You are NOT supposed to tie a knot in a Mamba sling according to Texora (the manufacturer). The Mamba sling from Texora has an aramid core (cut and heat resistant), a polyester sheath, and is rated to 49 kN MBS. They specify how you CAN use it including a straight pull, basket hitch and a girth hitch (NO knots allowed), but what happens if you use it in other ways like a BFK anchor or the adjustable sling hitch (the "Belgian knot")? We tested all these on the Mamba, plus 8mm dyneema and 18mm nylon slings for comparison. Thanks to Valor Rescue of Canada for buying all the new slings for this test, it was an expensive one!
RESULTS: Basket hitch was double strength compared to straight pull (typical result). The girth hitch surprisingly was almost full strength in all 3 materials wrapped around a 0.5" diameter pin. In an equalized 2-point BFK anchor with the Mamba (NOT approved use), it was stronger than the girth hitch by over 20% lol. Perhaps the rule comes from the fact aramid fibers weaken substantially through repeated bending (like tying knots). The adjustable hitch was MUCH worse for the Mamba sling, slipping and tearing before failing completely at only 50% strength. Might be super good enough if you basket hitch it first and/or keep the loads low, but don't try that with dyneema as it slipped at 6kN.
SLINGS TESTED
Texora Mamba https://hownot2.com/products/texora-black-mamba-sling
Ocun 8mm Dyneema https://hownot2.com/products/8mm-dyneema-o-sling
Black Diamond 18mm Nylon https://hownot2.com/products/18mm-nylon-runner-black-diamond
Valor Rescue https://www.valorrescue.ca/
Texora's Mamba Impact Test
https://youtu.be/qMfxG8GV9oM
Climbing Sling Myth Episode
https://youtu.be/AsketX8wO9I
Figure 8's Tested
https://youtu.be/nUCR_W-xCqY
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00:00 Not supposed to Knot
01:54 Straight Pulls
03:04 Basket Hitch
06:09 Girth Hitch
09:26 BFK
12:59 Adjustable Sling
17:27 Conclusions!