Team New Zealand set new wind-powered land speed record on South Australian Lake(abc.net.au)
abc.net.au
Team New Zealand set new wind-powered land speed record on South Australian Lake
https://www.abc.net.au/news/2022-12-12/new-wind-powered-land-speed-record-set-on-lake-gairdner/101761048
25 comments
The linked background story [1] in the article has a bit more detail on that, worth checking out. Choice quote:
It might sound paradoxical that a vehicle entirely powered by the wind can travel significantly faster than it.
But, as Dr Karl explained, the principle has been exploited by sailors for centuries.
It involves something called "apparent wind" — and relies on the fact that travelling at an angle to the wind can generate more speed.
For a different take I would recommend the propeller-based vehicles [2] that go faster than the wind without using sailing techniques.
[1]: https://www.abc.net.au/news/2022-07-28/americas-cup-winner-g...
[2]: https://en.wikipedia.org/wiki/Blackbird_(wind-powered_vehicl...
It might sound paradoxical that a vehicle entirely powered by the wind can travel significantly faster than it.
But, as Dr Karl explained, the principle has been exploited by sailors for centuries.
It involves something called "apparent wind" — and relies on the fact that travelling at an angle to the wind can generate more speed.
For a different take I would recommend the propeller-based vehicles [2] that go faster than the wind without using sailing techniques.
[1]: https://www.abc.net.au/news/2022-07-28/americas-cup-winner-g...
[2]: https://en.wikipedia.org/wiki/Blackbird_(wind-powered_vehicl...
Here are the Veritasium videos on the exact matter
https://www.youtube.com/watch?v=jyQwgBAaBag
https://www.youtube.com/watch?v=yCsgoLc_fzI
https://www.youtube.com/watch?v=jyQwgBAaBag
https://www.youtube.com/watch?v=yCsgoLc_fzI
They are not sailing downwind in this case - they're sailing across the wind, which is why they are able to travel so much faster.
Sort of a yes and no thing. Once the apparent wind is forward of the beam you are effectively sailing upwind.
You can sail downwind faster than the wind: https://www.youtube.com/watch?v=jyQwgBAaBag
This propeller method is a completely different way of doing something similar, but straight downwind.
Imagine pinching an ice cube. One finger applies force like the sails, the other finger applies force like the keel+rudder, and the cube is the vessel.
This...but the ice "cube" has a slight taper to it, like a wedge. As you might recall from high school or freshman Physics, a slight-taper wedge has a large "mechanical advantage". By squeezing it, you use that in reverse - a slow-but-strong push from your fingers (the wind vs. the keel+rudder) results in a fast-but-weak movement of the ice "cube". (Hence the ultra-streamlined shape of the vehicle, low-rolling-resistance tires, etc.)
Wind powered craft are generally powered by deflecting the wind at an angle, rather than using the wind behind them to travel forwards. It's the same reason that sailboats can move into the wind.
It's very hard for me to explain without diagrams, this wikipedia article explains it pretty well: https://en.wikipedia.org/wiki/High-performance_sailing
It's very hard for me to explain without diagrams, this wikipedia article explains it pretty well: https://en.wikipedia.org/wiki/High-performance_sailing
Echoing the sibling comment from byhemechi, performance sailing vessels generally do not sail directly downwind (or directly upwind for that matter).
The sails are positioned at an angle to the wind, so that they deflect the incoming air in such a way as to propel the craft forward. It might help to imagine air "coming out the back" of the boat.
The fastest set-up is for the boat to travel roughly perpendicular to the wind, with the sails set at (approximately) 45 degrees. In sailing jargon this is called "reaching".
The speed of the craft is determined by the balance between the force exerted on the sails by the air, and the drag (air resistance) and friction between the boat and the water -- or, in the present case, the ground. In a world without friction or drag the boat would accelerate indefinitely, provided there is some wind to deflect.
Note that although it's not generally how fast boats are sailed, "sailing" a wind-powered craft directly downwind faster than the wind is also possible by, for example, using propellers.
The sails are positioned at an angle to the wind, so that they deflect the incoming air in such a way as to propel the craft forward. It might help to imagine air "coming out the back" of the boat.
The fastest set-up is for the boat to travel roughly perpendicular to the wind, with the sails set at (approximately) 45 degrees. In sailing jargon this is called "reaching".
The speed of the craft is determined by the balance between the force exerted on the sails by the air, and the drag (air resistance) and friction between the boat and the water -- or, in the present case, the ground. In a world without friction or drag the boat would accelerate indefinitely, provided there is some wind to deflect.
Note that although it's not generally how fast boats are sailed, "sailing" a wind-powered craft directly downwind faster than the wind is also possible by, for example, using propellers.
The propeller method was explored in a fascinating series of videos by Veritasium and Xyla Foxlin:
https://www.youtube.com/watch?v=jyQwgBAaBag
https://www.youtube.com/watch?v=yCsgoLc_fzI
https://www.youtube.com/watch?v=VUgajGv4Aok.
https://www.youtube.com/watch?v=jyQwgBAaBag
https://www.youtube.com/watch?v=yCsgoLc_fzI
https://www.youtube.com/watch?v=VUgajGv4Aok.
