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Old 03-19-2002, 08:13 PM
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Default Scale Speed

Scale speed has more to do with the visual perception of flight characteriatics than the theory of fluid flow and Reynolds number.

In judging scale competition flights, flying in a scale like maner garners additional points.

For example: For a 1/4 scale plane to appear like its scale counterpart in flight it would have to:
1. Be 1/4 the distance from the viewer as the full scale plane it was being compared to.
2. Cover the same visual angle as the fullscale plane (at 4 times the distance) in the same elaped time.

This means that to appear scale like in flight the 1/4 scale model must fly at 1/4 the speed of the full scale plane. If the wind is blowing at 5 MPH and the full scale plane stalls at 44 MPH, the ground speed of the full scale plane will be somewhat above 44-5=39 MPH.

In the same 5 MPH headwind the 1/4 scale model will have an airspeed a little in excess of 11 MPH and a ground speed a little in excess of 11-5=6 MPH. To have a ground speed 1/4 of full scale, the wind speed can only be 1.25 MPH for the model.