Just ask Pinocchio what happened when Gepetto sneezed.
What I like about the Buzz is that the comments are by folks who have been in similar situations with real-world experience. This isn't theory, it's refinement of arboricultural rigging practice.
Yes, it would have been nice if the rope had been allowed to run. But I don't believe it would have been possible with the available combination of tools.
It wouldn't have surprised me if any of those pieces had clipped the rope in half on a corner of the block or a stub. It would have caused a chunk to go thru the guy's driveway, making it difficult to collect payment at the conclusion of the job. On this job I was an employee, so that prospect didn't bother me as much as it would have if it had been my contract. We just made sure everybody was standing well out of the way during tipping.
If there was a block available with a larger diameter sheave, that may have been helpful, but not as much as if a GRCS or similiarly-sized LD was used.
Cinching up the 3/4" sling on the block with a Stilson Hitch was the best we could do under these circumstances. Getting the rope tight is exhausting.
The trunk was decidedly not cylindrical, what with the stub scars and gaps from bark furrows. The knot is tied while partially out of view of the climber. After loading, the parallel wraps of the Stilson Hitch were slanting lopsidedly downward on the pulley side, and were definitely not symmetrical.
The climbers flipline is placed just beneath the block hitch. The block hangs from the splice and hits the trunk below the flipline, which can be unnerving. The flipline is precluded from placement above the block sling, as any lower placement of the pulley causes more shock load.
It may appear that the block can cut the flipline, but don't be deceived. This is of prime significance to the climber, as death can occur from any downward sliding of the block that transfers load from the trunk to the climber. That's a no-no (emphasis mine). Get the block sling tight.
So far, no one has ventured a guess at how much these 300 pound logs weighed.
To calculate the dynamic force on the rigging, we can use a standard formula of computing double the weight unit of the work, plus one unit per foot of drop.
So, if the log weighs 300 pounds and falls one foot, that is 900 pounds on the rigging. If the log falls 2 feet, that is 1,200 pounds. Stretch may mean it is falling 3 feet, which is 1,500 pounds of force on the various parts of rigging.
During lockoff (which is what we have here) probably the lightest forces are on the sling securing the porty to the trunk. The highest forces are on the block. The weak link in the chain is the lowering line where it rolls over the block.
As the load hits the line, the knots cinch down and the ropes squeeze the bark at various places. After about 6 inches or so, everything stops moving and starts shrinking. Heat builds up at all these friction points and on the strands inside the layers of rope fiber.
Thanks for the comment about the orientation of the face. A Humboldt or wide face merely allows the piece to tip farther towards horizontal, or maybe just a bit beyond, prior to release of wood fibers in the hinge.
As the piece begins to tip, slack develops in the lowering line as the butt hitch moves closer to the pulley. As it begins to pass 90 degrees, the rope starts tightening up. When the work tips upside down, do I understand you to say that the load may be more vertical than diagonal?
If there were a downward pointing face, can the work actually move quicker as it spins thru a longer arc?
Gallileo said stuff only gets up to 66 feet per second in the first second of drop. So, no, I don't use Humboldt faces on lowering too much.
A wider face usually becomes a deeper face, due to saw handling difficulties. Here's where chainsaw accessories such as bubble levels on the handles and a laser kerf indicator need to be incorporated into product design by the manufacturers. More cleaning up of the cut face surfaces with the toy saw results in fatigue & delay. Any-old clean face ensures the work commits to a fall line above the block, and stays below the block. This means it doesn't spin around the tree and nail the climbers legs.
A deep face is known as, "cutting a lean into the tree". This change in the center of gravity wasn't needed because of the separate tag line tiptied on the work to commence the fall.
Here is where a GRCS would have allowed less slack by stretching the rope during linesetting. A porty just cannot compare. The sling securing the Portawrap to the trunk must be very low to the ground, so the holeman can lift the rope upward with enough force to get the rigging tight. Trunk flare can make tying this Stilson Hitch difficult. A marlinspike can tack it down. A round of wood used as a step next to the trunk can help the roper get get high enough to take the slack out of the lowering line.
The climber's best viewing option of the saw in the kerf to line up the final inches of the back cut is from the side. The best point to push and be out of the way, however, is directly behing the cut. Thus the pause to stow the saw, move back around and help push. This pause allows communication without the interference from noise of the saw.
