80 knots on a foilkite

[Schietwedder]

I just came across the Swiss group of university students, engineers and scientists from Switzerland, who want to design and build a kiteboat using a Foilkite going 80Knots breaking the world speed record. https://sp80.ch/

Now besides the problem with traction, platform aerodynamics and cavitation, projects like this usually have to face, lets assume they work out a platform which can go 80 knots....

What will a foil kite do in 80 knots boatspeed (maybe 100knots apparent) ? Maybe some Paragliders, Race Foil kiters and kite designers among us could help out on this discussion.
I wonder what a foilkite would behave like in those high and low pressures acting on the wings surfaces and also from the inside.
One should get quite some canopy deformation, at least on the wings upper surface where positive pressure from the inside and negative pressure on the outside will not cancel out but add up.

Will light nylon ripstop still work? Maybe we get a North sails 3DL kite from composite laminate in the end or even a composite wing with very few flying lines.
What will be about drag from the flying lines and bridles (pipes/round cylinder has a horrible resistance coefficent and there will be quite some loads on the bridle so they will be quite thick)
Where in kitefoiling is the lift to drag ratio a problem? On the foil or on the kite? Which prevents you from going faster? Of course besides having to go on a up and down course through maneuvers which brings some compromises.

I have no Idea with those kinds of speeds maybe if you size a foilkite up the loads/pressures is actually not a problem, hard to say without experience.

Are there people who went 100km/h and more on a Buggy/Snowkite on Ice?

Some brainfood:

[tkaraszewski]

It seems easy enough to test this with a kite flying off the back of a car. Rig up your test kite at a place like Bonneville on a calm day and drive the car up to your target speed and see if your kite comes apart. Making a kite that flies in high winds stronger isn't really a problem, though, it'll just be heavy, but that doesn't matter at these windspeeds. Use carbon reinforcements like in boat sails.

But it would be an easy enough experiment to do by tethering an existing foil kite in the back of of a pickup truck and accelerating up to speed.

> One should get quite some canopy deformation, at least on the wings upper surface where positive pressure from the inside and negative pressure on the outside will not cancel out but add up.

Why do you say this? Positive pressure from underneath combined with negative pressure from above never cancel, there's nothing that changes somewhere between the current top end of kites (50-ish knots?) and 80 knots that would affect this.

[plummet]

World speed record for kiting is 82.9 mph as far as I know.

Held by a kite buggy on a dry lake bed with a fixed bridle foil race kite.

I think the biggest problem is the parasitic drag from bridles and lines.

As ground speed increases the wi d window shifts further and further back. The kite has to fly far forward into the window. There comes a point where the kite/craft cannot go any faster due to the limitation of drag and apparent wind window angles.

Ultimately it won't be kites holding sailing speed records due to lines/bridle drag.

[Mossy 757]

Ultimately it won't be kites holding sailing speed records due to lines/bridle drag.

Yeah, I'd put my money on foiling craft with hwingsails on something like the Vestas sail rocket or maybe one of these new America's Cup monofoilers if they went back to a wing instead of a soft sail.

[kgb]

This IS something like sail rocket

And an ac75 has no chance of 65 let alone 80 kts solid rig or not.

[RedSky]

88mph / 76knts / 142.9 kph Cabrinha Switchblade

If you want to go fast then use a small kite in very high wind. I don't know much about sailing on water but I imagine that using a hydrofoil design and two small kites in very high wind might work.
One small kite won't be enough and a larger kite has too much drag.

[bohme]

Wow. 76kn on a switchblade.
Apparently, the stern-steerer ice yacht Debutaunte was timed over a measured mile at 124 knots on the ice of Lake Winnebago in 1938.
I guess you do not need high efficiency. You might even consider the complete opposite.
If you want to do 80kn, dig a trench and go out i 160kn wind with an old fashioned parachute?
Perhaps kiteloop your Switchblade

[joriws]

Not wow, that was downhill assisted run, not kite powered only run

[kitexpert]

If you want to go fast then use a small kite in very high wind. I don't know much about sailing on water but I imagine that using a hydrofoil design and two small kites in very high wind might work.
One small kite won't be enough and a larger kite has too much drag.

This is incorrect, two small kites are worse than one bigger and very probably even more difficult to handle. Size does not affect a lot for efficiency (L/D ratio), or if you want to be precise bigger kite works with higher RE number and is more efficient. Stacking kites is quite a lot like biplane airplanes or even worse triplanes, they lose for efficiency.

[Bille]

Not wow, that was downhill assisted run, not kite powered only run

THAT changes things ; not a record for pure kite-power .
Still ---- Fast as Hell though !!!
It would be like calming a world record for highest jump, off the
water,with a kite ; when you used ridge-lift from a cliff, to do it.
Nope -- it don't count.

Sailrocket has a LOT of parasitic-drag , that could be addressed
in order to get some more speed.
That sailrocket design, only went in ONE direction ; i'll be
impressed, when it can go that speed, in Both directions.

The Greenbird landsailer, did 126.1-mph (World Record) ; and it
could go Both directions .


Bille