When commercially available kevlar first appeared on the scene, small kevlar cords were put into use on sport parachutes. Before even 100 uses, some jumpers experienced line-breaks. It was a surprise, as the very thin kevlar lines were supposed to be over twice the strength of the polyester lines they replaced. In the end, I believe the failure was attributed to dirt getting into the uncoated kevlar cord and setting up deterioration due to abrasion process at a scale too small to visually observe.
On Sat, Jun 21, 2014 at 11:22 AM, Kevin McGowan <[email protected]> wrote: > I use Kevlar for the foot loop on my frog system for years. I worked > great. > > KM > > Sent from mobile device > Kevin McGowan Photography > 5250 Gulfton, Suite 2F > Houston TX 77081 > Studio: (713) 665-3818 > Cell: (281) 433-2474 > > > > On Jun 21, 2014, at 12:42 AM, David <[email protected]> wrote: > > > > In the news today, it was announced that the chemist credited with the > > discovery of Kevlar, > > has passed away. Stephanie Kwolek was her name. > > > > Sometime around 1986 or 87, I was taking a materials science course at > > A&M and had access to a tensile-test machine. I asked the professor > > if I could test a piece of 5mm Kevlar cord. > > > > I put a figure 8 knot in each end. and tied each end to the steel bar > > connectors. I think I had about 15 inches between the knots. > > > > It broke in the middle of the upper knot at around 10,000 pounds. > > The professor was > > quite surprised. > > > > I used the cord in my Mitchell System, from my foot to an upper Jumar, > > several times over a 2 year period, on some pits that were under 200 > > feet. At the foot attachment, I tied the Kevlar cord into a > > chicken-loop rig, described by James Jasek ( I think ) in a Texas > > Caver in the late 70's or early 80's. So that the Kevlar cord was > > the only thing holding my foot to the Jumar. I did not tie the cord > > to the Jumar eye-hole, but wrapped it around the handle and tied it > > off. > > > > While I would not recommend doing that now, I would say the cord is > > light enough to throw in the cave-pack for an emergency or as a > > back-up. > > > > David Locklear > > > > --------------------------------------------------------------------- > > Visit our website: http://texascavers.com > > To unsubscribe, e-mail: [email protected] > > For additional commands, e-mail: [email protected] > > > > > > --------------------------------------------------------------------- > Visit our website: http://texascavers.com > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > >
