ORIGINAL: cchariandy
Wow...I can't believe how many ERAU grads there are on this forum.
With the Anhedral stab I don't belive that we can"resolve" the areas like a vector and add some in the vertical plane. The anhedral stab works differently from the standard because some of the surface is below the area of the wing downwash. We have to avoid trying to invent theory purpose built to rc aircraft, rather use fullscale design principles and methods to explain what some of our experiments tell us.
Anhedral stabs on full scale are usually because the designer is trying to avoid unfavorable downwash or jetwash and has no other choice structurally than to "lean" the stab away.
I really doubt if the tiny fin is actually impacting longitudinal airflow due to the spiral propwash as both Electrics (big mass of air being moved slowly) and Glow (small mass moved quickly) both seem effected similarly. Additionally, do the improvements go away when you trottle back (as in a downline)?
Someone should build a small smoke tunnel, say 2'x2'x2' and run some experiments to visualize the effects....any takers?
Colin.
OHHHH??? Really!!! Explain then how a pencil thin fuse with low wing and ample dihedral will knife edge far better than a pencil thin fuse with zero dihedral, mid wing platform. All else being equal
Areas are indeed additive or subtractive. The higher dihedral indeed introduces a significant vertical component at mid-ships. Don't take my word for it...do the experiment
As far as the small wing and its impact, there's little doubt that it affects how the model behaves..... the fact that full scale aerobats are not using such devices yet, matters none at all. Well, according to friends who knew him, Leo Loudenslagger was experimenting with such on his aerobat before his untimely motorcycle accident.
The effect we seek from the small fin is small indeed. In my experiments with larger fins, I wasn't happy with the results for aerobatic purity but sure were fun to play with.
As far as theory invention, hogwash. All theory is invented....then one follows the scientific method and either proves or disproves it. That's basically what I do both in my vocation and avocation.
One final thought and I'll leave this subject, roll couples can be induced or removed by canting the dorsal fins. In other words, one could remove or add roll couple with applied rudder simply by placing dihedral or anhedral on the horizontal surface of the cannabalizer. The effect isn't great but is proportional to the area canted; for trim, it's another way to do some aerodynamic fine tuning rather than touching it with electronics. Just another little tidbit from my experiments
Best regards and happy holidays everybody
MattK