Directional pull line for felling

[Ekka]

Lets say you have a 100' tree and you have the pull line going through a fork up the top. You have 2 options of where to tie it ...

A/ Tie to the top fork (running bowline etc)

B/ Tie off on trunk at base

My question is, is it the same?

Before you answer please consider that all we are doing is trying to settle a debate on which is better and we want it qualified with engineering fact not opinion. Some trees such as Norfolk Pines etc are extremely difficult to isolate the top due to the volume of branches. The rope passing down the trunk makes it easier but do you get the same amount of force onto the tree because energy is transfered via the rope down the trunk, also the top fork may create a vector... I've searched and searched for some facts but cant find any

 

[NeTree]

The leverage applied is the same, since the effective attachment point is the same, pulling force being equal.

The only thing that changes is rope stretch; since you've used more rope, there's more stretch.

 

[tnttreeman]

I've always understood that with a big enough lever you could move the world. I am a firm believer in the higher the tie in the better for a pull, but when push comes to shove I try to at least to be higher than the midpoint in height on the tree. I don't have any proven engineering facts, but I know that when I've tried to pull at less than the midpoint I have encountered trouble when trying to overcome a back lean. I will try to find facts to prove this, and I imagine some search on fulcrums and levers would help.
Also, my attachment point may not be the same when the rope is higher in the tree. I think it is more difficult to pull at a steep angle than at a lesser angle. I agree there is more rope stretch and the pulling force on the ground is equal, but I think there is more leverage above the midpoint than below.

 

[treeman82]

Keep on searching, I know kenny did a thread on this a couple of years ago, it should still be around.

 

[P_woozel]

I dont think you get the same amount of leverage by tying to the base, as you do by having the line tied and isolated at the same point. You would be able to see this more readily on a leaner. :blob5:

 

[tnttreeman]

I posted my version of your question to the physics guys at www.madsci.org. If they answer it for me I will share the reply.

 

[John Ellison]

That will be interesting to see what their take on it is tntreeman, I dont believe that there will be much if any diff.

John

 

[Can-Do-It]

Good Question

Let me see if I understand the question.

Which has more pulling power,

1) Bull rope tied at the top of a tree or

2) Bull rope tied at base, rope then runs up the back of the tree(not front) and comes out at the same point as option 1).


At this point we have to make some assumptions:

- Equipment used will hold the pulling force
- Pulling force is the same

That being said,

Option 2 .... is better, IMO.

Option 2 distributes the force of the pull along the entire back side of the tree. The energy that the pull is applying is not isolated at one point but spread out along the entire length of the pulled item.

The question that has to asked and answered is .... which option gives you better control of the item being pulled.


Have a Blessed Day :angel:

 

[Can-Do-It]

I'd say the pull is the same, or very close.

I like the drawing Mike.

I always top tie because I'm looking to throw the tree in a certain direction, and get the center of gravity going in the direction of the pull. Like we all want and do.

It's like using wedges but its applied at the top. :Eye:

 

[bottlefed89]

From the drawings, I think since the leverage would be the same, it wouldn't matter, other than the above mentioned rope stretch. Only thing I can see being any different would be in a situation where tying directly to one side of the fork might cause any spin when pulling, where going through the crotch might give you a more direct pull. I think that would be a pretty rare situation, but not unfathomable.

 

[topnotchtree]

ok, heres my opinion. I think you will get more leverage tying directly to the top of the tree. Send a rope thru a crotch and tie near bottom of tree. When pulling on pull line, you will spread energy the entire length of the rope. Upwards from base of tree, thru crotch, then to whatever is pulling on rope. When tying to top of tree and pulling, energy is spread along rope again, but only in one direction, from tie point, to whatever is pulling the rope. I do want to add that the difference between the 2 methods will be not enough to worry about.

 

[belgian]

from my engineering point of view, tying directly to the top of the tree (option 2)is better :

1. some pulling force will be lost in vertical direction in solution 1(the rope will stretch a little)
2. you will have more control of direction (if the pulling force can be maintained during tree movement)

hope I don't make a fool of myself now, since I'm not a professional logger.

 

[KentuckySawyer]

I'd say the amount of pull is going to be the same with either method. If you have a 1,000lb come along pulling a tree over, its only going to exert 1,000lbs of pull. When you pull a tree (or log) over, you want the point of pull in the tree (point A) to be as high as possible (whether that be routed through a crotch and tied at the base, or simply tied to a high limb) and the point of pull on the ground (point B) to be as far away from point A as possible. This is because the angle between the ground and the rope is more acute. A smaller angle is closer to a straight pull, which means a more efficient transfer of energy ( in this case pulling power).

Generally I'll tie my tag line at the base for simplicity on small to medium trees. One less chance for the throwball to get stuck.

