PMI Multi Strap

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Re: PMI Multi Strap

Postby NZcaver » Jul 18, 2010 4:01 pm

Nice work. I particularly love your "BFK" :clap:

I'm going to have to tie myself one of these to play with. Or buy one. I'm guessing the smooth-surface Bluewater webbing I have won't work as well as the ribbed stuff.
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Re: PMI Multi Strap

Postby chh » Jul 18, 2010 5:40 pm

doesnt' seem to matter nz. I use smoother tubular webbing and it grabs just fine.
Still can't figure out how to keep the load strands from crossing directions in the multi-strap configuration though. I'd really like to see one.

edit:
Instead of Snoboy's BFK, I just tied a frost knot and put one carabiner in the small loop and clipped the big loop to it. Same deal as the rap ring with a little bit of a smaller profile. I also played around with clipping a biner into and tying a rap ring into the knot. Having the rap ring tied into the small loop above the frost knot didn't seem to work quite as well because my rap ring is small and so it sat right on the knot which caused a little extra friction. Though tying it into the frost knot seemed to work fine. Two biners seems to be the way to go though. Everybody has a length of webbing and two biners lying around :grin:

Also, there is a problem with this set up that we haven't really discussed, but in my mind doesn't really make it a substitute for a jigger and that is that it doesn't really release smoothly. It is, essentially, a one way deal.
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Re: PMI Multi Strap

Postby snoboy » Jul 18, 2010 11:47 pm

NZCaver - mine is tied with nice soft smooth new webbing and seems to work fine.

chh - Sounds like you and I were doing the same things at the same time... I tried the Frost knot variation with the ring and with a carabiner. I also ended up with a similar version with a double length spectra sling, tie a loop in one end, and clip two carabiners to it. The spectra seems to grip fine. I have hung myself from it now, and am able to easily lift myself up if I hang it with the ring at the bottom so I am pulling down. I think that might actually be a usable configuration to make up out of stuff you might have along.

I have the same issue with it being a one way deal, but probably good for some situations. I don't think I would want to use it as a litter tender attachment though. Or a litter bridle. If you don't tie it off, it seems to me to rely too much on the exact placement of the webbing, and I don't think I would trust that in a dynamic situation. For rescue use, it seems a bit too single purpose for me to carry in our kit.

For a pickoff I think I would use it "upside down," you would only get 3:1, but you would be pulling down.

Note the position of the stitched part of the sling - that seems to give maximum travel to the system. I measured 45 cm of lift, from 60 cm to 15 cm, not counting carabiners.

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Re: PMI Multi Strap

Postby chh » Jul 19, 2010 12:13 pm

snoboy wrote:chh - Sounds like you and I were doing the same things at the same time... I tried the Frost knot variation with the ring and with a carabiner. I also ended up with a similar version with a double length spectra sling, tie a loop in one end, and clip two carabiners to it. The spectra seems to grip fine. I have hung myself from it now, and am able to easily lift myself up if I hang it with the ring at the bottom so I am pulling down. I think that might actually be a usable configuration to make up out of stuff you might have along.


I tried the spectra version as well, and allthough it worked it seemed even less reliable if there was a sudden shift in weight on the sling. I felt I had to be much more precise about how everything got positioned with the spectra. I think the regular 1" webbing is actually more stable.

snoboy wrote:
For a pickoff I think I would use it "upside down," you would only get 3:1, but you would be pulling down.


I agree.
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Re: PMI Multi Strap

Postby sherppa » Jul 19, 2010 7:02 pm

chh wrote:Sherppa,
So tell me if I have this imagined correctly. There's the "dogbone" or stiched portion of the multi strap. A bight exits this portion, makes a loop and goes to the ring which is also stitched into the dogbone. That's it right?

chh, the design is simple, but it´s difficult to me to explain. Definitely I need to take some pics, but my bad, I´m out of town. I found another pic where you can see the stitched portion in a better view (and there is view of the end of the webbing attached to the black binner. There´s nothing more between). Can you see the black tape stitched to the orange tape? Is just a sign to let you know what portion (and direction) of the webbing you need to pull as a pick off strap. In this exercise, the "dogbone" is attached to the rescuer´s harness. The end of the strap is attached to the victim´s harness, so you need to pull up. The multi-strap is not long enough (+ 3 ft as a pick-off starp) to attach it to the rope (above you) and pull down.

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Image

:)
P.S I know, the guy is not wearing helmet :rant:
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Re: PMI Multi Strap

Postby Scott McCrea » Jul 19, 2010 7:36 pm

He's also cross-loading his rack biner. :tonguecheek: :laughing:
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Re: PMI Multi Strap

Postby sherppa » Jul 19, 2010 7:51 pm

Scott McCrea wrote:He's also cross-loading his rack biner. :tonguecheek: :laughing:

:oops:
well... with "general use" rated binners (> 40kN) ... ok, ok :big grin:
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Re: PMI Multi Strap

Postby chh » Jul 20, 2010 9:24 am

Cool sherppa, thanks for the additional photos. I sort of figured out the answer to my question. The strands cross at the load carabiner on the multistrap, because the load carabiner redirects the pull. I'm abe to get all the strands of webbing to move in the same direction when tensioning the webbing in my slack line because everything is linear. This wouldn't be appropriate for a pick of strap or other such tool without a seperate back up because there is a free end in the equation. I presume PMI made it a closed system to address this issue. Even if the advantage slips because the strand with the black tab slips out, you're still attached to a burly loop. Not so with the linear system. Or at least, not so without some stitching.

