So .... The physics of tip-tying is still a bit tricky for me, even though I taught college physics for 28 years before getting into tree work.)
Sounds like you have an interesting story... career change from college professor to tree man at age 50+???
Tip tying is not that complicated.... When the piece is tip tied, the but goes down and the tips go up... If the rigging line is in line with the limb (directly above the limb/ crotch), as the but drops, the tips are going to lift up and slam directly back into the tree above the crotch, which puts the climber at some risk, as that's where he just made the cut... If the tips have not been cut off that looks like lots of brush coming right up into your face, which can hurt , but probably isn't going to kill you... With but tying , the tip goes down and the but goes down.. so it all ends up below you, which is very good for safety...
So in general tip tying is only more useful than dangerous when you need to swing a piece. (Some guys like to rig upright wood with a tip tie to keep it as static as possible, but that's a different subject). When there is something like another tree or a house right under a large limb, rather than climb out to the tips and take it in small enough pieces to clear the obstacle, you can use a tip tie to swing the entire piece away from the obstacle BEFORE it drops. When the rigging line is offset from the limb, the limb will swing that way as it starts to move.
When done right (combination of good rigging set up and a good cut) it looks smooth and sweet... the tip of the limb starts to sweep (or arch)
slowly down and to the side, as it does it puts more and more weight on the line, until the full weight of the tips are on line as it comes to rest directly under the rigging point before separation at the cut. When the cut is finished, the piece slowly see-saws to stasis directly under the overhead rigging point. Its like a ballet... Anyone that would like to see some video PM me.. Depending on the distance of the offset and the size of the piece and how much clearance is needed, the ground man can let the rope run a lot, some, or none.. When the rigging line is pre-tensioned and positioned properly you can get the limb to swing 90-180º without dropping at all, which is pretty cool the first time you see it happen. This can also be done with a "near balance point" tie off (slightly tip heavy)... the idea is to be able to get enough lift on the limb to allow the hinge to function without failure until the face fully closes... Depending onthe weight of the limb and the ability to pretension the line, sometimes you got to go out further and tip tie it. I prefer a near balance point tie off whenever possible (which is almost always).
What makes tip tying dangerous is that the tip(s) are going to come up... Up is where the climber is. If there is a large offset from the tie off point to the overhead rigging point, the limb is going to swing wildly past the plumb line of the rigging point, and then slam back into the tree on the back swing. Often times a large piece will helicopter as it swings out and come all the way around the back side of the tree, so if the climber doesn't move he can get hit in the back of the head. Human's near death video is a perfect example of that.. If the tree still has a lot of limbs on the back or side, they can act as a blocker to protect the climber from getting hit, which I have used in the past, but generally its best to avoid that helicoptering, back swing, and slam.
Hope that helps... generally best to avoid tip tie, especially on anything big like, unless its absolutely needed, and then should only be done by an highly experienced climber. I mentioned the non-functioning but line in the comments on youtube. Human replied that he thought there would be enough friction on the line (sounds like just from a trunk wrap or two without anyone holding it).. That was a miscalculation that almost cost him his life. An experienced climber would have known that a little friction isn't going to retard the movement of such a massive piece. He's lucky to have survived that one and we should be happy to have the video, a perfect example of what NOT to do.