Another application for the redirect pull method would be if the tree is dead, hence structurally questionable. If you were pulling a tree over with this method and the crotch/limb you're pulling from breaks out, the rope is still attached to the tree, can still catch another crotch, and still bring the tree down. Or maybe stop it from landing on the power lines behind you. Another measure of safety would be to spiral the rope down the trunk, like a candy cane. This gives support to weak spots in the wood, etc.

As far as rope stretch. The stretching rope is absorbing the energy of the come-along (actually the person cranking on it) and then releasing that energy when the tree starts to come over. This lengthens the moment in time where you are affecting the fall of the tree (hopefully). The rope traveling down the back of the trunk isn't stretching as much because of friction against the trunk, so it isn't as effective at storing that energy. I'd say if you're flopping a big tree and the pull is critical, you're better off with all of your rope between points A and B, rather the losing 40-50 ft of it down the trunk.

 

[Gord]

It's hard to say that either case is better.

Here's Spydy's original thread:
http://www.arboristsite.com/showthread.php?t=4074

• The leverage will be the same if either the rope is tied to the crotch or is just running through it. The horizontal force is still applied at the same point.
• Although the tree will likely not need to be pulled as far before it becomes committed to the fall in the second scenario, due to the extra elasticity in the rope taking over as the necessary force decreases as the tree gets closer to plumb, this advantage is likely negated by the extra work required to tighten the rope to the necessary force.
• The other force that could be considered is the crotch-to-butt compression on the spar. In either case the rope must take this force so the only difference again is the length of rope.
• It's often easier to untie and pull out a rope that has been tied off to the base of the tree.

I usually tie off to the base if I can't easily isolate the line just where I want it, but if I'm already in the tree or can easily isolate the line just where I want it I tie it directly to the limb or stem.

 

[arboromega]

we agree to butt tie if the line cannot be isolated in the canopy?
if the line can be and it is just a matter of choice then i go with the canopy pull.
when the rope is butt tied your force on the line will be placed on the backside of the trunk and most likely be coming from behind the hinge by a distance equal to diameter from the back cut to the back portion of the hingewood. i would imagine this creates slightly more downward pressure on the hinge. in other words the pull force arrives from behind and directly above the hingewood.
if the line is in the canopy in front of the hinge you will achieve more of a forward and sloping force on the pull line helping the hinge work in a more natural fashion.
any thoughts?

 

[glens]

I'd weighed in extensively in the other thread linked-to above, so I'm not going to go into much detail here.

I will say, however, that if you merely drape the line and fasten back at the bottom, 1000# pull on the line will result in more line being pulled through the device to achieve that tension than if it were directly fastened at the top.

Also, you'll get the most leverage at the highest point you can achieve, but that might not be the best choice in the big picture.  You'll want to maintain adequate strength in the stem for the task at hand.  Both of those statements I feel are painfully obvious, of course, but I contend that neither route for the rope will provide an advantage over the other for marginal conditions.  Unless you consider the greater compressive forces of the draped method, which just might cause failure when the direct might not.

Glen

 

[NeTree]

Stretch is irrelevant to pulling force. 1000 pounds is 1000 pounds.

Glen, are you referring to compressive force as in say,- splitting the crotch out where the rope runs down?

 

[glens]

If the rope stretches 1" per 10' at 1000# and you've got half again as much rope between terminations you'll pull half again as much stretch before the load cell reads 1000#.  More rope pulled is more cranks on the hoist, right?

Yes, splitting the crotch is one possibility.  Another is that the stem, if not straight, will be induced to bow more so than it would when pulled solely from the top.

Glen

 

[NeTree]

Glen, to the first part:

You're still going to hit 1,000 pounds. You just have more stretch to take up to get there. 1000# of pull at the hoist will equal 1000# of pull at the crotch, no matter if it's tied directly or "fishing pole" (as Murphy calls it). Correct.

Sometimes this stretch can be useful (the strech alone will keep the tree moving as it nears center of balance), sometimes it's a PITA (like if you're using a comealong short on working length).


Second part: I agree/ I agree. Another good reason to (usually) get the rope high- less force needs to be applied to achieve the pull. In actual practice, each tree should be examined on a tree-by-tree basis for the suitability of one method/technique over the other, and how high the line should be placed to balance pull needed vs. structural inegrity.

 

[OutOnaLimb]

The only time I tie off to the top of the tree is when I have topped off everything and am pulling over a spar. Usually I run a line through the highest crotch and down the back side, and tie off using a running bowline about a foot above my face cut. Alot of times its hard to isolate a branch at the height that I like to have using a running boline. Not only that, but the higher your line is set and the further distance you pull from gives you more leverage.

Ken