Loading ...
Sorry, an error occurred while loading the content.
 

Stiffer Nodes (Max Power from Membrane Wing-Mills)

Expand Messages
  • dave santos
    Over years of building and flight testing flapping membranes for power extraction, many design principiles revealed themselves. Today s versions are better in
    Message 1 of 2 , Dec 16, 2012
      Over years of building and flight testing flapping membranes for power extraction, many design principiles revealed themselves. Today's versions are better in every way. Nice airspace and planform geometries are worked out. Internal load-paths are aero-elastically tuned for certain firing. Battens run as they should to enhance membrane normal mode harmonics. Turbulators and inertial regulators are validated. Loads are variably matched. Most such refinements have been described. These "flipwings" made power, but did not quite yield the amazing power-to-weight suggested by predictions. A missing ingredient was needed.

      The hint was the drogue corner-block line-tensioners that allowed flipwing pumping output to change direction back to the anchorpoint with far less loss than pumping damped around a loose line catenary to the suspended flipwing. This was noticed as a transverse wave dispersion problem, with the fix being to make the wave longitudinal by guy-lining it as a still node. It was now clear that a proper guy-lining of the nodal points acted on by the flipwing (as anti-node) allows maximum power-out. The new configuration, in the simplest case, has two pairs of flipwing node guylines to a pair of anchors, as an arch variant. Power is extracted as a two phase pulsing at the anchors. For single anchor needs, the older flipwing method still gives useful power, the trick is to use more kite and drogue to tension nodal points.

      The new AWES lesson here is to rig airborne harmonic nodes as stiff as practical for efficient lattice-pumping. We already knew the ground itself is the stiffest nodal medium, but the new understanding is how passive stiffness is the vital property for active wingmill antinodes to act against. The latest wingmill tests are almost daily validating the improved understanding. 2kiteSam has sewn several fine wingmill variants the last few months, and some of my weird cymatic Tyvek creatures will have to be seen on video to be believed.


      CC BY-NC-SA (same as coolIP)
    • roderickjosephread
      Brilliant, Can t wait to see more detail Dave S. Guying, anchoring, flip wings, wingmills the lot of course. ... even whatever a cymatic Tyvek is. I m trying
      Message 2 of 2 , Dec 17, 2012
        Brilliant, Can't wait to see more detail Dave S. Guying, anchoring, flip wings, wingmills the lot of course. ... even whatever a cymatic Tyvek is.

        I'm trying to make a parametric fit model for rope meshes suspended by catenary lines onto defined anchor points... Whether valley (super tight) or kite rigged, it could be really useful for design, testing and control.

        The two phases tugging at the anchors... is that from having the flip wings mounted to two pairs of guying lines? The phase being the timing difference between front and back turning to the next direction... or is it flipwings on two sets of guylines?

        To provide for optimal top line tension, Arch kites will probably evolve ... flattening and thinning at the top, more bulging and layered out at the 10 and 2 clock positions.

        Exciting




        --- In AirborneWindEnergy@yahoogroups.com, dave santos <santos137@...> wrote:
        >
        > Over years of building and flight testing flapping membranes for power extraction, many design principiles revealed themselves. Today's versions are better in every way.�Nice airspace and planform geometries are worked out.�Internal load-paths are aero-elastically tuned for certain firing.�Battens run as they should to enhance membrane normal mode harmonics. Turbulators and inertial regulators are validated. Loads are variably matched. Most such refinements have been described. These "flipwings" made power, but did not quite yield the amazing power-to-weight suggested by predictions. A missing ingredient was needed.
        >
        > The hint was the drogue corner-block line-tensioners that allowed flipwing pumping output to change direction back to the anchorpoint with far less loss than pumping damped around a loose line catenary to the suspended flipwing. This was noticed as a transverse wave dispersion problem, with the fix being to make the wave longitudinal by guy-lining it as a still node. It was now clear that a proper guy-lining of the nodal points acted on by the flipwing (as anti-node) allows maximum power-out. The new configuration, in the simplest case, has two pairs of flipwing node guylines to a pair of anchors, as an arch variant. Power is extracted as a two phase pulsing at the anchors. For single anchor needs, the older flipwing method still gives useful power, the trick is to use more kite and drogue to tension nodal points.
        >
        > The new AWES lesson here is to rig airborne harmonic nodes as stiff as practical for efficient lattice-pumping. We already knew the ground itself is the stiffest nodal medium, but the new understanding is how passive stiffness is the vital property for active wingmill antinodes to act against. The latest wingmill tests are almost daily validating the improved understanding. 2kiteSam has sewn several fine wingmill variants the last few months, and some of my weird cymatic Tyvek creatures will have to be seen on video to be believed.
        >
        >
        > CC BY-NC-SA (same as coolIP)
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.