adjustable spectra/dyneema/HMPE footloop?

[NZcaver]

How did your friend rig up the chest Tibloc? Through the harness maillon? Would that eliminate the need for a chest harness?

Good question, I don't know. I didn't witness this system with my own eyes. I guess I'll have to ask him next time I visit. A tibloc in the harness maillon sounds very efficient in theory... but how would you attach/detach/downclimb? Not very practical!

Yeah, maybe I should patent my harness design and go into production. Make some pocket money. Hmmm...

[ek]

A tibloc in the harness maillon sounds very efficient in theory... but how would you attach/detach/downclimb? Not very practical!

I don't know...to attach when standing on solid ground, simply open the maillon, take off the Tibloc, put the rope through, put the Tibloc back on, and close the maillon. Downclimbing could be accomplished by pressing down on the top of the Tibloc to prevent the maillon from pushing the teeth against the rope.

For safety, the Tibloc would have to be on the rope at all times--after all, when rappelling, you never know when you might need to change over. In order to prevent the Tibloc from engaging, it would be necessary to push down on the Tibloc while rappelling. Surely nobody would push down on a Tibloc in panic, so this would also be a reliable automatic self-belay for rappelling.

Perhaps greater speeds could be achieved by adding a foot-mounted Tibloc. Holding one's foot at an angle would not remove the device, but it would cause minor sheath damage.

Unfortunately this system does not pass knots and rebelays, but this is not an insoluble problem. To climb past a knot with this system:

(1) Attach yet another Tibloc to the rope above the knot, on the short cowstail.

(2) Move the upper Tibloc up above that one, so now there are two points of attachment above the knot. Note that these Tiblocs, not weighted, may be subject to falling down by themselves repeatedly and should be pushed back up as many times as necessary if that happens.

(3) Press down on the top of the chest Tibloc to lower it enough that the upper and third Tibloc take up the weight.

(4) Untie the knot, attaching the lower half of the rope to yourself so as not to drop it.

(5) Attach the chest Tibloc to the upper rope (by feeding the upper rope's tail down through it) and set and weight it.

(6) Retie the knot, remove the third Tibloc, and continue ascending.



Anyway this is getting so I guess I shouldn't ask you if you have any similar ideas for passing rebelays and switching from one rope to another with this system.

[NZcaver]

No, you really shouldn't. My head hurts already.

[ek]

To get back to the foot loop thing;

indeed.

I got a bit of Spectra/dyneema tape and had this sewn into a foot loop using the sewn bit as stiffening on the bottom of the foot loop which nicely holds the footloop open so you can get your foot in easily, the foot loop is fairly tight for two feet and about right for a single foot meaning I can use 1 or 2 feet in the foot loop. I have tied spectra cord from the tape footloop up to my hand ascender and have enough cord I can convert to a mao, tied off with a bowline, because if I want to be able to convert I'd better be able to get the cord undone.
So far this setup is working well. BTW the extra cord also means the footloop is adjustable.

Where did you get the Spectra webbing?

Do you find that the bowline is a knot that holds well without slipping in Spectra?

[fuzzy-hair-man]

Where did you get the Spectra webbing?

An outdoors store climbers use it for quickdraws and slings, it's reasonably thin though ~ 1 - 1.5 cm wide but that doesn't worry me.

Do you find that the bowline is a knot that holds well without slipping in Spectra?

It seems to have held so far, it tightens up after some use so it can be a little difficult to get undone.

The spectra cord I got was from a marine place not a climbing store but given your footloop is not life support it doesn't really matter. It's also only core there's no sheath but seems to be wearing OK so far.

To get the Beal dyneema / spectra cord I'd have to order it from either Expe (France), MTDE perhaps, or Inner Mountain in the US which is kind of a lot of hassle for a couple metres of cord me being in Australia.

[ek]

Where did you get the Spectra webbing?

An outdoors store climbers use it for quickdraws and slings, it's reasonably thin though ~ 1 - 1.5 cm wide but that doesn't worry me.

I've only seen Spectra sewn into slings or dogbones for this purpose, not actual lengths of Spectra webbing--was this a walk-in store or an Internet retailer?

Do you find that the bowline is a knot that holds well without slipping in Spectra?

It seems to have held so far, it tightens up after some use so it can be a little difficult to get undone.

Have you tried the water bowline?
http://www.geocities.com/roo_two/waterbowline.html

[fuzzy-hair-man]

I've only seen Spectra sewn into slings or dogbones for this purpose, not actual lengths of Spectra webbing--was this a walk-in store or an Internet retailer?

Walk in store called Mountain Designs, but I figure that's not much use to you because AFAIK they are only in Australia and New Zealand.

