Front	Rear

Technical Details

I made this Wood Crab in 2021, basing it on a photo of a Russian version that Artyom Babin (Артём Бабин) posted on the Facebook Vertical Museum page.

This Wood Crab is 140 mm. tall, 127 mm. wide, 17 mm. thick, and weighs 146 g.

Артём told me that the original was made from 13-layer plywood, corresponding to 18 mm., and so I made mine out of nominal 3/4-inch (19 mm. Baltic Birch plywood that measured 17.3 mm. thick - close enough. I scaled dimensions from the photograph, assuming that the rope channels were 1/2 inch (12.7 mm) and rounding the dimensions to convenient numbers in the archaic unit of length used here.

I used a router and files to cut the grooves in the central portion of the Wood Crab. Артём thinks that the originals were worn, but I looking at the photo, I think that the grooves were initially hand-cut and then enlarged by wear. No matter.

As a final touch, I applied a Danish Oil finish so that it might catch fire on rappel.

Comments

While I understand the motivation for making homemade gear to same money, plywood is not a good material for descenders. As long as the rope runs parallel to a face, the wear will not be too bad, but running the rope across an edge is just asking for splintering and delamination.

A standard oval carabiner barely fits, and many carabiners are too small. This Wood Crab works best with a larger Halbmastwurfsicherung (HMS) carabiner.

Used as a free-running descender, this idea seems to be suicidal, since disintegration of the wood will leave one plummeting downward without any significant braking, a non-habit-forming event.

A safer method is to use the old-fashioned over-shoulder braking used for the once-standard carabiner rappel. While this would not provide much friction, at least it protects the user if some event (e.g., a sudden attack from a swarm of voracious termites) reduces the structural integrity of the Wood Crab to the failure point.

Don't let your wood crab rot. That would seriously reduce its strength.

Warning: DO NOT EVEN THINK ABOUT USING ONE OF THESE.