Quote:
Originally Posted by Jim Bullis
aerohead,
No, the Morelli shape is not a miracle shape, but the discussion of aerodynamics backed up with test data is quite excellent in the actual 1982 paper by Morelli.
But in that paper, Morelli does not proclaim this shape to be a great answer in the real world, though it gets a Cd of .047 for the low to the road position. He goes on to discuss the essential changes that would be needed, including wheels, and this pushed Cd up to .19, again, as I recall, for wind tunnel tests of that form.
My appraisal is that the Morelli shape is quite inefficient from the volume perspective, even though Cd defined on frontal area is very low.
It might be of interest that Cd for airships in the old test data is defined on a volume basis, specifically, the cube root of volume squared to get area like dimensions.
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Jim,if you can snag a copy of Sighard Hoerner's book,Aerodynamic Drag,he's got formulas to convert Cds from surface area,volume,and frontal area.
He also does a minor drag breakdown on airship 'Los Angeles' ( LZ 126 ) designed by Paul Jaray,perhaps similar to the Akron.