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[ksurf] Re: C-Quad

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  • Debra Smith and Paul Watson
    At the risk of adding to the air of mysticism that seems to be beginning to surround the Peter Lynn C-Quad, I would like to offer a few observations about some
    Message 1 of 2 , Jan 4, 1999
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          At the risk of adding to the air of mysticism that seems to be beginning to surround the Peter Lynn C-Quad, I would like to offer a few observations about some early examples we have been lucky to play with here in Newcastle, Australia.
          For a few months now we have been using early 2m and 4m (protos, I think), and lately, a 6.3m foam l.e. kite (for buggy and ksurf) and have been astounded by their efficiency. Specifically, compared to parafoil traction kites, C-quads seem to develop more power for equivalent area (perhaps 1.2x ?), have a superior L/D ratio (look at how steep they fly overhead!), and be capable of accelerating very rapidly (great for high jumps!) and flying at higher speeds. Added to this is the not insignificant consideration of their price - they are comparatively cheap. How is all this possible? The Peter Lynn crowd could best answer this, however, I'll offer some of my own tentative veiws.
          Firstly, it must be acknowledged that Peter Lynn has opened up a new genre of (traction) kite design. The C-quad is a hybrid design that incorporates design elements from both parafoil and framed kite design. The advantage of the combination of these design elements (parafoil derived rigging and GRP (or Carbon) flexible rod for some structural form) is that many of the performance and cost limitations of parafoils and framed kites can be somewhat overcome:
       
      * The number of rigging lines (and thus parasitic drag) can be reduced (compared to parafoils of similar size) because of the use of spars.
      * The spars themselves are not fragile like the ones used on deltas and can easily bend according to the sail cut (see the leading edge) allowing more efficient planforms.
      * Being single skin and utilising relatively inexpensive GRP (and Carbon) rod reduces material cost per unit.
      * Labour cost is probably reduced (compared to a parafoil) because of the reduced number of lines to tie and seams to sew.
      * The aerodynamically crucial portion of the airfoil (the first third of the chord from leading edge) is given a clean shape by the tensioned GRP leading edge rod.
       
      There are some disadvantages, however:
       
      * It is not possible to pack C-quads up as small as parafoils and the Wipika. This is due to the spars. They can, however, be folded up in a fashion similar to the collapsable shelters one sees at the beach nowadays.
      * They have a tendency to "luff" or tuck under (and thus fall out of the sky in a luffing dive) if set up incorrectly or flown incautiously - particularly at the edge of the window. This is due to the very sharp, low radius leading edge combined with a rather low rigging angle (causing rapid and progressive negative angle of attack airflow separation (Hello to any surviving 1970's pre-reflex rogallo Hang Glider pilots - you will recognise this hassle!)). This "problem" is avoidable through correct trimming and sufficient flying experience. One needs to sensibly use the "brake" or pitch control faciltity to keep a safe angle of attack (very easy with sufficient practice).
      * They are usually not relaunchable (at least by anyone I have flown with!) on land or water when they belly or back land - i.e. they are laying flat. On the other hand they are very easily relaunchable from the nose or tail if the sail has wind in it.
       
          To conclude, the C-quad is an innovative traction kite that opens up a whole new genre of design (As a personal design exercise, I have been playing with a rather different hybrid of my own design for a good few months now and am very impressed with the possibilities (and wary of the limitations, too!) of this type of traction kite!). Ksurfers who have been fortunate enough to develop their kiting skills with the superb (but by comparison to the C-quad, not as high-performance) Wipika will necessarily have to develop some new flying skills (you have been rather spoiled by the very good nature of the Wipika, folks). On the other hand, with a C-quad you will be able to enjoy a traction kite that is cheaper than just about any other performance traction kite around, has astoundingly high performance (the upwind performance of your board will be exhausted a long time before that or your kite) and posses good manoeuvrability and de-powering characteristics. Although it seems that no kite has yet challenged the Wipika (and Kiteski relaunch system) in terms of  water relaunch capability, the C-quad challenges both in terms of price and flight performance (beware of the cursed flat landing, however!).
       
      Smooth air to all,
      Paul Watson
       
       

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    • Martin Rothwell
      ... You what??? ... eGroups.com home: http://www.egroups.com/group/kitesurf http://www.egroups.com - Simplifying group communications
      Message 2 of 2 , Jun 2, 1999
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        henning.carstens@... wrote:

        > Sic itur ad astra

        You what???


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