Also, I would think 3 feet would be enough to rig the multi strap to pull down, but this very much depends on the way you are performing the pick off. With how I learned to do a pick off you always pull down because this gives you the best use of your body weight to assist you in lifting the load. A counterbalance method I'm sure you know. But this is light and fast small party rescue. I'm not a professional.
And this is also assuming you can physically get NEXT to the person you are picking off. If you can't because the space is too confined and can't haul on the line they are attached to or just install a seperate haul line, I could see how a tool like the multi strap or a jigger might come in handy. Or if you are an extremely light individual picking a heavy individual off a single rope.
As far as the length goes. I honestly just grabbed the 20 feet of webbing and 3 lockers that live in my cave pack. This gives you +4.5 feet as a pick off strap with anything shorter as easy as tying the knot in a different place and minding the tail.
It's neat to add another use to the 101 for the webbing and lockers. Thanks for bringing the multi strap up. I don't think I'm clever enough to have figured that out on my own. :kewl:
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Re: PMI Multi Strap

Postby chh » Jul 20, 2010 9:52 am

Once again my pea brain couldn't grasp a simple concept.. :doh:

It IS possible to get the 2 strands on the load carabiner to travel in the same direction with the multi strap. You just have to do something a little different. You don't just drop the load carabiner into the loop formed by the 2 strands exiting the dogbone and just pull on the bottom strap. This creates the "redirect" scenario.
As soon as I figure out how to explain it without confusion I'll post that up.
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Re: PMI Multi Strap

Postby sherppa » Jul 20, 2010 5:09 pm

chh wrote:Even if the advantage slips because the strand with the black tab slips out, you're still attached to a burly loop.

exactly

chh wrote:Also, I would think 3 feet would be enough to rig the multi strap to pull down, but this very much depends on the way you are performing the pick off. With how I learned to do a pick off you always pull down because this gives you the best use of your body weight to assist you in lifting the load. A counterbalance method I'm sure you know.

yes, I agree that there are many ways to perform a pick-off. Attaching a MA system above the victim to pull down will be a better option than pull up as you said (pic 1) or even better, using a telescoping pole to attach the victim and make all the maneuvers from the top (pic 2 and 3), etc. In this particular case, in the excercise the student has to demonstrate the skill to pick off a hanging victim attaching the pick off strap to his harness, that´s why I think that pull down is not an option. The usual strap to perform this excercise has just a MA 2:1 ( http://www.cmcrescue.com/product.php?dept_id=1252 ), so, having a MA 4:1, the multi-strap working in the same way coud be a better option.

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Re: PMI Multi Strap

Postby chh » Jul 20, 2010 7:49 pm

You guys sure do have a lot of toys sherppa! I've used a telescoping pole with a squid (sp?) attachment before. I didn't like it much and ended up just using some judiciously applied athletic tape I had in my bag. In lieu of a pole I've also used tent poles and plain old sticks off the ground :laughing: .

As far as the multi strap goes, in order to get the strands on the load carabiner to move in the same direction you just have to turn and twist the inside loop. This puts a twist in the leg you pull to tighten it, but since it's just slack I don't think it matters much. In fact, having these two loops move in the same direction may not matter much. I don't know that it would improve the MA in any perceivable way. It's just a hunch.

Got me thinking about other commercially made pick off straps. Is there a regular 2:1 that you can think of that allows you to lower in a controlled way without using a counterbalance? This has got me thinking thinking about how to make one of those out of what I normally carry in my cave pack.
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Re: PMI Multi Strap

Postby NZcaver » Aug 13, 2010 6:42 pm

Confessions of a Gear Junkie....

OK, I had a weak moment in the IMO store at Convention and walked out a shiny new PMI Multi Strap. :oops:

:banana_yay:
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Re: PMI Multi Strap

Postby Stridergdm » Aug 15, 2010 10:37 pm

NZcaver wrote:Confessions of a Gear Junkie....

OK, I had a weak moment in the IMO store at Convention and walked out a shiny new PMI Multi Strap. :oops:

:banana_yay:


You have a lot of weak moments. :woohoo:
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Re: PMI Multi Strap

Postby cavedoc » Aug 16, 2010 7:20 pm

NZcaver wrote:Confessions of a Gear Junkie....

OK, I had a weak moment in the IMO store at Convention and walked out a shiny new PMI Multi Strap. :oops:

:banana_yay:


And????????

C'mon Jansen, what have you done with it? Is it really better than a pick-off strap?
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Re: PMI Multi Strap

Postby NZcaver » Aug 17, 2010 12:13 am

It seems to work well with me laying on the couch in my living room. I can "pick off" my big toe with it rather effectively. :laughing:

No, I haven't been on rope since I got it. I think the apartment complex people would take a dim view of me rigging to things around here. :shhh: But there is a vertical practice scheduled for early next month, so I hope to play more with it then. Perhaps sooner if I can find another vertical caver type person around here who wants to take a ride up into the mountains.
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