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Old 11-07-2004, 05:16 PM
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Jim OHaver
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Default RE: Can Anybody provide Help Creating a scale flying tail for a Cessna Cardinal?

I use flying stabs and/or plug-in stabs on almost everything anymore--even on aircraft that had fixed stabs. The floating stab makes incidence angles a function of elevator trim--which is very nice if you don't care to cut into your nice new scale model to shim the decalage if you got it wrong off the bench!!

I don't use any special hardware, but you do have to plan ahead. I use a pivot of music wire which runs inside a fuselage-mounted tube of brass or aluminum. You don't need much, and remember, it's weight at the tail!!, so think lighter and smaller. I see no need for any wire pivot greater than 1/8" M.W. for .60 size. My 64" PICA Spitfire has plugin stab halves that ride on 3/32 wire, which is sufficient.

If you don't care about the actual scale pivot point, then I suggest you avoid the hassles of having to do aerodynamic and mass balancing efforts and put the pivot where you will minimize these issues. (1) Find the centroid of the plan view of the stab. (2) Put the pivot just barely ahead of this point--by about 1 diamter of whatever size pivot tube isto be embedded into the structure. This will put the mass of the stab almost--but not quite--divided evenly fore and aft about the pivot which defines the aerodynamic mass, and will eliminate flutter problems. Once you have the pivot estqablished, you need a second tube embedded into the structure, parallel to the pivot; this will receive the drive-wire. The drive wire can go either fore or aft of the pivot.I findthat usually putting it in front of the pivot works out better; (3) The trick (and here is the plan ahead part), you build the pivot tube and drive tube into the stab as part of its structure, and when everything is done except finish, you cut through all the tubes with a razor saw to sparate the parts. This leaves the tubes exactly lined up and ready to receive the wire that passes through a hard mounted tube in the fuselage for the pivot and a wire that passes through the fuse in an eccentric slot and engages the drive tubes. (4) the actual drive mechansim is a piece of crimped brass tupe, cross-drilled to match the diamater of the drive wire, and soldered to whatever your linkage is. (5) Keep control movement very slight (such as no more than 2 or degress, plus or minus off center); when the entire stab is moving, your control will be very positive around neutral and it will take very little movement to effect large changes in angle of attack.
I'm leaving out the actual nuts andbolts of the how-to in this, but hope you get the idea. An additional plus is that you can take the stab off to transport, which takes up much less room in your car!. The wires can be secured with small grub screws (I use 2-56s, tapped through the structure to bite the wire.)

If you insist on the actual scale pivot point, you are going to have to mass-balance the stabilator (a pain), and even then, you may encounter flutter problems at high-speed dives with the aerodynamics involved. I don't know what they are, but when I put the pivot just forward of the centroid, I don't get any problems. Have fun.
JGO