Staggerwing Wing Incidence
 

I found one modeler who has built a staggerwing model from the same plans as I am using. The model is very very close to scale with the semi-semetrical airfoil as well. He passed on some bad news that the plane did not fly well. The model tip stalled on landing unless the speed was kept very high. He attributed the bad flight characteristics to the wing incidence. The scale plane and the plans call for the following:

- 2 3/4 degrees engine down thrust
- 3 degrees positive wing incidence (both wings)
- 2 degrees negative rear stabilizer

These seem to be very odd but that is how the scale plane was set up. This modeler suggested that I change the main wings to 0 degrees incidence. However, that is not easily done since the lower wing is set with the fairing (fillets) coming from the fuse. The top wing is set to fit and conform to shape a contour from the windscreen to the back of the cabin. So I am stuck with the 3 degree positive wing incidence.

However, I have not installed the rear stabilizer yet. Another modeler (builder and designer) said that changing the rear stabilizer to +1 degrees would have the same effect as changing the main wings to 0 degrees. The plane would fly with the tail a bit higher but that would be an acceptable trade for better flight performance.

Any thoughts on how the change in rear stabilizer incidence will work?

Will this change actually have the same effect as changing the main wings to 0 degrees?

If the stab is changed, should the engine down thrust be altered as well?

RE: Staggerwing Wing Incidence
 

Changing the stab to achieve the same relative incidence should obtain the same GENERAL effect. It will not, however, change the flight path of the fuselage. That is controlled entirely by the wing angle of attack for the given flight conditions. Changing the wing incidence would have done this.

I will let others with more experience in the area comment on any impact this may have on tip stalling. A thought or two though - the Staggerwing had flaps on the upper wing in early production models and switched with the ailerons at some point (or do I have that backwards?). I think the use of flaps, amount, and where will have a dramatic effect on the landing characteristics. Obviously, wing washout/in (read - 'warpage') will play a big roll, too. Another big roll player will be CG location.

Nice looking bird in th bones!

Good luck.

Bedford

RE: Staggerwing Wing Incidence
 

Changing tail incidence just changes how much elevator trim you need, which can reduce the amount of 'up' throw you have. This is the long way to solving a stall problem. Just use less throw to begin with! Of course, double check the CG as well and make sure it's conservative for the first flight. With any biplane, it's desirable to have the forward wing stall first. Thus, it can have higher incidence.
With a plane that always drops a wing, it could be out of lateral balance, wing twisted or the rudder trim is off.

RE: Staggerwing Wing Incidence
 

I've never had a stagger wing so can't be sure; but, on 7 Aeromasters, 2 Phaeton 90's, 2 Phaeton 40's and several other bipes, ALL required that the upper wing incidence was about 1.5 degrees less than the lower wing in order to fly well. Some were downright dogs until the upper wing incidence was reduced to less than the lower wing had. And, yes, all required right and down thrust. Slight changes in downthrust made some major improvements in how the plane handled.

RE: Staggerwing Wing Incidence
 

Tip-stalls are usually a sign of a high wing loading on a scale plane.
I wouldn't expect them as a result of wing incidence alone.
The wings on the Staggerwing are essentially rectangular, which generally stall at the root first.