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rob

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    "Reeling In" a Falling Leader

    in Newbies

    Posted

    Slide rule? Nah, that's what my calculator watch is for. cantfocus.gif

     

    Also your math only works for static ropes. More likely with rope stretch the leader will still fall 10 feet but on 13 feet of rope now for FF = 0.77

     

    But, if the rope stretched, wouldn't that increase the rope length, too? wink.gif

    "Reeling In" a Falling Leader

    in Newbies

    Posted

    Reeling in would seem to lessen the fall factor, wouldn't it?

     

    Take the following situation: 5' from the last pro, 15' up from the belay. In a normal (unreeled) fall, the leader will fall (5' x 2) / 15 = FF .66, right?

     

    Now convert this to a "reeled" belay: Let's say the belayer manages to reel in 2' of rope during the fall. The leader is still going to fall the original 5 feet to the anchor, regardless of how much is reeled. But, he will only fall an additional 3 feet below the anchor, since 2 feet of rope was removed from the system. That would be an 8' fall, with 13 feet of rope, right? 8/13 = FF .61

     

    Is my math right?

     

    I guess you would need to decide if the FF was high enough to warrant the possibly dangerous task of trying to take in quick enough while still locking off in time to catch the fall.

     

    As to the question posed in the OT, I'm not sure how you could safely take in more than and arm's length of rope, and if you would want to.

    How to not die while rappelling

    in Newbies

    Posted

    I thought the scenario is this: If your backup prusik is on the guide hand (above the device), and you lose your brake hand (due to a fall/accident/picking your nose), your guide hand might instinctively grip the prusik and prevent it from loading, resulting in a fall/grounding. Letting go of the guide hand is non-instinctive.

     

    However, if you set an autoblock below the device, controlled by your brake hand: If your brake hand grips tight, the autoblock may not engage, but what's the problem? Your brake hand is still in control of the rope and the device catches you. But if you lose the brake and grab with the guide hand (instinctively), the friction below the device will catch and prevent your untimely death.

     

    This is how it was explained to me, anyway. I didn't think the purpose of a backup prusik was to prevent rapping off the ends of the rope, anyway -- I thought it was to serve as self-belay. If you rap off the ends of the rope, it seems unlikely you will have the instincts to let go of your guide hand to allow the prusik to engage quickly enough to prevent the rope from pulling through it.

     

    Am I off base?

    How to not die while rappelling

    in Newbies

    Posted

    Another step that may prevent this error from becoming fatal is to have a prusik back up knot located above your belay device.

     

    This is what I was taught too, but recently someone turned me onto using autoblock backup instead (beneath the rope). It seems that the more I read, the more accepted this method seems to be, especially since it isn't as hard to unload and you don't have to worry about the natural tendancy to grab the rope (and thus the prusik, preventing it from loading) with your guide hand during a fall.

     

    Are there any other pros & cons between these two backup methods (Prusik above the device vs. autoblock below)?

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