> The secret to Blackbird, Cavallaro explained, is that once the wind gets the vehicle going, its wheels start to turn the propeller blades — they're connected to the blades by a chain. As the vehicle speeds up, its wheels turn the propeller faster and faster. The propeller blades, in turn, act as a fan, pushing more air behind the land yacht and thrusting it forward. That's a terrible explanation - no wonder people…
Its actually the correct explanation tho. This article sucked by the way. It said "Any sailor worth their salt can tell you that a boat can travel faster than the wind by cutting zigzag patterns; that's called tacking." Any sailor worth their salt knows that is not true at all. This practically destroys any credibility on this topic by this author.
A wind-powered vehicle that can travel twice as fast as the wind itself
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Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#72> The secret to Blackbird, Cavallaro explained, is that once the wind gets the vehicle going, its wheels start to turn the propeller blades — they're connected to the blades by a chain. As the vehicle speeds up, its wheels turn the propeller faster and faster. The propeller blades, in turn, act as a fan, pushing more air behind the land yacht and thrusting it forward. That's a terrible explanation - no wonder people…
Its actually the correct explanation tho. This article sucked by the way. It said "Any sailor worth their salt can tell you that a boat can travel faster than the wind by cutting zigzag patterns; that's called tacking." Any sailor worth their salt knows that is not true at all. This practically destroys any credibility on this topic by this author.
What's not true about it? According to Wikipedia [1] there are a bunch of speed records for sailing faster than the wind by tacking downwind.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#73> The secret to Blackbird, Cavallaro explained, is that once the wind gets the vehicle going, its wheels start to turn the propeller blades — they're connected to the blades by a chain. As the vehicle speeds up, its wheels turn the propeller faster and faster. The propeller blades, in turn, act as a fan, pushing more air behind the land yacht and thrusting it forward. That's a terrible explanation - no wonder people…
Its actually the correct explanation tho. This article sucked by the way. It said "Any sailor worth their salt can tell you that a boat can travel faster than the wind by cutting zigzag patterns; that's called tacking." Any sailor worth their salt knows that is not true at all. This practically destroys any credibility on this topic by this author.
I think it's just very poorly worded. Sailboats can go faster than the true wind speed, like in the America's Cup, and typically do it do it going upwind. The addition of tacking is not wrong, it is zigzagging upwind, but just very oddly worded.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#74Earlier quoted context omitted.
So, did/does the vehicle in the desert start with a push (from a force other than the wind) or did it really get started moving by the wind pushing it? Edit: FYI in the video he does sort of cover his claim even if it got started by a non wind force by stating the vehicle can maintain a speed faster than the wind pushing it. But I'm still curious, was a non wind force needed in the desert to get it started?
Any wind that's strong enough to overcome static friction would do the trick, and I can't see why 10mph wouldn't be enough. The small models that you can build at home (sorry, can't find the plans anymore; this was 10 years ago now) do not require a push to get started.
The fan blades are an airfoil, which have a minimum speed to create the lifting effect.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#75Is there an equivalent for water/hydrofoils maybe?
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#76Earlier quoted context omitted.
Its actually the correct explanation tho. This article sucked by the way. It said "Any sailor worth their salt can tell you that a boat can travel faster than the wind by cutting zigzag patterns; that's called tacking." Any sailor worth their salt knows that is not true at all. This practically destroys any credibility on this topic by this author.
What's not true about it? According to Wikipedia [1] there are a bunch of speed records for sailing faster than the wind by tacking downwind. [1] https://en.wikipedia.org/wiki/High-performance_sailing
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Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#77large ocean yacht racing boats can go much faster than the wind:
https://www.kqed.org/science/8503/how-do-these-boats-sail-fa...
Also this: "According to the World Ice Racing Circuit, ice boats can sail four to five times wind speed. In March 2009 a land sailboat reached 126 miles per hour on a dry lake bed in the Mojave Desert" from: https://www.straightdope.com/21344013/how-can-racing-yachts-...
I think I read somewhere that an ice sailboat did 143 mph.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#78Sailing faster than the apparent wind[0] has been going on for a while, especially on v.high performance land and water yachts. [1] The physics involved still twist my brain, but there's nothing terribly new here. [0] https://en.wikipedia.org/wiki/Apparent_wind [1] https://en.wikipedia.org/wiki/High-performance_sailing
No, the issue in question here is sustained sailing faster than the wind directly downwind, which is not what water yachts and sailboats are doing. The connection (belt, gear) between the wheels and the propeller is necessary to do the former.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#79Is there an equivalent for water/hydrofoils maybe?
I think in his original video he described how a tacking boat can go faster than one going straight down wind. As I understand it, that was the inspiration for the propeller. Here is a good site explaining it:
https://newt.phys.unsw.edu.au/~jw/sailing.html
> How can boats sail faster than the wind? Lots of boats can – especially the eighteen footer skiffs on Sydney Harbour. Ask a sailor how, and he'll say "These boats are so fast that they make their own wind", which is actually true. Ask a physicist, and she'll say that it's just a question of vectors and relative velocities.
Re: A wind-powered vehicle that can travel twice as fast as the wind itself
#80Actually, knowing it works now. Even internal combustion engines have only a 40% energy efficiency in converting gas to power, the rest is lost as heat.
In this case, I'm trying to think how the wind energy is lost, and it seems that some of that might be lost to the static friction in turning the wheels, and also the attached propeller. However, the energy used to turn the propeller is outputted again, as thrust. Since the initial wind was enough to overcome the static friction, any additional power might be causing it to move faster than the wind. I'm no physicist, but this is pretty cool.