Bipe wing incidence
01-22-2005 | 05:38 PM
#1
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From: Everberg,
AK, BELGIUM
Bipe wing incidence
I am building my first Bipe : a small Christen Eagle (Protech - 1.25 m - Saito 91)
The manual says nothing about upper / lower wing incidence.
Is there a standard setting ? Pitfalls ?
thanks fo any info
The manual says nothing about upper / lower wing incidence.
Is there a standard setting ? Pitfalls ?
thanks fo any info
01-22-2005 | 06:07 PM
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From: Winnipeg,
MB, CANADA
RE: Bipe wing incidence
In general, the lower wing will be at 0 degrees incidence. The upper wing may also be at 0 degrees, but it can also have a slight positive incidence (called "decalage") - say about +2 degrees or so. This causes the upper wing to stall before the lower wing, which may sound counter-intuitive but it makes the entry into a stall gentler and easier to control.
There may be some negative effect on aerobatic performance but I am not familiar with such things. No doubt there will be others more experienced than I who can fill in the details.
There may be some negative effect on aerobatic performance but I am not familiar with such things. No doubt there will be others more experienced than I who can fill in the details.
01-22-2005 | 07:07 PM
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From: ralston, NE
RE: Bipe wing incidence
I fly a few biwings, to name a the a bucker jungmann bucker jungmeister aeromaster pitts. all have 0 to 1 deg. bottem wing a 1 deg NEG. on the top. hope this helps. fxd
01-22-2005 | 07:26 PM
#4
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RE: Bipe wing incidence
The old story about additional incidence on the upper wing making the stall gentler was proven false in the early 1930s in wind tunnel tests. The reverse may actually be closer to the truth, since as the upper wing stalls, its drag increases far more than its lift decreases, and the extra drag, well above the center of gravity, tends to cause pitch up. I rig all my bipes with between zero incidence difference, and a maximum of one degree less incidence on the upper wing. A little negative incidence on the upper wing seems to slightly help aerobatic line holding, at least, if the airplane has positive stagger.
01-23-2005 | 12:01 AM
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From: Winnipeg,
MB, CANADA
RE: Bipe wing incidence
ORIGINAL: Rotaryphile
The old story about additional incidence on the upper wing making the stall gentler was proven false in the early 1930s in wind tunnel tests. The reverse may actually be closer to the truth, since as the upper wing stalls, its drag increases far more than its lift decreases, and the extra drag, well above the center of gravity, tends to cause pitch up. I rig all my bipes with between zero incidence difference, and a maximum of one degree less incidence on the upper wing. A little negative incidence on the upper wing seems to slightly help aerobatic line holding, at least, if the airplane has positive stagger.
The old story about additional incidence on the upper wing making the stall gentler was proven false in the early 1930s in wind tunnel tests. The reverse may actually be closer to the truth, since as the upper wing stalls, its drag increases far more than its lift decreases, and the extra drag, well above the center of gravity, tends to cause pitch up. I rig all my bipes with between zero incidence difference, and a maximum of one degree less incidence on the upper wing. A little negative incidence on the upper wing seems to slightly help aerobatic line holding, at least, if the airplane has positive stagger.
01-23-2005 | 09:48 AM
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RE: Bipe wing incidence
I have flown lots of bipes; 7 Aeromasters, 2 Phaeton40's, two Phaeton 90's, 3 Lazy Aces, and ALL required that the upper wing be 1.0 to 2 degrees more negative than the lower wing in order to fly decently. It is surprising what a small amount of change in that upper wing incidence will make on the way the plane flys. If possible, set the upper wing up so that you can easily make minor changes so you can get it tuned to your liking, there will be one spot much more enjoyable than the others. Each plane will be slightly different, even if built from the same plans.
