Read why designer 'Bill Hansen' thinks Constant Curves are better.

Constant Curve / Blog

Lately, I've been seeing a number of inflatable kites on the market with highly angular segmented leading edge tubes and considerable canopy distortion at the joints. Some have only a minimum number of segments (only 1 or 2) between struts which exaggerates their visibility. To me, this just seems wrong. But, I see little if any talk of it at the beach or in internet discussions about the merits of one kite over another. It is as though most kiters just do not notice it or if they do, don't see it as a problem.

Generally, clean smooth surfaces are intuitive and experimentally shown to be correct for constructs intended for use in fluid flow situations. Most things that fly or swim are naturally streamlined and smooth curves, even with birds having a jointed skeleton, are the norm.

As a designer, I have worked extensively to construct kites with smooth curves whenever possible because they are aerodynamically and structurally superior. The reason the work is extensive is that constant curve kites are much harder to design and build because they are not particularly CAD friendly at the pattern stage. That is not to say CAD software cannot do it. But, when a 3D model is broken down into 2D panels to create a sewn construct, the curves are approximated by reducing them into segments. Clearly, the more segments used, the closer to the desired curve the final outcome. But, there is a point where the segment number vs degree of curvature and expense of production and added weight of numerous seams comes into play.

My solution to this trade-off is to create 'constant curve' tubes which in fact are truly curved and have no angular joints. In order to maintain the fabric thread lines along the load, there are a number of curved segments joined with seams to create the complete tube. There are some problems with this approach. First, complex shapes with several changes in plane cannot be easily made with constant curve tubes. Second, because the geometry is naturally curved, the canopy attachment must also be curved. But, the canopy is made of panels where again, there is a trade-off between panel number and production/weight considerations. In the end, the canopy attachment curve and position on a constant curve tube are a bit difficult to accurately predict. More traditional hands-on sailmaking techniques come into play to adjust the canopy fit. This procedure can be time-consuming and require several iterations to get it right. I suspect this is one of or possibly the primary reason we do not see more constant curve kites on the market in today's highly CAD-oriented world.

So, does it really make a difference? I believe it does. I believe constant curve proves itself in the efficiency and upwind ability of our kites. Method, Element, Nitro and Combat are all very efficient. One of the reasons they are efficient is that a kite does not always see straight leading edge to trailing edge (chordwise) airflow. Instead kites are constantly 'crabbing' into the wind or turning with a fair amount of spanwise flow which will have to encounter the 'bumps' evident in highly angular segmented kites. Clearly, it is a matter of degree but still a matter of growing concern as kites, boards and riders improve.

I think constant curve kites are just plain better. I also think they just plain look better too...

Cheers!