where does the model roll?

[Kenneth Velez]

Tom.

  The datum line is a point of reference that the manufacturer of an
aircraft gives to measure distance to the equipment to be installed on the
aircraft for weight and balance to determine the weight / arm ratio.
Airplanes move thru 3 axes, vertical or rudder yaw goes from top to bottom
at the CG point, lateral or pitch goes from wing tip to wing tip thru the CG
and longitudinal or roll witch is front to back thru the CG, not necessarily
thru the engine line since it depends on the position of the wing, hi, low,
mid etc... As you can see the common point is the CG were all the weight of
the aircraft is carried, so I would say it rolls around the wings. The axis
will be located on the center of the fuselage going fwd and aft thru the
wing core center line. That's why aerobatic airplanes have mid wings so the
roll is as thru as posible. Hope it helps.

Ken V
----- Original Message -----
From: "Koenig, Tom" <Tom.Koenig at actewagl.com.au>
To: "'Discussion'" <discussion at nsrca.org>
Sent: Wednesday, January 08, 2003 6:31 PM
Subject: where does the model roll?


> Hi Guys,
>
> I've just been asked this question.........it never occurred to me to
really
> think about this, now I'm open to opinions, facts and anyone that has the
> cold hard knowledge.
>
> I have always assumed that a model rolls around the datum line ie: the
> crankshaft center line (not taking down and side thrust into
consideration)
>
> Now a mate of mine swears black and blue that in actual fact the model
rolls
> around the wing center line ie: it is the wing that rolls and all else
> scribes an arc around this.
>
> Can anyone can set us straight......please?
>
> Thanks
>
> Tom
>


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