By Dave Santos on Aug. 9, 2019

28030  Re: kPower's current testing

kPower's crosswind power arch experiments today were the best ever, the accumulation of small improvements in recent years. Advanced rig topology and geometry seems optimal; perfection now a question of tunings and detail-engineering. In hot gusty wind at Dripping Springs Texas City Park the starting AWES kite was a Prism 1.8m2. The parafoil tended to overfly its crosswind PTO power-zone, but with close attention stayed in-bounds and did the job if not fully accelerate.

Then came the best part; I switched the parafoil out for a Born NPW 4m2. Immediately hope was fulfilled that a larger more powerful SS kite will nevertheless fly the tightest turning pattern of any power kite (and not overfly the power zone). The PTO gone-wild was unloaded, but would have netted a few kW (time to haul out the groundgens). As a sub-test, I added a 2m2 Pilot Delta to the NPW's nose on a 10m bungee line et voila, a rig that stays up whether the power kite is driving the PTO loop or killed, but refinements were wanted, so I took it off. Then a solid derecho gust set in and the NPW went totally nuts, driving the PTO with fast powerful load motion of ~10msec at ~1Hz half-cycle. Suddenly both control lines parted, each rated at about 100kg, and the session was over before I could futz a phone video.

Its great when lines bust this way, because the power is so tangible, and its so easy to upgrade lines. Who would have guessed that "ugly" super-powerful SS kites actually turn faster than any other type, and that their Dutch Roll "dancing hippo" wobble is the densest powered-up sweep mode? It took a decade and thousands of power-kite AWES test sessions to hit on what looks obvious now. I enjoyed every session, even the many kitemares, thrilled there is still more to discover and prefect. Thank goodness the core power-kite design space was not any larger, for those impatient for solutions.

These maturing low-complexity rigs will be easy to replicate. Finally just about anyone will be able to make high-power pumping with just anchors, rag, string and a handful of pulleys, with less critical failure modes of any AWES architecture so far. Wubbo Lives! Thank You Dave Culp and Joe Faust.

Message history
On Monday, July 29, 2019, 12:52:01 PM CDT, dave santos <> wrote:

 A bit of an update on kPower power-arch experiments, where a power kite drives a crosswind cableway (the "arch") in extended figure-of-eight motions. Its taken this long to get simple AWES designs identified from virtually infinite possible rigs. Every developmental prototype is both a step forward and a dead-end in one. Each requires meditation on the complex observations and how to rig next. Both the topologies and geometries evolve; topologies in leaps, and geometries by tunings.

Flying an 8m2 KiteShip OL and 7m2 NASA NPW much like WindSled and others before. The control line rigging art is advancing detail by detail, in safety and handiness. On a fixed anchor in strong wind SS power is scary, compared to kite sports where falling off downwind tames the surges. Finding: It will be necessary to work the depower function closely in strong conditions.

The current architectural direction is to implement a small pilot kite just above the work-cell, to assist launch with a halyard line. Everything else had been flown until worked out fairly well, excepting early-relaunch without walking downwind to reset the kite for launch. Seven pulleys are in the current design, close to what a small sailboat might have. This includes control lines, crosswind cableway PTO, and pilot-lift halyard function.

AWE is now way beyond what anyone knew how to do back in 2007, when this Forum started as a handful of email contacts. AWES rigging could mature rapidly on the theoretic and experimental foundation laid. Its emotionally odd work, where tiny kitemare after kitemare must be experienced and overcome, and everything finally works ~great~. Once all operational modes have been ~perfected~, the kPower game will turn back to decent measured power; then comes major scaling up, if all goes well.