1. #1
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    Default Proper Prusik length for tandem prusiks?

    What is a good rule of thumb for the length of actual cord used to tie the two prusiks meant for use with a PMP.

    Also, what is the relative distance that should be between the PMP and the first prusik when not under tension>

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    60" and 72"
    Triple wrap fisherman knots
    Tied onto the rope with triple prusik knot
    This will keep the prusik pretty close to the pulley catching the load quickly

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    I'll probably upset someone but I have to say it anyway. I am not a prusik purist. Yes, I know. I sound like a heretic and I'm ok with that. I use prusiks for so many things besides belaying that only having 60" and 72" lengths hinders the versatility of them for me. My "standard" lengths are 6 ft and 10 ft. Tying the ends together with a double overhand/fisherman's bend [a triple overhand bend is very hard to untie after it has been loaded] gives me a lot of options. I use the shorter prusiks for a triple wrapped tandem prusik belay. Just make the tails a little longer on one so there is a couple inches difference in loop size.

    I don't use a PMP when I am using prusiks for belay. Testing conducted by several knowledgeable rope people (Reed Thorne, Arnor Larson and others) have had a couple of documented failures where the prusiks didn't catch the falling load. It typically happened during a raising operation. As the slack belay line was being pulled through the PMP (as designed), the prusiks loosened up enough so that when the main line failed in the test the prusiks did not work. This was exacerbated by the PMP which feeds the belay line into the prusiks in a straight line with no curve.

    I haven't heard of any failures outside of testing but it was enough for me to change our tandem prusik belay operations and eliminate the PMP. We mind the prusiks by hand which is a little more work but it puts a sharp bend in the belay line where it enters the prusiks greatly increasing the chance for a successful catch after a main line failure.

    Once the catch has been made, all the rope behind the prusiks is slack rope. Drop a PMP into the system on the slack rope, attach it to the anchor and then turn it into a z-rig with another pulley and short prusik cord.


    ▸ With a prusik I can tie doors open to keep them from closing behind me during a search of a building for fire victims.
    ▸ I can extend the size and speed up the search of the area by giving one side of the loop to my search partner.
    ▸ I can loop it under the victim's back and up through his arms and get help from my partner in dragging out the victim if they are not wearing clothes or have had them burned off.
    ▸ It fits easily in my bunker coat pocket and it doesn't weigh anything to speak of.
    ▸ I can tie doors shut to keep them from opening behind me in a building search for "bad guys".
    ▸ I can girth hitch (single wrapped prusik hitch) a fire hose, electric cord, air hose, etc., and tie them to a handrail to keep them from sliding back down the stairs or over the side of the structure.
    ▸ I can use it to secure tools, equipment or the patient's hands.
    ▸ I can use it to hold my pants up.
    ▸ I can slide the double fisherman's knots apart and use the space in between them as an emergency bridle to slip over the snout of a horse, cow, goat, pig, alligator (whatever you think you are tough enough to ride bareback) when I get tired of walking.
    ▸ If I get clumsy and drop it off the top of a 400 foot flare stack, I pick it up after I finish whatever I was doing (I only want to climb 400 feet of vertical caged ladder once per day), dust it off and put it back in service.
    ▸ You can use prusiks on a wider range of rope diameters
    ▸ You can also use prusiks on doubled ropes
    ▸ You can use them for very short rappels (firefighter survival techniques)
    ▸ They can be used for anchor slings
    ▸ They can be used for improvised litter spiders
    ▸ They can be used to make a chest harness, diaper seat harness, gear sling
    ▸ I can buy 10 feet of it for less than $5 so I can buy a lot of it compared to the cost of a mechanical ascender.
    ▸ I can use it as a strap wrench to loosen stuck nuts
    ▸ I can use it as a back scratcher

    I love prusiks, can you tell?

    Mike Dunn

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    Love your reply Mike.

    Length isn't the big issue. Color is. We all KNOW that if you use the wrong color the safety of the system may be fatally compromised. This applies double for webbing....

    Wrong color = you're gonna die!

    To the OP re: distance. A hand-width seems to work nicely (think wrapping your hand into a fist around the line - rope will be running across your palm thumb to pinkie). Mike's comment about the prusik wraps working loose is spot on. Be vigilant.

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    My rule of thumb is there is no rule of thumb. The spacing perscribed by MtnRsq works great, but the actual length to acheive that spacing will be dependant on the pulley and carbiner's your organization uses. 72" may work great for a CMI pulley by may be too long (or short) for a Rescue Technology pulley.

    To get the measurements tie one side of the fisherman's bend. This will allow you to easily pull the slack to change the prusik measurement as needed. Once you have the proper spacing finish the bend and mark the tails. Then you can get the final measurement and cut the cord as needed.

    Mike you need to take that show on the road; very entertaining read! BTW - Glad you pointed out the problem with pulling the belay rope back through a PMP. Another example of applying what sounds like a good idea at the time.

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    [QUOTE=jmatthe2; Mike you need to take that show on the road; very entertaining read! BTW - Glad you pointed out the problem with pulling the belay rope back through a PMP. Another example of applying what sounds like a good idea at the time.[/QUOTE]

    Actually, I do take that show on then road. I enjoy teaching but it gets frustrating teaching the same thing over and over to new generations of rescuers who have been taught by inbreeding. The critical information we have all learned, sometimes the hard way, isn't being passed on effectively.

