3 ms·

It’s gearing. Albeit elaborate. Intuitively what’s difficult to get the head around is sailing directly into the wind. However the penny dropped when somebody

by rusk 5y ago

It’s gearing. Albeit elaborate. Intuitively what’s difficult to get the head around is sailing directly into the wind. However the penny dropped when somebody says it’s like sailing into the wind and that basically the propellers act like triangular sails that are continuously reorienting. The only tricky part bow is the “faster than wind” bit. Presumably this “dynamic sail” is better at harnessing any divergent energy coherently. Kind of like how a LASER coaxes her photons out in phase to produce a coherent beam. The balancing coefficient is the (variable) pitch of the blades.

thehappypm 5y ago
When you're going at exactly wind speed, there basically is no wind at all. If you had frictionless wheels, you could turn off your propellors and you'd just be coasting along, feeling no force whatsoever from the wind, as if there was no wind at all and you were not moving. The difference here -- you ARE moving, relative to the ground. You can, instead of coasting, reach down and grab some power from the huge mass rolling by below you. That'll try to slow you down -- it'll apply a force in the direction of the ground speed -- but if you harness some power and use it to drive a high efficiency propellor, you might be able to get a little extra speed, but as you speed up, you have more resistance both from the wind and the ground, so you can't do it forever.
- rusk 5y ago
  What you suggest sounds analogous to a flywheel. You’re using the mass of the vehicle to stabilise your speed and drive the propellor when the energy stored in your momentum > the energy you get from the wind. However, this does not account for the full experience they are describing where you can attain speeds far greater than wind speed. If that’s the case there must be a different “angle” to it, pun intended. He’s not just harnessing the purely linear “push” from the wind. There must be other vectors superimposing. Could well be the lift provided by the Bernoulli effect on the propellor blades. As I mentioned elsewhere once you get to that level it’s all very domain specific.

by rusk 5y ago

thehappypm 5y ago

When you're going at exactly wind speed, there basically is no wind at all. If you had frictionless wheels, you could turn off your propellors and you'd just be coasting along, feeling no force whatsoever from the wind, as if there was no wind at all and you were not moving. The difference here -- you ARE moving, relative to the ground. You can, instead of coasting, reach down and grab some power from the huge mass rolling by below you. That'll try to slow you down -- it'll apply a force in the direction of the ground speed -- but if you harness some power and use it to drive a high efficiency propellor, you might be able to get a little extra speed, but as you speed up, you have more resistance both from the wind and the ground, so you can't do it forever.

rusk 5y ago
What you suggest sounds analogous to a flywheel. You’re using the mass of the vehicle to stabilise your speed and drive the propellor when the energy stored in your momentum > the energy you get from the wind. However, this does not account for the full experience they are describing where you can attain speeds far greater than wind speed. If that’s the case there must be a different “angle” to it, pun intended. He’s not just harnessing the purely linear “push” from the wind. There must be other vectors superimposing. Could well be the lift provided by the Bernoulli effect on the propellor blades. As I mentioned elsewhere once you get to that level it’s all very domain specific.