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Aileron differential uses???

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Old 05-22-2003, 01:32 PM
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Ernie Misner
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Default Aileron differential uses???

Greetings,

I am experimenting with aileron differential. I do understand that this will help eliminate the "adverse yaw" that is associated with aileron inputs. Origionally I thought this was mostly needed with flat bottomed types of airfoils because down movements had more authority than up movements. Now it makes sense? to me that even on symetrical airfoils that some differential would help with setting up for the proper direction of roll and turn (yaw). Obviously when flying upside down (which I do only a small part of the time) the differential would be "backwards". I don't know if that would be a problem or not.

Is anyone using differential for sport flying with a symetrical section?

Ernie
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Old 05-22-2003, 06:50 PM
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MinnFlyer
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Default Aileron differential uses???

This is one of those many areas that I think too much emphasis is put on, and yours is the perfect case-in-point.

Adverse yaw, in a model plane is, in most cases, so mimimal it hardly needs mentioning. But there are those who want everything to be perfect, but, as you stated, when the plane is inverted, so is your differential, so you're beyond "back to square one".
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Old 05-22-2003, 07:35 PM
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Default Aileron Differential

Ernie,

Most of our sport models are fairly low aspect ratio and use strip ailerons. This tends to mnimize the need for differential. Where it does come into play to reduce adverse yaw is on planes with long wings and barn door ailerons. Just to get the definitions correct, by "barn door" I mean the inset ailerons that are usually half span or less as opposed to the nearly full span ailerons. A Piper Cub is a perfect example.

The full span Cub has wide ailerons out near the tip and long wings. (As I recall, some of the smaller kits have strip ailerons.) The Sig quarter scale Cub has considerable adverse yaw and requires rudder coordination or differential.

Watch planes when they turn. if the nose tends to stay high and the turning movement is slightly delayed, the plane needs rudder coordination or differential, sometimes both.

Here's another point that has to do with using or not using differential. The down aileron that causes the drag and adverse yaw, also creates a lot of rolling force. When you put in a lot of differential, you lose rolling force which will slow down your roll rate. Some of us like a high roll rate.

In addition, speed also comes into play. obviously a high speed plane will need to deflect the ailerons less for a roll so you get less adverse yaw. It's just those slow speed Cubs and the like that cause problems. I have a quarter scale, clipped wing Cub and it rolls pretty well. I do have an OPS 1.8 in it.
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Old 05-22-2003, 11:36 PM
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Ernie Misner
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Default Aileron differential uses???

Ed and MinnFlyer, GREAT information and well said! This is the kink of thinking I was looking for. Computer radios are interesting. It is SO easy to add things like differential or take it away. We kind of loose sight of building 'em straight and light and simply flying them well.

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Old 05-23-2003, 10:16 PM
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Default Aileron differential uses???

First time I had adverse yaw it scared me to hell . was flying a 1/4 scale Stampe [82"] . going downwind , the worse time for that infliction I think , SO gave it left aileron & plane turned right , thought radio problem , gave left rudder & all was well . On big bipes especially use the rudder on turns , I also use differental on the ailerons , well worth setting up .
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