While you guys are trolling the forums waiting for the next release of LFS, I thought I'd contribute to the noise.

A landsail is similar to a sailboat but uses wheels. An icesail is similar to a sailboat but uses skates.

It is stated that either of these can sail downwind faster than the wind if they are also moving crosswind fast enough. For example, if the wind is 10mph, and the landsail is moving 38 degrees to the side and down wind, with a "beta" of 14, it's speed will be 32.57 mph, with a cross wind speed of 20.05 mph and a downwind speed of 25.67 mph, over 2 1/2 times the actual wind speed. Myth or truth?

Then there is the Jack Goodman DWFTTW (downwind faster than the wind) cart:

http://www.youtube.com/watch?v=aJpdWHFqHm0&fmt=18

Amazing, this is a gear box applied to the power of wind!

With a zero reduction ratio (fan does not turn) it works like a small sail.

With a positive reduction ratio, the fan pushes against the wind, and it is like using a smaller sail in a faster wind. Higher top speed, but less force.

And with a negative reduction ratio, the fan pushes in same direction than wind...so the wind turns the fan, and the car goes backward!!

whats interesting on this video?

the wind goes forwarth as the cart nothing odd

edit:

saw it now it goes faster than the wind

if true pure genius thanks for sharing

edit:

its obvious direction is remote controled i think it might have an engine as well

Quote from JeffR :

It is stated that either of these can sail downwind faster than the wind if they are also moving crosswind fast enough. For example, if the wind is 10mph, and the landsail is moving 38 degrees to the side and down wind, with a "beta" of 14, it's speed will be 32.57 mph, with a cross wind speed of 20.05 mph and a downwind speed of 25.67 mph, over 2 1/2 times the actual wind speed. Myth or truth?

Some boats with well-designed enough hulls (read: mostly shallow and not meant for open waters) can achieve faster speeds than the speed of the wind which is apparently propelling them - but not downwind, only with crosswinds and in what would look like slightly upwind IIRC from what a pal who's into sailing was telling me as it all has to do with maximizing relative wind speed - a bit of quick trigonometry would probably give you the ideal angle that would give you the largest possible speed vector.

However I doubt that the difference would be that big between boat speed vs actual wind speed on a boat. On land however that there's less friction it just might be possible.

Don't have a clue about the cart though - I'd need to read up a bit on that.

So is it like some kind of horizontal Autogyro effect?

The wind comes in from an angle (I guess as you are talking about crosswind), turns the Sail/propellor which then propels the Cart along?

So instead of creating lift like an Autogryro does, the propellor/sail is tilted 90 degrees so that it provides thrust instead?

Even if it may have little use in boating, its still fairly cool.

Quote from JeffR :

For example, if the wind is 10mph, and the landsail is moving 38 degrees to the side and down wind, with a "beta" of 14, it's speed will be 32.57 mph, with a cross wind speed of 20.05 mph and a downwind speed of 25.67 mph, over 2 1/2 times the actual wind speed.

Note, the numbers stated here are real. Although landsailers claim they can achieve a net downwind speed 2 1/2 times the wind, I'm not sure of the actual heading or speeds involved to do this.

Quote :

Then there is the Jack Goodman DWFTTW (downwind faster than the wind) cart: http://www.youtube.com/watch?v=aJpdWHFqHm0&fmt=18

I have my doubts on this one. although others have tried making similar devices.

Quote from JeffR :

While you guys are trolling the forums waiting for the next release of LFS, I thought I'd contribute to the noise.

Loving the introduction.

Quote :

A landsail is similar to a sailboat but uses wheels. An icesail is similar to a sailboat but uses skates.

It is stated that either of these can sail downwind faster than the wind if they are also moving crosswind fast enough. For example, if the wind is 10mph, and the landsail is moving 38 degrees to the side and down wind, with a "beta" of 14, it's speed will be 32.57 mph, with a cross wind speed of 20.05 mph and a downwind speed of 25.67 mph, over 2 1/2 times the actual wind speed. Myth or truth?

Then there is the Jack Goodman DWFTTW (downwind faster than the wind) cart:

http://www.youtube.com/watch?v=aJpdWHFqHm0&fmt=18

omg tw33k hax. Next we find out it's powered by a reverse hand brake.

Quote from JeffR :

Then there is the Jack Goodman DWFTTW (downwind faster than the wind) cart:
http://www.youtube.com/watch?v=aJpdWHFqHm0&fmt=18

Quote from spankmeyer :

omg tw33k hax. Next we find out it's powered by a reverse hand brake.

I heard that this may have been related to the fact that in an older version of LFS, cars could be made to go faster by pitching the nose higher than the rear so that the downforce would also propel the car forwards.

Looks like DDWFTTW (directly downwind faster than the wind) has been done now. A guy name Mark made the mini-cart shown in this video. Instead of using a wind, the equivalent is done by using a treadmill running at 8.5 to 10mph in still air. When held back, and then released, the mini-cart accelerates and then maintains forward speed on the treadmill, especially on the last 3 runs which were longer. On the last run, the mini-cart runs into the far end of the treadmill. The treadmill was angled slightly upwards to eliminate gravity as a power source.

youtube DDWFTTW video

I'm not sure of the math for the spiraling path of the propeller, but in the case of a landsail or icesail, the apparent crosswind, the component of wind perpendicular to the directon of travel of a vehicle, is equal to the wind speed times sin(angle between wind and vehicle veocity direction), and this is independent of the vehicles forward speed, since it's the component perpendicular to the direction of travel. For example, with a 10 mph, and a heading 30 degrees offset from the wind, the crosswind component on the vehicle = 10 mph x sin(30) = 5 mph, regardless of the vehicles speed. This 5 mph crosswind is the power source, and the limiting factor on the vehicles top speed is related to the efficiency of the sail versus the aerodynamic and ground related drag factors. If the vehicle in this case can travel forwards faster than 11.55 mph (11.55 mph x cos(30) = 10 mph), then it's net downwind speed will be faster than the 10mph wind. The sail on the vehicle diverts the apparent headwind into a true upwind component, enough to offset the difference between the vehicles speed and the wind speed.