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Tangential line angular difference to circular velocity.

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**Chris Wilson**:

Hi all,

Is there a formula for considering the angle the models roll axis sits on compared to the circular flight path?

For example the problem to me is that if the model is set at a tangent, thrust, model centre line rudder etc but it's forced to fly in a circular path then surely there is a measurable angular difference between the two?

Thanks, Chris

**BillLee**:

Should be easy to figure:

Alpha = arcsin ( D/L )

where

D is the distance from the CG to whatever point where you want to know. E.g., to the nose of the model, or to the rudder, or ....

L is your line length

(Or arctan. At these small angles, they are essentially the same.)

Howard, is this correct?

Bill

**Chris Wilson**:

Thanks very much Bill!

I got lost in a world of slope calculations that didn't solve the question.

Chris.

**L0U CRANE**:

If the CG is where you start and the roll axis is considered tangent to the flight circle, that puts the prop and the 'rudder' at a very slight angle out.- rudder's angle about twice as great as prop's . This calculation relates to straight lines not radians. (IMHO part of 'springiness' sensed includes the difference in pull as we apply more force on one line than the other to move the surfaces for control input...)

We know the length along that axis from CG to, say, prop and 'rudder'. Even on small stunters and shorter lines, THAT makes very small angles. Of course, any built-in offsets add or subtract...

How important? These angles may be smaller than errors in construction or estimated line sweep angle reaching the leadouts- which also may vary depending on presentation to wind..

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