DDWFTTW#.avi

3d-illustration related to faster than the wind directly down wind speculation.

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Education

Tags:

• DDWFTTW#

[WindSphinx]

The ice-boat analogy is bogus. They can go very fast on a reach of 90 to 110 degrees, but there is no record to prove they exceed 2 times windspeed on a 135 degree run. Please show us a confirmed record with gps numbers or a polar diagram of actual ice-boat speed.

I have searched the web and can find no such data.

[axelerat3d]

@WindSphinx

from ladnsailing -dot net :

"The slowest point of sail for a landyacht is dead down wind when it sails a little slower than the wind speed. By sailing at 45 degrees off directly down wind the yacht can sail much faster than the wind. The 'velocity made good' down wind is often over twice as fast as sailing directly down wind. In moderate wind, the fastest point of sail is a little below a beam reach."

[oEQjet]

I dont think this method will actually work. the reason you can travel faster then the winds top speed going somewhat perpindicular to the wind is because once you go past the speed the winds still putting force, i mean the theoretical top speed would be Top speed=Speed of wind/cos(angle from wind)

Direct Down wind machines work if they apply force backwards... well hell then maybe it will work... I doubt it will though.

[axelerat3d]

Ice boats beat windspeed with great margin traveling to straight down wind marker (by tacking - well jibing) ie. when an iceboat is traveling in a downwind tack its straight downwind component is faster than the wind - not just its speed in the direction of travel.

Those boats don't travel straight down wind but they do beat the wind. It needs to tack to keep having apparent wind.

The whole thing is counter intuitive but doesn't fight any laws of physics.

[balleroom]

Actually it's not tacking, it's jibing because the stern is moving through the wind.

But that's just a minor point. Excellent deonstration! Thanks.

I will use this video to finally convince my friend of the possiblity of the principle, I hope.

[axelerat3d]

That is of course true - it is changing tack but not tacking.

[ioscope]

If designed with great care, it would work. Ice boats, land yachts, and racing sailboats alike are known to be able to net a VMG better than the downwind wind speed, even on a DDW course. So if you could tow this box from an ice boat, it would undoubtedly work. (If the box was made of unobtainium)

[subductionzone]

Didn't you even read the response to your post? Iceboats do this all of the time, just without the framework around the iceboat. By jibing with the wind they can get an average velocity in the straight downwind direction of three times the speed of the wind or more.

[oEQjet]

well no, i mean, its not counter intuitive at all! I mean i just described the formula to calculate their maximum speed based on their angle to the wind. And the reality is by using a swerving motion in your machine you could build up speed, and use that momentum by turning right down wind, then turning back to cut the wind and build it up again and that would be faster then the down wind speed. I don't think that's what you are illustrating here though.

[axelerat3d]

the program is called 3d studio max