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NPWC v8

This is version 8 of a single skin sparless kite based on NASA's Parawing (NPW) series. It is still in the experimental development stage. If you are looking for the best NPW available today, then I suggest Fredrik Lejonklou's Teega, or Jan Claes' HA. An excellent plan calculator for the HA (among other NPW goodies!) is available from Tom White. More background on the NPWC series is back this way.

Unlike the first NPWC's, I wanted to try this one with a minimal bridle. I talked with my wife about putting a wind tunnel in the apartment in order to quickly tune the bridle. There is a clear path from the kitchen window to the living room window which would be ideal. Unfortunately, she did not buy the idea even though I explained that, to the right buyer, a wind tunnel would significantly increase the value of our apartment. Alas, I was vetoed and forced to the beach with a bridle tuning jig I improvised with clam cleats and dog anchor stakes. See the pictures for details.

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After sewing. Bridle adjustment jig. Flying 1. Flying 2. Flying 3. Flying 4.
Flying 5. View from back. Closeup 1. Closeup 2. Plan design.

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All the outdoor shots were taken at 55°39'45"N 12°38'16"E. Copenhagen's artificial island is so new that it is missing from Google's satellite view. As you can see from the pictures, 3:30 is close to sunset during winter time in Denmark.

The wing outline is described by a Cubic Bézier curve. Information about Bézier curves can be seen in the wikipedia. Most CAD programs support Bézier curves. The below macro was used with Rhino to draw a full sized wing panel:

; Rhino macro for creating NPWC v8 wing panel
; Bill Ola Rasmussen 2006-7-8
; in Rhino open with: Tools, Commands, Read from file...
;
; clear previous drawing
;
_selall
_delete
;
; change units to centimeters
;
_-DocumentProperties units unitsystem centimeter no enter enter
;
; create wing panel
;
_polyline 0,7     0,0 5,0 enter
_curve    0,7 2,9 6,4 5,0 enter
;
; scale panel
;
_selall
_scale2d 0 16.4 enter
_zoom _all _extents enter
;
; grid for a4 paper 21x29.5, lines just inside drawing area of page
;
_polyline 0,27 0,0 18,0 enter
_invert
_array 10 10 1 18 27
;
; all done, remove selection
; 
_selall
_invert
;
; It would be nice to array a point across all the lines
; to give better printing, but for now we do this manually.
;

Findings:
The nose seemed to be collapsing a lot, perhaps I was trying for too low an AOA.
The bridle tuning rig seemed to work. I was able to adjust the 4 line lengths on each side while the kite 'took care of itself'. I should have tried leading the lines to one location to see if stable flight was possible on a single line.
There was not even a hint of latitudinal folding, next version will be flatter to see how far I can push this.

Have fun!
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©2007 Bill Ola Rasmussen