Sailing directly downwind faster than the wind
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Onyx8 wrote:How come you didn't directly answer any of my questions?
So what starts the wheels turning?spork wrote:Four things to keep in mind:
1) The prop never turns the wheels. The wheels turn the prop
Would you mind backing that assertion up?
2) Inertia doesn't factor into it. Even exactly at wind speed we can tow a trailer all day long.
Actually they are traveling in a helical path, but nevertheless they are still traveling at exactly the speed of the wind. If it can't 'feel' wind then it can extract no energy from it.
3) When the vehicle is going directly downwind at wind speed, it feels no wind over it. The "prop" is also going downwind at wind speed. The blades of the prop however are not going directly downwind. The blades are following a spiraling path so they will always feel relative wind even when the cart is going downwind at wind speed - remember their tangential velocity.
4) When the cart is going the speed of the wind - it feels no wind. But that doesn't mean there is no wind. It simply means there is no relative wind. There's still wind moving over the ground, and that's precisely the energy this vehicle exploits. It leaves a path of slower moving air in its wake - having taken some of its energy.
but nevertheless they are still traveling at exactly the speed of the wind
Onyx8 wrote:spork wrote:
The blades are following a spiraling path so they will always feel relative wind even when the cart is going downwind at wind speed - remember their tangential velocity.
Actually they are traveling in a helical path, but nevertheless they are still traveling at exactly the speed of the wind.
Onyx8 wrote:spork wrote:4) When the cart is going the speed of the wind - it feels no wind. But that doesn't mean there is no wind. It simply means there is no relative wind. There's still wind moving over the ground, and that's precisely the energy this vehicle exploits. It leaves a path of slower moving air in its wake - having taken some of its energy.
How does it extract energy from air that is not moving relative to itself?
You cannot use your own inertia to accelerate yourself. When the cart accelerates, all its parts accelerate as well. So they are not using any inertia for acceleration.
Macdoc wrote:
except under turntable or treadmill conditions which I consider completely spurious nonsense.
What net force? Why are you being so cagey?
You cannot use your own inertia to accelerate yourself. When the cart accelerates, all its parts accelerate as well. So the cart in not using any inertia for acceleration.Onyx8 wrote:spork wrote:
The blades are following a spiraling path so they will always feel relative wind even when the cart is going downwind at wind speed - remember their tangential velocity.
Actually they are traveling in a helical path, but nevertheless they are still traveling at exactly the speed of the wind.
Wrong, you forgot the tangential velocity. At wind speed, the blade velocity vector is the vector sum true_wind + tangential_velocity. Different speed and different direction than the air.Onyx8 wrote:spork wrote:4) When the cart is going the speed of the wind - it feels no wind. But that doesn't mean there is no wind. It simply means there is no relative wind. There's still wind moving over the ground, and that's precisely the energy this vehicle exploits. It leaves a path of slower moving air in its wake - having taken some of its energy.
How does it extract energy from air that is not moving relative to itself?
Push it back to slow it down.
spork wrote:Four things to keep in mind:
1) The prop never turns the wheels. The wheels turn the prop
2) Inertia doesn't factor into it. Even exactly at wind speed we can tow a trailer all day long.
3) When the vehicle is going directly downwind at wind speed, it feels no wind over it. The "prop" is also going downwind at wind speed. The blades of the prop however are not going directly downwind. The blades are following a spiraling path so they will always feel relative wind even when the cart is going downwind at wind speed - remember their tangential velocity.
4) When the cart is going the speed of the wind - it feels no wind. But that doesn't mean there is no wind. It simply means there is no relative wind. There's still wind moving over the ground, and that's precisely the energy this vehicle exploits. It leaves a path of slower moving air in its wake - having taken some of its energy.
chaggle wrote:So the vehicle is moving faster than the wind? In that case the wind "in its wake" hasn't reached it yet.
chaggle wrote:SHow can it have taken some of its energy?
Onyx8 wrote:ignoring observations like chaggle just made.
jaydot wrote:i love it when people say "it can't be done." and some clever chap comes along and shows that it can.
jaydot wrote:
heavier-than-air machines were once considered an impissibolity - until those pesky wright brothers came along.
chaggle wrote:So the vehicle is moving faster than the wind? In that case the wind "in its wake" hasn't reached it yet. How can it have taken some of its energy?
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