running bowline vs base tie

[CutHighnLetFly]

ive only used a running bowline for anchoring a pull line when felling a tree and i want to hear why some prefer sending a line up and then tying at the base of a tree instead.

 

[bonner1040]

It is easier to get the line out for one, the feller can untie it after it falls and the puller can pull it right out. It usually doesnt get stuck. You dont have to isolate it.

 

[brendonv]

You don't have to isolate a single limb. That's the only reason why I'll base tie vs. sending a bowline up. Depends on the tree. Sometimes you have to isolate if the rope isn't long enough.

 

[TreeClimberMike]

I find basal tie to be faster than isolating for a bowline, the faller can untie, and you can get away with a sketchier TIP because of the fishing pole effect from the line running down the trunk.

 

[ginkobalboa]

base tie is nice too because every branch below backs up the one you are over, if for some reason it fails.

 

[Outdoorcrazy]

Can someone explain how you can even get a running bowline in a conifer?

 

[bonner1040]

With a bucket truck or spurs.

 

[macswan]

Does anyone feel that you lose any pulling power with the pull line anchored at the base?

 

[oceans]

[ QUOTE ]
Does anyone feel that you lose any pulling power with the pull line anchored at the base?

[/ QUOTE ]

There's more flex in the system due to the dynamics of the crown, and more rope in the system which allows more stretch. You may need to pre-load with a good sweat or pulling device, but I believe the leverage would be equal whether base tied or choked.

When base tied, you just need to be real sure that you're in a good, upright crotch (more critical than choked) if you need the pulling to compensate for considerable leans. As the tree comes over and the angle of the branch changes, it could be possible for the rope to slip off.

 

[SingleJack]

FWIW: Just a thought on the subject of 'isolating' for a Bowline. It's NOT necessary to isolate to cinch for a pull-line or SRT. In fact, sometimes, it's good to cinch around several branches ... especially in thin, crowded tops. Check out the bottom right photo on page 72 of Jerry's Fundamentals.

 

[Outdoorcrazy]

[ QUOTE ]
With a bucket truck or spurs.

[/ QUOTE ]

Thank you. That's the only 2 ways I know too.

 

[whiz]

If I'm not mistaken you actually gain mechanical advantage when base tying. Not quite 2:1 but there's still MA.

 

[Erlend]

[ QUOTE ]
If I'm not mistaken you actually gain mechanical advantage when base tying. Not quite 2:1 but there's still MA.

[/ QUOTE ]

Sorry, but you are mistaken. The fundemental laws of physichs declare the force of the pull will be somewhere between the line where people are pulling and the stem of the tree. So yes, you do loose some power. Compensate by moving furhter away from the tree (longer rope)

 

[whiz]

I guess I don't understand. If I'm going to climb the tree srt and I choose to base tie and my line is possitioned at approximately 180 degrees is there not twice my body weight in force at my t.i.p? If I'm going to pull the tree over and I leave my base tie and move away from the tree well past my felling zone, is there still some MA or am I back to 1:1 just as if I sent a running bowline up?

 

[Erlend]

The force at the branch where the rope crosses will be doubled (-quite a bit for friction and stretch). The point is that since you say have 30 KN pulling on the rope, and 30 KN pulling straight down the stem of the tree, the direction of the force working to pull the tree over, will be somewhere between the two (the red arrow on the attachment), thus making it less efficent

 

[roadmaster]

anybody ever tie a stationary knot in the pull line to capture the whole tree in aloop of the rope as opposed to a "running" bowline? Perhaps on a large hemlock or Norweigan spruce that has long drooping limbs making it impossible to get real close to the stalk? This way if a few branches break out the rope is still around the tree as high as originally installed.Key is putting all the force necessary to pull the tree over before starting chainsaw cut.

 

[whiz]

Yes sir, less efficient but is there more MA with a base tie off then a running bowline? You're probably thinking "you idiot, Kristian. It's entry level physics!" You're very patient.

 

[ginkobalboa]

you idiot, Kristian. It's entry level physics! For some reason it makes sense to me that there is no MA with a base tie. Even though the TIP is feeling 60kn, you are still only applying 30kn with either method. Is this correct? This is how I understand it.

You're not an idiot Kristian.

 

[Erlend]

Sorry, but my second post was wrong. (something about it was bugging me, so I've been mentaly working on it, and now the soulution suddenly came). There is a MA with a base tie of, but its not 2 to 1, since you're pulling with a angle (+ friction of course.) If you were to stand right by the stem and pull, the rope would make an angle of 0 degrees, and you would have a 2 to 1 MA (But it wouldn't help you pull the tree over.)

When the rope forms an angle of 80 degrees, you pull with it a force of 70 kilos, the force at the crothc will be 100 kilos. But the force will be working on a 40 degrees angle downwards, thus making the leverage much less.

Understandable?

I've added a new uppdated drawing, might help

 

[SRTsteve860]

easiest way to think about it is through static analysis (im studying civil/structural engineering at UCONN);

Think of the tree as a lever arm, like a wrench or breaker bar , with a string attached to the end of that bar (handle end) when you pull on the string, (as you will to pull over a tree) you are imparting torque in the system (force x distance). If you were to impart too much load in the system, and the bolt you are trying to free doesn't give, you will bend or break your bar. same principal in a tree, if it weren't for a notch/back cut and hinge, you would either pull the tree out roots and all, or snap the spar at the weakest point, (im sure plenty of you can relate to seeing this happen). the idea with torque, is that it only relates to being perpendicular to a system, thats why the more horizontal your pull line is, the easier you can pull the tree over. anything in line (parallel) with the line of action, will impart NO mechanical effect on the system, (neglecting shear forces and moments).

working with this idea that parallel force will add no advantage, and only perpendicular will impart force, we can look at a base tie and tied at the highest secure point:

both will have the line exiting at the top of the tree, and lets use a perfectly perpendicular line angle (you had your greenhorn go on top of a hill and pull from there) so you have the most effecient system to pull, and since a base tie, has the tension in a leg of line parallel to the system it will add or cost nothing to the system.

easiest way to see this:

take a combination wrench. tie a string to the closed end, and pull the string to release a nut. (even use a scale to be precise) next, loop the string around a "tooth" on the open end, feed it back through the closed end, and repeat. this will result in the same force imparted, all because torque comes from a perpendicular force, and anything parallel to the Line Of Action will provide nothing.


might be a little confusing, but this is out is an applied mechanics text