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Looping Parafoil Under a Pilot Kite

Published on Nov 18, 2013
6 sq meter parafoil trimmed to loop under a pilot kite. Listen to the foil wail at the ~16-17 second mark ... that is the power stroke. Note that this system is a fully autonomous kite energy system that needs no computer, no sensor, no pilot...
                      Test occurred on Nov. 18, 2013 at the Texas AWE Encampment
                       cc by 3.0 - attribution kPower

We have successfully completed a fully autonomous test of a looping parafoil under a pilot kite. Fully autonomous means no pilot, no sensor, and no computer! See the video on kPower's YouTube channel:   Looping Parafoil under a Pilot Kite  0:21

Using kPower's original delta as a pilot kite, the stock 6m parafoil exhibited great power in a moderate breeze (10-12 mph). Although the foil generates it's own lift, it would spiral into the ground without the help of the pilot kite. We even witnessed a passive re-launch of the parafoil, thanks to the delta flying stably above.

Indeed, the power was Awesome! In the video you can hear the parafoil wail at the 16-17 second mark. The day's testing ended when all four 500 lb test spectra lines snapped!

Once we replace the lines with 1000 lb test plasma line, it will be coupled with our single stroke kite engine. The power stroke will occur when the parafoil moves through 7 o'clock, the point of peak power. At the top of the stroke, the kite engine will reset and the cycle will repeat...

CC BY NC SA with attribution to kPower    ~ edoishi    18Nov2013              Discuss at:  airbornewindenergy10641
  • Thanks to Batiste and Rod for the appreciation for the latest kFarm passive-autonomy demo.

    The session goal was to show dynamically-stable scalable Low-Complexity AWE potential with an ordinary soft-kite (sport parafoil). The approach avoids need for radio-links or control pods with RATS. Launching is easy and secure, with self-landing and self-relaunching shown.

    The Runaway Mishap was a nice test-to-failure, which went well; the pilot spiraled down steeply to a soft landing with the power-kite streamered. Nothing but the Spectra lines broke, and could have been reconnected in minutes with fisherman's knots, had we needed to.

    The 6m2 Pansh was trimmed neutrally (no four-line turn input). Looping depended only on the retarding effect of one wingtip attached to the pilot line. Due to the open loop pattern (we will fly tighter with better trim), we had one crash, but nothing was harmed. The kite self-relaunched and flew its best before the lines parted.

    The 20ft WS Delta was a forced pilot-kite choice; already too heavy at that scale. Deltas by design dump gusts and tugs, especially compared to a classic pilot parafoil. We did not have an ideal soft-kite pilot in our quiver. The loop would have been tighter, faster, and higher with the right pilot kite.

    Next, we will try various PTO rigs (one, two, and three-phase) to drive our workcells.   
    ~Dave Santos        19 Nov. 2013


  • Control Line Input past a Swivel (BMX "Gyro" Detangler)
    How do we kill or depower a looping foil? What mechanism bypasses a swivel? BMX bikes often have a "detangler" mechanism so that the front stem can be spun without snarling brake lines. These are not hard to find in community bike shops, since kids often remove them. "Gyro" is the most common brand (also generic slang).

    In our looping-foil app, the entire stem set is compressed (shortened head-tube) and becomes a thrust bearing, good for a few tons of force if properly set up. A tag-line input can activate a "kite-killer" to stop the rotation (slack A-Lines into a B-line stall or slack AB v D)*. The unit might need safety padding, and workers need helmets.

    There are even simpler DIY tricks possible, but this is a good COTS start-
    •    *By AB versus D-line I meant a balanced Full Stall where the kite neither goes forward or backward.

      B-line stall is similar, but requires special rigging (compared to sport wings). C-lines are usually not needed, and can be removed for less drag and weight.

      For a looping foil, full stall hangs the kite down, and even helps weakly pull down where it can be caught.           

    ~~~~ Public Domain Safety Method


  •  This photo is a close-up detail of the hardware necessary to make a stock parafoil loop under a pilot kite:
    1. the colored rope (and yellow nylon strap) was anchored to the ground
    2. this was connected to a heavy duty swivel
    3. which was joined to the plywood hardware plate with a steel link
    4. the hardware plate spreads 4 pieces of red and white polyester rope
    5. the lines were further spread with the use of (in this case) a PVC pipe spreader -- very important detail!
    6. finally the kite's 4 lines were lark's headed onto the knots tied into the red and white rope

    Not shown is a fifth load-bearing line that ran from one side of the hardware plate up to the pilot kite. On one corner of the parafoil a solid brass ring was attached by way of a short leader. The load line went through this brass ring. It is around this point that the parafoil looped.

    As described in the original post, all four 500 lb test spectra lines snapped. This photo reveals how the two inner brake lines snapped close to the hardware plate while the steering lines snapped up close to the kite's bridle. We are unsure how exactly this happened, as it happened so fast!

    cc by 3.0 (attribution kPower)

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