Pre-tensioning rigging lines

[Dendronaut]

In France some of us use this tool :

 

 

 

 

 

Edited September 23, 2017 by Dendronaut

[Steve Bullman]

Looks handy.  Whats it called?

[nepia]

That does look very handy doesn't it due to its simplicity.  It's a comealong of some kind but I'd like to know more.

[AndyFromMerthyr]

I find the cheapest option is a single prussick above your bollard with a pulley in it.  Wrap a few wraps around the bollard and take the tail end through the pulley.  The prussik then gets removed before lowering so it doesn't get in the way.  I think pretensioning loads where the load is below your rigging point is a much safer, more controlled way if rigging.  As mentioned above, our rigging lines aren't designed for big dynamic loads so the more tension you can take up the better for the rope and your rigging points too.

The GRCS and SmartWinch do it perfectly but not many people have half a million quid sitting around doing nothing so a pulley and prussik it is for now.

[Joe Newton]

I find the cheapest option is a single prussick above your bollard with a pulley in it.  Wrap a few wraps around the bollard and take the tail end through the pulley.  The prussik then gets removed before lowering so it doesn't get in the way.  I think pretensioning loads where the load is below your rigging point is a much safer, more controlled way if rigging.  As mentioned above, our rigging lines aren't designed for big dynamic loads so the more tension you can take up the better for the rope and your rigging points too.
The GRCS and SmartWinch do it perfectly but not many people have half a million quid sitting around doing nothing so a pulley and prussik it is for now.

I thought that's exactly what our rigging lines are designed for.

The idea that you need a winch system or mechanical advantage for negative rigging is a joke. For lifting limbs etc it has an application, but with a decent bloke on the rigging there's no call for pre tensioning ropes for blocking down.

[AndyFromMerthyr]

There's no need to pretension for blocking down stems where the load is above your rigging block no.  It's definitely useful for removing limbs though.  Big lateral limb over a target, spiderweb the whole limb, pretension, gob in the side to swing it away from the target.  Barely any drop in the limb and total control.

I think pretensioning makes things safer and more controlled.  Obviously it's not always necessary but it's definitely useful in a lot of situations.

Our ropes are basically designed to hold a load in an almost static situation and lower to the ground, they're not designed for shock loading.

Most of the time, if your groundies are good on the rope, they'll let the rope through the bollard as it gets loaded to extend the impact time as it were.

Edited September 23, 2017 by AndyFromMerthyr

[Joe Newton]

There's no need to pretension for blocking down stems where the load is above your rigging block no.  It's definitely useful for removing limbs though.  Big lateral limb over a target, spiderweb the whole limb, pretension, gob in the side to swing it away from the target.  Barely any drop in the limb and total control.
I think pretensioning makes things safer and more controlled.  Obviously it's not always necessary but it's definitely useful in a lot of situations.
Our ropes are basically designed to hold a load in an almost static situation and lower to the ground, they're not designed for shock loading.
Most of the time, if your groundies are good on the rope, they'll let the rope through the bollard as it gets loaded to extend the impact time as it were.

I misread your post Andy. I agree that on balancing limbs pre tensioning is a good idea. However if there's one thing our rigging ropes are built for shock loading. Just look at the cycles to failure ratio of Polydine.

Most of our rigging lines are over engineered to the point that they should be the last point of failure in any system.

[Dendronaut]

On 23/09/2017 at 19:01, Steve Bullman said:

Looks handy.  Whats it called?

It's a "Tirvit" made in France by TRACTEL.

[Swampster]

http://www.abaris.co.uk/prod/Rescue Kits/Tractel-Evak-500-Winch.htm#description

 

 

For synthetic rope, as opposed to wire.

[WesD]

Does anyone rig in its most basic form ie just using a rope and the tree your in?