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I made the Open Eight prototype in 2004, but the design dates from ahout 1980.
The Open Eight prototype is milled from 1/2-in (12.7 mm.) 6061-T6 aluminum.
The idea behind the Open Eight is to create a Figure Eight-like descender that does not need to be unclipped for rigging or derigging. The Frendo canyoneering Eights provide one nice solution to this problem, but they don't pack as well as a flat eight. I started working on the ideas for this eight in the early 1980s. This is actually the third paper design that I developed (I'll backtrack and make the copies of the earlier versions later.) When I showed it to people at the 2004 NSS convention, I was quite pleased with the interest shown in the Open Eight.
One disadvantage of my design is that the rope can come out of the Open Eight if the rappeller is not careful.
The prototype works well on flexible ropes, but the shank is too short for stiff caving ropes, resulting in too much friction in that case. I would also like to widen the Open Eight to allow for doubled rope.
This is one of the earliest projects for my new milling machine, and since it was never intended as more than a proof-of-concept, the design is somewhat angular. Now that I know that the design works, I can make a more finished version. I do not intend to put the Open Eight on the market. If someone else does so, can you send me a freebie?
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Version B is an improvement based on lessons learned from the Proof-of-concept Prototype. In particular, I made the following improvements:
I plan to add a springwire gate when I get the materials and the time to do so.
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