At Switch, we are always on the look-out for new fabrics and materials to improve the performance and durability of our kites. As part of the Element kite development (both version 2 and version 3) we experimented with and tested a number of different canopy materials.
The testing involved laboratory testing as well as long-term flight testing in a number of different kites in the Combat, Nitro and Element lines. Since performance is directly linked to creating and maintaining an optimum built-in profile, the inherent stretch characteristics of any given fabric play an important role in their selection for production.
The differences in kite performance when an identical kite is made from different fabrics can be dramatic and the resultant choice is either rejection of the fabric altogether and moving on to others or adjusting the design and patterns to utilize the specific attributes of a particular fabric to advantage.
In order to discuss Kitesurf fabric properties, there are some basic parameters to understand. First is the woven fabric's thread line orientation as defined by either weft (fill) or warp.
As a fabric is woven, the weaving process can be varied in many ways to produce differing properties. Generally, fabric can be denoted as either fill-oriented or warp-oriented depending on which direction it has the lowest stretch. Traditional older canvas-based and early dacron-based sail cloth was fill oriented meaning the fabric had lower stretch across the roll. This was due to the weft fibers being pulled taut and remaining straight in the weaving process while the warp threads travelled over and under them creating crimp with an associated longer path. When loaded, the weft fibers are already straight and directly take the load while the warp fibers elongate as the crimp is pulled out. Thus the warp direction stretches more than the weft direction.
In sailmaking, the fabric's stretch characteristics often determine the orientation of the panels to preserve the 3D built-in designed shape. As fabrics improved, the sailcloth makers altered the weaving process to produce warp-oriented fabrics which allowed for panel orientations which minimized loads across the seams.
The state-of-the-art material in inflatable traction kites has long been Teijin T9600 which is an excellent lightweight polyester warp-oriented ripstop fabric. The ripstop feature is accomplished by adding higher denier inserts during the weaving process. The inserts can be varied in spacing, weight and in some cases made from a different fiber type.
The load on a typical inflatable traction kite is transmitted through the flying lines along the canopy leading and trailing edges. While the LE is supported by the inflatable tube, the TE is supported only by the canopy fabric and any reinforcing placed there. Using proper sailmaking technique to make use of the fabric's stretch properties, we typically arrange the panels to make use of the lower stretch direction in the TE to preserve shape under load and as the fabric and kite ages.
In addition, we can use a tougher, even lower stretch material in the TE to improve on a simple change in fabric orientation
Our alternative fabric testing has been ongoing for two years as additional fabrics have become available from several manufacturers. We accomplish this testing by first obtaining small samples with the maker's weight, stretch and tear analysis. Next, is obtaining sufficient quantities of a proposed material to produce sample kites for extended flight testing. At the same time, we proceed with our own laboratory testing to verify the technical numbers for ourselves and compare the various materials to each other in a consistent way. In the process of extended flight testing, we have rejected several of the available new materials because they either stretched too much or too little destroying the performance and range of an existing design.
In the end we selected what we learned in our testing to be a strong, more durable material which supported the desired performance for the Element3 production. While no new fabric is perfect in every way, each has certain strong points which can be viewed as an improvement when used appropriately.
Following are several videos which show our laboratory fabric testing:
VIDEOS of Canopy material testing.