I have a 4 inch Bob Hunt bell crank (in a nice brodak packet) what kind of ratios or flap and elevator horn lengths should I be looking at?
I have a low time ST 60 as motivation( RSM tongue muffler coming), probably going for a plastic clunk and adding a metal u plate mount with the usual cross grain balsa between bearers.
I intend to cover with light film on the wing and dope silk over it and the rest aiming fo my my stand a long way off finish.
Also going for non tapered flaps and elevator stab at 3/.8th elevator at 1/4 for that that dead air no hunt thing
Yes I am crazy but am I way off whack with any of my ideas?
Control ratio - start with 1:1 if not otherwise stated, but make sure you can vary the ratio (by altering the length of the elevator horn) in fine increments or a slider, and expect to have to speed up the elevator with respect to the flap to as much as 2:1. I expect that you will find that the original had the CG far forward and a very fast elevator WRT the flap, and it would be worthwhile to do some more research to figure out how it was done on the original - and then do that.
Putting silk/dope over plastic film sounds borderline crazy to me - dope doesn't stick to plastic film at all, it just sits on the surface. This seems like a formula for delaminating in the heat, or when removing the masking tape. And, it's going to weigh almost as much as a silk/dope finish, the only thing you are saving is the clear dope required to fill the weave, which is a tiny fraction of the weight of the finish overall (which is mostly in the filler and the color) and you are adding the weight of the film itself, and all the ill effects of film.
The "non-tapered flap" seems to work OK.
The "smaller elevator VS stabilizer" does something, but "not hunting" isn't one of them. Hunting is almost always caused by friction or some mechanical drag in the control system somewhere, it is not an aerodynamic issue in any case I have seen. I have seen one case where it appeared to be an aeroelastic issue with one kit of one design, where the thin flat sheeted foam stabilizer with nearly no taper appeared to warp up and down as you moved the controls to oppose the pitch motion it caused. This happened almost exactly the same way on every one of these kits I ever flew (which was 5-6 different examples from 3 different pilots). In every case that it was solved, it was solved by changing to a solid balsa stab and adding some taper - which put it much closer to the original plans.
Brett
Topic: Ratios (Read 825 times)