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Old 03-18-2009, 06:26 AM
  #11  
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Originally Posted by xjcaptain
Cessna finally figured it out!!!!!!!!!!......40 years after everybody else. Let's see............pointy nose.......swept wing...............more thrust........... It goes FASTER!?!? Who'd a thunk it!?
I know you are half serious here, but you've drawn me out for a short lecture . Obtaining minimum drag on a blunt body is not very closely tied to how pointy it is. Fineness ratio is the ratio of cross sectional area to length. Some common examples of non-pointy, low-drag bodies are the noses of the Space Shuttle booster rocket and the leading edges of most supersonic delta wings such as the Concorde. If you look at these items, you will see they are not as much pointy as curved. Ogive is the technical term. Ogive shaping reduces drag at supersonic and high subsonic speeds. Before they discovered this, the early F-102 Delta Daggers showed that high fineness ratio alone does not reduce drag enough to permit supersonic cruise. The first F102 was made as sharp as they could make it and it failed to work out as planned.

Delta Dagger and Drag Reduction

Someone said the earlier Citations are slow which is relevant here. The joke used to be "Slowtation" before the Ten came along. Cessna did not bother to develop higher fineness ratio shapes for these airplanes because compressible drag does not begin to spike until about M= 0.82. This incidentally is why most civilian airplanes only go M=0.82. Citations do not go anywhere near this fast and so do not experience the drag penalty for a less pointy nose-shape. The air has plenty of time to get out of the way without shock waves forming.

Last edited by Cubdriver; 03-18-2009 at 09:43 AM.
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