Motorcycle aerodynamics, a slippery and windy, slope?

[sendler]

Too bad they really don't go into any specifics of the design as to stability tries and fails. We must also keep in mind that land speed machines are never run if it is at all windy. And barely have traction at either end during a run so they are more dominated by ballistic stability theory than a motorcycle that still has both tires stuck to the road. Hence the long, high, tail like an arrow needs.
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Another unrelated thought: This bike's solid aluminum front wheel cannot corner the bike via camber thrust the way a normal motorcycle does.

[Grant-53]

As for aircraft design, modern sailplanes have an oval cross-section. Older planes like the Spirit of St. Louis or Ford Trimotor had flat rear panels mostly as a cost savings in labor.

[sendler]

Originally Posted by Grant-53

design

Have you ever approached Cornell University about using their wind tunnel?

[Grant-53]

I checked into the Cornell University wind tunnels and they are 1' x 1' size. The big tunnels are in Buffalo and are run by Calspan. I checked their website and they did not list any rates or info on testing motorcycles or bikes. You could contact them for a quote.

[Grant-53]

This is a concept fairing for a Honda CBR 250 based on the Template C drawing in the Aerodynamics forum.

[Grant-53]

Here I am trying to investigate the effects of side wind on a full fairing.
A standard motorcycle and rider will have a CG in the gas tank and above the
CoP so an aero induced torque will likely help the tendency to lean.
On a scooter the CG is lower and further aft. If the CoP is above the CG, the induced aero torque will tend to resist a lean into the wind. These forces and dimensions could be adjusted to complement to the over all handling of the machine.

What I find on a bicycle is that frontal profile is like an ice cream cone, round at the top and tapers to the bottom. By making the air going under the bike to move faster some reduction in lift can be generated. A big difference between a bicycle and a motorcycle is the ground clearance. For my bike fairings I stop just below the knee and have 20 inches clearance. A motorcycle may have 4-5 inches clearance.

[Grant-53]

This is a fairing based on a glider body for the Honda CBR 250. Note that it is similar to the optimum Morelli / Aptera shape. It would likely work with a Vetter front piece or could be completely fabricated using cut and fold techniques. This is what I hope to adapt to a small scooter.

[renault_megane_dci]

The starting vehicle is very much important.
If starting from a scooter, the gearing is difficult / expensive to alter so the potential of the fairing is likely not to be fully unleashed.
I would go for a regular bike without hesitation.

[sendler]

Originally Posted by Grant-53

This is a concept fairing

Now you can adapt the shape further to incorporate a scale rider.

[Grant-53]

There are 1/10th model kits that have motorcycle riders and I have a wrestling action figure that size. A better solution would be to have someone take a picture of yourself on your bike with meter stick visible to help scale. I am just under 6 ft. and my inseam is 31 in. Make a figure template with movable joints if you like to compare positions.

The Template C profile was, I believe, developed for cars which are at least twice as wide a motorcycle and dates prior to WWII. The Morelli shape is based on more modern research. For a café style motorcycle the weight is forward say 55/45%. The Rifle Yamaha shell and the AeroTech Bonneville fairings used by Fred Hayes are designed for such a riding position. For a cruiser, scooter, or a Feet Forward design the CoP needs to be more aft and front lift is more of an issue. Rather than champion one form over another I suggest each have limits and benefits that are applied to a total design.

I am using a scooter since that is what I have: Honda 50cc 2 stroke. I will experiment with aero bars on the handle bars to lower the profile height. The profiles are scalable and can be adapted to local conditions by changing the angle of attack or adding a small vertical stabilizer. I live in a river valley and sendler lives on a lake plain so weather patterns are different. How we carry luggage can also play a part.