Speed line and stem pieces question.

[Dilz]

more looking for confirmation on this question - but -  it relates mostly to when having to drop stem pieces on a speedline when the line is set on the stem (i.e just below the chog about to be pushed) 

 

Instead of tieing off the speed line rope using a running bowline or timber hitch at the top - would a base tie and running the rope through a ring on a whoopie sling or similar at the top allow for greater energy absorption due to the increase of rope in the system?   

 

To me it makes sense and tomorrow i will try it out .  I also think the forces will be better distributed rather than everything focused at the top.   

[Steve Bullman]

Good question.  I seem to recall someone saying base tying actually creates more of a load at the top.  I've never quite got my head around that.

[Mick Dempsey]

It might be due to a 2:1 multiplication of force, like a carters hitch.

[Steve Bullman]

Maybe, but at the same time won't a base tie take a bit of the shock out of the system?

[Dilz]

Yeah a mate ive been chatting to has just brought that up - the ring at the top would have to take the load from the running end of the speed line and down to the base - but then the angle needs to be taken into account - 

 

 

A very rough calculation (and not allowing for any shock absorbtion and based on the log being snatched to a stop at the end of a rope) 

 

a 200kg log dropped 0.5m (generating 625kg of force)  with an angle of 70degrees at the top ring would generate 775kg of force at the top point (387,5 at the base and other end of the speedline 

 

This is i reckon is quite a fair bit over the forces that should be generated using the set up i have in mind but its just a rough calculation 

[Vespasian]

I've wondered about that as well, that is the shock load being only half at the top as opposed to something base tied..   which is why I imagined the rope wrench had some distinct advantages when I looked at that thread last week..   

 

not being much of a tree surgeon but somethin of a thinker, I was wonderin if a metal artificial hinge might be invented to tie to both ends of the stem before it goes over..  this artificial hinge would take most of the shock forces out of play...   once it was over, you lowered your stem safely..   I was thinking of this the other day...  now winter on its way I have time to think about these kind of things..   

[Dilz]

3 minutes ago, Steve Bullman said:

Maybe, but at the same time won't a base tie take a bit of the shock out of the system?

Exactly - the rope (black marlow) has a fair amount of stretch in it and I think this system would give it a lot more stretch to absorb to logs when they first drop onto the line. 

[Dilz]

Just now, Vespasian said:

I've wondered about that as well, that is the shock load being only half at the top as opposed to something base tied..   which is why I imagined the rope wrench had some distinct advantages when I looked at that thread last week..   

 

not being much of a tree surgeon but somethin of a thinker, I was wonderin if a metal artificial hinge might be invented to tie to both ends of the stem before it goes over..  this artificial hinge would take most of the shock forces out of play...   once it was over, you lowered your stem safely..   I was thinking of this the other day...  now winter on its way I have time to think about these kind of things..   

5

You think deep and dangerous thoughts!  But yeah - a top tie with SRT generates a lot less force on the anchor point. 

 

[carlos]

i think a common way round that prob is to have two systems tied under the cut, one for normal snatching with capstan then attatch to the diagonal speedline, this takes to force out of the rope on the angle and also allows for a controled speedling of pieces, i ve never really tried it though.

another option is to run the speedline through a block under the cut and then instead of running verticle to the base of the tree you take it out the back to the base of a neighboring tree, this would take out the 2:1 effect of tieing it to the base below.

ive not done much zipping of heavy timber, so could be talking crap! i tend to use speedlines for branches.

plenty of vids on youtube.

carl

[Coletti]

When speedlining lumps of timber (or anything a little heavy for a safe hand hold) we often just tie of as normal on the stem just below the chog but run the other end through a flying capstan type lowering device (Stein rc1000 in my case). This does 2 things, 1. It seriously reduces the risk of the groundy losing control and flying towards the tree and 2. It allows the ability to "let it run"so to speak to dissipate the initial shock load and dissipate a lot of the energy.