Where the aero template came from...

[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). What reynolds numbers was the template run at?

[Ken Fry]

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).

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.

[skyking]

Originally Posted by drmiller100

car is 45 inches tall (Aren't they all?????).

Cockpit is 9 feet long.

Tallest part of the car is right above drivers head (aren't they all?). Behind the driver is 6 feet.

What is drop in car of the first 2 feet behind driver's head? Next 2 feet? Final 2 feet?

I want to do the sides also. Widest part of the car is at the driver's elbows (aren't they all?). which is 40 inches wide. Need the same numbers.

Your car is half scale of my trailer. I took the image of the template, scaled it to fit in irfanview, and made some prints till it would measure up with an engineering scale.
I scaled your car as follows:
10% = 15.3" aft = 44.7" = 3.5° slope
20% = 30.6" aft = 43" = 7.5° slope
30% = 45.9" aft = 40.75" = 12° slope
40% = 61.2" aft = 37" = 15° slope
50% = 76.5" aft = 32.25" = 18.5° slope
60% = 92" aft = 26.7" = 21° slope

Looking at that, I would move the highest point forward of "right over the driver's head".
The headroom does not lessen appreciably in that first 10%. I'd put the 10% point over the driver to maximize headroom when you lean forward to get out, and maximize the drag reduction at the back.
You get back to that ~20° slope which is near maximum.

[drmiller100]

hmmmm..
Thank you for running those numbers. Not at all what I was hoping for in terms of results.

[aerohead]

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). What reynolds numbers was the template run at?

In elevation,the Litestar's aft-body is a perfect match to the 'Template.' I have no plan-view of the vehicle,so I'm no good to you there.
The 'Template' is not intended for laminar boundary layer,as that would raise drag by leading to premature flow separation (see any fluid dynamics text,especially 'Boundary Layer Theory',by Herman Schlicting.
As to Reynolds number,for the length of automobiles and the speeds they operate at,the 'Template' will provide proper 'critical' turbulent flow Reynolds number.
The curvilinear profile of the 'Template' will provide laminar flow outside the boundary layer,with no separation until you get to the back,or wherever you make the truncation.

[aerohead]

Originally Posted by drmiller100

hmmmm..
Thank you for running those numbers. Not at all what I was hoping for in terms of results.

I did a rough look at your project scaling 45" at max camber point.
*at 24" aft you'd be at approx. 43.82"
*at 48" aft,40.48"
*at 72" aft,35.0"
At this terminus for the body,it would put you at 42.5% of the 'Template' aft-body with a potential for around Cd 0.17 if everything is very clean up to that point.(think AEROCIVIC)

[Grant-53]

The Template C appears to be an exponential curve as in a Poisson distribution and will generate lift if air flows under it. Cars vary in length, ground clearance, and height. Consider the ground clearance (6 to 9 inches) as considerable work has been done in the last decades on ground effects and downforce at high speeds. A combination of ellipsiod quadrants can approximate a 5:1 streamline shape. Functions can be calculated using a spreadsheet program and plotted as 3D graphs. Experiment with positioning an angled 'bug deflector' on the hood reduce high pressure at the base of the windshield.

[Frank Lee]

Experiment with positioning an angled 'bug deflector' on the hood reduce high pressure at the base of the windshield.

Those are known to mess up aero.

[Grant-53]

That is usually the case as most are mounted vertically at the front of the hood. I'm looking at something at a 40 degree angle a foot or so from the wipers.

[Frank Lee]

So that creates high pressure in front of the dam and turbulence behind it? I'm not imagining the mechanism for improvement...