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Old 28-07-2021, 14:17   #76
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Re: Novel Propeller propulsion, going faster downwind than the wind

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Originally Posted by JoeRobertJr View Post
The prop on this car is never acting as a generator. It is the propulsion, pushing on the air. The video of the model on the treadmill helped clear this up for me.
And for the up wind faster than wind speed vehicle it is the opposite with the propeller driving the wheels. (With different ratios)
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Old 28-07-2021, 14:26   #77
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Re: Wouldn't this be cool ...

I don’t think it would pwork on boat, too much drag on the hull and too much slip between prop and water
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Old 28-07-2021, 14:35   #78
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Re: Wouldn't this be cool ...

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If it could be adapted for water, that is.

https://www.yahoo.com/news/youtuber-...120100405.html


Be sure to watch the youtube video which explains it all.

You might want to check out this thread.
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Old 28-07-2021, 14:41   #79
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Re: Wouldn't this be cool ...

Merged with existing thread on this topic.
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Old 28-07-2021, 14:46   #80
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pirate Re: Novel Propeller propulsion, going faster downwind than the wind

There's a catamaran with that rig but no way can/will it sail faster than the wind..
However foiling boats do sail faster than the wind if you watch the Americas Cup videos.
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Old 28-07-2021, 19:28   #81
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Re: Novel Propeller propulsion, going faster downwind than the wind

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There's a catamaran with that rig but no way can/will it sail faster than the wind..
However foiling boats do sail faster than the wind if you watch the Americas Cup videos.
but not dead downwind. You need apparent wind to generate drag.
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Old 28-07-2021, 20:12   #82
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Re: Novel Propeller propulsion, going faster downwind than the wind

How about this from The American Journal of Physics, Oct 1978 about a "push me, pull you" boat which would sail directly upwind at a max of 2x wind speed.
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Old 28-07-2021, 20:24   #83
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Re: Novel Propeller propulsion, going faster downwind than the wind

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There's a catamaran with that rig but no way can/will it sail faster than the wind..
However foiling boats do sail faster than the wind if you watch the Americas Cup videos.
Agreed, the cat won't do it, but it might be quicker than tacking? Hypothetically, if you towed a better, more suitable version of that cat to be up on foils it's possible.....

I'm not sure of the exact numbers for the AC boats but they probably will be sailing upwind with a target TWA of about 55° @ 18° AWA, with a VMG of only a little better than true wind. As apposed to 180° TWA @ 0° AWA and a VMG of 2.8x true wind for these.
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Old 30-07-2021, 08:09   #84
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Re: Novel Propeller propulsion, going faster downwind than the wind

Another example of the same effect the car is using:
https://www.amazon.com/July-miracle-.../dp/B08923LQQK

Might be easier to see how it works on the toy. Your hands don't move anywhere near the speed of the prop tips. This is the same effect as locking the wheels to the prop on the car. Once the car starts moving, the prop tips are moving far in excess of the speed of the wheels. The energy is extracted from the speed difference between the wind and the ground. Directly behind the prop center, wind speed will be reduced by the amount of energy pushing the car forward, plus friction, plus the energy transferred to accelerated wind out near the prop tips.
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Old 31-07-2021, 18:22   #85
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Re: Novel Propeller propulsion, going faster downwind than the wind

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Originally Posted by Corvidae View Post
Another example of the same effect the car is using:
https://www.amazon.com/July-miracle-.../dp/B08923LQQK

Might be easier to see how it works on the toy. Your hands don't move anywhere near the speed of the prop tips. This is the same effect as locking the wheels to the prop on the car. Once the car starts moving, the prop tips are moving far in excess of the speed of the wheels. The energy is extracted from the speed difference between the wind and the ground. Directly behind the prop center, wind speed will be reduced by the amount of energy pushing the car forward, plus friction, plus the energy transferred to accelerated wind out near the prop tips.
https://youtu.be/kJ9F23nZaVo
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Old 01-08-2021, 05:21   #86
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Re: Novel Propeller propulsion, going faster downwind than the wind

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But the land yacht or whatever it's called has an external source of energy, the wind.

Here is the world speed record for an RC glider doing 877kph in (I think it was) 110kph wind by using the same principals. This time the power was leveraged crossing the boundaries of wind shear behind a sharp drop off.

https://youtu.be/MoaWlKC3wIM
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Old 01-08-2021, 10:42   #87
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Re: Novel Propeller propulsion, going faster downwind than the wind

I don't know about surface based vehicles, but the fastest a glider has been recorded is at 343knots overground in straight and level flight.
It was going downwind and the record was set in January this year.


Can't be doing with kmh or mph.
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Old 01-08-2021, 13:30   #88
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Re: Novel Propeller propulsion, going faster downwind than the wind

Anyone fraudster can make a "YouTube claim" . And many do. There is wisdom in dismissing all such claims
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Old 01-08-2021, 14:00   #89
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Re: Novel Propeller propulsion, going faster downwind than the wind

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I don't know about surface based vehicles, but the fastest a glider has been recorded is at 343knots overground in straight and level flight.
It was going downwind and the record was set in January this year.


Can't be doing with kmh or mph.
This was 476kn in sustainable flight. There are reported higher speeds but not official. - https://www.avweb.com/aviation-news/...record-flight/

The speeds quoted here have been bettered, but this is a good description of wind shadow gliding or dynamic soaring.
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