Motorcycle Fairing Question

[ChrisLenahan]

Has anyone tried using the Kamm effect in designing a motorcycle front fairing?  What I mean is to make the frontal area a little larger in order to be able to taper the fairing and direct the air over the rider.  I know its a trade off between frontal area and Cd.  The exposed front wheel and rider seems to be the biggest problem areas in motorcycle aerodynamics to me and I'm just trying to apply what I've been learning to the problem. 

[saltwheels262]

I think it's worth a try.
still trying to get my fairing to fit the chassis.

[wobblywalrus]

The Triumph fairing uses the principal of the teardrop shape where is is a little bit wider in the front so it has a gentle taper toward the tail, like you are talking about.

[RidgeRunner]

     Check out: http://capttop.blogspot.com/2008/02/motorcycle-years-from-motorcycle-design.html?zx=e43e964c7483c550.  Some interesting relevant information on Wixom's aero development for the HD race program in the '60's about 1/2 way through.

           Ed

[slimjim]

Yes. 

[ChrisLenahan]

I'm asking the question because most fairing designs I see for land speed racing designed to have the minimal frontal area require to cover the rider.  My though is that if you slightly enlarge the fairing ahead of the rider you can taper it back and direct the air so that it misses the rider completely.  I guess it would be possible to do away with the streamlining behind the rider as the air is being controlled by the front fairing  but the center of pressure would be too far forward.  A crosswind might also work against this design as the taper on one side may be negated by the relative wind angle.

[fredvance]

As Pork Pie says it is not how you open the door it is how you close it. Since the "new" long tail rules, APS, went into affect speeds have gone up dramatically. Both ends must work together.

[donpearsall]

Just a clarification, the "long tail" for APS is for SCTA rules only. The BUB/AMA event still requires there be NO "Long tail."
Darn. Maybe next year they will come out of the dark ages. Crossing my fingers.
Don

[ChrisLenahan]

Fred, I agree  and with a motorcycle there are 2 doors to close one where the front fairing ends and the rider begins and one at the tail end.  My question is about the first one. 

[Old Scrambler]

Chris............I think the PS design that will best work for you must be tailored to your specific bike and basic profile. I suspect that numerous small HP bikes choose the wrong fairing because the records indicate they go slower than UN-faired. I shall find out with my own adaptation of an RS125 fairing to my TRIUMPH Cub to run at the BUB.

On the high-speed end of things.......Two years ago Mr. Warner (311-MPH) complained about a very light front-end at high-speed which may have been caused by too much upward air-pressure combined with vacuum-drag at the top.

The long-tail design may be safer at high-speed, but I think it also leads to overall faster speeds without considering the tire-safety aspect and the limitations on design at the front.

[SaltPeter]

Chris............I think the PS design that will best work for you must be tailored to your specific bike and basic profile. I suspect that numerous small HP bikes choose the wrong fairing because the records indicate they go slower than UN-faired. I shall find out with my own adaptation of an RS125 fairing to my TRIUMPH Cub to run at the BUB.

On the high-speed end of things.......Two years ago Mr. Warner (311-MPH) complained about a very light front-end at high-speed which may have been caused by too much upward air-pressure combined with vacuum-drag at the top.

The long-tail design may be safer at high-speed, but I think it also leads to overall faster speeds without considering the tire-safety aspect and the limitations on design at the front.

I run a relatively low power Bike in APS/G 250. I made a Fairing as per SCTA APS Rules myself. I made the Front Fairing as wide as my shoulders and and shaped so that it would direct the majority of the Air around the sides and not over me. I also tried to get my feet forward so that the sides of the Rear Tail section were as long as possible. I found that it did make a difference. The power was pretty much the same,  geared for a slightly higher speed.

In 2010 in M/G 250 once I got to around 110 mph and I was in full tuck, it would slowly wind out to a top speed of 119mph. On the first Timed Track run this year, I got up to a speed that was relatively stable (had a crosswind), I was in 4th at around 110mph, I changed into 5th and opened the throttle and the Bike accelerated, (it became a bit too skatey as I was also dialing in my new suspension) so I eased off a little to a stable speed, then went through the Timed Mile averaging 113.751 mph. Had engine dramas after that so did not get a flat outrun.

Next year I am going to run the Bike unchanged, so I should know a bit more then.

Pete

[Old Scrambler]

OK.......its well below zero in my garage........so time to catch-up on a few things. 

My RS1215 fairing seems to work quite well on my Tiger Cub. We set a new record but think we can go faster with more power to the plug. I agree that pushing the air to the side in direct relation to the type of hole your making in the air should be the most efficient. At my low speeds, I don't know about closing the hole other than minimizing obvious drag. 

While on the course, I noted the slight feel of wind on my arms but when I twisted my wrists to move inward, the air was gone. Did I have laminar flow and then created drag?

My goal for 2014 is to lower the fairing, narrow my seat tail, and GO A LITTLE FASTER.