Going down the mine ...

thanks for that. now i can force my crew to ut the kite up on windy days for "scientific reasons"

i am but a humble feva sailor so i do not have any experience of playing with realy big kites. however when we get a SW breeze blowing up the western solent it piles up the waves and we get tremendous surfing conditions which gets our small kite easily on the plane. the trouble occurs when we chicken out because its too windy and we quickly realize that with no kite the feva goes bow down in the big waves off Hill Head very quickly. when the kites up the bow does still go into the next wave but the boat does not burry itself past the shrouds in water. therfore i have come to the conclusion that kite = lift of bow = no nosedives

Check out   

http://www.sailworks.com/04-05/pages/video_gallery.cfm

A minute or so in, the guy starts jumping. Check the attitude of the rig when he is going for the biggest jump, compared to the attitude of the rig when he is sailing normally.

It is tricky to say if the kite lifts the bow it certainly can as the boat jumps waves, however it definatly pushes the bow down less than the mainsail/jib combination.

If you work out the vectors for the where the kite attaches, then for a verry short mast and a verry long pole the kite would lift the bow.

I think that a more significant effect comes from where fore and aft the driving force comes from, with the main/jib it comes from about hounds height above the mast step. with the kite up I think it comes from a bit lower down but much further forward possibly in front of the bow.
This makes a difference in the torque link between the driving force and the drag force, which acts to push the bow down, this force is less the larger the distance fore and aft between the drag and the drive.

Originally posted by Chris 249 Which may just show how complicated the whole aspect of rake, lift, aerodynamics etc is!

Yep I agree with all that you say, the sheeting out may relate to slight loss in power causing you to return to the water quicker.

either way it worked, and bringing the rig slightly to windward increases air time!!

And one thing is for certain its very complicated!!