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Long Tails Versus Short Tails in Aerodynamics

Published online by Cambridge University Press:  14 September 2016

G. H. Bryan  and
S. Brodetsky
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Extract

Consider any form of aircraft provided with a small rudder plane placed behind its centre of gravity and at a certain distance l from it, which we may speak of as the length of the tail. When this tail is subjected to a given wind pressure, the moment of this pressure about the centre of gravity, tending to turn the machine round, is proportional to l. From this point of view a long tail is preferable to a short one.

On the other hand, the pressure of the air on the tail plane depends on the normal velocity of the wind relative to it. Hence the normal velocity of the plane itself is limited in magnitude, and the angular velocity with which the machine turns about its centre of gravity must therefore be less when l is large than when lis small; that is, the long–tailed machine turns more slowly than the one with a short tail, and this is a disadvantage.

Type
Research Article
Information
The Aeronautical Journal , Volume 20 , Issue 78 , June 1916 , pp. 50 - 55
Copyright
Copyright © Royal Aeronautical Society 1916

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References

Note on page 51 Note.—If the velocities of two moving bodies be represented in magnitude and direction by two sides of a triangle, both drawn from their common vertex, then the third side represents their relative velocity. Thus in the above figure where KC and KB represent the velocities of the wind and dart, the relative velocity is represented by CB or BC according to whether we are considering the relative motion of the dart or of the wind. This simple construction for relative velocity can he easily verified by supposing two bodies to start simultaneously from the point K with the velocities W and V; then in a unit of time they will have arrived at C and B, so that the line CB will show the change of relative position in unit time, and will therefore represent the relative velocity. This explanation appears necessary because the treatment of relative velocity in many text books is very confusing, and it is our experience that even advanced students frequently make mistakes in consequence.