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Old 07-21-2012, 02:13 PM   #439 (permalink)
aerohead
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sides

Quote:
Originally Posted by Varn View Post
Thanks for the responses.

Do you guys consider the sides to be similarly shaped. with a radius something like 1/2 the width X 5.6. At least for the first part.
I've meant to do a thread for plan-taper 'n haven't.
Since you bring up the topic I'll do something quick and dirty.
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Looking over some vehicles which have represented plan views,it appears that designers have taken a cautious approach with the sides of the vehicle.
Since the air along the sides is slower than over top it would have less kinetic energy and it makes sense that we'd handle it with kidd gloves.
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Low-drag vehicle sides,viewed in plan view, appear to have been designed as a symmetrical wing/strut section.
From Goldstein's research it was found that the lowest drag is found with a length-to-thickness ratio of 3.84:1.
At this ratio the aft-body of the section forms a 'tail' which is 2.4X thickness.
*VW's Cd 0.14 'long-tail' Flow body of 1981 uses this 'tail.'
*Walter Lay's Cd 0.12 car models use this 'tail.'
*CALSTART's Showcase EV used this 'tail.'
*Moto Guzzi's world speed record motorcycle of 1955 went a little longer with 2.56:1.
*the Cd 0.12 MG EX 181 of 1957 went longer,with 3.13:1.
*Paul Jaray's Cd 0.20 'small' kombination car of 1922 Patent application used 2.14:1.
*Paul Jaray's Cd 0.13 'pumpkin seed' of 1921 used 1.88:1
*the OLDS AEROTECH of 1987 used 1.82:1.
*LEXUS' 1994 LS 400 used 1.892:1.
*The VW 2000 of 1980 had 2.169:1.
*Mercedes-Benz Cd 0.178 C111 III used 2.08:1
*The 1995 TNE-3,Cd 0.10,solar racer would be around 2.4:1
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So far,my take on this,is to just go with the (2.4 times body width) aft section of the 3.84:1 streamline section as the basis for body side curvature near the ground plane.
If your project allows,you can be adding tumblehome higher on the body as you move aft,blending into the greenhouse.
This form is already working on low-drag,high mpg vehicles and land speed record cars,so it looks like good off-the-shelf technology.Yes?
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