Kite Foiler

[Doug Lord]

From Sailing Anarchy: fighter pilot https://sailinganarchy.com/2021/04/19/fighter-pilot-3/

 

[jehardiman]

Finally, after 50 years somebody is finally going to build one.

 

[Dejay]

Wow that looks awesome. Almost looks like a hybrid hydrofoil / wing in ground craft (but it's not).

I assume the kite will be controlled from the inside through the arm in the back? Lots of info on sp80.ch but I'd be curious if they use manual control of the kite or some electronic controller.
Ok looking some more it seems they are optimizing just for the speed record where the kite is always on one side and balances forces with the hydrofoil.

 

[TANSL]

I do not understand so much admiration, the truth. It is just an animation, it is not real. Now, if the admiration is caused by the quality of the animation, not by the object that sails with the wind, I agree, it is quite good.
Award for the best animation film, not the best boat design. Buit this is a boat design forum.

 

[Dejay]

Well students put 6000+ hours of design into it. It exists in their minds. They think it, therefor it exists right?

Or do boat designers even do any work at all?

 

[TANSL]

Well students put 6000+ hours of design into it

6000 hours is always many hours (3 years of work by one man) but 6000 hours to achieve this ... frankly, if that's true, it wasn't worth it. In any case, once we have felt admired by the video, why don't they try to admire us by giving some of the technical details of the design, details of the tests carried out, in short, anything that allows us to appreciate the many advances, or the improvements made to that design in relation to others that seek to achieve the same. I do not want you to describe the technical solutions, which logically should be reserved from the malicious curious, but to explain the problems solved and why they have been solved in a more favorable or efficient way than in other designs (tests carried out and comparison of results). I really would like to be amazed by the technical aspects and the originality of the solutions adopted in this design.
It is always convenient to make clear the difference between a beautiful render and a great design.

They think it, therefor it exists right?

No, of course it does not.

 

[Dejay]

It seems most of the info is on their youtube channel. That's just the medium today to build up hype. In order to get a new generation interested in boating it's not a bad thing.

Personally I'm not that interested in speed records, I'd be more interested in a usable kite foiling cruising boat.

I assume eventually they will release a paper on it. They also mention a patent.

 

[BlueBell]

"Talk's cheap, until you get the bill."
This project's been in the works for a while.
No data, just hype and excellent quality video graphics.

 

[Dolfiman]

Personally I'm not that interested in speed records, I'd be more interested in a usable kite foiling cruising boat.

A small company from Brittany, Armokite, is on this idea :
Armorkite – bateau kite, une navigation innovante et inoubliable

 

[Skyak]

From Sailing Anarchy: fighter pilot https://sailinganarchy.com/2021/04/19/fighter-pilot-3/

This is a great project for some great kids. I am sure the animations will trip the BS detectors of many members here, but they have already come a long way from a completely unworkable concept to this and they seem to be still open and evolving. I think they will evolve even closer to sail rocket before they break the record. I think the L/D of even the best kites is vastly inferior to sail rocket's wing but I would love to see some serious development of high performance kites. The one negative I noticed is that they are considering launching from a powered craft -that moves development away from commercially viable kites/products. It seems to me that some time ago speed records were an average of the out and back on both tacks -when did it change?
These projects are always good for attracting cutting edge technology like Datasheets (thinplytechnology.com).

 

[Dejay]

I think the L/D of even the best kites is vastly inferior to sail rocket's wing but I would love to see some serious development of high performance kites.

I'm a total novice but wouldn't the best kite be something like a sailplane that can reach glide ratios (= D/L) of 40-60:1?

The other question would be if D/L even matters that much since a cloth kite is cheap and can be as large as you want it to be so can generate as much force as you want without the "penalty" of requiring more structure besides stronger lines.

Also kites can capture stronger winds higher up and the righting moment is different of course.

About launching, I wonder if we'll see some kind of kite control unit that has a propeller or ducted fan to launch the kite using battery power.
Or in the case of a hard sail you could have a ducted fan that is retracted like "landing gear". For the Makani project they also used a kind of telescoping mast with compressed air to launch a simpler sailplane prototype.
But soft, inflatable kites seem like the way to go just for safety and cost. Maybe you could also integrate a kite control unit into an inflatable kite that could help with launch with a prop.

 

[Skyak]

I'm a total novice but wouldn't the best kite be something like a sailplane that can reach glide ratios (= D/L) of 40-60:1?

The other question would be if D/L even matters that much since a cloth kite is cheap and can be as large as you want it to be so can generate as much force as you want without the "penalty" of requiring more structure besides stronger lines.

Also kites can capture stronger winds higher up and the righting moment is different of course.

About launching, I wonder if we'll see some kind of kite control unit that has a propeller or ducted fan to launch the kite using battery power.
Or in the case of a hard sail you could have a ducted fan that is retracted like "landing gear". For the Makani project they also used a kind of telescoping mast with compressed air to launch a simpler sailplane prototype.
But soft, inflatable kites seem like the way to go just for safety and cost. Maybe you could also integrate a kite control unit into an inflatable kite that could help with launch with a prop.

The your question sets up discussion of the important distinctions for this application -a wind over water speed record is very different from regular fast sailing.
1. the target speed is well above water cavitation speed so everything below the waterline is supercavitating or ventilated. It's a fancy name but in practice it means the foils get all their lift from the pressure side and the suction side is a bubble of air at atmospheric pressure. This in turn means the L/D of the water foils is low to the point there is no advantage to foiling. Despite the thread title this is a plaining design not foiling. The only thing you can do to improve performance in the water is to increase the foil aspect ratio and minimize wetted contact area and control losses.

2. in the air there is no value to flying the kite higher because this is only a record attempt. This craft will only operate in a place where powerful winds are blowing off shore (no fetch for wave development). The wind at the surface is more than you need (by venue selection) and flying the kite higher either loses attack angle or adds significant line drag. Then there is the benefit of endplate effect from staying close to the surface of the water.

Our conventional intuition is to assume the boat is the overwhelming source of drag and the kite is the overwhelming source of power. This would lead us to the bigger kite>more power>more speed. But I say that is not the case here. The power is the kite/cavitating foil couple. The water foil can only be smaller and higher aspect to the limits of material strength and stiffness and its drag can't be separated from the kite power. So L/D of the kite is not just important, not just the main thing, it is the only thing!

Conventional kites top consideration is weight minimization -for lower wind speed and control. This speed record attempt removes the low speed requirement, so I see opportunity to greatly improve L/D at the cost of some weight. I suspect the control lines will be less like string and more like super high aspect wings.