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Monday
Feb052018

VT Prusik

Many individuals on technical rope teams have been using VT prusiks for personal rope access. I thought a short article on its history might be interesting.

The Valdotain Tresse was developed many years ago in France. It was used as a rescue device in wet canyons or caves. A short section of 11 mm dynamic rope (used for rock climbing) was cut open. A few strands of the core were removed. The ends were sealed. Figure eight on a bit knots were made at both ends, i.e., “end eyes.” Thus, it was very flexible. It could be tied in a certain way around the main rope such that it would grab like a prusik. Or, it could be released while under load. A person could use it as a rappel device. In particular, if a subject was hanging on the rope below, the rescuer could use the Valdotain Tresse to descend the loaded rope and pickoff the subject. There is one huge drawback to this device. It is nylon acting on nylon. If both the Valdotain and the main rope were dry, the Valdotain would quickly melt through in a very short distance. The rescuer would fall to his/her death. Hence it could only be used on ropes that were saturated with water. Rich Carlson, an American rock climbing/canyoneering guide, imported the technology to the USA many years ago. However, at the time, canyoneering involved mostly dry canyons. The Valdotain Tresse as described above was not so useful.

Jump ahead a few years, new aramid materials become popular for cords and ropes. In particular is Technora which has a much higher melting point than nylon. Rich Carlson partnered with BlueWater Ropes to make the VT Prusik. It has kernmantel construction with a Technora sheath over nylon core with sewn eyes. This allowed the device to be used on dry ropes. It has slowly caught on in the USA canyoneering world. It comes in two sizes for different diameter ropes. It has many uses beyond those mentioned above. A creative technical rope user will come up with many applications.

The concept has progressed in the USA canyoneering world. Atwood Gear now makes various sizes of Tech VT with Technora sheath over nylon or polyester core.

Meanwhile arborists around the world have incorporated the Valdotain Tresse in their tree climbing systems. They too have developed specialized double sewn eye hitch cords.

There are two main methods of tying the hitch such that it releases under load. They are depicted in the video linked here:  (http://youtu.be/4HnhhVSevvY). A person must experiment with the two methods in order to determine which is best. Variables include the body weight of the rescuer as well as conditions of the prusik and rope; material the cord and rope are made of, new vs. used, clean vs. dirty, wet vs. dry.