The double overhand may indeed come from the industrial safety side of things. A double overhand is the standard knot for industrial rigging and construction. (as opposed to TECHNICAL rigging)

I have not seen it used for rappels before. I use a figure of eight with 50 cm of tail. (or a double fishermans if there is no cracks for it to get caught in)

I seen a few CF knots but this one is some thing else so far. in one image ,the rope with a knot looks like is adjustable knot similar to purcell ( prusic) system plus, do climbers run rope over webbing (software x software) ?

I seen a few CF knots but this one is some thing else so far.

in one image ,the rope with a knot looks like is adjustable knot similar to purcell ( prusic) system plus, do climbers run rope over webbing (software x software) ?

I then wonder what you have seen elsewhere. this is absolutely a standard double overhand knot which has not been pulled tight in order to let some people see how the knot is constructed. Next to it you see it tighened up. ... it is a knot used for joining 2 ropes for rappel.

I then wonder what you have seen elsewhere. this is absolutely a standard double overhand knot which has not been pulled tight in order to let some people see how the knot is constructed. Next to it you see it tighened up. Based on your comment below you did not get that a knot can be shown in 2 states, did you ?


Majid, it is a knot used for joining 2 ropes for rappel.
Please note that it is very common for mountaineers to use a bare sling to rappel. when you pull down the rope, there is more friction than when using a biner or a rappelring or a quicklink but it is cheap and works well for the first rappel. As long you do not tensioin both sides (such as in tp-rope), the rope will not seesaw into the sling.

I seen a few CF knots but this one is some thing else so far.

I am sorry, is this CF called standard double overhand knot to join to rope which has not been pulled tight ?

[URL=http://imageshack.us][IMG]http://img124.imageshack.us/img124/1531/screenhunter001yz1.jpg[/IMG]

As I said, as summerprophet said, knudenoggin said

Yes, it is a double overhand knot
[image]http://www.animatedknots.com/stopperrescue/DoubleOverhand.jpg[/image]
if you build it simply, it is the standard form it takes (the picture does not do justice to a tightened double overhand).
If you dress it up while tightening it, you arrive at a half-a-grapevine setup as knudenoggin explained.
[image]http://www.animatedknots.com/stopper/knot.jpg[/image]

No, it is not a CF knot.
because if it was, this would mean that, my dear, everytime you have made a double fisherman (aka a Grapevine) you have been doubling up on the CF.
And this, I am not yet ready to believe

rocknice2,
I researched your statement about the overhand knot vs. the Figure of eight knot, and indeed you are correct. Thank you for the heads up and my rappels will be revised from here on.

It seems the rules change (as test data becomes available), as when I was a guide (ten years ago), they presented data to begin using the figure of eight rather than double fishermans for rappels.

I am going to pull all of my prusics out and re tie them using this new CF double overhand knot method

Thanks

The rethreaded fig-8 is absolutely bomber, no problems using that for rappels.

The non rethreaded fig-8 where both tails are together is a terrible knot, i doubt any knowledgable source has recommended this. Fig-8 knots need to be loaded on both ends!

For a while i believe it was taught during (french) guide training that this was the knot to use for joining 2 ropes during rappel (that was when bowline knot became frowned upon because of accidents).
The thinking was "After all if the knot was good enough to attach, it should be strong enough for rapelling, so let's use and let's teach only one knot". Only a series of accident or near-accident led to further investigation and test. Tets such as Tom Myer's demonstrated the capsizing risk of fig-8.

[This shocks me because in my opinion you don't need a test to show that it is a poor knot. It really scares me the amount of climbers out there who do things without analysis.

The rethreaded fig-8 is absolutely bomber, no problems using that for rappels.

The non rethreaded [offset] fig-8 where both tails are together is a terrible knot, i doubt any knowledgable source has recommended this.

This shocks me because in my opinion you don't need a test to show that it is a poor knot. It really scares me the amount of climbers out there who do things without analysis.

Knudenoggin could probably point us to alternative knots for joining ropes of different diameters.

and you can also find my repeated rejection of the myth that the OOB is somehow MORE risky with ropes of unequal diameters

--in fact, if one orients this asymmetric bend's parts so that the thinner rope makes the outermost/initlal binding of the ropes at the entry point, it should be MORE secure against rolling (the thin rope being more impeded by the thick against this).

thank you. if i had a dollar for every time someone warned against two different sized ropes, without any reasoning or explanation ...

that the thinner rope makes the outermost/initlal binding of the ropes at the entry point, it should be MORE secure against rolling (the thin rope being more impeded by the thick against this).

can you point to any pictures of this?

A simple overhand knot is better for rappel than both the fig8 and 2fish.

It doesn't roll over like an 8.
Passes over edges WAY better than a 2fish.
Has a very low profile.
Is strong enough to lower even the fattest of asses.

Here's some testing information on the various knots under discussion:

http://www.xmission.com/...yer/testing/EDK.html