Driven by wind, downwind, faster than the wind...

[APenNameAndThatA]

I found this amazing. 

 

https://www.vice.com/amp/en/article/bvzyx8/science-youtuber-wins-dollar10000-bet-with-physicist?__twitter_impression=true

 

I will try and embed a video. 

 

 

 

[IBob]

Yep, that's a curly one to get the head around......)

[spacesailor]

The new era yachts go faster then the wind that powers them !.

10 knts wind, plus 6 knts boat travel,  = 16 knts apparent wind ,.

spacesailor

[skippydiesel]

Wow!!!!!!

[poteroo]

After a lifetime of flight planning, I have found a workable formula, (= rule-of-thumb), for dealing with wind.

 

Halve the tailwind component that you have calculated, and double the headwind that you calculate.

 

happy days,

[FlyBoy1960]

it proved one thing to me, hot chicks like science !

 

Shame I am not smart enough !

[turboplanner]

  On 04/07/2021 at 3:09 AM, poteroo said:

After a lifetime of flight planning, I have found a workable formula, (= rule-of-thumb), for dealing with wind.

 

Halve the tailwind component that you have calculated, and double the headwind that you calculate.

 

happy days,

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You should write a Thesis on that and call it Dark Aeronautics; Melbourne Unit would probably give you a Masters in aeronautics for that.

[Thruster88]

The worst part is we spend more time flying in head winds than tail winds.  

[nomadpete]

Sailors have the same problem.

It seems to be a rigid rule of physics.

 

I'd call it 'The perversity of nature'

[kgwilson]

In the recent Americas Cup racing in Auckland the AC75 foiling monohulls regularly topped 50 knots in under 20 knots of wind. The world record stands at around 65 knots. This was a bloke from Namibia called Paul Larsen & his boat called Sailrocket was designed to just go in one direction fast. The peak speed was 68 knots in setting the record in 2012 and the wind speed was between 26 & 31 knots.

[jackc]

This was an Australian effort that I was involved in,  supplied the Radio Telemetry electronics for the vessel.

 

https://www.clubmarine.com.au/exploreboating/articles/24-3-50-knot-out

 

[IBob]

The foiling sailboat performances are certainly outrageous. Having said that, the dynamics, or mechanics, or physics, or whatever we should call it......of the foiling sailboat speeds are a completely different thing than what is going on with this downwind land-yacht.

None of the foiling sailboats, regardless of how refined, will go directly downwind at or faster than the wind speed.

[RossK]

  On 04/07/2021 at 12:14 PM, kgwilson said:

In the recent Americas Cup racing in Auckland the AC75 foiling monohulls regularly topped 50 knots in under 20 knots of wind. The world record stands at around 65 knots. This was a bloke from Namibia called Paul Larsen & his boat called Sailrocket was designed to just go in one direction fast. The peak speed was 68 knots in setting the record in 2012 and the wind speed was between 26 & 31 knots.

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Just being picky - Paul Larsen is actually an Australian, the record run was done in Namibia.

[Flightrite]

Just found this, a good watch:-) I loved that this so called educated boffin got called out....that's the best part:-):-)

[APenNameAndThatA]

  On 04/07/2021 at 8:59 PM, IBob said:

The foiling sailboat performances are certainly outrageous. Having said that, the dynamics, or mechanics, or physics, or whatever we should call it......of the foiling sailboat speeds are a completely different thing than what is going on with this downwind land-yacht.

None of the foiling sailboats, regardless of how refined, will go directly downwind at or faster than the wind speed.

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Yeah. I thought that I understood it because boats can sail faster than the wind. Then I realised that I still didn't understand it. IIRC, the wheels drive the propeller, FFS. 

[APenNameAndThatA]

  On 23/08/2021 at 4:12 AM, Flightrite said:

Just found this, a good watch:-) I loved that this so called educated boffin got called out....that's the best part:-):-)

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Yeah. He couldn't stop himself being a bit sarcastic when he was saying that it could not be done. 

[facthunter]

He wouldn't be alone. It takes a bit to get to grips with. It's anti intuative. Nev

[APenNameAndThatA]

  On 23/08/2021 at 8:37 AM, facthunter said:

He wouldn't be alone. It takes a bit to get to grips with. It's anti intuative. Nev

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I still don't understand it. The wheels drive the propeller. The wheels are pushed by the body of the car... which is pushed by the propeller. 

[facthunter]

It's not perpetual motion though when you get and use  energy from some thing in an efficient way.. Nev

[Thruster88]

I am a little sceptical. This very simple idea has been tested since at least 1969. One of the very few such vehicles to appear in a video, the Blackbird can supposedly travel down wind at 2.8 times wind speed and up wind at 2.1 times wind speed, very impressive but no real evidence of this performance.  It was not long after the car arrived that people were racing them. Why no racing for propeller driven land yachts. 

[pmccarthy]

I am stuck in understanding it. If the propellor is driven by the wind, the effective wind is zero once the car reaches wind speed. If it goes faster than the wind, effective wind speed is negative at the propellor. Then the propellor cannot drive the wheels through gears. 

[onetrack]

The wheels are actually driving the propellor via leverage, the wind is not driving the propellor. The propellor is pushing the vehicle forward, against the tailwind. There are multiple factors at work here, propellor efficiency being just one of them.

 

Put simply, the car is leveraging the available energy from the tailwind, to travel faster than the wind speed.

 

https://docs.google.com/document/preview?id=10qzwC8BmR3fr-ezvSveZ1cOJxZ_4gObOk3DHHaPp2GY

[pmccarthy]

Ok I actually understood that!

[Flightrite]

I can't see the difficulty here, we have a power driven vehicle, simply as that!

[Thruster88]

  On 24/08/2021 at 11:07 PM, Flightrite said:

I can't see the difficulty here, we have a power driven vehicle, simply as that!

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I can't see the difficulty in shooting a decent video using a drone and some balloons that get released as the vehicle approaches at 2.8x wind speed on a big dry lake bed. A readout of wind speed and ground speed in the corner would be nice. I remain sceptical. We know wing suits work and can do amazing things because there are many excellent videos on the net.