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Re: [AWES] Overspeed? what's that?

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  • roderickjosephread
    I m imagining the situation of a controllable scoop mothra lifting the hub of a ring of kites. In a low wind the back line of the mothra would be tightened to
    Message 1 of 10 , Dec 14 11:03 AM
      I'm imagining the situation of a controllable scoop mothra lifting the
      hub of a ring of kites.
      In a low wind the back line of the mothra would be tightened to lift and
      drag more with more tarp presented to the wind.
      High winds, pay out the back lines and stretch the back foot back, front
      foot fore. presented face decreases but overall lift and drag remains.

      As for the generating component ... It's not a constant airspeed ...
      it's near constant relationships of ring rotational velocity to wind
      velocity that I see as essential for survival...
      This way the sail does load up force progressively as it reaches top
      storm speeds, but stays within it's acceptable parameters.
      Just like the jet engine turbine rings are doing, the blades on that
      ring are wings too.

      Kites can flex a gust away, flatten off a bit, but we want them staying
      tight and not being battered about by a big wind.

      As for sucker wind, with a sprung or counter balanced launch wand
      tempting a mothra leading edge upward, At least it's trying. What
      problems occur if it doesn't get up? on the day it doesn't get up ,
      there's no wind. When it's there it's there high up, we are going for
      good high air.




      --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...>
      wrote:
      >
      > Its an interesting idea, to try and keep airspeed constant in
      �the hope to avoid variable wing states. Makani proposed stopping
      its normal looping to ride out high winds flying in place.
      >
      > There are a lot of problems still. Load-matching capability is reduced
      by this "one-speed" strategy. Looping or not is somewhat an all or
      nothing event, with a large gap in speed between the two states (figure
      eights can transition more smoothly). Even just looping tends to vary
      airspeed, unless you slave variable to airspeed. High winds mean
      turbulent gusty conditions, so actuator churn and hairier control
      processing are further costs to the constant airspeed requirement.
      >
      > Yachts and aircraft share a great need to operate at varied airspeeds.
      With aircraft, safe practical take-off and landing typically require
      slow-speed flight relative to normal cruise. Hence the elaborate
      variable wings seen on airliners. Even simple types usually have flaps.
      Slow flight of a hot wing is a dangerous flight mode. Trying to maintain
      sweeping flight in a fitful low wind is similarly high
      risk.�Trading away early launch in light air is quite problematic:
      "Sucker wind" is a pattern of weak puffs that tempt the kite control to
      order constant launch and land cycles in a vain struggle. A
      one-speed-fits-all trade-off expands the sucker-wind
      envelope.�Another way to look at the problem is to ask "Underspeed?
      Whats that?".
      >
      > Its hard to avoid the conclusion that only the most flexible set of
      wings operating over the widest range of windspeeds can really laugh at
      overspped and underspeed as critical limitations.
      >
    • dave santos
      What sort of airborne hub is megascalable?  It seems well established that flying 3D rigid structure is a scaling dead-end. Even at your modest experimental
      Message 2 of 10 , Dec 14 11:48 AM
        What sort of airborne "hub" is megascalable? 

        It seems well established that flying 3D rigid structure is a scaling dead-end. Even at your modest experimental scale, your experiments gave you a nice clear indication that larger torsion hubs can hardly fly up high into better wind. That's a great result, since it confirms a design path to avoid. Instead, you chose that architecture for a Kite Power Coop logo :) 

        Test every idea, even the obvious dogs. Unpromising results hide lessons that can steer us toward real solutions. The more failure-lessons one can bear, the greater the eventual success. Too many folks in AWE sink with their ships, rather than jump onto a better one. At best, only a large surface hub (that does not fly) is megascalable (carousels and ring tracks).

      • roderickjosephread
        That analysis might be a bit harsh. The lifting kite we used had a couple of thin flexible spars in it ... rigidity The steering for the lifter is a metal
        Message 3 of 10 , Dec 14 3:19 PM
          That analysis might be a bit harsh.
          The lifting kite we used had a couple of thin flexible spars in it ...
          rigidity
          The steering for the lifter is a metal frame, radio, servo..rigidity
          The top hub used was from a mountain bike and was too big for what was
          needed... rigidity
          All of the rigid matter up top lifted fine.

          The problem with our last test was that the stem was too flexible to
          hold the weight of the bottom hub (The hub bellow the ring set) and the
          brake and the cuff and the tethering wheel...
          It was all on a long flexible pipe.
          This had the unfortunate side effect of drastically misaligning the
          tethering ring and the kite ring.
          In the rare seconds that they aligned, it looked good... really rare.

          The first ring prototype never had that problem as there was no
          alignment issue, all the tethering ran from 1 point.

          If that extended ring set idea or even just one lifted ring idea is to
          be lifted , then the bottom hub should be balanced in a gimbal to allow
          the tension from the kite ring to align it...
          Furthermore, the first (lowest ring or only ring) should be set as a box
          ring kite (one ring sparred to a front tethering ring)

          The lifted hub (yes it is weight up high) is not a heavy weight, It does
          have to cope with the line tension, that will be a maximum when all the
          rings stall and collapse... otherwise if the rings are flying the line
          tension is reduced due to ring kites lift.

          I am opposed to weight up high as well. But it is a simple elegant
          method.

          If we want to control kixels by line, we will need rigid smooth rings
          mounted on our loadpaths to run control lines. OK they're tiny too but
          still rigid.

