Pump me up wrote:
Fast-turning big kites need to be fat & long middle struts,
but the payoff is poorer upwind ability and slightly inferior low-end.
Birds, wasps, stunt kites, and planes are rigid.
ALL high performance aircraft (eg hang-gliders vs paragliders) have rigid structures.
Rigid hang gliders out-perform soft paragliders on all measures. Interestingly,
the trend in paragliders is towards increased rigidity, e.g. stiff mylar reinforcements,
plastic stiffeners in the leading edges and carbon fibre rods sewn into the ribs.
These stiffening innovations have resulted in paragliders that are so successful in competition
that old-style soft gliders are no longer competitive.
Similarly, kite manufacturers are always looking for ways to make kites more internally rigid,
eg by joining the struts firmly to the leading edge, adding fifth lines, and mini-bridles.
Cheers to Pumpy and to the Veterans also
But I think Pumpy needs to update his concept about the need of rigidity and struts,
since the recent successful strutless one just proves everything the opposite of the above