I had way too much coffee this morning, and i had
to pee , when i started your video ; forgot all about the bladder, till
the video ended !!!
That was Fun , and educational to watch !!!!! ---you get (3)
I have a "personal view on it" which is : the wing act neither like a rotor (where commonly it should accelerate particules coming from upstream the vehicle) nor a wind turbine (where rotation is energized by the wind) ... it acts like a ... rotating spinacker ... (with massive and pure drag) : rotation is here to always present a surface with less speed vs ground than the vehicle its self = compensate for related speed of the vehicle (so do not "suffer" from the related wind) and constantly offer a surface to be pushed by particules coming from its back !Herman wrote: ↑Wed Mar 04, 2020 6:34 pmRégis-de-glens
The point is, no relevant closed sailing system works because of apparent wind. The DTW generates apparent wind because it has a rotor. The apparent wind on the foil is created by the sum of the rotation and vehicle movement. The concept that is not easily explained, imho, is that the energy input can only be from the existing wind but the forces involved at any given instant of time have to be analysed by including the accumulation effects of the craft's acceleration-velocity. It becomes easy to make the intellectual mistake,imho, that this is bringing something or driving the system.
Not that it matters from a kiting or sailing point of view. When riding or sailing it is the art of continuously exploiting the actual flow over the aerofoil at each instant that maximizes the potential of the wind. Of course, the actual flow is the summation of the real and apparent wind.
Could you please do the vmg for the 34th America's Cup Catamaran for a typical down wind leg in 18 knts of breeze. If you can't find the relevant polar diag the Olympic Tornado would do. That polar diagram is definitely available on line.spork wrote:
>> DWFTTW can be achieved with just wind power. If memory serves the 2013 America's Cup was expecting to achieve a ratio of 1.6 faster than wind speed. Of course it is relatively easy on ice.
Yes - DWFTTW is possible with a traditional sailing craft as I describe above (a broad reach). But DDWFTTW (Directly DWFTTW) is not possible with a traditional sailing craft on water or ice.
If there's a specific case you guys are trying to analyse perhaps I can take a crack at it with a simple vector analysis.
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