Thread: Bi plane wing
View Single Post
Old 09-12-2020, 07:50 AM
My Feedback: (29)
speedracerntrixie's Avatar
Join Date: Jun 2010
Location: Happy Valley, Oregon
Posts: 8,043
Received 58 Likes on 55 Posts

I agree that this thread could be more insightful if we knew what charictaristics you are trying to correct. By thinking you have too much wing area I can only assume that you feel the model is " floaty" in flight. Small air disturbances may seem to push it around a bit more then you like? If that is the case, I would be interested in knowing what the incidence is set at for both wings. My Divergent wing's specification is very close to your model's wings. The prototype Divergent weighs 5500g, the one I am currently flying weighs 4500g. No change in wing area between the two and the lighter one tracks in wind just as well as the heavier. My thoughts are that wing incidence plays a big part in how a bipe flies. On both of mine I have the upper wing set to zero. The light model has the lower wing set to +1 degree while the heavier one has +1.5 degree. I have the stab set to zero on both models and adjusted the lower wing incidence until level flight and straight up lines were achieved with the desired CG.

The offset incidence angles ( in theory ) fool the airplane into flying like it has a higher wing loading while in level flight. Change the flight AOA and then the additional area of the top wing kicks in. Invert the airplane and the incidence offset remains the same a certain amount. The now bottom wing has to be flown at a positive AOA while the now top wing is still close to zero. The difference now is that the stab and motor are at a slight positive angle and is verified by an increase in elevator sensitivity if the same throw is used for up and down. I currently run about 10% less down throw then up throw to compensate for this.