BillinIndiana

Still working on my 1st build, a SIG Kadet Mark II.. I'm working on a single aileron servo and connecting the pushrods.. Which servo arm should I use? Round, 4 way or 6-way? Should I make both pushrods the same length and set the differential with my radio?

Charlie P.

If you trulywant differential with a single servo you will have to use the round "arm" and drill holes offset from 90° by 30° (120° apart). Or, youcan use the 4-way arms and offset the contol horns so the holes are not over the hinge line (not recommended). You coud use the 6-arm head, but using twoarms 120° apart .

For best results you want more up throwthan down, by the way.

BillinIndiana

Thanks

mike109

G'day

From my experience of Sig kits, the differential aileron function (if needed) is built into the torque tubes that operate the ailerons from the servo pushrod. So you should just use a straight aileron arm and the geometry of the provided torque rods should give the amount of differential needed (if it is needed at all). It is a while since I built my Mk 2 and as a result, I don't remember whether the supplied torque rods were offset or not.

I will have a look tomorrow and let you know but basically if you follow Sig's instructions, you won't go far wrong.

Cheers

Mike in Oz

mike109

G'day again

I just went out to my shed and had a look at my plane. I cheated. I used two aileron servos. Sig suggests that using differential ailerons is not necessary so you can fly without it if you wish. If you later want to change to a differential setup, it is only a matter of changing the positions of the pushrod connections on the servo wheel.

As you have only one servo, you need to do it mechanically with the offset method which Sig and Charlie P suggested above because if the torque tubes you were supplied are the same as the ones shown in the instruction manual, the differential is not built into the tubes the way it is in more recent designs. It is not possible to set up differential ailerons with your computer radio and only one servo. In some models, it is relatively easy to put two servos side by side so that each operates one of the ailerons. I did it by putting each servo about half way along the wing on ply plates which I fitted between two wing ribs.

As I mentioned way back when you started building this kit, the Kadet Mk II is a very old design and did not anticipate things like dual aileron setups. When this plane was designed, a four channel radio with servo reversing was very delux. If the user wants to use dual aileron servos, it is up to him how he implements them. I just made up ply plates which I set into the wing about half way along the wings and operated the aileron horns with metal pushrods directly.

To get the differential effect using your computer radio, you need to assign each of the two aileron servos to a separate channel. Most computer radios have a simple way of setting this up. You then use the end points for each servo to get the differential effect.

Mike in Oz

JohnBuckner

My Feedback: (1)

Mechanical differential can can be a good thing on certain types of airplanes. It normally may not provide as much diff as can be accomplished electronically but still very useful. Charlie P's chart is of course correct but still may be confusing to some so to the Original poster here it is applied to a single servo high wing airplane Notice the pushrods go past a line drawn between the output bushing and the two pushrod connections to aheve the desirable differential that causes the upward moving aileron to move further than the downward moving aileron.

Mike is also correct in that the mechanical differential can also be acheved even with a two servo setup simply by the fore and aft control horn positioning out on the aileron in relation to the hingeline. The most well known application of this was the anniversery addition of the Goldbergh Cub which acheved diff of almost fifteen degrees via control horn placement on purpose. I don,t know about sigs but anyway perhaps this photo can also help:

John

Hossfly

Charlie P has it right. Regardless of any kit's directions otherwise, in a high wing trainer type, differential can be a real helper and save a model especially from a lesser experienced flier. Another item that helps even the experienced flier (NOT 3D, Pattern, etc. which has different needs) is the use of setting ailerons - on flat bottom wings and scale models - UP about 3-5 degrees. I know it doesn't "look" right, but it saves many a model from a snap roll on take-off and/or a landing, since that left hand on rudder seems to freeze up!!!