lezo wrote:I had a great response from a longtime foil kiter:
Can anyone help to clarify this? I'm having a hard time visualizing how the wind window shifts in relation to apparent wind.
Imagine yourself with no speed with the wind right behind you, about to go in a direction 90 degrees to the wind. The wind you feel (the apparent wind) is the same as the true wind.
Now what happens when you pick up speed? There is a component of the wind which come from the direction you are riding towards (same as when you are riding your motorbike).
This component, added to the true wind is your apparent wind. It will appear to have shifted from right behind your back to somewhere nearer to the direction you are going.
If you keep the kite at the edge of the window (with the same angle of attack - or incidence - or bar position) it will move backwards by the same amount the apparent wind has shifted forward.
A little drawing would be worth 1000 words. Next time if the above is not enough!
The explanation which was given to you was as clear, if not clearer as mine, but perhaps you only needed to see it from a different angle
As the longtime foil kiter says, the great thing is that the apparent wind can be significantly stronger that the true wind enabling you to go faster than the wind. I typically clock 20-22 knots in 10-11 knot winds, on flat water. Far better can be achieved with a raceboard or a foil board.
PS: whilst I was writing this up, Kami posted the link to the excellent, albeit somewhat longish (quasi encyclopedic) article on the combined effects of wind, the riding speed etc...the same topic seen from yet another angle; easy to understand when you know it all already.
PS2: you might be interested to see what sort of speeds can be achieved for various wind directions on the polar diagrams show at the bottom of my blog about the use of GPS. You can see that the VMG (velocity made good - component of your speed in the direction of the wind) was up to 7 knots and max speed exceeding 20 knots in wind of 8-10 knots the days of the logging. Better digest Kami's article before trying to deal with polars graphs and VMG.http://www.nautikites.net/blog/index.php?entry=entry090905-145635