FYI - Lucky Charms bolts

[gwest]

We were down in the North Wash area a few weeks ago and did the Lucky Charms loop. We found someone had bolted the 200ft dry fall. We were planning to rappel the dry fall using natural anchors (and there was a large boulder which could've easily been used), but since they were there, we used them. They're on the west side at the top of the drainage. TR here:
http://picasaweb.google.com/gwest1000/LuckyCharms

[Stick]

We were down in the North Wash area a few weeks ago and did the Lucky Charms loop. We found someone had bolted the 200ft dry fall. We were planning to rappel the dry fall using natural anchors (and there was a large boulder which could've easily been used), but since they were there, we used them. They're on the west side at the top of the drainage. TR here:
http://picasaweb.google.com/gwest1000/LuckyCharms

I hiked the lucky charms loop about three years ago. I wonder if those bolts you found are the same ones we found. At the time the bolts looked brand new. The were also placed 4 or 5 inches apart. Other people in my group talked about coming back to remove those bolts, not because they were necessarily offended by them but because they constituted a safety hazard being so close together. We didn't do that rappel.

[gwest]

Yeah, probably the same ones. They still looked pretty new, so I didn't know if they had just been put in this year.

[Brian in SLC]

The were also placed 4 or 5 inches apart. Other people in my group talked about coming back to remove those bolts, not because they were necessarily offended by them but because they constituted a safety hazard being so close together.

That distance apart wouldn't be a safety issue, methinks. If you look at the distance recommendations in the Powers manual for bolts in concrete, you'll see its pretty close to that.

I usually shoot for no closer together than the span of my hand, between the tip of my pinky and thumb, at the widest I can make it. Leaves a bit of margin for error.

Sometimes closer makes for a more compact and less obtrusive anchor.

-Brian in SLC

[ratagonia]

At the time the bolts looked brand new. The were also placed 4 or 5 inches apart. Other people in my group talked about coming back to remove those bolts, not because they were necessarily offended by them but because they constituted a safety hazard being so close together. We didn't do that rappel.

Statements about the hazard of bolts placed too close together have been rather exagerrated.

To maximize strength, bolts should be 2X the length of the bolt apart. Thus assuring that the 45 degree sheer cones of the two bolts do not intersect and that the bolts can be truly termed independent.

But we don't place two bolts because we need the strength. We place two bolts because bolts are not inspectable, bolts are hard to place correctly, and therefore we wish to improve the reliability of the overall anchor via redundancy. Placing bolts too close together to compromise their reliability would involve placing them close enough that the web between the two holes is in danger of collapse or fracture. I'm thinking, bolts at least 2" apart are probably just fine in our sugary navajo sandstone.

It is, however, possible that drilling a hole "close to" another expansion bolt could compromise the original placement, due to vibration and shock waves. Seems like, again, we are talking 2-3 inches. The possibility does, however, suggest that if putting in two bolts quite close to each other, you should probably drill both holes first, THEN set the expansion bolts in the holes.

Capiche?

Tom