Imagine pushing a matchbox car on a table with a ruler, where the ruler is perpendicular to the direction of movement. When the car is on an angle, the car will be moving faster than the ruler (wind). The steeper the angle, the faster the car can go relative to the wind.
The video shows them using a "tailplane" on the main sail, presumably to adjust sail angle without needing sheets, etc.
Is this used in normal sailing? It seems far simpler.
Is this used in normal sailing? It seems far simpler.
On a Bermuda-rigged sloop ideally the jib and the main balance each-other out such that the amount of rudder drag introduced in order to maintain a constant course is minimized. This requires sheet, sheeting angle halyard, and potentially even a cunningham on the tack to adjust the sail shape. When you're doing a speed record, sail shape is likely gonna be decided in a meeting room, not out on the "Water".
With the speeds on this thing It's more akin to a Moth's wand adjusting the foil flap automatically. Larger foiling boats have a flight controller hand control the foil and flaps by hand.
Using human power to adjust the sail is more efficient (for the boat) than introducing more sail area and therefore more drag to trim the sail automatically.
In the case of this vehicle, the foil and adjuster thing behind the pivot point are both incredibly efficient high-aspect foils, as well as all the hardware which controls it are being engineered and rigged "pre-trimmed" for the specific wind speed planned to attempt this record.
With the speeds on this thing It's more akin to a Moth's wand adjusting the foil flap automatically. Larger foiling boats have a flight controller hand control the foil and flaps by hand.
Using human power to adjust the sail is more efficient (for the boat) than introducing more sail area and therefore more drag to trim the sail automatically.
In the case of this vehicle, the foil and adjuster thing behind the pivot point are both incredibly efficient high-aspect foils, as well as all the hardware which controls it are being engineered and rigged "pre-trimmed" for the specific wind speed planned to attempt this record.
Normal sailing require many more adjustments to shape than just sheeting angle. On a typical boat the backstay, a component of the rigging would interfere. There are many sailboats without backstays, but not a likely scenario for nrmal sailing.
See also DDWFTTW ("Directly downwind faster than the wind"): https://www.wired.com/2010/08/ddwfttw/
I’m no physics expert but I’m told water has a speed barrier and that coming of as vehicle into water at speed is like hitting concrete, the thought of going this fast in an unpredictable environment (waves, or ‘big ripples’ in a lake) would be super scary
The current limitation of in-water sailing vessels at the moment is cavitation.
Cavitation is the process by which the pressure of water is reduced so low on the trailing edge of a foil at high speeds that the water instantly boils, turning to vapor, making your lovely laminar flow over the trailing edge of the foil turn into a turbulent flow.
No fun if you were nicely balanced ripping along at 40 kts on an AC75. Now only the leading edge of your foil is working, it needs a higher angle of attack to maintain the same lift, which increases the drag, slowing you down and causing your owner to cry into his billions of dollars because you just lost him the America's Cup.
Cavitation is the process by which the pressure of water is reduced so low on the trailing edge of a foil at high speeds that the water instantly boils, turning to vapor, making your lovely laminar flow over the trailing edge of the foil turn into a turbulent flow.
No fun if you were nicely balanced ripping along at 40 kts on an AC75. Now only the leading edge of your foil is working, it needs a higher angle of attack to maintain the same lift, which increases the drag, slowing you down and causing your owner to cry into his billions of dollars because you just lost him the America's Cup.
the "lake" is long dried out. this was done on land in a vessel with a cockpit. there's a video toward the bottom of the article.
Lake Eyre is dry most of the time, but does fill briefly every few years. Notably, the reason why Mad Max Fury Road was filmed in Ethiopia instead of Australia was that rains filled the lake a week before filming, and turned the desert into a field of wildflowers unsuitable for the apocalyptic setting.
horonuku = swift movement?
From this video [1] "[horonuku] is a bespoke name created specifically for this purpose of what your new land yacht is all about. "horo" means speed, it means to move swiftly, and nuku, has a double meaning, means movement again but it also means the Earth".
The video is well worth a watch because it gives insight into the origin of the words and the deeper cultural meaning of them to the tangata whenua (indigenous people) of New Zealand.
[1]: https://youtu.be/cjIQueGLRjg
The video is well worth a watch because it gives insight into the origin of the words and the deeper cultural meaning of them to the tangata whenua (indigenous people) of New Zealand.
[1]: https://youtu.be/cjIQueGLRjg
It looks like the outboard "wing" is on the windward side. Is it actually a counterweight to prevent the vehicle from tipping over in the wind? I would have expected it to be more like a sideboard on a sailboat being a sort of leeward stabilizer.
Regardless this is absolutely crazy, hard to believe they think they can go even faster. And 22 knots isn't even that unusually fast wind (over water, speed records have more like 25-30 knots) I wonder if on land the speed improvements are more about material sciences and preventing the vehicle from breaking apart or tipping over
Regardless this is absolutely crazy, hard to believe they think they can go even faster. And 22 knots isn't even that unusually fast wind (over water, speed records have more like 25-30 knots) I wonder if on land the speed improvements are more about material sciences and preventing the vehicle from breaking apart or tipping over
I am sure someone has already explained this elsewhere on HN, but how is it possible for a wind-powered craft to travel faster than the wind?