I'm not surprised the knot failed. Have you stopped to calculate the forces involved? I calculated there is about 4000N of force on the rope and a knot can reduce a ropes strength buy up to 40% Correct me if im wrong on these figures!
i find it interesting that you guys used a bowline for a termination on that last bit. arborists are not allowed to tie in with a bowline becuase of possible sideloading the carabiners gate. maybe if it had been a tripple scaffold knot, it woulda held.
@joshuarugg Yeah - I think we were anticipating that the friction part would slide. Certainly some other type of termination would have been stronger.
I wish you could add more to the conclusion of this video. Maybe show exactly how the ropes were set up. Many different definitions of SRT vs DRT out there, and it isn't apparent exactly how the ropes were set up. I also wonder what the fall factors, like .8, actually means. Why the difference in the 2 ropes used between the two tests DRT vs SRT. Thanks
@thwackaddict Sure thing. The setup was a split tail double rope over a bare branch (or pulley block) with a blake's hitch as the friction knot. During some past tests we saw the blake's hitch slide under very high impact forces. We did this test to more closely resemble a real situation - where an inexperienced person climbs without tending the slack in the line. Fall factor = Distance of fall / length of rope being fallen on.
@CornellTreeClimbing Thanks for the reply. Was the split tail 5/16 or 3/8 ultratech? I wonder if the 3/8 ultratech tied in a 4 or 6 wrap prusik would have held the drop? This would have given it two strands instead of one strand to absorb the shock correct? Just curious as I am just getting into climbing. Thanks a bunch and love the videos! Was the SRT drop one single strand of rope, or was the blakes around two strands of rope hanging down like in the beginning of your ascending video?
@thwackaddict I'm fairly sure that the cord was 5/16. It was definitely around just one strand of the climbing rope. I can't say for sure what a prussik would hold with this cord, as it may have cut at the gate of the carabiner. In general terms two strands are certainly better than one, but even still, this impact is pretty high. Previous factor 1 tests with regular utility cord snapped a three wrap prussik...
I'm not surprised the knot failed. Have you stopped to calculate the forces involved? I calculated there is about 4000N of force on the rope and a knot can reduce a ropes strength buy up to 40% Correct me if im wrong on these figures!
krackanz 7 months ago
@krackanz Oh, sure - We're pretty good with the numbers. We just like to break stuff!
AizkoLaritza1 7 months ago
i find it interesting that you guys used a bowline for a termination on that last bit. arborists are not allowed to tie in with a bowline becuase of possible sideloading the carabiners gate. maybe if it had been a tripple scaffold knot, it woulda held.
joshuarugg 10 months ago
@joshuarugg Yeah - I think we were anticipating that the friction part would slide. Certainly some other type of termination would have been stronger.
CornellTreeClimbing 10 months ago
I wish you could add more to the conclusion of this video. Maybe show exactly how the ropes were set up. Many different definitions of SRT vs DRT out there, and it isn't apparent exactly how the ropes were set up. I also wonder what the fall factors, like .8, actually means. Why the difference in the 2 ropes used between the two tests DRT vs SRT. Thanks
thwackaddict 1 year ago
@thwackaddict Sure thing. The setup was a split tail double rope over a bare branch (or pulley block) with a blake's hitch as the friction knot. During some past tests we saw the blake's hitch slide under very high impact forces. We did this test to more closely resemble a real situation - where an inexperienced person climbs without tending the slack in the line. Fall factor = Distance of fall / length of rope being fallen on.
CornellTreeClimbing 1 year ago
@CornellTreeClimbing Thanks for the reply. Was the split tail 5/16 or 3/8 ultratech? I wonder if the 3/8 ultratech tied in a 4 or 6 wrap prusik would have held the drop? This would have given it two strands instead of one strand to absorb the shock correct? Just curious as I am just getting into climbing. Thanks a bunch and love the videos! Was the SRT drop one single strand of rope, or was the blakes around two strands of rope hanging down like in the beginning of your ascending video?
thwackaddict 1 year ago
@thwackaddict I'm fairly sure that the cord was 5/16. It was definitely around just one strand of the climbing rope. I can't say for sure what a prussik would hold with this cord, as it may have cut at the gate of the carabiner. In general terms two strands are certainly better than one, but even still, this impact is pretty high. Previous factor 1 tests with regular utility cord snapped a three wrap prussik...
CornellTreeClimbing 1 year ago
nice work!
TheExtremetree 1 year ago
a little common sense goes a long way
murphy4trees 1 year ago