# Issues with rigid wings and possible solutions (reply to Dave Santos)

I was trying to describe my view of the racecar vs truck argument. There are many ways around this, requiring AWE to advance a little more than single wing Yoyo. The twin kite yoyo on a Y line is one example of a possible way forward. There are plenty more, I wont go into detail, perhaps they are not all described yet

Soft kite developers propose recycling their polymers by standard processes. Its rigid kiteplanes that have more troublesome recycling issues, especially when they crash and burn.

“Fidelity in actuator precision” is not a requirement of passive-dynamic operation, like kPower’s looping foils. The only required actuation is engaging the load and a kite-killer. AWES that fly actuators are burdened by comparison.

Agreed, “evolving soft kite design is hard and time consuming”, but its the best fun the greatest designers know; what they were born to do. Its fatalistic to think these folks cannot succeed in beating critical rigid wing statistics, at least until graphene airframes and perfected flight automation emerges.

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Thanks for replying @kitefreak.

Do you have any ideas on this?

As this isn’t my research interest I won’t have many ideas on it, so I asked you and others to comment.

I do have some ideas though. We can for example multiply the probabilities of the failures to get a system that very rarely catastrophically fails. To use made-up numbers, say an automated system fails every 2000 hours, you can add a safety mechanism that works 95 percent of the time, and another that works 95 percent of the time, to get a system that on average can be expected to only fail every 2000 x 20 x 20 = 800,000 hours, or 91 years.

Like with most things in this day and age we don’t have to start from scratch.

Holding up hot fragile kiteplanes under a pilot-lifter prevents crashing, no active flight automation needed. In lulls, the kiteplane calms down and lands soft, while the pilot usually continues to fly, then relaunch the plane when wind recovers.

kPower has done many variations. including flygen. Just let the kiteplane go nuts and harvest the pumping at a groundgen via a low-stretch PTO line. Use an elastic tether to buffer disturbance of the pilot-lifter, it will return excess surge energy to the kiteplane in recovery phases of patterns.

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What is PTO?..,.,

Power Take-Off, after the aux power shaft in the rear of a farm tractor

Am I right that most crashes would occur during take off and landing? What are some ways to make that safer?

During flight I assume you could make the requirement to never fly below n meters and have a parachute on board for example so there crashing becomes almost impossible?

Ceterum censeo safety can be an afterthought for any large scale awes. Just secure a perimeter.
The case is different for things like the kitewinder small scale product where that is not an option.
And if a system is very unsafe it’s also unreliable, which makes it unviable.

The Golden Age of Kites established runaway kites as the primary public hazard. Paris’ power was cut in one instance, and a train stopped in another. In our time, airspace safety is a function of aircraft mass and velocity, and a fast massive kiteplane can travel a long way in runaway mode.

Ceterum censeo, it only suffices to secure a perimeter for many-connected (topologically stable) soft-kite networks.

Does anyone have links to AWES architectural scaling barrier predictions better than linked posts from the Old Forum?

Rod and Tallak in a related topic want something better. Sadly, there do not seem to be any in-depth academic studies. There are dozens of rigid-wing AWE start-ups somehow presuming scaling barriers will not prevent their architectures from going big.

Heuristic kPower warnings are not seen compelling nor rigorous enough, even if eventually proven correct.

Another idea I had. I have no opinion on its feasibility:

Don’t make one monolithic wing. Assemble your wing from shorter sections that you attach to each other using connectors that you can release on command.

So after your software failed and your plane goes below its nominal path and can’t recover, and you released the tether from the plane and after your first and back-up parachutes failed to deploy, you can detach the wing sections from each other to on impact with the ground only impart to the wing sections their own kinetic energy. The individual wing sections also then might start acting something like parachutes fluttering to the ground. For kicks you could also add mini-parachutes to the wing sections.

Other benefits this might have: easier and cheaper construction, and less risk in testing. If you also add bridles to each individual wing section you can also reduce strength and thus weight of the wing sections.

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Tallak,

We call this a “metawing” concept, a “wing of wings”, for several years now. Its a quite common notion, from Mothra to MegaFly. Also, assembly of meta-structure in the sky is long anticipated. The units are called “kixels”.

Moderation here does not allow mention of where these AWE ideas were greatly elaborated, unless a link is provided, page-by-page.

This is a serious scaling method that pilots fully believe in. Automation? Later.

There has been some study on how to fly individual winglets from a rotor after they have broken off…
https://spectrum.ieee.org/automaton/robotics/drones/watch-this-drone-explode-into-maple-seed-microdrones-in-midair

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Or another very similar idea is to incorporate failure points in your wing, and forego that release on command part of the idea. So you make your wing (or blade) from multiple section that you then connect to each other (possibly allowing some flexing). The connection points are the failure points.

Random quote:

A bit analogous to rip-stop nylon.

If I were to try to make a rotary system (like @Rodread, @Kitewinder, or @someAWE_cb), this might be how I would construct my first prototypes of a long slender blade.

My blades are held in the hub by rubber bands. The idea is that the rotor throws them off when spinning too fast.

Hasn’t happened yet as RPM control via generator/esc has not failed yet and wind speed has not exceeded 10m/s.

There are plenty of well documented purely mechanical overspeed protection systems for small wind turbines available. I guess my next design would be spring loaded. When the centrifugal force is bigger than spring force the blades move out - while changing their angle of attack.

/cb

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I learned that many windmills are stall controlled… a simple proven mechanism for non-pitchable blades… (for TRPT rigs)

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Rigid blades are not doomed in a crash.
Daisy testing demonstrated repeated tip ground-striking of rigid kite turbine blades.
The same rigidised foam blades which dug small channels still fly fine with little damage and no material loss.

Today - I blew out 2 cell seams on an 11m foil kite and within an hour burst the bladder of a 12m LEI.

Sure a similarly sized rigid would have been damaged by the same treatment.

A small foil can run full speed into the ground with no problems

Large kites are not resiliant is my general rule. (excludes single skin soft kites… Dare you try flying a huge one though)

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Only larger “rigid blades” (spars >3m L) are “doomed in a crash”.

Single-Skin KiteShip ship-kites and Mothra1 at >300m2 scale have been flown without much fuss by the experts. These represent the most crashworthy approach to large powerful AWES wings.

Velcro blow-out panels seem to protect parafoil cells from bursting when “thumped”. A blown parafoil cell is a simple repair (super-glue field-repair, even). A composite airframe is reliably destroyed by full-velocity crash.

An example is given on http://www.kitegen.com/en/2014/09/12/kitegen-power-wing/.

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