moves are available. I just finished a larger version for a G26 that I hope to fly this weekend.
Anyway, I know lots of you folks design your own profiles and thought this info might be helpful.

Dave
Old 10-20-2004, 12:14 PM
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Default RE: Diamond airfoil

Pictures?
Old 10-20-2004, 01:34 PM
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Default RE: Diamond airfoil

I don't have the ability to do pictures, sorry. But I think the key ingredient is the airfoil. On all the designs I tried different things like tapered trailing edge, hershey bar wing, long tail moment, short tail moment, Stab high and ahead of the fin like a CAP, Stab low, etc. And while they all flew a bit differently, they all shared great harriers and transition to 3D. So I figured there might be something to this for 3D funfly planes.
Old 10-20-2004, 02:15 PM
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Default RE: Diamond airfoil

how thick did you make the aorfoil?
Old 10-20-2004, 04:15 PM
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Default RE: Diamond airfoil

3 inches thick, usually. I can get you area/span figures if you want tommorow.
Old 10-20-2004, 05:55 PM
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Default RE: Diamond airfoil

Please, I'll post a pic of something that will explain all of questions tomorrow

Thanks
Old 10-20-2004, 10:37 PM
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Default RE: Diamond airfoil

Kinda off topic but I've done several Deltas with diamond airfoil and a giant flat bottom (chisled) airoil...

http://www.crazyherb.com/JacksDelta/IMG_0937.jpg

www.crazyherb.com

I use 1.5 inch and 2 inch thick foam with a hot wire 90 degrees from normal....cut leading edge, top/bottom root to tip then trailing edge top/bottom.

I wouldn't mind doing a 2-4 hr construction diamond airfoil profile foamie fun-fly...

CrazyHerb
Old 10-21-2004, 09:04 AM
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Default RE: Diamond airfoil

ok....so I mostly used a 17 inch chord which includes 5 inch ailerons. The thickest point of the airfoil was 3 inches and it was 3 inches from that point to the leading edge. I arrived at this by taking measurements from an existing typical funfly wing and just making the lines straight. I have a friend who is a retired fluid dynamics engineer for Boeing. Air is a fluid, get it? I asked him why this works. He drew some graphs, hopped around on one foot and chanted in three dead languages, none of which I understood. So anyway, there is probably some important 3D enlightenment in all of this, I just know it works.
Old 10-21-2004, 03:43 PM
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Default RE: Diamond airfoil

I think that`s why flat foam planes harriers well also, the sharp LE is the key I guess
I have experimented with diferential airfoils with excelent results to make the root stall ALWAYS first, and the tip then; thus you can use more taper in the wing (better snaps rolls and spins) and still have a nice elevator/harrier. My 2 cents
Old 10-21-2004, 03:56 PM
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Default RE: Diamond airfoil

I was working on this a couple months ago. Spastic built a plane similar except his wing was totally flat. I was not happy with the way I built the wing, so I threw the wing away. I have the fuse with tailfeathers hanging in the garage. Maybee, I will re-do the wing and get it flying. The fuse is light as air and super stiff.
Old 10-21-2004, 03:57 PM
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Default RE: Diamond airfoil

woops forgot the pics
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