Dudu and Betsy tried out a couple of new rokkaku kites this morning, and he, Don, and Betsy went out this evening to try some more. The photos preceding each label depict that model in flight.
Our prototypes from versions 26 27,28,29 and 30 are made with the 2 piece light Dacron material with the closing seam on top of the tubes. This caused the curve to be flatter than usual.
We tried to fix this issue on version 30 by adding more curve to the design, but we also changed the curvature flow, getting more curve at the center than the tips. This resulted in the same maximum, but the new flow is not ideal, making the kite unstable.
The ideal curvature flow is to be flatter at the center and curvier at the tips, so the center gives maximum lift and structure (not buckling) and the tips give maximum dihedral effect where it is most significant.
The last Cuben Tech prototypes (version 25) have tapered segments and stitch closing seam with Dacron reinforcements. The intersection segments are full light black Dacron to withstand the inflation pressure at the complex connection.
To improve the design, we should have the strut curve modified, go back to segmented strut curves for best results, and keep the simple two-piece spar model with segments at the back angle break where the back strut is attached.
More: Kite Tests on Land and Water