Speedline shortening knot?

[Rowan the Bruce]

I suppose a groundies arm would suffice!

[munkymadman]

sounds incredibly old skool set up you don't want to be tieing or untieing any knots, except for the slings your zipping bits off with.

[Sciadopitys]

Don't ya just love speedlines!

[rbtree]

the knot I was using before wasnt a sheepshank but like it and tied off twice at the top and bottom? I dunno can't really remember. Prussik sounds like a simple idea that can allow you to slacken the speedline easily, will give it a go - don't know if the force of the piece hitting it will cause problems though?Thanks for the info guys.

 

 

Use a prussic-- VT or Klemheist. To keep your loads from hitting it, keep it as close to your lower anchor as possible, and still be able to tension the line as needed. Depending on the amount of tension needed, we use a Z-rig, or more if say, 5-1 mech advantage is needed. The groundies will tension the line, perhaps after the load is on it, then quickly let it go as it is sliding down, so that the load hits ground. Sometimes, it will impact the prussic, which only means a bit extra time to detach the slung branches. Put a knot in the rope end, so it won't come out of the pulley system.

 

In this video, you'll see us using the chipper winch to tension the line, with an old Portawrap 1 as the adjuster. It was out too far a couple times. With some, we were applying a lot of tension to lift and swing lower limbs around the tree. Some are let fly, some use a control line.

 

[ame]

[/ame] Edited March 30, 2009 by rbtree

[coolie]

The middle pulley is where the tensioning takes place and the rope is fed through before being tied off, also where the section zipped out stops.

 

For a lightweight speedline or zipline a truckers hitch will give you a quick 2 to 1 tensioning.

[sse arb]

if you want to stop the load hitting use a porta wrap on the return line to controll the speed of the falling timber this will also allow you to stop the load when ever you want to

equally if its light then a fig 8 will do the trick nicely or a munter hitch

[Rowan the Bruce]

yeah good advice, we had to use the munter hitch on a few bits and used a prussic for the middle z rig pulley which after smashing a heavy piece into it burned half through :angryfire:and was respectfully binned, the job is done now and we are waiting for some photos from the archeologist who was paid to watch my every move for two days. Not really possible to use somone else on the control line as most of the time I was way out over a grade II listed mill building which was in a very bad state. English Heritage the local council and myself breathed a big sigh of relief after that one.

Here are some site photos. Note the large ganoderma.

 

[sse arb]

you can use a 5-1 pulley system to tension the line and if the trailing end of your tensioning rope is put through a fig 8 then you can lower the system as required use po65 pulleys and if you want to keep the lne at a constant tension pop in a protraxion pulley to lock it off but keep a small amount of slack or you wont be able to release the lock. happy times ahead