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Old 07-19-2011, 07:11 PM   #34 (permalink)
aerohead
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radii

Quote:
Originally Posted by orbywan View Post
I don't drive it much now but it's good knowing it's efficient for it's size. I still have to finish the A/C unit, skin the undercarriage (that's going to be serious fun) and do some mods to the front so I'm hoping there's better numbers ahead. Time will tell.

I was surprised the Dryden tests didn't show better numbers for rounding off the front, so I went after the tail first. I found another chart on a truck products company's web site, which I can't find at the moment, that shows rounding a brick shape object in the front reduces Cd by 50%, which I think is the way the average Joe thinks, including me until I tried the boat tail.

Anyway, I'm going to try several things up front, there's serious room for improvement there also.
Moller improved the Volkswagen 'brick' from Cd 0.76,to Cd 0.42 with front radii.
Walter Lay,in 1933,built a full-size brick on a GM truck chassis.Leading edge radii cut drag from Cd 0.88,to Cd 0.42.
In 1963,GM investigated 18-wheeler drag.A fully radiused front was just a smidgeon ( sp?) better than an 18-inch radius.
In 1936,Fachsenfeld modified an Omnibus bus,with an inflatable boat tail which brought the drag down to Cd 0.158.His tail is the best I've seen so far.It's in Hucho's book.
The NUNA-3 team boat -tailed 'everything' on the car and achieved Cd 0.077.
The back really is where the pot-of-gold it hiding.

Last edited by aerohead; 07-20-2011 at 06:52 PM.. Reason: mis-spelled word
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