Quote:
Originally Posted by drmiller100
I'm not seeing the love.
I don't see any way in heck the Litestar fits the aero template listed above.
I totally believe the Litestar/Pulse is VERY aero, and I somewhat doubt the aero template listed really stays laminar at higher speeds (over 70 or so).
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Hi Doug,
You asked previously about the numerical basis for airfoils. Many streamlined sections are the graph of fourth or fifth order equations. The formula for the four digit NACA sections is in Abbott and Doenhoff, (Theory of Wing Sections) which you can find in most university libraries (and on line). This link provides a typical formula:
Airfoil Geometry
There are several free or low cost airfoil design programs that will let you design foils and analyze 2d flow. (I like PANDA from Desktop Aeronautics.) A look through Abbott and Doenhoff, which has actual wind tunnel test data for numerous airfoils will convince you that there is no single shape that is "streamlined".
I have not put the Hucho template over a Pulse, but if you did so, I'd expect that you'd find that the aft section of the body (viewed in elevation) slopes more gently than the template (ignoring the vertical stabilizer). The sides slope far more gently that the template. In theory, at any slope less than the template slope, flow remains attached, if it is attached at the maximum cross sectional area. However there is a great deal of interaction between top and sides, and there are some very streamlined shapes with negligible roof slope and some with greater-than-template roof slope. The original Jaray, for example, appears to have an impossibly steep roofline when viewed from the side, but when viewed from the top, you can see that the basic airfoil shape has been turned on edge. (More obvious is the difference between the VLC and the Aptera, with the first splitting the flow along a vertical plane, and the second splitting it along a horizontal plane.)
The Litestar was reasonably aerodynamic, with a Cd of .193, with almost fully enclosed wheels. Most people got 50-55 mpg at normal highway speeds,
as you can see here. This is as expected from the weight, the frontal area, the Cd, and the middling BSFC of the motorcycle engine.
A general rule is that you can have far more bumps and edges on the front half of the body than the rear. It is a good assumption that your shape would be more efficient without the two-step rear taper, (and instead a smooth curve) but a little time spent with 3D CFD would clarify that. There is likely a university not too far away with Solid Works and Fluent, and a kid who'd be happy to run the computer. Tufting it once it's built is equally good for finding transition points.