The word is out, we are "top-roping off a jumars". Someone spotted us, that's what we do[?]. I was trying to think of a good name for the way we belay, and I guess that is as good a term as any[?]. However I would have called my invention something else.
How to "top-rope off of a jumar".
If you are with a few people the best way by far to top rope on any section of rock [like Millbrook], is first for each person to rappel down using their own rope and grigri. Now here if you need to get under a roof your partner[s] can swing you in under there, even if the roof is big. You can really get a full pendulum going on to go anywhere you want to.
The next little secret is that one of your partners is holding the brake line on the grigri over your head. This works great because you can have a number of people all working on a roof on and off at the same time like a bolder problem, and you do not have to change the rope system over your head, it works fast, it's simple, and it can be safer. However, you need to use a static line and watch for abrasion from the rock more often. You may need to place some more gear and attach it to the rope to stabilize the rope.
Now, if and when you are going to climb past your partners over their heads, THEN you need jumars on the ropes over your head to keep the grigri tracking up the rope. However in the process the belay is really self belay on your rappel grigri. Your "belayer" is just there to help track the grigri up the rope and needs to learn not to weight the jumar. However, if perhaps there is an error, and the rope is snug between you and the tree at the top of the climb as it should be, the most amount of weight that the jumar would encounter is body weight. Yet in that case, where you could actually call this "belaying off of jumars", I would call that an accident. You don't want to do that. This is why I would have called this something else, like "belaying off a grigri". It's really not a toprope at all because you have eliminated the top rope anchor and simplified the system down to one anchor [a tree] rather than two [a tree and a belayer]. And now there is half the weight on the rope, tree, and grigri. So, you can't even say this is an upside down belay because it's not a toprope at all. The best name for this might be a "reversed reppel".
Let me just make a disclaimer and say that if you want to try this that it needs professional instruction to get it right or even look at it apparently. If you don't know what you're doing, if you don't know what we are doing as you see us working this system, you might assume that we are actually top roping off jumars to be choppin ropes. I don't want people watching us to get confused, if you are actually top roping off jummars you are going to chop your rope. And that's not a good thing. Another problem you can encounter in this system without proper training is a fall can result it rope being fed through the grigri rapidly in reverse. This is because sometimes the grigri does not always work immediately when it is unweighted. And in this case, and in this way there can be a system failure and you can hit a ledge. This letter here is not meant for instruction, but to discourage anyone from tying this on their own. I am sure the operation is not approved by the manufacturer.
[BTW moderator could you please delete the post I asked you to delete? Thanks.]
The Mohonk Mountain House and the Mohonk Preserve have done a great job protecting the environment thus far, but ... it's all down hill from here http://youtu.be/9AU8fMo8v4k.