Posted By RJortberg on 21 Jul 2009 02:49 PM
I also have been using a Petzl ascender as an alternate attachment device. ... but it is more on-off when descending. I think descending with the ascender is fine on a medium steep roof, but for a really steep roof or for controlled rappels (let's say if your ladder is not tied off and falls) the grigri would be a much better device since it is more gradual in terms of stopping. So, I think the grigri is probably more versatile of the two devices.
Gotcha - good on your feedback. Similar to your experience, I like the Petzl ascender for going up because it attaches so quickly to the rope. It can be removed very quickly, which is a plus. You get up, and switch over to a Gri-Gri or whatever.
If you try to DESCEND using the Petzl ascender, it is possible for the rope to "pop out" of the device if you get carried away releasing tension on the device (that would never happen with a rope-grab). That actually happened to me once when I tried descending with the Petzl ascender, so I put a carabiner through the holes located at the front of the ascender, to make sure I don't get separated from the rope.
You may want to look into the Petzl Rescuescender (which is very similar to the Gibbs Rope Grab) if you want something to give you some security going up the roof, and it "can" be used for a controlled descent by easing the tension on the cam that presses against the rope. The big difference is that it has a ribbed cam, but no spikes that would snag on the line during a descent.
he commented that we should tie a knot in the rope at about the gutter line on each side of the house.
May sound good in theory... but I don't think anyone who does this very often would do that. None of the group of 12 Two-Story-Steep teams (24 people) I was working with recently did that. I suppose the words "impractical" "overkill" come to mind. You get to trust your equipment, know the boundary of the roof, and just get it done.
Usually I have each end of the rope tied to something like a tree, or pole. If there is a "loose end" of the rope (such as when you have a ground person on the other end) it is absolutely a good idea to tie a knot at the end of the rope.
You can use 2 ascenders if it is a really steep roof.
Wow. I only use one, and connect it to the harness with a foot or 2 of webbing (or a "Zorber" like the photo I took of Tony on earlier page, with Petzl Ascender). One hand is on the Ascender, the other is HOLDING the rope so that the ascender can be PUSHED forward. You make your way up the rope a step at a time, pulling yourself, then grabbing another length of rope.