Thread: Morelli Shape
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Old 09-02-2010, 05:14 PM   #12 (permalink)
Jim Bullis
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Morelli Shape

Old Tele man

The tail evolves from the ideal teardrop but is widened to the tail which is then angled to minimize pitch torque which comes about from the camber.

The main thing is the camber for countering ground effect which is discussed in the context of wingtip vortices. This camber allows the front of the body to be close to the ground but pays for it by providing high ground clearance rearward. Thus, there is high velocity and low pressure forward, but lower velocity and higher pressure rearward. This means that air is first sucked under and then pushed out from under the body, so that the final velocities above and below the tail are equal.

What I call the Morelli rules are the way he uses ellipses to reshape the body of revolution acircular cross sections, yet retains the cross sectional area plan of the original tear drop shape. As I interpret this, the ellipses avoid drag generation as air moves in an S shape along the body length, for the pressure variation reasons I described.

Though I describe this process as Morelli rules, there is still quite a lot of art in how this is actually done since the ellipses can be more or less extreme according to designer choice.

Thanks for the discussion,
Jim Bullis
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