Re: Re: F1D CG poll

From: Tapio Linkosalo <tapio.linkosalo_at_helsinki.fi>
Date: Fri, 14 Dec 2007 09:12:41 +0200 (EET)

The wing flies at some positive incidence to the incoming airflow. Thus,
if wing is rigged at 0 degrees relative to the fuselage, also the latter
flies at the same positive incidence, and the motor thrust is not parallel
to the flow, but upwards. Now, if the wing incidence is about 5 degrees,
only less than 0.5% of the thrust is _not_ parallel to the flight path. I
do not think that makes any difference. I do not think that the fuselage
would produce any usefula mount of lift, either, it has extremely poor
aerodynamic properties to that (very low aspect ratio), and I think the
drag produced by angled fuselage overcomes the lift by a large margin.

Why is it then good to fly with a drooping tail? My guess is that the
banefit comes from larger vertical separation of tailplane and wing. With
zero incidence in the wing, the plane flys tail low, which will put the
tailplane lower relative to the wing, and most of all, away from
thedownwash caused by the wing. Thus the tailplane operates in a "cleaner"
air, in a more efficient manner. And probably also with lower drag, as the
airflow is less turbulent.

But now, are there no comments on the CG location? Is this classified
information?



-tapio-
Received on Thu Dec 13 2007 - 23:12:46 CET

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