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Rigging Study
- Thread starter treelooker
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Blah blah blah blah blah blah blah
Old Monkey
Treehouser
- Joined
- Mar 9, 2005
- Messages
- 8,764
Don't make me come out there and...
Interesting study. It shows how difficult it is to put mathematical formulations on a biological.
Not discussed on the half hitch/marl backup of the primary knot, strength loss issue was one of the primary reasons for using that setup to begin with.
When lowering a limb, you are often able to use a primary knot by itself tied within a crotch or behind a stub. On a heavy, slippery log, such as eucalyptus, especially when lowering off the stem itself, no matter how much slack is taken up on the line, when the log starts to tip over the rigging goes slack. At that point, the running bowline eye becomes loose on the log. The log will then, very often, slip right through without even slowing down. The marl or half hitch were used to prevent this loosening of the eye on the primary knot, which they do very well.
I also wished they had done some off-angle oscillation studies. It would have been nice to add a few more pages to this study.
We found in the interest of reducing the yo-yo effect in the slack/tension combination and to avoid bashing your lowering line that sending the butt-hitched log off a few degrees to the side would accomplish this. The resulting vibrations felt odd but were manageable. Just would have liked to have known what types of stress that scenario produces.
Dave
Not discussed on the half hitch/marl backup of the primary knot, strength loss issue was one of the primary reasons for using that setup to begin with.
When lowering a limb, you are often able to use a primary knot by itself tied within a crotch or behind a stub. On a heavy, slippery log, such as eucalyptus, especially when lowering off the stem itself, no matter how much slack is taken up on the line, when the log starts to tip over the rigging goes slack. At that point, the running bowline eye becomes loose on the log. The log will then, very often, slip right through without even slowing down. The marl or half hitch were used to prevent this loosening of the eye on the primary knot, which they do very well.
I also wished they had done some off-angle oscillation studies. It would have been nice to add a few more pages to this study.
We found in the interest of reducing the yo-yo effect in the slack/tension combination and to avoid bashing your lowering line that sending the butt-hitched log off a few degrees to the side would accomplish this. The resulting vibrations felt odd but were manageable. Just would have liked to have known what types of stress that scenario produces.Dave
T
TheTreeSpyder
Guest
The running bowline gets pulled at an angle and the marl or half hitch gets pulled inline (correcting the angled pull on running bowline by full loading, and giving buffered pull to it instead) i believe securtiy rather than strength is the issue hear(arguing in favour of marl/hitch. If there is a branching that can dawg Bowline, can go without Half/Marl, have more strength, and more elastic line in formulae, with less Turns that might turn that factor against us.
i think block should be as close to CG as possible, hitchings should be b4 CG. First hitching/catch farther from block gives potential for more elastic buffering(because more line b4 frictions); but also can allow slack to give impacting(unless 'tuned' out).
Best is not shock loading, snubbing when it does shockload, including pulling over to travel farther on hinge b4 release to linewith line pull or bar/wedge push), and even retightening out slack on support line during hinging over. And that hinging being slower/ mopre controlled (as long as the slow leveraged length doesn't then cause problems by going too slow givng more problems than more impacting.
i think block should be as close to CG as possible, hitchings should be b4 CG. First hitching/catch farther from block gives potential for more elastic buffering(because more line b4 frictions); but also can allow slack to give impacting(unless 'tuned' out).
Best is not shock loading, snubbing when it does shockload, including pulling over to travel farther on hinge b4 release to linewith line pull or bar/wedge push), and even retightening out slack on support line during hinging over. And that hinging being slower/ mopre controlled (as long as the slow leveraged length doesn't then cause problems by going too slow givng more problems than more impacting.
