Small Scale Kite Power Kite Type Options

@DudeInCorner intends to implement a yoyo (“reeling out” “then reeling back”) kite which is not a crosswind kite (“to stay away from power kites”). In these conditions a kite with a frame would be difficult to depower if it is even possible. A soft lifter kite could be partially or fully depowered by using an additional line that is fixed on the nose.

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As a rule, a single-line pilot-lifter and a multi-line power kite do not perform each other’s function well. There are two basic soft PLs, a parafoil or SS (single-skin), and neither “powers” or “depowers” well. WPI did a pilot-sled AWES, but that’s not soft (has sticks), and it did not work well. Skysails uses a power kite, but its a rather complex solution with control-pod and software dependence.

A flat stick kite depowers better than a soft kite (but does not scale as well). The kite messenger in the video is seen depowering as a stick kite, proven “possible” as a traditional method. Depowering with an extra line on a lifter is hard to reel collectively for power and control.

Kite store practice is to carry only good kites and let the buyer choose as their heart wishes. KAP kites are great, with many fine web recommendations. The messenger completes the AWES without a “crosswind” power kite.

Personally, I would get a ten-foot Delta like this Gomberg Falcon, and make an extra large messenger to get 20W in moderate wind. Standard toy messengers are more like 5W equivalents.

A round parachute kite with an additional return line could be a possibility.

True, a Varidrogue could do the pumping, but there are no tutorials like the messenger videos. They will have to solve it if they can.

The patent shown is problematic, with no good proof available. Drogues do not like tilt, and would pull better trailing downwind from the line.

Dude, the basic idea is to pull the apex of the drogue upwind (and/or slack the lines), to pump your reeling cycle.

Hi all, thanks very much for the replies and the help, allow me to catch up.

tallakt : The main purpose of the system is to produce power while remaining somewhat compact, the payload is just an additional accessory which would be fun to have but again is not really our main goal. Our current plans on making the 20 W are to have a reel in and out system, it appears this is called a “yoyo” system as Pierre posted below your comment. The Kitewinder seems really cool, however it also appears to be out of our skill range. Thanks! :slight_smile:

PierreB: Thanks, we have not really considered that a stiff kite would be more difficult to depower than a soft kite. Though, would a soft kite still be able to generate the lift needed to support a payload? If I am thinking right, soft kites do not generate much force.

Kitefreak: We did not at all consider the usefulness of a kite messenger, but now this seems like it would end up being the best option for our goals, thank you very much!

So now I guess the question becomes what kite messenger to use? This parachute kite link you posted Pierre seems interesting however as kitefreak mentions wouldn’t a parachute kite have some issues ascending the line when tilted?

Thanks again all :slight_smile:

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The answers you’ve gotten assume you want the system to work without you using your hands. You’ll be able to make more power and have more fun if you do use your hands, by flying a multi-line stunt kite or power kite. You’ll also be able to experiment with flying patterns and see what patterns generate more electricity.

A search for all Kite Messenger videos and pages will reveal many traditional variations, plans, and design ideas.

If you are being graded for AWES autonomy, the messenger is magic. Windy Skies is right for you not to neglect feeling kite power. Try a kite like this Prism Synapse, for ~50USD, and maybe get ideas for future work.

image

Consider AWE as a hot career path, not just a great student project idea.

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Hi @DudeInCorner ! :slightly_smiling_face: Welcome to the forum!
I’m the main admin here with little technical expertise. How have you found us?

The easiest way to get your 20W would be to just stick a DC generator with a turbine on a large lifter kite line.^^ Very boring though and not really a challenge.

Don’t underestimate soft kites!

@kitefreak the kite messenger is a great idea!

Hi @DudeInCorner :wave:t3:
Does the payload have any power requirement?
Or Minimum altitude or stability requirement?
Is the power only needed on the ground?

Is there a particular classic use case in mind? Wind, sand, trees, fence posts…
Roddy

Hi @DudeInCorner,
A non crosswind yoyo reeling kite is not easy to do because of the expected low difference between the power and depower phases. With a crosswind kite (“with flying patterns” like @Windy_Skies indicates) the difference will be higher, allowing an easier management.

The Acro Kite was sold as a RC stunt kite. Perhaps it can be transformed in a yoyo kite.

Hi. I’m going to go against the wood grain here compared to the other guys on the forum and give you some alternative recommendations (not to say that the other recommendations are bad).

As the scale is so small, weight is not a big issue. If you want to loop, a RC sailplane should be able to do the trick and have everything pre-assembled. You could use a plane without a propeller, although a plane with propeller will allow you to launch easier - perhaps some kind of hover capable plane is usable if you have the flying skills. Make sure the plane has dihedral or swept wings. I can’t vouch for any of the following planes, but they could be a starting point:






The tether should be in the approximate length 50x-100x the wingspan, and should not be thicker than absolutely necessary. Use dyneema fishing line that takes only the exact load you require. You might also want a slightly weaker piece of rope to use as a weak link to protect your wing from breakage. Remember the wing is only dimensioned to withstand the approximate weight of the fuselage. Perhaps do some simple tests with weak links before you fly. Fasten the line around the center of gravity below the fuselage. All of this will probably take quite a bit of tuning in order to make it work.

If you want to increase the load, perhaps take a look at the “hydrid bridle” described in Windlift’s patent.

