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
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...
Thanks to Batiste and Rod for the appreciation for the latest kFarm
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
~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
*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
For a looping foil, full stall hangs the kite down, and even helps
weakly pull down where it can be caught.
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
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
cc by 3.0 (attribution kPower)
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