Prussik knot testing

In July a few Swiftwater Rescue instructors got together to find out which method of tying a Standard 3 wrap prussik would hold the most load.

The discussion was on whether placing the knot of the prussik loop on top of the 3 wraps (right hand photo above) was better or worse than the traditional 3 wrap where it is placed at the side out of the knot (left hand photo above).

Main line used in test: Edelrid soft static 10.5mm - 10 years old - Good condition.

Prussik cord used in test: Edelrid 7mm cord - 5 years old - New condition.

Test one: Traditional 3 wrap prussik (left hand photo)

3cm Slippage occurred at 822kg loading

Prussik cord snapped at 1115kg loading

Test two: Innsbruck 3 wrap prussik (right hand photo)

2cm Slippage occurred at 402kg loading

3cm Slippage occurred at 702kg loading

Prussik cord stripped main line of sheath at 1055kg loading

The traditional 3 - wrap wins on both overall strength and first slippage. Don't forget that strength of prussik knots is dependant on the type and diameter of cordage used as well as the knots used to tie them.