Quote:
Originally Posted by drmiller100
but there is only one top, and two sides.
And the advantages on the bottom are TOUGH to not screw up.
Again, I'm not very sure on this, and am TOTALLY willing to discuss it.
I think you do 1:3 on the top and sides, and radius about a foot at the transition from the tail to the trailer.
Be CAREFUL during that foot - don't do anything to create separation, but don't worry about the 4 corners around your tail- if you screw up the corners, you create a vortex which helps fix any separation.
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*Looking through my materials I've noticed that others have apparently used the 'width' as the datum for streamlining when the vehicle was 'tall',and the height as the datum when wider than tall.
*When I did my VW Bus I used 20-degrees for top and sides incorporating some beginning curvature provided by VW's original design.There was no 'diffuser',as in 1980,there was no talk of such things yet.
*NASA did the Econoline slowly wrapping the rear corners into a progressive slope,ultimately acheiving 20-degrees.
*GM's 'OPTIMUM' boat tail which appeared on the cover of Texas Tech's Engineering magazine appears to brake directly into a constant 19-20 degree slope at top,maybe same at sides (no true-length images provided in article),10-degrees at bottom,with outer edges softened with radii.
GM's tail extends back 65% of trailer height and ends at about 40% of frontal projected area of the trailer box.
No figures are given,as this may have been a proprietary project (they attempted to camouflage the tail markings) and may not have been for public consumption.
*This tail would be a lot easier to construct.
*I couldn't vouch for any numbers,but GM's got some really sharp aerodynamicists and this may have been an 'optimized' tail when looking at the entire life-cycle-cost-analysis,versus an 'ideal' tail.I'd be compelled to give it my blessing!