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Flap Expo (how do you set this up?)

Konrad

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I'm seeing that a lot of higher end glider radio programing templets have a feature to tune the exponential response of the snap flaps.

I'd like to learn is why have this feature and how to use it?

In the old days we normally set up the servo for servo arm rotation to be 45° ether side of neutral measured at the airfoil chord line. Today most flap servos are set up the to be 90° and Zero degrees. Zero degrees being the locked* position for the down flap. Now most DSing ships have the flaps set up for zero degrees and 90° with the zero degree locked position being the up flap position (in profile). As the servo rotates away from the zero position the first few degrees (30°) of rotation results in very little linear response in the push rod.

I'm assuming that the radio templets that offer a way to adjust the exponential response of the snap flaps are doing this to balance the mechanical response from flap linkages that use this mechanical lock set ups.

So what I'd like to learn is what are you looking for in how the snap flaps respond in flight? I'm assuming that one wants the flaps to be dampened during the early (around center) elevator movement. And that as we pull more and more up elevator the flaps become more aggressive. I suspect this is done to keep the ship from having a jumpy feel as we make small elevator corrections.

*Locked servo linkage pertains to the condition where the servo output axis, the servo arm to push rod pin, and push rod pin the control horn are all in a straight line. This removes most if not all the rotational load on the servo gear train.

All the best,
Konrad
 
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Wayne

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On a DS ship they are wanting to avoid flutter, so locking down the surface makes a lot of sense.

For my fun planes I like to have some up flap movement as I find this aids most planes roll rate. I rather move the flaps than move a lot more aileron for a similar roll rate. I honestly do not know what would be less drag, but my guess is smaller throws from the combination of flap and aileron would be slightly better than larger throws of just the aileron.

The expo on the flap in interesting. My "race" profiles are usually very low rates and I would not combine flap with my aileron. I try to fly as smooth as possible. After some Expo conversations with various people in the shop, I am starting to come around to flying a little higher rates with lots of expo dialed in to tame the center. Thus I can have higher rates when it is a MUST, but can use small inputs to control the plane in the race. So adding an Expo where the flaps would come into play to follow the ailerons is interesting.. Good creative use as it does follow my thinking of what would be less drag.. Could be something to it when trying to get just a bit more out of the plane...

Let the radio do more of the work to tune the plane. This is where OpenTX gives lots of options.
 
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