Rob Creighton asked how giant soft-wing power-kites could reduce C_L (Coefficient of Lift) for stable return-phase reeling.

One well-developed solution is Mid-Span Reefing of giant cargo parafoils. The technique was developed for US Army cargo drops as a means to reduce opening shock of the packed parafoil. Its a standard method closely related to the sliders used in sport parachuting for the same purpose. Such techniques generally will work in reverse (back-drivable) for AWES use in modulating C_L.

Cargo Parafoils are a close analog of Power Kites under any Similarity Analysis. They have been proven to scale past 1000 m2 with reefing and steering capabilities. Unlike rigid wings, the ultimate megascale limit of variable C_L soft-wing is unknown, with no looming scaling law as a barrier. The mid-span reefing method uses drawlines and rings or grommets across ram-air cells to let them open (or close) controllably. The reefed unit flies stably with a far lower C_L.

Unlike reeling AWES with soft-wings, reefing is not the operational basis for direct crosswind or short-stroke AWES generation schemes, but can serve for matching the wing to wind conditions and to facilitate launching/landing operations.

• CoolIP*                      ~Dave Santos                 5 Oct 2012             AWES7367

Comment and development of this topic will be occurring here.       
All, send notes, drawings, and photographs!

• Terms and aspects:   
  • Reefing      wiki/Reefing
  • C_L      wiki/Lift_coefficient
• Related links and concepts:
  • Variable area
  • Morphing
  • Variable porosity
  • Variable geometry
  • Pinching, gathering, collecting,
  • Segment depowering
  • Shading, hiding
  • Closing
  • Furl, furling
  • Luffing
  • Flagging
  •  
• Commentary is welcome:
  • v