From our previous blog post, we know that the amount of force in a perfect scenario applied to the rigging point is 200% the weight of the piece being lowered. The force applied to the rigging point will bisect the rope’s angle. According to this, 200% of the weight of the log will be applied straight down on a leaning rigging point. As we all know, wood is much stronger when pulled or pushed straight along it’s grain opposed to bent across it’s grain. By applying this force downward on a leaning rigging point we are applying lots of force across the grain. This is a very easy way to break out a rigging point and possibly cause a catastrophic failure.
One of the most dangerous times we will be rigging in is during storm situations and we need to stay on our toes when it comes to the forces involved!An easy way to mitigate this risk is to transfer the force into the tree where the tree is stronger. If the force bisects a rope’s angle, we just need to make that force go into the stronger parts of the tree. This next diagram illustrates how easy this is!
As you can see, once the rope angle is bisected, the force is transferred into the tree. By easily setting a redirect for your rigging line, the risk can be mitigated. One thing to keep in mind is the amount of force on the terminal rigging point. The terminal rigging point is the point farthest from the ground worker. This point will result in more forces than the second or third redirect but by changing the angle at which the force is exerted the force can be directed to where the tree is stronger.
Another great thing about redirecting the rope is the safety of your ground workers! In the first diagram the ground worker was standing directly under the piece of wood being lowered. Seeing as the force was directed downward on that leaning rigging point, the chance of failure was greater. If the rigging point had failed the ground worker would have no place to go. By redirecting the rope, the ground worker can now be out of harms way and work safely throughout the day.
By planning out your rigging with these things in mind, your day can become safer and more efficient. By redirecting the forces into the tree in a smarter way larger pieces can safely be lowered making your time in the tree shorter and shorter! Stay safe!