Oh noes! You just girth hitched a cord loop to the bottom of your ascender?
[Takeaway: the girth hitch on the bottom of an analog "broke" at about 49% of full loop strength, which scales to well over 3000 lbs in my actual ascender. The break was actually in the double fisherman's knot, NOT in the girth hitch]

A terrible confession: I have used my CAMP SOLO 2 ascenders with a loop of 6mm tech cord (3800 lbs bs) simply girth-hitched through the bottom carabiner hole. The hole is 16mm diameter, and is through 4mm aluminum; the hole has been polished to have rounded edges. That 4mm puts a severe bending radius on the cord. Therefore, strength reduction is expected; but how much? Some sources suggest more than 50% reduction when the radius ratio (rope to bend) is less than 1.

 

I didn’t want to place my ascenders in harm’s way, so I made a quick analog from sheet metal, for a pull test. Since I planned to use 5 mm cord (vs. 6mm) in the test, I made the holes 13 mm in diameter (a ½” drill bit, with some rounding out), in 3.2mm (1/8”) sheet aluminum.; the pictures below show the actual ascender and the analog.

solo2
 analog


 

 

I put a steel carabiner through one hole in the sheet metal, and tied figure-8-on-bights to each end of a 2m length of 10.2 mm dynamic gym rope. One loop of the 10.2mm went over the carabiner, and the other on the tow hook of my Jeep. I tied a loop in 5 mm Maxim polyester ( 1124 lbs bs). I joined the ends of the 5mm Maxim cord with a double fisherman, and girth-hitched the 5mm cord through the second hole. The other end of the cord was attached to a linescale 3 load cell, which was then attached to a rigid steel post in the ground.

 

Then I drove the jeep as slowly as I could, and snapped the Maxim loop. The force was 1096  lbs at breaking, and the break was in the double fishermans knot used to tie the cord in a loop, NOT at the girth hitch. The strength of the loop should be at most 2x1124, where 1124 is the bs reported by Maxim for a single strand, so we got about 49% of the loop breaking strength. Scaled to the 3800 lb bs (single strand) of the cord I actually used on my ascenders, that would be 3705 lbs projected to break the girth hitch on the real ascender. That is a ridiculous amount of force to put on one ascender, and would likely desheath the main rope long before the cord broke. From experience, the reported single-strand strength of the Maxim may be 20% low, but still get at least 3000 lbs projected.