Quote:
Originally Posted by aerohead
The car guys always defer to 'drag-factor',or,CdA.And Cds are always in the context of frontal projected area.
Since most modders aren't going to chop the roof off their car or do extreme alterations to frontal area,we've kinda defaulted to drag coefficient as the thing of primary interest.
Jaray got the whole 'Streamlined body of revolution in ground reflection' going back in 1922.
Jaray,Kamm,Lay,and so many others ended up using the body of revolution as their starting point,it seems like the convention with road vehicles.
Hucho used it at Volkswagen and he's the one who cited the L/D 2.5:1 Streamline form,or elliptical form as the 'minimum' for drag.
He chastised Mercedes_Benz for not honoring it with R&D of their C-111 III.
I've been looking for anything which demonstrated the lowest Cd with minimum structure and so far,for something in ground-effect,which cannot benefit from the jet pumping action of a body in free-flight,I've never come across anything "shorter" than L/D 2.5,which would translate to a vehicle with Length,5X it's height.
Al's closing gotta go,will pickup tomorrow.
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With respect to streamlining,the authors of fluid dynamic texts,when referring to automobiles say a 'hemispherical' nose(half of it) is adequate below 250-mph.They say the rear part of the vehicle is most important.Moving the point of separation back is the key,and the only way you can do that is with a tapering tail.If a 2.5:1 teardrop tail section is the "shortest" separation-free "tail",then perhaps it's a safe model for us.It worked for Jaray.It worked for Kamm.It worked for Lay.It worked for Reid.It worked for Heald.It worked for R.G.S.White.It worked for Hucho.It worked for AeroVironment.
I'd like to see the 3.33 form.So far,nobody has posted a photo of it.And I would like to know the context in which it's performance figures were derived.
When a prosecutor makes a claim against a defendent,they provide a brief of particulars.It's only common courtesy.