Quote:
Originally Posted by Stacygifford
Hey guys, it has been a LONG time since my last post.
I am currently building a 4x4 Astro camper van, but my inner ecomodder keeps showing through. the van now has a 6.0 LS with a 6l90 for double overdrive as well as a partial camper conversion.
I have been wanting to buy a high top (from a junk yard) but I'm not sure i can stomach the fuel economy hit with how awful most high tops are. I really want to keep the thing getting over 20mph hwy. (goal of 25mpg @60mph)
So, the logical idea is to build a high top in the Foamy style following the aerodynamic template.
Which of theses 3 do you think will work best? all 3 have been set to the exact same height (13" higher than the factory roofline) Assuming frontal area is the same between all 3.
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* The overall height and position of the new roof's apex determines alignment with the 'AST Template.'
* And it must include the 'roadway' in order to protect the pressure gradient along the roofline, and with it, the boundary-layer attachment.
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* Additionally, the AST-Template is intended for use with coupes, sedans, and small crossover utility vehicles ( CUVs), where the 'height' of the vehicle is the 'minimum' component of the frontal area.
* With a 'squareback' van, there are aerodynamic 'solutions' better suited for your use, as the 'width' of the van ought to dominate the 'calculus' we'd want to use for streamlining.
* I recommend that we add the 13", determine where the high point to the roof occurs, then place 'that' under the template, and see where it leads.
If we don't include the overall height of the van, we'll end up with a roof-flow deceleration 'overshoot', and impose such an adverse pressure gradient, that the boundary-layer will just 'throw it's hands up and say,'see you later,' triggering separation,losing any drag benefit.