    Having a PMP in place on the belay line works just fine.....IF......the person operating the belay is conscientious and paying attention and acting like someone's life depends on them doing the job right. Unfortunately, the person with the least amount of knowledge and experience often gets "stuck" on belay because it gets them out of the way of the "Real" rescuers. And besides, we only set up a belay line because that's expected of us now. We know we will never ever have to use it in real life. Attitudes like that are what perpetuate the problems I see regularly as I travel around the world teaching.

    It's the same problem with underwater rescue and recovery and RIT on the fireground. Who do you want as your back up diver? The most experienced person on the team or the least experienced? The same question goes for RIT. Who do you want backing you up?

    I'm a 2nd generation firefighter, began my career in 1967 and am still actively responding to calls. My father taught me a very important lesson that I have never forgotten. Never go inside a burning building until you know who is backing you up! That applies to any emergency scene.

    Don't let your knowledge leave with you when you retire. Pass it on!

    Mike
    Last edited by rsqman; 10-14-2013 at 08:53 AM.

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    Quote Originally Posted by MtnRsq View Post
    Love your reply Mike.

    Length isn't the big issue. Color is. We all KNOW that if you use the wrong color the safety of the system may be fatally compromised. This applies double for webbing....

    Wrong color = you're gonna die!
    Oh Damn MTN..... I'm using orange prusiks, white prusiks and yellow prusiks; dark blue, red, lime green, orange and purple webbing and red, blue, yellow, lime green, orange and American Flag colored main line ropes. Please don't tell me these are all Death colors......LOL

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    My rule of thumb is to just have 1 prusik about two inches longer than the other.

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    Quote Originally Posted by rsqman View Post
    Oh Damn MTN..... I'm using orange prusiks, white prusiks and yellow prusiks; dark blue, red, lime green, orange and purple webbing and red, blue, yellow, lime green, orange and American Flag colored main line ropes. Please don't tell me these are all Death colors......LOL
    You are definitely going to die with those colors! I'm surprised you haven't seen catastrophic failures every time you load the system

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    Quote Originally Posted by MtnRsq View Post
    You are definitely going to die with those colors! I'm surprised you haven't seen catastrophic failures every time you load the system
    I owe it all to fancy footwork and clean living.......or something like that.

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    Taught by inbreeding. Statement of the decade. Would you mind if I used that?

    Check out Tom Pendley's site, desert rescue research. It has videos of them doing Belay tests. If I remember correctly the first videos have the issue with the PMP, in place. In a recent RTR course I was in, they recommended no pulley for the belay.
    Last edited by rescue2emt; 10-15-2013 at 08:16 AM.

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    Quote Originally Posted by rescue2emt View Post
    Taught by inbreeding. Statement of the decade. Would you mind if I used that?
    You are more than welcome to use it as long as you understand the context of where I'm coming from with it.

    Back in the old days (mid to late 60s) when I was growing up in the fire service is when many fire departments started getting into rope rescue. Some used WWII civil defense techniques, which are still valid today when the major disaster hits and you have to build your own tripod, bipod, monopod, etc., Others looked around the country looking for people who used ropes a lot and found caving and mountain climbing groups. They would pick one firefighter and send him to a cave or mountain rope class. He was supposed to take good notes, learn everything the instructors knew and bring it back to his fire department where he became the "Rope Rescue Expert". Because he didn't remember or understand everything they did in the class his fire department got a condensed version, some of which was wrong.

    Soon he would be promoted out of training. Unfortunately, budgets were tight and the fire department couldn't afford to send another firefighter across the country taking rope classes so one of his students in the fire department would be named as the new rope rescue expert. He didn't remember or understand all that the 1st "expert" taught him so he only taught what he remembered. This has been repeated throughout the years and they got dumber and dumber and increasingly more dangerous.

    This is training by inbreeding. I still have students in my rope classes in 2013 that believe that the NFPA standards require you to destroy your ropes once they have been used one time for a rescue.

    You only need to do a quick search on YouTube for "Rope Rescue Training Gone Wrong" and watch the local rope rescue "experts" drop a TV news anchor and a litter tender off the top of the drill tower. It should have been a simple, safe, easy lower if they knew anything about rescue techniques. Instead it became a real life test of their belay system and they were very lucky that the belay worked and nobody died. Yet another example of training by inbreeding.

    Tight budgets are just an excuse we like to fall back on. Great rope rescue information is widely available in books and on the internet and most of it is FREE. It only requires you to devote some time and effort to learning new techniques and equipment. If a brake bar rack and a tandem prusik belay is all your dept can afford then become very proficient with it. If money becomes available to buy an MPD, for example, then you should know how to use it long before it is purchased. The FREE information on how to use it safely is out there. Join forums like this one and ask questions. Someone will likely have experience in that subject and be able to willingly help you out.....for FREE.

    Training by inbreeding....Don't be that guy!

    Mike

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    We use 53" and 67" lengths of cordage to tie a set of prusiks. Double fisherman's, and triple wrapped. Leaves very little room (a good thing) when using a full sized PMP, about a thumb's width (ha,ha, rule of thumb).
    ~Drew
    Firefighter/EMT/Technical Rescue
    USAR TF Rescue Specialist

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