Switchkites Riders Blog: Is your kite's leading edge as strong as it looks?

Is your kite's leading edge as strong as it looks?

This entry was posted on May 28, 2014 by Bill Hansen.

Is your kite's leading edge as strong as it looks?

In the last blog, we discussed the various aspects of Leading Edge Tube diameter as it relates to structure and performance of an inflatable kite. We also understand that smaller tubes may have aerodynamic advantages which must be balanced with structural considerations so the kite will not buckle or distort improperly.

That is, smaller tubes need higher pressures to have the same structure under load. What we did not discuss was the actual strength of the Leading Edge tubes and the forces it must withstand to avoid bursting.

The Hoop stress (around the tube) on a closed-end pressurized cylinder is proportional to the pressure times the diameter:

That means, the larger the leading edge tube and the more we pump it, the more likely it will burst. If we increase the LE diameter from 12cm to 15cm and pump it to our usual 7-8psi, the stress trying to pull apart the LE Seam will increase 25%.

Those who have witnessed a leading edge bursting know that it usually happens more in the center of the kite where the Leading Edge Tube is largest. Clearly, many bursting episodes have to do with damage from scrapes or other incidents or possibly weak stitching. But regardless, it almost always occurs in the center of the kite because the stress is highest there for any given pressure. Assuming there is no damage and the stitching is intact, the resistance to bursting will be a measure of the fabric tensile strength in the hoop direction and the integrity of the closing seam and fabric where the seam is made.

At Switch, we know our quality and durability have to be superior and notably so to build trust in the brand. Our very first project was to develop a clearly superior Leading Edge Closing seam because failures there are not only catastrophic, they are also a prime indicator of design, construction and attention to detail. We set about constructing the strongest leading edge closure possible that would approach the strength of the leading edge dacron material. We also equally applied ourselves to approaching every construction detail in the same way. Now, after three years of producing kites, Switch has gained a reputation for quality of construction and durability. But, just doing it is not enough because the end user may not be educated sufficiently in construction of sewn products to notice or understand it.

The Switch Testing Lab

Traction kiting is a dynamic, exciting and potentially dangerous sport. In the course of growing the brand and for the benefit of our customers, we understood the need for a true engineering and testing approach to all facets of the products. That meant building a sophisticated state-of-the-art testing laboratory where we could directly determine for ourselves the true strength and durability of our products. A dedicated in-house testing laboratory requires substantial investment, staffing and time to develop and operate. It shows the commitment Switch has made to develop and make the absolute highest quality products and place real numbers on their strength and integrity. We are continually adding to our database of knowledge regarding strength of materials, construction and possible modes of failure.

Since we started in the beginning to build the strongest leading edge closing seam in the industry, some of our first kite construction lab testing was devoted to testing it.

Following is a video which demonstrates our success at doing it.
Caution: If you are in the kite repair business, you may not want to watch this. However, If you are looking for a quality kite, you should...

VIDEO of leading edge construction testing.