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Stab Descender
(#1150)

Front View Rear View Side View
Front View Rear View Side View
 
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

 

Technical Details

I acquired my Stab Descender on eBay from Steven Messer in 2008.

The Stab Descender is 234 mm. tall, 91 mm. wide, and 69 mm. thick. Mine weighs 960 g.

The Stab Descender consists a aluminum back plate a stamped steel cover assembly, a handle assembly, and numerous minor parts. The back plate is a 230 mm. tall, 77 mm. wide, irregularly shaped piece of 5.2 mm. thick aluminum with a 14.3 mm attachment eye near the bottom. There are four fixed bollards attached to the inside of the frame with 5/16" (7.9 mm., top two bollards) or 1/4" (6.4 mm., third and fourth bollards) socket head cap screws passing through holes in the plate. The top bollard is 17.7 mm. in diameter and 19 mm. long. The exposed end is counterbored 12.7 mm. i.d. to a depth of 6.45 mm., exposing the end of the cap screw. The second and third bollards have a 16.7 mm. diameter, 19 mm. long cylindrical section topped by a mushroom head. The fourth bollard is similar but only 10.8 mm. in diameter. A fifth bollard at the base is the same length as the others and 13.9 mm. in diameter. The normal spacing between the bollards is, from top to bottom 58 mm., 50 mm., 50 mm., and 31.5 mm. There are two holes that allow alternate positions for the fourth bollard, 17 mm. higher and lower than the standard position.

The cover assembly is a 217 mm. long, 24.3 mm. internal width square channel stamped from 3 mm. steel. It pivots on a 1/4" (6.4 mm.) socket head cap screw attached to the fifth bollard. five notches on the side provide clearance for the mushroom pins on the second through fourth bollards, with the remaining two available for the alternate locations for bollard three. A small bracket riveted to the distal end of the cover supports a pin that holds a red knurled knob in place. The knob has a 5/16-18 UNC internal thread on the inside end. When the cover is closed, this engages the cap screw supporting the top bollard, holding the cover closed.

The lever assembly rides on a bushing bolted to the back plate with a 5/16-18 UNC socket head cap screw. The lever assembly consists of an eccentrically mounted cylindrical cam mounted between a handle piece and a guide piece. The cam is circular with a flat face. Three countersunk socket head screws hold the cam in place. The handle and guide are made from 5 mm. aluminum. The end of the handle is 112 mm. from the pivot point. There is a small plastic button fastened to the end of the handle with another countersunk socket head screw.

The final piece is a bollard mounted on the outside of the back plate, opposite the fifth internal bollard. It is 19 mm. in diameter near the back plate, but enlarges to 14 mm. 29 mm. out, and remains this diameter for the final 3 mm.

The rear of the back plate is marked with "STAB DESCENDER," "(PATT. PENDING)," and "STD. No." in white, followed by the stamped characters "00068C."

Comments

Steve listed this as a "Special Operations STAB descender" and described it as an "[e]xperimental self-braking descender used by SEAL Team in early 90’s. Releases when handle is squeezed and rope is properly routed."

The first thing that I noticed about the Stab is that it is hard to open for rigging. The problem is that the bracket holding the red knurled knob is weak and easily bent. When this happens, the red knob cannot clear the counterbore in the upper bollard, and the device will not open. Once I fixed the bracket, the Stab behaved better until the next time I bumped the bracket - and on most rappels, this is easy to do.

The rope is rigged by passing it to the right of the top bollard, around the cam, to the right of the second bollard, and above the third. For extra friction, continue the "S" bends around the third and fourth bollards. To descend, squeeze the handle, and release it to stop. This has the obvious disadvantage of requiring the rappeller to let go in an emergency. Experience shows that this is not natural.

I find the Stab to be too heavy and complex for my taste, and would prefer to use something simpler on my clandes… never mind, you didn't read that.