Anchor overkill?

[pale]

Ya'll ain't gonna get a more newb question than this. Just finished a top-roping course with ACC. Went to crag. Found one (10") tree as anchor. Found another 10" tree 12ft away as backup. Biner'd slings together to meet and equalized.

 

Is this a typical setup, to use two solid trees as an anchor, or would one have done with two slings? I went with the two just in case.

[klenke]

If the main tree were to pull out with a fall you'd have as much to worry about being clobbered by the tree as you would falling to your death or to serious injury--especially if you couldn't fall because the back up held. Hard to say. I'd have to see the set-up in person. But on the face of it it does seem peculiar.

[forrest_m]

well, without having seen the setup, i would agree that one 10" dia. tree - if it's healthy and well rooted - is likely more than sufficient. i mean, think about how much force a decent wind puts on the top of the tree, with the whole tree as a lever arm. the extra weight of a climber is pretty insignificant.

 

however, if you are a beginner, creating a second redundant anchor that separately connects to the rope isn't a BAD thing. it's not so much that you are worried that the first tree will fail, more that it protects you in case you did something dumb with the first anchor (screwed up the knot, carabiner gate over an edge, etc). while doubling up the anchors isn't the most efficient thing in the world, it's also unlikely to cause any harm.

[catbirdseat]

If you have a BFT anchor, and a 10 inch tree seems to qualify, you are set. You'd like either two independent single slings or else a wrap-three-pull- two if you happen to have a triple sling. A locking biner and you are good to go. Some folks will add a second, non-locking biner, but it isn't necessary.

[chucK]

I don't know what you mean by a "wrap-three-pull- two", but it sounds like it might not be a redundant system.

 

IF the tree is really good. I agree you don't need an independent anchor point. However, there is still the reasonable possibility that a newbie or experienced climber could make a mistake with respect to locking a biner or tieing a sling. Thus, I think it would be a very good rule of thumb to set up two independent sling/biner combos around the tree.

[forrest_m]

wrap 3 - pull 2 is rescue-speak for wrapping a sling around an anchor in such a way that the knot is subjected to the least possible strain*. you're correct that it is not, in itself, redundant. as i said before i don't believe that people just learning to TR should be discouraged from adding additional redundancy to their system. optimization can come with experience.

 

* i.e. if you simply tie a sling around a tree, the weak point of your anchor is the knot in the sling. if instead the sling passes around the tree several times, you can get the full strength of the sling material. like this: wrap 3 pull 2 = three times around the tree, pull the two strands furthest from the knot towards the load and put the carabiner through both. adjust the knot until it is flat against the tree (on the side facing the load). that way, the load on the knot is reduced by all the friction of the sling passing against the anchor - around a medium sized tree, the knot will actually remain almost slack even under rescue loads. the same principle can be applied to any number of wraps if your anchor is smaller diameter, i.e. wrap 4-pull 3, etc.

 

edited to add description of wrap 3

Edited June 30, 2005 by forrest_m

[chucK]

Right thanks!

 

Sounds useful to know, for a rescue situation. I know you're not disagreeing with me here. I'm just going to restate...

 

In a toproping situation the risk of inadvertent fuckup is way more likely than sling failure due to insufficient strength. Best to focus on doubling up the system instead of getting all crazy about knot strength.

[Bill_Simpkins]

I've used trees and bushes down to 2 inches. Sometimes in the mountains around here you can get stuck girth-hitching slide alder.

I top rope soloed off two equalized 2 inch diameter trees at Squamish a week ago.

A 10 inch tree, if it looks healthy would probably hold

[pale]

Great, thanks for the replies. It is as I suspected, but being so green I figured better play safe with two trees. Also I felt rushed because my partners were waiting below me (and yelling up every five minutes), so I forced myself to take time and remember what I've learned.

 

I understand that as a newb the most likely thing would be for me to improperly assemble the anchor. Which leads me to my next question, which I'll ask in another thread.