It's about time for this thread to pick up again. Much has been discussed in various other places since the last posts here. Some of my conceptions:
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Motorcycles automatically lean and corner into a side wind simply due to the trail in the steering geometry as shown by the dramatic correction of the ecomobile video. As long as the handle bars are not burdened with a terrified rider's rigid arms.
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Keeping the CG on the roll axis high accentuates this to a good effect.
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Keeping the side CoP low helps push the bottom of the bike out from under the top to lean into the wind to a good effect.
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Streamlining a motorcycle turns it into a vertical airfoil which generates horizontal lift when sidewinds combine with the headwind of forward motion to create an angle of attack. This increases the side lift beyond what a normal, dirty motorcycle would see.
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A streamliner only sees a crosswind when it is getting blown off the kick stand. At highway speed, even a 30 mph side wind gust will combine with the head wind of the forward motion to form a vector at a slight angle to the nose. This angle of attack causes the vertical airfoil shape to create lift (side).
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The greatest lift of an airfoil is located just behind the max thickness. An interesting experiment showed the best place for the max side lift to occur to activate the self correcting aspect of the trail of a two wheeled vehicle is actually at the head tube. Not well behind the center of gravity as would be best for an arrow. Because bicycles have two tires anchored to the ground with front steering trail and turn by leaning. A bicycle was ridden while a helper traveled along side tugging on a string that was alternately attached to the bike at various places. When attached to the seat post or the luggage rack above the rear wheel, as in a long, high tail, it was easy to pull the rider off balance and out of line. The higher, the worse. When attached to the head tube, the bike self corrected from the effect of it's trail to lean against the string as hard as it was being pulled. Unfortunately, the max lift ends up being well behind the head tube in practice. So Craigs streamliners use a vent across the lap of the rider to equalize the pressure differential. Another option for a fully enclosed machine would be a spoil strip running up the nose.
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An easy mistake to make would be generalizing two wheeled vehicles, multi wheeled vehicles, and aircraft. Motorcycles turn by leaning after COUNTER steering. Cars turn by steering. A vertical stabilizer on the tail of a motorcycle that still has traction from both tires will be counter productive to cross wind stability.
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Camber thrust - Wikipedia, the free encyclopedia
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Cornering force - Wikipedia, the free encyclopedia
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Precession - Wikipedia, the free encyclopedia