settind a block using a throwline?
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canopyboy
ArboristSite Operative
I've done it two ways. If you want to rig from a crotch, just use the throwline to pull a bull rope up over the crotch with the block tied or clipped to the other end.
If you want to tie to a spar and there is a small branch to keep things from sliding down the tree (and catch your throwline), pull your bull rope up over the limb and back around the trunk. I then tied in my block with an alpine butterfly knot about half the circumference from the end of the rope (plus length to tie another knot in the end.) With the end I put a bowline around the down rope. Before sliding it up the tree, I also attached my throwline to the bowline in order to retrieve the line when done. Once cinched up to the tree, I doubled the downrope back and tied it off tightly to a nearby tree.
If there is no crotch and no limb, someone else is going to have to chime in with ideas.
As a disclaimer, tree work is a hobby for me...not what pays the bills.
If you want to tie to a spar and there is a small branch to keep things from sliding down the tree (and catch your throwline), pull your bull rope up over the limb and back around the trunk. I then tied in my block with an alpine butterfly knot about half the circumference from the end of the rope (plus length to tie another knot in the end.) With the end I put a bowline around the down rope. Before sliding it up the tree, I also attached my throwline to the bowline in order to retrieve the line when done. Once cinched up to the tree, I doubled the downrope back and tied it off tightly to a nearby tree.
If there is no crotch and no limb, someone else is going to have to chime in with ideas.
As a disclaimer, tree work is a hobby for me...not what pays the bills.
Not that complicated really. Throw line over/through crotch. Tie bull rope to it and pull in. Tie block to bull rope and pull to desired height and then tie off to same or near by tree.
COUPLE THINGS TO REMEMBER
If its windy, tying to same tree may keep the rope from rubbing the crotch as much as the wind sways the tree back and forth.
If you hang 500 pounds on that block, the resulting downward force on tie off rope is also 500 pounds. You now have 1,000 pounds of downward force on that block. 1,000 pounds downward force on the block hanging on bull rope, plus 1,000 pounds on that tie off rope to hold block in the air, and you end up with 2,000 POUNDS OF DOWNWARD FORCE ON THAT CROTCH!!!!! Increase for shock loading????
Pick a strong crotch yes?
COUPLE THINGS TO REMEMBER
If its windy, tying to same tree may keep the rope from rubbing the crotch as much as the wind sways the tree back and forth.
If you hang 500 pounds on that block, the resulting downward force on tie off rope is also 500 pounds. You now have 1,000 pounds of downward force on that block. 1,000 pounds downward force on the block hanging on bull rope, plus 1,000 pounds on that tie off rope to hold block in the air, and you end up with 2,000 POUNDS OF DOWNWARD FORCE ON THAT CROTCH!!!!! Increase for shock loading????
Pick a strong crotch yes?
That sounds pretty simple and kind of along the line i was thinking, for some strange reason I thought I had to attach the block and sling to a bull rope and pull it over the crotch...duh!!! thanks for the knowledge, may the force be with you luke!
md_tree_dood
ArboristSite Operative
Just remember to pull the block out with your rigging line, else you'll be climbing up to get the thing when you're done.
Placing a line over a branch to hold a pulley , that then holds a support line, has a 4x potential loading on the supporting branch. That loading would statically by less by frictions and non-pairallell lines to the bend in each line (lines to pulley and to branch). Dynamically it is less these frictions and open angles, and also less the elasticities/deformations of the lines and support. For, if these give up distance, they don't resist to give equal and opposite power, giving less loading..
A false crotch, would be a choked sling, holding a pulley, and only have 2xLoading potential. This can even be done remotely, by inverting a sling into a choked position with another line. Even though this places another leg of line to ground like the 4xLoading potential, this leg isn't loaded in use, only in installation and removal. MTL:Remote False Crotch shows this with a ring and line, that could just as easily be a sling and line. But, more commonly in our work is a Bowline on the end of a line, so that the pulley and rig line is krab'd to the Bowline as support. If doing this, it is best to have a DBY type Bowline for strength and security. But, further more we should realize that a Bowline is usually constructed to pull inline with the length of line to it; but in this case THE PULL IS ACROSS RATHER THAN INLINE to the length of line. Therefore, it is recommended, that we too, the turn the LOCK OF THE BOWLINE sideways, to suit to be as empowered and as positive to task. So, therefore we should make a Jacked Bowline that locks better from pulls across the Bowline ring, rather than down it's length. When working mechanics in remote positions,we should all ways and always make sure, this uninspectable position is even more super secure etc. (by positive mechanics)than usually.
A false crotch, would be a choked sling, holding a pulley, and only have 2xLoading potential. This can even be done remotely, by inverting a sling into a choked position with another line. Even though this places another leg of line to ground like the 4xLoading potential, this leg isn't loaded in use, only in installation and removal. MTL:Remote False Crotch shows this with a ring and line, that could just as easily be a sling and line. But, more commonly in our work is a Bowline on the end of a line, so that the pulley and rig line is krab'd to the Bowline as support. If doing this, it is best to have a DBY type Bowline for strength and security. But, further more we should realize that a Bowline is usually constructed to pull inline with the length of line to it; but in this case THE PULL IS ACROSS RATHER THAN INLINE to the length of line. Therefore, it is recommended, that we too, the turn the LOCK OF THE BOWLINE sideways, to suit to be as empowered and as positive to task. So, therefore we should make a Jacked Bowline that locks better from pulls across the Bowline ring, rather than down it's length. When working mechanics in remote positions,we should all ways and always make sure, this uninspectable position is even more super secure etc. (by positive mechanics)than usually.