Have you tried the water bowline?
http://www.geocities.com/roo_two/waterbowline.html

Never heard of it looks good though thanks Any ideas on how it's strength compares to a normal bowline? I imagine it's about the same.

[ek]

I've heard from several unreliable sources that the water bowline is slightly (~10%) stronger than an ordinary bowline, and from one unreliable source that it is slightly weaker.

I any case, I wouldn't assume that knot strength figures determined for traditional fibers like nylon, polyester, hemp, manila, and sisal carry over to spectra, as spectra has very different properties--it is very slippery and very hard, and my understanding is that when bent (i.e. subjected to tension when not straight) or flexed (i.e. bent back and forth cyclically) it loses strength much more than traditional fibers.

Somewhat related thoughts: The only life-support knot I have ever seen recommended for use with Spectra is the triple fisherman bend, so you can probably find Spectra-specific knot strength numbers for that knot. Spectra has an interesting failure mode with some knots (at least the double fisherman) where the sheath breaks at the knot and then the core slides out--the third turn supposedly keeps this from happening. I guess if you have only core and no sheath, it would just slide out. (Of course in sport use this would only occur in a major shockload.) In *Life On A Line, 2nd Edition*, Dave Merchant suggests that the figure nine on a bight might work as a loop knot on Spectra, if you needed something like that for a life support application. Given that we know that the triple fisherman bend works, I would think that the triple fisherman's eye (the endline loop version of the triple fisherman bend) would be the most likely endline loop to work. But then, like the triple fisherman bend, it would be impossible or almost impossible to untie.

[Jeff Bartlett]

Is there a US supplier for spectra at all? i know Expe has the 5mm Beal spectra cord (Black Diamond, the US supplier for Beal, says they don't carry it and won't order it). And I believe Expe and BU56 both sell the pre-made MTDE spectra footloops.

but MTDE doesn't make a "large opening" single footloop for use with one or both feet; they have a small single foot one (for use with a tibloc on the other foot) and a double-loop one (which seems like a waste). and either way, I'll have to bankrupt myself paying shipping on an order from Europe =)

[Tim White]

BlueWater carries 5MM TITAN CORD which is manufactured from Dyneema.

[Rick Brinkman]

I found spectra cord here:

Gossamer Gear - Spectra

[snoboy]

I'm dragging this thread out of retirement because I have recently seen a very clever solution to the OP's question.

There is a product by Sampson called Amsteel, other manufacturers have different names, but it is 100% spectra rope. It is a simlpe 12 strand braided cobnstruction. Available for an arm and a leg at your local yachting emporium.

The hollow core 12 strand is very easy to splice, and Sampson has detailed instructions on their site. Make sure you follow the Class 2 instructions.

What you want build is known as a whoopie sing - a fixed eye on one end (could be permanently attached to ascender if desired) and an adjustable eye onthe other... instructions in this PDF: http://www.samsonrope.com/site_files/12 ... e_2008.pdf

[barleywino]

another option would be to use a Wild Country Ropeman to make the foot sling adjustable. I see that the Ropeman 3 is rated down to 7.7mm cord so any use below that is strictly at the user's discretion (a large diameter biner may help for thinner cord). however it supposedly works for webbing as well as cord. I have used the ropeman 1 on cord thinner than the rated diameter to make my seat sling and foot sling adjustable and also to make an adjustable daisy. not a fan of the ropeman 2 which tends to snag the sheath more.

[Caver John]

Just thought I'd throw this up here, something I've been playin around with to make a double adjustable footloop.
Very easily adjustable and each footloop is independent. Using a wildcountry ropeman for the adjustment of the legloops.
That and the kong slyde make for a very adjustable setup!


http://i177.photobucket.com/albums/w226 ... 0cf01c.jpg

[chh]

I've used a whoopee sling as a foot loop, and just long nylong runners. I've used them at work when I was planning on using either the whoopee or the slings later in the climb for rigging, and all the better if they have more than one purpose as the footloops that don't serve double duty are just hanging around getting snagged on stuff after the access.
I will say this though, for caving I used to think I wanted an adjustable footloop. I tried a bunch of different ways of making one. I climbed around with several of these concoctions and I came back to just a plain old tied footloop. There will always be something "extra" with an adjustable set up, and in 100 percent of all the caving I've done, I've never had to use an adjustable footloop.
I think having your footloop removable IS worth doing though. I have removed my footloop from my upper ascender on numerous occassions to streamline things on an easy self belayed climb or hanging around at a lip. And if you tie your footloop with cord and some bowlines you will be able to untie it for something else in the VERY unlikely event that you would need to.
That's my 0.02