Re: Power Loading

Douglas R. Jones (
Tue, 16 Jan 1996 23:03:23 -0600

>I feel I must chip in on this discussion about surface finish.


>I accept that a rougher surface finish MAY produce more drag and probably
>ONLY if it pokes through the boundary layer adhering to the surface. If
>the boundary layer is thick then the quality of the surface finish will have
>little effect on drag.

Interesting. Why? (Dumb question I know but I know code not aerodynamics)

>Increased wing loading will have a significant effect on drag because drag is
>a byproduct of lift. If the airplane is heavier it must generate more lift and
>to do that it must fly faster or at a higher angle of attack. Thus there is
>more drag in both cases. To fly at the same speed at a higher angle of attack
>or at a higher speed at the same angle of attack requires more power (this is
>where power loading becomes important assuming equal propellor efficiency).
>So it is better to be light than heavy for the same wing area. Counter to that
>argument is the one where a higher wing loading is less affected by gusting
>conditions but wing profile camber is also important in this case.
>Light pattern ships with zero camber are much less affected than trainers or
>WW1 models with significant camber.

Yes! Yes! So why can't people seem to get with the concept? Or maybe I
should say Americans?

>I would expect an SE5 or SPAD to be less affected by gusts than an Albatros
>because the wing profiles of the first two have much less camber. In fact
>the wing section used by many British types were little more than modified
>flat plates. Sections with little camber generally have a smaller Cd than
those with more. That is a significant reason why the boxy SE5 had a slightly
>better performance than the streamlined Albatros D.Va. Less profile drag from
>the wings and therefore better performance with similar amounts of power.

Neat! Thanks, Paul!