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115 lines
5.7 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
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<title>CUCC Expo Rigging Handbook: Artificial belays - bolts</title>
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<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
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<body>
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<h2 id="tophead"> CUCC Expo Rigging Handbook</h2>
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<h1>Bolt belays - choosing a location</h1>
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<p>Deciding where to put the bolts for a new pitch is something of a black art,
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which can be acquired only through much practice and wide experience of SRT in
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general. This guide cannot substitute for experience underground.
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<!--Particularly as the author has only ever bolted three pitches.
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--></p>
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<p>Inasmuch as there can be such a thing as a "typical" pitch, the "typical"
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rig might be something like this. Start off a traverse line somewhere nice and
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far back; often this gives you enough choice of location that you can use a
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natural. Approach the pitch-head carefully, gardening as much loose material as
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you can before there are cavers or ropes below for it to hit. Look for
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somewhere good to place a Y-hang; if the pitch is awkward, this may have to
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become a tri-hang - a very typical Expo pitch-head technique is a Y-hang
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followed immediately by a deviation, to give full three-dimensional control
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over the position of the hang. (Showoffs can achieve the same effect with a
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triple bowline, if they know how to tie one.)</p>
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<p>Having got the pitch-head bolts in, descend carefully, looking out below you
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for any potential rub points, and looking around for good places to rebelay or
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deviate. Remember that a deviation to avoid a rub point is only any use if it's
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some way above the rub; don't just ab down until it starts rubbing and then
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start looking for a rebelay or deviation.</p>
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<p>Placing mid-pitch bolts is often a challenging business requiring you to
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dangle on miniscule ledges or wedged against the walls while you drill. Don't
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overdo it; if it's difficult to put the bolt in, it'll be difficult to rig off
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in future. Many seasoned riggers swear by skyhooks as a means of positioning
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yourself while you bolt, but don't rely on everyone else who uses the bolt
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owning a set! Another trick is to use a borderline natural, which you wouldn't
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trust to rig off, to support yourself while you drill.</p>
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<p>Some caveats:</p>
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<ul class="spacedout">
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<li> Watch out for poor rock quality. In most cases the choice of anchor
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placements is a compromise between the requirements of the hang and the
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necessity of putting your spits into decent rock. Cracks are obviously to be
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avoided; mineral veins are also apparently bad, but often there are so many of
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these there's no way you can avoid them. Once you've settled on a
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likely-looking location, get your hammer out and give the rock a few taps with
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the pointy end. It should give a convincing high ringing noise, not a hollow
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thud. (The difference in sound is much accentuated by a hammer with a metal
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shaft, such as the Petzl bolting hammers, which are expensive but very good;
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the club's cheap fibreglass-shafted hammers are rather more difficult in this
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respect.)</li>
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<li>If your chosen location is in a large block of rock which is well held
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together but not well attached to the wall, it can look and sound fine, but
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hold a nasty surprise in store. I was once about to start drilling in a
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promising-looking location, marred only by a crack in the rock at least 20cm
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away from where I wanted to bolt. Some suspicion made me stick the point of my
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hammer in the crack and lever on it, at which point a plate of rock about a
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metre across and half a metre thick slid off the wall and down the pitch,
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taking my proposed spit location with it! Be alert for this sort of thing.</li>
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<li>Bear in mind how difficult the rig will be for the user. In most cases, if
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it's difficult to rig it'll be difficult to pass and vice versa, but watch out
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for subtle gotchas like putting your Y-hangs too low down; this can make the
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pitch impossible to get off! Don't force yourself and your companions into
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dangerous manouvres like prusiking up one arm of the Y-hang.</li>
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<li>When considering how the rope will hang from a particular location, don't
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forget to take into account the length of the hanger and maillon. It almost
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always needs to be higher up than you expect.</li>
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<li>Spits are very much stronger when loaded perpendicular to their axis; so it
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is usually best to place spits horizontally into the wall, which is usually the
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easiest method anyway. Bear in mind the safe loading angles for the different
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types of hanger - only rings, clowns and bollards can take a straight outward
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pull. Bends are good for Y-hangs, where the pull is at an angle away from the
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wall; twists are best left for straight downward pulls.</li>
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</ul>
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<hr />
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<ul id="links">
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<li><a href="../index.htm">Expedition Handbook</a> - Contents
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<ul>
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<li><a href="index.htm">Rigging Guide</a>
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<ul>
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<li><a href="intro.htm">Introduction</a></li>
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<li>Choosing bolt locations</li>
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<li><a href="boltin.htm">The mechanics of placing a bolt</a></li>
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<li><a href="exporig.html">Expo-specific rigging tricks</a></li>
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</ul></li>
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<li><a href="../look4.htm">Prospecting guide</a></li>
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<li><a href="../survey/index.htm">Surveying guide</a></li>
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<li><a href="../rescue.htm">Rescue guide</a></li>
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<li><a href="../photo.htm">Photography guide</a></li>
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</ul></li>
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<li><a href="../../infodx.htm">Index to info/topics pages</a></li>
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<li><a href="../../indxal.htm">Full Index to area 1623</a>
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<ul>
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<li><a href="../../areas.htm">Area/subarea descriptions</a></li>
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</ul></li>
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<li><a href="../../index.htm">Back to Expedition Intro page</a></li>
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<li><a href="../../../index.htm">Back to CUCC Home page</a></li>
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</ul>
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</body>
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</html>
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