Quote:
Originally Posted by orbywan
That is fabulous information Wyatt, thank you very much. I am inspired to carry on with this project. That curved four-sided approach is exactly what I thought might be the best shape for back there. The last few feet of the tip not making that much a difference is also encouraging
Judging roughly by the photos, the rear truncated cone is about 23% of the length of the modified vehicle shape. That means to be somewhat proportional, my rear cone would be about 6 long, that's totally doable. I was thinking more like 10 feet since the box is so big.
The drag reduction numbers for this project are staggering. Square at both ends, .89CD, fully rounded front, truncated rear cone, full belly pan, .242CD. That's only a 72.8% reduction in drag!! Wow. Now I just have to figure out what materials to use to build the cone. Thanks again, great information. Yea, NASA!
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orbywan,in the 1960s some of the lowest drag semi-trailer setups were ones in which most of the air was shunted around the rig,not over it.
Since these vehicles are taller than they are wide they are in a world of their own,aerodynamically.
One might just take the width to be the parameter for design.That said,one could multiply the width by 1.78 and this would be the theoretical distance behind the vehicle at which a boat-tail would come to a point.This would be 100% 'Template.'
It's only an assumption.
GM's 'OPTIMUM' boat-tail,at Texas Tech was about 5.5 feet long,for an 18-wheeler with 8-foot wide trailer van.It was just chopped off like a loaf of bread,as Breer,Fachsenfeld,Kamm,and others had done.