The problem will be actually flying the thing. I recommend using a bridge or a tower to practice so that the kite will not hit the ground. Another alternative is buying a simple KAP kite of Pilot kite (1-2 square meter for light winds) and fix the tether for the RC plane somewhere on the tether of the large kite. If you use a kite like this, flying the RC plane will feel really spongy. In ideal conditions, you might be able to loop the kite using only the rudder.

Dont use a winch until you are comfortable looping in wind. Just tie it down at first.

Once you are capable of flying this, add the winch and then possibly a servo controller to program the flying paths.

I should warn you that what I described will take heaps of effort, broken propellers, crashed planes etc etc. But it’s a lot of fun though.

Take care with the heavier model - they will be lethal weapons once subjected to wind.

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Following up on Tallak’s suggestions, kPower has long proposed that passive pilot-lift solves excessive crash-risk of current software-dependent kiteplanes. Note the wing remounted upside down for “negative-lift”, the turbine-guard as added forward vertical surface, expanded empennage surfaces, and fully self-flying dynamics.

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https://www.lhc-ilc.physik.uni-bonn.de/research-groups/experimental-physics/prof.-k.-desch/research/airborne-wind-energy

There’s this project, perfect for student projects.

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Lets be very careful advising students in AWE, a demanding aerospace field.

Students should design and fly at least a 3x tether-load safety margin, not zero safety margin. Moderate loss of performance for a student is not a problem, and limited velocity is safer. Very few students have easy access to the bloated airspace and extreme altitude being implicitly recommended (“50x-100x the wingspan”).

Be careful about costs, most students are poor. Pay-to-play tech is bad education. Kiteplane advocates rightly assert many crashes will occur, but how many replacement gliders should a student buy? Not as many as oversold Venture Capitalists can buy. A cut-and-paste shopping selection of gliders is more consumeristic display than great education.

I personally use the products suggested, and know the developers. kPower salvaged the same cheap junk Foamy UBonn suggests, and did not even need the radio/servo/control elements. Instead of ~1000euros, kPower only spent 30USD for a Dan Tracy flygen turbine, and a good pilot lifter is not much more than 100USD.

Critical-flaws inherent to common kiteplane AWES architectures are mentioned, but a student might not heed concerns. While risk is fairly low here, advocating known-dangerous AWES architectures presents moral and legal risk. Student projects should not fail due to buggy third-party beta code either, unless its a computer science class.

A modest AWES demo can be more revolutionary than a flashy VC fad architecture. Lets not saddle students with high-complexity AWES nightmares. Traditionally progressive toy and hobby kite culture is the best match to popular and student AWE interest and resources. Such kite culture teaches AWES topology exploration far better than AWE VCs so far. Low Complexity creative exploration is where AWES educational gold lies, and maybe also for industrial gold.

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This should not be a question of optimal architecture. I believe if the smaller planes are chosen, it is not very expensive not very dangerous in case of an accident. For sure find a place to fly where noone gets hurt.

They wanted to build a yoyo rig, so thats the advice I gave. They might have wanted to build any other rig I would have welcomed that also.

With regard to cost, its always nice to find something used/disposed and make it work for free. But sometimes its also nice to get the correct parts in time and without too much searching. Even so, the costs for the listed equipment is almost as low as you could hope for.

The comments you made in the post above seem out of proportion and even non subject for the thread.

So I stand by my initial advice as pretty sound. Also read DS’ comments about safety and be careful.

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Tallak,

Optimal AWE education is the meta-topic here. This should not be a question of a suboptimal educational architecture. No student should fail at their own developmental level. Its up to the curriculum developer to make sure every student can succeed, from kinder and special-needs, to post-grad. Optimal methods tend to help.

The pumping Messenger offers a simple stable reliable reeling basis. The choice of crashing new airplanes is “very expensive” for most students. Access to shared optimal low-complexity AWES methods may be best for both students and energy markets. A beginning student should not be made to copy overly-complex design, Let them succeed at a KIS experience of finding creative solutions in a fertile engineering exploration space.

Fortunately Dude can pick whatever best fits his needs. Lets think ahead for future AWE students of every kind. What are the best lessons? NASA really pushes simple self-flying kites in its K-12 curriculum, and adding an AWE WECS component would be simple.

@DudeInCorner
get a bunch of foam gliders and tie them into a kite turbine rig

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It is also possible by using the full wings of semi-rigid gliders like this:

or half of the wings like this:

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Some concerns were raised about the risk of using “rigid wing” (in this case EPP foam) kites.

The HK kinetic is ~600 gram with added electronics. Due to the limited maximum lift I expect the line will cause at most burns.

The impact danger could be asessed by comparing non-lethal weapons. I found this chart

Source: https://www.researchgate.net/publication/306559973_Kinetic_Non-Lethal_Weapons/link/57bf1f6408aeb95224d0fbf2/download

It seems for this plane and a person mass 70 kg, we get ~5 on the Y-axis (3 cm radius of the plane node) and ~13 on the X axis (assuming 30 m/s attained speed). You end up in the “mixed results” section of the chart.

Be careful and keep a good distance to yourselves, other people, buildings etc. A speeding model plane like this is no joke. Also keep out of the really high wind speeds at first. 6-8 m/s wind should be plenty as a start.

Safety issues compound as advice is applied to many students. Losing an eye, or harming a small child, is possible with fairly small masses at terminal velocity, like a battery pack that falls loose (dropped-object risk). Ordinary gliders are not designed to snub-up violently against tethers, which can cause mid-air break-up. Tethers pose various special risks. AKA Member Flyers are insured for non-commercial risk.