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how can we ride 40-50 mph in only 20-25 mph of wind?

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ImagineParadise
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Postby ImagineParadise » Thu Jun 08, 2006 10:16 pm

ryansurf1 wrote:imagineparadise....i don't think i know what i am talking about, but i know you don't know what you are talking about.

kiters can travel well in excess of the actual wind speed....kiters on ice can travel at speeds multiples of the wind speed.
untill you show me some evidence (like a video) I think you need to go sit down and count your fingers son.

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Klaus (c:E
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Postby Klaus (c:E » Thu Jun 08, 2006 10:29 pm

Hai,
Tinman wrote:Klaus I'm not sure I would call a "Fahrt" fair wind...... more like bad wind.
well that´s what the dictionary delivered as a maritime term for the component of the apparent wind that´s caused by the movment of a ship.
Another dictionary (and an english sailor novel) gave "head wind".

Sea You: Klaus (c:E

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jakemoore
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Postby jakemoore » Thu Jun 08, 2006 10:37 pm


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spork
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Postby spork » Thu Jun 08, 2006 10:44 pm

http://www.windjet.co.uk/index.php?opti ... &Itemid=50
The current ice sailing speed record was set on Lake Winnebago in Wisconsin (USA) by John D. Buckstaff in his stern steerer "Debutante", similar to the craft pictured left. In 1938 Buckstaff reached 143 mph (230 km/h), reportedly in a 72 mph (63 knot or 116 km/h) wind.

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Postby Anders » Thu Jun 08, 2006 10:57 pm

Spark:

That crazy part about you were abel to go downwind faster than the wind. Could you explane that part?

I have basic fysics knowledge, but I still don't understand.

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spork
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Postby spork » Thu Jun 08, 2006 11:32 pm

Well, there are several ways to do it. I'll almost certainly get my head chewed off for any approach I offer, but what the hell. Let's start with this one...

Take a wagon with big spoked wheels. Put sails on the spokes that accordian in and out. Deploy the sails while they are below the axle (deploy them in the direction of the axle - so there's no inherrent work done deploying or retracting). Retract them when they're not below the axles.

Given a system with reasonably low frictions, the sails will be going downwind at near wind-speed. Given that sails are at mid-spoke, below the axle, the axle (and therefore the cart) will be going downwind at twice that speed.

There are more conventional, and more practical approaches, but they're a bit more difficult to describe.

RC

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Postby ImagineParadise » Thu Jun 08, 2006 11:43 pm

sweet link! I wonder if the metric relationship of Kite to Windsail is similar or not.

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alpower
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Postby alpower » Fri Jun 09, 2006 12:27 am

Sorry, I can't buy the concept of going faster than the apparent wind which can be significantly faster than true wind unless some other energy input is involved and if you are going dead down wind the fastest you could go in theory is the wind speed. And as far as apparent wind speed goes it has nothing to do with wind over the sail or watermelon speeds it is just a simple vector analysis of the wind speed coming from a certain direction and the board speed relative to that. If the apparent wind is forward of 90deg from where you are headed it is greater than true wind speed, if it is behind you then it is less than true wind speed. Apparent wind will continue to build, as will board speed until the forces created by the drag of the kite and the drag of the board equal the forward force created by the airflow over the kite (this is where the wing analogy comes in). Less drag (ie ice kiting) equals more apparent wind, which equals more speed.

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spork
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Postby spork » Fri Jun 09, 2006 12:50 am

alpower wrote: if you are going dead down wind the fastest you could go in theory is the wind speed.
Wanna bet?
alpower wrote:And as far as apparent wind speed goes it has nothing to do with wind over the sail or watermelon speeds
You're mixing and matching concepts from various posts. I agree that apparent wind is simply the vector sum of "true" wind and your speed. But then that's exactly what I said above. Watermellon seeds have nothing to do with apparent wind, but I assure you they have more to do with why we can go faster than the true wind than the apparent wind explanation does. Sailing on a beam reach the apparent wind simply adds a direct headwind to the equation. But you can still sail faster than the true wind on this course.

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Postby Cadet_C » Fri Jun 09, 2006 1:42 am

This is all about aerodynamics
Don't know if you ever heard about About ICE WINGS t its sails some six times faster than the wind in light wind. That is 12 m/s (24 knots) in 2 m/s (4 knots) of wind. Top speed is around 120 km/h (75 mph) with the gusty winds . In more even wind you can sail faster. If you build a really small wing you get a better top speed, 160 km/h (100 mph)?
All figures are very approximate and depends very much how you build your sail. You can chose everything from simple and inexpensive to fast and sophisticated. Variations are explained in the building instructions.
The great performance is due to the streamline shape and that the sailor makes no air resistance as he is inside the wing.

Chris


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