          This whole parametric algorithm design course I'm putting myself through
          is mincing my head though...
          I am definitely going to end up drawing meshes of organic loadpath
          arches with triggered twitchy gill sails

          Another good laddermill idea you'll not approve of Dave S.... may use 2
          hubs lifted up to opposite sides inside an arch. a continuous rope with
          the outermost edge of many kites runs through the hubs (wheel sets), the
          inner edges of the kites are banded on a short band and the tethering
          for the kite ring is collected to a central tether (spinning or
          swivelled) Power is taken from the band at the arch feet as the band
          runs through ground wheels.





          --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...>
          wrote:
          >
          > What sort of airborne "hub" is megascalable?�
          >
          > It seems well established that flying 3D rigid structure is a scaling
          dead-end. Even at your modest experimental scale, your experiments gave
          you a nice clear indication that larger torsion hubs can hardly fly up
          high into better wind. That's a great result, since it confirms a design
          path to avoid. Instead, you chose that architecture for a Kite Power
          Coop logo :)�
          >
          > Test every idea, even the obvious dogs. Unpromising results hide
          lessons that can steer us toward real solutions. The more
          failure-lessons one can bear, the greater the eventual success. Too many
          folks in AWE sink with their ships, rather than jump onto a better
          one.�At best, only a large surface hub (that does not fly) is
          megascalable (carousels and ring tracks).
          >
        • roderickjosephread
          you might have a good point about the logo Dave S needs to be a more cooperative design. a lifter and a crosswind driving device... Maybe an arch with big
          Message 4 of 10 , Dec 14 3:39 PM
            you might have a good point about the logo Dave S
            needs to be a more cooperative design.
            a lifter and a crosswind driving device...
            Maybe an arch with big "ears kites" pinned on to third way along the load path to stretch it out and lift a crosswind power device...


            --- In AirborneWindEnergy@yahoogroups.com, "roderickjosephread" <rod.read@...> wrote:
            >
            > That analysis might be a bit harsh.
            > The lifting kite we used had a couple of thin flexible spars in it ...
            > rigidity
            > The steering for the lifter is a metal frame, radio, servo..rigidity
            > The top hub used was from a mountain bike and was too big for what was
            > needed... rigidity
            > All of the rigid matter up top lifted fine.
            >
            > The problem with our last test was that the stem was too flexible to
            > hold the weight of the bottom hub (The hub bellow the ring set) and the
            > brake and the cuff and the tethering wheel...
            > It was all on a long flexible pipe.
            > This had the unfortunate side effect of drastically misaligning the
            > tethering ring and the kite ring.
            > In the rare seconds that they aligned, it looked good... really rare.
            >
            > The first ring prototype never had that problem as there was no
            > alignment issue, all the tethering ran from 1 point.
            >
            > If that extended ring set idea or even just one lifted ring idea is to
            > be lifted , then the bottom hub should be balanced in a gimbal to allow
            > the tension from the kite ring to align it...
            > Furthermore, the first (lowest ring or only ring) should be set as a box
            > ring kite (one ring sparred to a front tethering ring)
            >
            > The lifted hub (yes it is weight up high) is not a heavy weight, It does
            > have to cope with the line tension, that will be a maximum when all the
            > rings stall and collapse... otherwise if the rings are flying the line
            > tension is reduced due to ring kites lift.
            >
            > I am opposed to weight up high as well. But it is a simple elegant
            > method.
            >
            > If we want to control kixels by line, we will need rigid smooth rings
            > mounted on our loadpaths to run control lines. OK they're tiny too but
            > still rigid.
            >
            > This whole parametric algorithm design course I'm putting myself through
            > is mincing my head though...
            > I am definitely going to end up drawing meshes of organic loadpath
            > arches with triggered twitchy gill sails
            >
            > Another good laddermill idea you'll not approve of Dave S.... may use 2
            > hubs lifted up to opposite sides inside an arch. a continuous rope with
            > the outermost edge of many kites runs through the hubs (wheel sets), the
            > inner edges of the kites are banded on a short band and the tethering
            > for the kite ring is collected to a central tether (spinning or
            > swivelled) Power is taken from the band at the arch feet as the band
            > runs through ground wheels.
            >
            >
            >
            >
            >
            > --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@>
            > wrote:
            > >
            > > What sort of airborne "hub" is megascalable?�
            > >
            > > It seems well established that flying 3D rigid structure is a scaling
            > dead-end. Even at your modest experimental scale, your experiments gave
            > you a nice clear indication that larger torsion hubs can hardly fly up
            > high into better wind. That's a great result, since it confirms a design
            > path to avoid. Instead, you chose that architecture for a Kite Power
            > Coop logo :)�
            > >
            > > Test every idea, even the obvious dogs. Unpromising results hide
            > lessons that can steer us toward real solutions. The more
            > failure-lessons one can bear, the greater the eventual success. Too many
            > folks in AWE sink with their ships, rather than jump onto a better
            > one.�At best, only a large surface hub (that does not fly) is
            > megascalable (carousels and ring tracks).
            > >
            >
          • dave santos
            Sorry to seem harsh. The point is not how well your hub worked at its small scale, which looked OK (if a bit elaborate). KiteLab testing has consistently found
            Message 5 of 10 , Dec 14 4:45 PM
              Sorry to seem harsh. The point is not how well your hub worked at its small scale, which looked OK (if a bit elaborate). KiteLab testing has consistently found that small hubbed rotors at low altitudes work well.

              The intended lesson is that even at your current scale you are getting definite indications of just how severe the cubic-mass scaling penalties will be, once you know to look carefully for the harsh scaling law's predicted effects.

              Our harshest critic is reality, which often whispers.
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