Pete K
Well-known member
@Cave_Troll playlist sorted, thanks for spotting that.
As mike says above, the rig has to be set that way. The apparent missalignment of the drop weight as the tests progress with each knot is not a fault of the rig, it is that the bowline variants all acted like a slip knot for the loop formed by the active end and essentially 'unequalised' themselves.
I'm nowhere near as experienced to answer some of these questions as Bob so hopefully he will pop along soon.
@ianball11
The Peak Force is the ammount of force transmitted to the other components in the system (anchors/caver etc...). This figure is relative in these tests, so a lower peak force shown is a greater amount of shock absorbtion through slip etc of the knot. The higher the peak force, the less slip and absorbtion in the knot.
10kN is equivilant to 1000Kg of force. 0.5kN is equivilant to 50Kg of force.
Drops survived give an indicator of the knot's (and rope for that matter) ability to repeatedly absorb shock. The failiure comes when the rope can give no more elasticity to absorb or heat has damaged it enought to make it weak and break.
Essentially a knot with a higher number of drops survived would be a good choice where a shock load risk could occur, i.e. cave bolt failing etc...
@jopo
Clip your cowstail carabiner into a single strand of each loop, thus connecting you to both loops, not entirely around one. Very easy to do on Bowlines, harder on Fig8's.
@stu
I see your point about the Fig8 loop / tied on the bight. I'll pass that on to Bob who wrote the report.
Can I just remind everyone that this was one set of testing only and cannot statictically prove a trend. Yes the DBoB survived mentionably more drops than the others in this test but even Bob thinks we'd need dozens and dozens of tests to be able to make a solid statement.
The BCA have made comment on the BotB. The French have chosen one route. We have provided film and testing. Cavers will choose to continue to use it or not, it is up to them. I hope that the research we have managed to do recently will just allow everyone to make an informed choice on knot selection.
If in doubt speak to an experienced club rigger or a CIC.
As mike says above, the rig has to be set that way. The apparent missalignment of the drop weight as the tests progress with each knot is not a fault of the rig, it is that the bowline variants all acted like a slip knot for the loop formed by the active end and essentially 'unequalised' themselves.
I'm nowhere near as experienced to answer some of these questions as Bob so hopefully he will pop along soon.
@ianball11
The Peak Force is the ammount of force transmitted to the other components in the system (anchors/caver etc...). This figure is relative in these tests, so a lower peak force shown is a greater amount of shock absorbtion through slip etc of the knot. The higher the peak force, the less slip and absorbtion in the knot.
10kN is equivilant to 1000Kg of force. 0.5kN is equivilant to 50Kg of force.
Drops survived give an indicator of the knot's (and rope for that matter) ability to repeatedly absorb shock. The failiure comes when the rope can give no more elasticity to absorb or heat has damaged it enought to make it weak and break.
Essentially a knot with a higher number of drops survived would be a good choice where a shock load risk could occur, i.e. cave bolt failing etc...
@jopo
Clip your cowstail carabiner into a single strand of each loop, thus connecting you to both loops, not entirely around one. Very easy to do on Bowlines, harder on Fig8's.
@stu
I see your point about the Fig8 loop / tied on the bight. I'll pass that on to Bob who wrote the report.
Can I just remind everyone that this was one set of testing only and cannot statictically prove a trend. Yes the DBoB survived mentionably more drops than the others in this test but even Bob thinks we'd need dozens and dozens of tests to be able to make a solid statement.
The BCA have made comment on the BotB. The French have chosen one route. We have provided film and testing. Cavers will choose to continue to use it or not, it is up to them. I hope that the research we have managed to do recently will just allow everyone to make an informed choice on knot selection.
If in doubt speak to an experienced club rigger or a CIC.