what rope and how do you all tension the line?

By "golden gate" I mean that if possible have the stationary anchor behind the tree you are rigging and lower than the rigging point. This way the tree is loaded in compression as opposed to being pulled on. So the tree becomes like the columns on a suspension ridge and the cable is your speed line. I am looking for a pic, but it eludes me.

Not always possible, but a good ideal to strive for.

Tony
 
Tony said:
By "golden gate" I mean that if possible have the stationary anchor behind the tree you are rigging and lower than the rigging point. This way the tree is loaded in compression as opposed to being pulled on. So the tree becomes like the columns on a suspension ridge and the cable is your speed line. I am looking for a pic, but it eludes me.

Not always possible, but a good ideal to strive for.

Tony
Click to expand...
This is the best case scenario. But you do need a long line. That's why all my rigging lines are 200'.
 
Yes, long lines are necessary. In my mind having a long rigging line is a requirement for a production arborist. Just as you would expect any tradesman to have the proper tools for his or her work.

Of course multiple lines could be used, but it adds complication somewhat needlessly.

Tony
 
So using the tree as a 'column' when you run 1 rope up and back down do you tie off at the top or run it through a block or some other re-direct?
 
Yes, but tied off at the base, or low on another tree. It decreases the bending moment that happens when tied off near the top of the tree being worked.
 
That makes some good sense. Unfortunately lately I've only been using ziplines for sections leaning over houses or past fence lines to get them into our clients yard so that's been a non option. But I'll be looking to try it.
What are the differences between this column system compared to a guy line back to an anchor tree and another line for the zip?
Less or more even forces or no difference?
 
Pick a place to anchor your rope.

Pick a spar or rigging point to anchor your block for the top of the zip line.

By using the spar as a redirect you're transfering some of the load of the zipline into compressive forces on the vertical trunk.

If you tie off at the top you will bend the top over which will lead to much higher loads.

A really fundamental thing that anyone building a zipline needs to understand is load amplification.

If you look at the sling load chart that is linked above and think about how those loads in the chart will be the same as in a zipline you'll see how important a strong anchor or redirect is to your system.

Turn the sling load chart upside down and see that it is a zipline. The load suspended in the middle of the 'sling' can amplify the load with attention getting multipliers.

Now, if you drop loads onto the zipline you're really likely to blow the whole works up and injure/kill someone. If you choose to use the zipline to move things laterally drop the loads onto standard rigging then transfer the loads to the zipline for horizontal movement.

If you use a winched rigging tool to tension the line you'll have a much better feel for what the load is like on the zipline.

Start to learn about ziplines by using it to move small branches and firewood around. As you work towards bigger pieces you'll have a better understanding of the loads and deflections of your system.
 
Hmmm...so Tom, you got me thinking. Say I want to pull a tree down. But instead of just pulling on the rope, i take the line and tie it 6' up the base of another tree (in line with the direction of fall). If I were to hang on that line, would I get more pulling power than just a straight pull? Hope that makes sense. Thanks...
 
good question I was wondering the same......So more than a few times this has happened to the crew : pulling over a backleaner with not enough mechanical advantage or man power. (oops) so we just grab another short line and throw one end of the rope over the pull line and hang on it just like Tree logic was saying....Of course since we already had a very tight line on the tree it didnt take much to pull it over. BUT it always seemed to feel like I was getting some Crazy leverage or something when doing that ;)
 
I was in a discussion today that you should not tip logs into a zip line and let them fly.
The idea was with any signifigant load of wood you should always use a tag line to ease the force. But if the ground (landing zone) is ok to get roughed up does it matter?
I understand the haul line to a porti takes the speed out of the equation as well helps hold some weight.
My question is even if you stop the load with the tag line how much weight would it actually take off the zip line?
Would the whole load not be dangling from the zip line so actually your tree top should be holding some where between 150- 200% of the weight depending on angles of course.
The only way to minimize weight or strain I know of is to sling the tip and the butt of a piece. The farther apart the less severe the bend, heat, load disipation, etc.

Does that make sense to anybody else?
 
Pulling in midline does in erase the load at the ends. Slam dunking loads onto a tensioned zip line does too

I remember when I realized the value in understanding the along loading graphic and started applying it in any other places

Look at the attachment point on your bridge. Same forces.

A good way to see how this works is to have a heavy strong person belay a line around their waist. Then have a couple of much lighter people hold the other ends of the line. Pay out about ten feet on each side. Start with he pullers opposite each other. Now have them pull and start to walk towards each other. Wait to see when the 'load, is pulled off their feet. Next have the smaller people off set the load to simulate the load sliding down the zip line
 
KevinS, I wouldn't call that a tagline. With heavy weights being unloaded into a speedline, they need to be lowered into it with a lowering line. A tagline is for getting a spar being felled to tip one way or another, or for pulling a lowered piece away from an obstruction. I'm sure you knew that, and just mis-stated it there...but for the sake of someone getting confused it seemed worth clearing up.
 
Very true tree logic that was my slip up thanks for catching it.

But would a zipline + lowering line at the same point make up to a 200% load at the tie in because each line is holding the load on itself?
 
IDK, good question. Probably would depend on how the lowering line ran up the tree to the block. If pulling vertically up the trunk from a Porta Wrap to the block I'd expect the compression would help dissipate the forces. However, if running from a Porta Wrap up to a block that was diagonally out in the crown somewhere, it might actually increase the forces on the anchor point, making the potential for a spar-snapping adventure even greater, I would guess.
Main point I take from this though is... that the "amplification of load" with a speedline makes bouncing heavy pieces into it dangerous. So, with heavier pieces it would always be safer and more controlled to lower them on a block to the speedline, then clip over to the speedline, disconnect the lowering line and let it roll.
 
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