[Teri_TX]

Originally Posted by sendler

Not threadjacking. Just guiding you to some reading to answer your questions so we don't have to sit and type it all out again. Tails and rudders were considered at length.

Hi Sendler,

Sorry, I didn't mean to sound so harsh. The position of the link you sent was an endless confusing argument of bike handling. However the link to Tony Foale was very interesting. I hadn't seen it before and it doesn't show in his articles link. How did you find it?

Tails and rudders are indeed a point of disagreement among other things, I'm neutral on them so far. Indeed, much is endlessly re-hashed in forums but not everyone reads every thread (and can remember). Posting a permalink to the applicable discussion would be extremely helpful and enlighting. Please do so when you can so your fingers can get a rest

The Tony Foale pages were very ingenious to show that trail, not rake angle, is the active ingredient in making a motorcycle stable regardless of rake which is really just set as a compromise between withstanding the bending forces that are trying to push the wheel back when you hit something, and the weight of the bike trying to bend it forward.

Going off topic for a moment, Foale's article cleared up a point I had always been curious about. His conclusion would suggest the Hossack or BMW's implementation, the "Duo-Lever", would be the ideal front suspension. For scratch builders of a streamliner not constrained by convention and appearance, this may be a fruitful approach.

... But I disagree with some of his statements regarding longitudinal center of pressure and long tails which are true for an airplane but are more complicated and counter intuitive when you still have two wheels stuck to the ground that are far and away the determining factor on the path of movement.

In my opinion, the Center of Pressure (CoP) should be slightly behind the Center of Mass (CoM) but not excessively so. Vetter is a long tail advocate mainly because of his obsession with lower drag. Hard to argue with but sometimes "too much is just too much" (vs. "too much is not enough") and a compromise must be made. Modern sailplanes have their rear empennage on a long boom for yaw and pitch stability due to their extremely long wings to avoid "close coupling". "Close coupling" makes for extremely manueverable airplanes but is potentially very dangerous for anything but aerobatic and fighter planes. Even 4th and 5th generation fighters aren't close coupled but are inherently unstable (for other reasons) anyway. The weight of the boom is a negative but it is a compromise for yaw and pitch stability. I am of the opinion their cockpit profiles are merely low drag envelopes and contribute little toward any other handling aspect contrary to someone's opinion.

The interesting addition to the conversation that was brought up in this thread was the nose foiler. I wonder if that is why many modern sport bikes have some sharp protrusions in the front bodywork on either side of the headlight?

I've wondered about this (sharp protrusions) too. I initially dismissed this as merely a styling exercise but I wonder if they have accidentally stumbled onto something. I believe they do this as Viagra (as if they need it) for wannabe boy racers. Spoilers, strakes, foiler, or whatever you care to call them would cause turbulance and drag on both the upwind and downwind side contrary toward Fuel Efficiency (FE). Conventional motorcycles are anything but low drag. Virtually everything on ordinary production motorcycles is for raw performance and appearances as this is what the market demands. Our goal here is FE which means low drag is a requirement. We have to keep our eyes on the prize, fuel efficiency. When subsidized (yes, it is) gasoline in the US gets to EU (and intensionally taxed) and unsubsidized prices, maybe FE will become the market demand.

Have you considered puting a stall strip (temporarily) on your bike's nose? Pete's [Ironside] initial experiments are easily implemented on any fairing. From your other postings, you report your Honda is very stable in cross winds with you laying on the tank. What about other body positions? At my age, bending my neck so extremely in a belly on the tank position is an absolute NO-NO for more than a couple of minutes.

Meanwhile, I eagerly await the results of Pete's [Ironside] additional experiments with the "L" sections he purchased.

-- Teri