View Poll Results: Does the wind help
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Settle A Bet - Perpendicular Wind
09-20-12, 11:37 PM
#26
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Now that I see how the conversation is going, I feel I can jump in without persuading the topic. Yes, my neighbor does not ride, and yes he feels that a cross wind is helpful to the cyclist. His argument is that if it is not a head wind, then it is helping the cyclist. Like the wind will wrap around the back of the cyclist and push the cyclist forward somehow.
I think one could argue that if the force of wind 'pushes' the cycles to the left or right, during travel, that this is a form of resistance. The cyclist will 'waste' energy compensating for the wind pushing the off the vector of travel, forcing the cyclist to turn into the wind slightly.
I am not sure the magic angle, but I would even go as far as to say that a tail wind at a steep angle, nearly perpendicular to the cyclist, is still a from of resistance. The cyclist will have resistance greater than the help the wind is doing pushing the bicyclist.
I think one could argue that if the force of wind 'pushes' the cycles to the left or right, during travel, that this is a form of resistance. The cyclist will 'waste' energy compensating for the wind pushing the off the vector of travel, forcing the cyclist to turn into the wind slightly.
I am not sure the magic angle, but I would even go as far as to say that a tail wind at a steep angle, nearly perpendicular to the cyclist, is still a from of resistance. The cyclist will have resistance greater than the help the wind is doing pushing the bicyclist.
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09-21-12, 07:49 AM
#27
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Nope. See the faired recumbent above. What matters is lateral sail area and the efficiency of the sail. The better of both, the more efficient the sail will be at extracting energy from the wind, from any angle. As Stan said, a tacking boat can sail upwind by sailing at an angle into the wind. Conventional sailboats make headway in quartering headwinds- more exotic rigid sails can make headway almost directly into the wind.
09-21-12, 08:19 AM
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Where's the money?
09-21-12, 09:43 AM
#30
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Sails do not push a boat. A sail pulls a boat based on the Bernoulli principle (on anything from a broad to close reach). A conventional bicycle and rider make a poor air foil. If anything the wind will cause the cyclist to slow a bit due to lateral resistance.
If the cyclist were able to fashion even a crude foil then some lift would be acquired aiding the cyclist.
If the cyclist were able to fashion even a crude foil then some lift would be acquired aiding the cyclist.
A better explanation comes from Newton. If you hold an aerofoil, sail or indeed a flat plate at an angle to the air flow, air will be directed downwards, creating lift as a reaction force (the air's velocity vector has changed). On the leeward side, the drop in air pressure increases the lift force, however flow separation will affect this component. If a particularly wide-shouldered cyclist could place himself at an angle while riding crosswind, a small aerodynamic thrust would be generated.
However, the problem lies with the angle of the apparent wind. Moving forward causes the apparent wind to shift forward. This limits the maximum speed of any wind-driven vehicle, and in the case of a cyclist will make it virtually impossible to get any meaningful thrust without a dedicated aerofoil or sail structure.
Sailing boats can turn a crosswind (and even a headwind to a degree) into thrust because they're aerodynamically designed to do so. A bike isn't, so can't.
(I'm an aerospace engineer btw
)
Last edited by Monster Pete; 09-21-12 at 09:48 AM.
09-21-12, 09:29 PM
#31
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I did ask "what kind of bicycle" at the beginning. Since you didn't clarify, I thought it was an open discussion.
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