Full Flying Surfaces
Hey guys!
I'm currently developing a design for an assault on the British fun fly nationals which includes an all moving tailplane (or stabilizer as you yanks seem to call 'em!) and all moving fin. I learnt an awful lot from my first design, though mainly what not to do! Check out my gallery for pics of the first, and the infinetly better second design (the blue and clear one!)...
I'll try and save you some grief by telling you my findings...
Firstly flutter is a big problem! It is very important to mass balance the surface so that any potentially catastrophic run-away oscillation is damped out. To do this make the surface nose heavy i.e. if unconnected from the servo, the tailplane should rotate so that its in the 'up' position (i.e. leading edge lower than trailing).
Secondly to avoid killing the servo you need to aerodynamically balance the tail - i.e. have the pivot point so that there is maybe 2/3rds the area behind, 1/3rd in front... roughly! Don't exactly know what the ideal ratio is, but as long as the servo is getting some 'help' it should be ok.
Naturally the same applies to the fin or any other surface.
To further increase you're chances of a second flight (!) make sure that any slop in the linkages is to a minimum lest flutter develop, and the ground rise to smite thee!
If not then you should fully expect your tail or whatever to explode quite spectacularly as mine did on one occasion. Coming out of a big loop (power off so not at a great speed) the tailplane powderised itself at which point i used all my british championship winning skill, promptly panicked and pulled full up. The plane pitched down due to the flaperons mixed in, and by the time i worked out down was up and vice-versa, i was 5 foot off the deck inverted! Phew! Anyway i landed ok! Just a cautionary 'tail' for you!
- Martin
ps. there is a post on the aerodynamics thread that talks about elevators vs all flying surfaces - could be of some use? There appears to be people of superior knowledge to me there!