Loose blades, tensile only

Imagine two rotating blades connected to each other, a lifter and to a tether for yo-yo. All tensile. How could those be kept at opposite ends without active control?
How could such a thing be landed?
Maybe a rod orthagonal to the lift line and the kite lines with two lines going to each kite. When the kite is too fast or too slow one of the lines has more tension than the other which coule be used to control the kites.

[edit: I’ve been stupid. Lets think about flygen or rope-drive instead of yo-yo.]

Like this https://www.youtube.com/watch?v=p7ilG78cBLg + lifter?
For such a rotating AWES the active control would be less challenging than for a crosswind kite, but nevertheless required (landing, recovery, blades control during reel-out/in phases).
A similar device with rigid blades is described on http://www.pes.eu.com/assets/misc_new/peswindissue17talkingpointskylimitpdf-891355291894.pdf.

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Oh nice, didn’t know this existed. Much like this but with a distance in the middle.
I mentioned the lifter only because I thought it might be neccessary.
Rotating is crosswind.

The lifter will put a heavy toll on your efficiency for yoyo/lift based AWE. Anyways you could control the direction of a rotating rig by changing the axis alignment from the ground (using control lines or RC) to move the rotating rig anywhere. Eg tilt up to move up. Im not sure if thats practical, but that would be my best answer.

Also some kind of «heavy» element is necessary in order for the kite to know whats up and down. Perhaps something hanging on a central shaft on ball bearings

To be honest why not just add some actuators to your wing. Plenty of power available and this is probably not the most difficult problem to solve

You’re right. It’s either yoyo without lifter or lifter with flygen or ropedrive.
For this thought experiment I would prefer the latter to add stability and security.

With ropegen not that different from Kiwee?

It is similar! However the blades of this concept would just be connected by bridling / tether and not connected in the middle by a hub. That would also mean that the axis of rotation probably has to be the ground - lifter line.

Definitely easier than doing the whole flight path. Wondering though wether there is a simple mechanical solution.

Trying to get the “Imagine just the tips of a windmill” advantage. (Which kiwee doesn’t have)

Just use two complete airplanes with a tether between the wingtips. I heard in one awec presentation that the wingspan to diameter ratio optimum was 9 or something. Might be worth checking out.

That might work. But I don’t think it’s neccessary and greater stability can be acchieved with bridling.

Interesting. That’s a really small diameter. Optimal for what ?
Illustration of radius vs diameter: ---------

For example Makani M 600 span is 28 m, and the swept area diameter is 270 m, so between 9 and 10 times the wing span. One reason is the optimization of the wing. If the swept area diameter is far lower the internal tip wing speed will be far lower, involving in a lower efficiency. As comparison a ground-based wind rotor diameter is only two times a blade span but the blades design is enough optimized so that Betz limit can be approached. Deducing 9 times wing span swept area diameter doesn’t allow optimizing Betz limit (I put also the link with a discussion in regard to Betz limit) with only one wing, even with two wings. It is the reason why (in spite of its 4/27 limit) a yoyo system remains competitive until more drag wings can safely be installed.

Following that I previously wrote, a rotating AWE system is analysed on https://pdfs.semanticscholar.org/e45a/aeba0b47e5e17559b04e4507d823cab29d4c.pdf, indicating that “…a blade in this rotary wing is about two times less efficient than the same blade in the straight flying wing.”

This whole consideration made me think more about the makani wing.
Do you think the makani wing is asymmetrical with one side at another aoa than the other? Is that why they fly in a circle and not the figure 8?

Here is an another related concept: https://www.youtube.com/watch?v=KHxbVHxo7bc That doesn’t look that well though out.

I didn’t understand your description with the orthogonal rod. To fixate wings relative to each other in a circle, you need at least 3 wings I think, like in the video. Then you need to control the angle of attack of the wings. I’m assuming you want to keep the AoA within 0.5 degrees of your goal. You can experiment in how to do that by suspending a plank from strings and see how you can make it stable.

Then a purely tensile system won’t be self-starting, so you’d have to start thinking about that at some later date.

I think @Rodread is trying to do something similar.

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I don’t think so. Here is a drag soft wing flying by figure 8: https://www.youtube.com/watch?v=_rLbvSATEbg.
Figure 8 is easier because there is no tether twist, but the circle can be more constant.

The circle is a simpler control mechanism, and allows you to keep the kite on average deeper into the power zone. The drawback is if course that some sort of swivel is required

But the speed of the tips would be different. This can be counteracted by different aoa like on regular turbines. Also the default position with aligned ailerons might be going in a circle.
(But I don’t think different aoa or default circle path are true)

Because the tether connects the wingtips, the roll angle should sort itself out. By itself having different speeds on the left and right wing should not be a big problem. You probably also wont be using the rudder much