Load release Hitches

[MichaelXYZ]

At work we use a CMC load release strap. For self training I try to duplicate what we use at work with my own equipment. I read using webbing for load release hitch is very dangerous as the webbing can fuse, (citation: Rope Tech I and II by Jeff Mathews).

So my question is this, is it okay to make a mariner using prusik cord? If so, how long should it be?
I already made a radium release hitch but the mariner is close to what we use at work.

Thanks

[Lewiston2FF]

No, cant make a Mariner with Prussik cord. Cordage is used in Radium releases hitches and BC Hitches. The mariners is made from strapping. I too have heard that webbing will fuse if used to make a mariners but that would only be if you loaded it. It shouldnt fuse on its own while practicing rigging the mariners.

[MichaelXYZ]

What I don't get about the Radium, is why the cordage is 30 feet long? Were just releasing a load, right?

[rsqman]

What I don't get about the Radium, is why the cordage is 30 feet long? Were just releasing a load, right?

It's 30 feet long because one of the potential uses is to pass a knot in the system.

[ADSNWFLD]

Here we use a LRH called a Larson Hitch, it uses 35' of 8mm cord. The main benifit is it releases well beyond a knot in the system or whatever.
Start with the middle of the cord on a carabiner or delta then the double cord makes a Munter hitch, on a second delta, run the legs back to the first delta and cross them, then wrap about 4 or 5 times then daisey chain the rest and tie the ends with a tripple wrap fisherman. secure with a carabiner to the delta to store the end. When done you count the cords to make sure it is correct. It should be 3-4-3 on the three carabiners
When extended the hitch is almost 8' long

[Rescue 2 Training]

Here we use a LRH called a Larson Hitch, it uses 35' of 8mm cord. The main benifit is it releases well beyond a knot in the system or whatever.
Start with the middle of the cord on a carabiner or delta then the double cord makes a Munter hitch, on a second delta, run the legs back to the first delta and cross them, then wrap about 4 or 5 times then daisey chain the rest and tie the ends with a tripple wrap fisherman. secure with a carabiner to the delta to store the end. When done you count the cords to make sure it is correct. It should be 3-4-3 on the three carabiners
When extended the hitch is almost 8' long

That sounds more like a Hokie Hitch or something, but it does not sound like you are tying a Larson load releasing hitch.

Here is a link with pictures on how to tie a Larson and a Radium. I'm sure there are better tutorials out there, this was just from a quick google search.
http://www.firedistrict13.com/traini...Rescue/LRH.htm

I'm not sure how wise it is to tie an overhand knot in the tail of the bight in the Radium as the directions show. I'm pretty sure that it would jam against the half hitches if the hitch were shock loaded.

The benefit of a Radium is that it is easier to learn, tie, inspect, and reset during use than the Larson.

[ADSNWFLD]

Based on the link it looks like a cross between the LRH and Radium.
The hitch we call a Larson starts the same as the LRH but after the Munter the two lines run to the opposite carabiner. The lines cross so in the event of a mistake by the rescuer the hitch can not drop the load (the fisherman knot will stop at the carabiner)
There is more then one way to do most rope work, most of our systems rely on back ups that prevent the rescuer from falling in the event of a personnel failure (passes the whistle test)

[EricUlner]

Based on the link it looks like a cross between the LRH and Radium.
The hitch we call a Larson starts the same as the LRH but after the Munter the two lines run to the opposite carabiner. The lines cross so in the event of a mistake by the rescuer the hitch can not drop the load (the fisherman knot will stop at the carabiner)
There is more then one way to do most rope work, most of our systems rely on back ups that prevent the rescuer from falling in the event of a personnel failure (passes the whistle test)

I don't see the logic in worrying about having an LRH pass the whistle test, when the very rack (that many teams use) on the main doesn't (assuming you're talking about the main).

As for the whistle test, the idea is to have a system that passes it. The belay (tandem Prusiks, I'D, etc.) accounts for this.

Anyway, if you've a set-of-fours handy (AZTEK), you can skip the LRH in the first place.

[TRT24]

Anyway, if you've a set-of-fours handy (AZTEK), you can skip the LRH in the first place.

You don't even need the set-of-fours, with an extra pulley and Prussik, you can turn your TWTP belay into a 3:1 to break the Prussiks.

[EricUlner]

You don't even need the set-of-fours, with an extra pulley and Prussik, you can turn your TWTP belay into a 3:1 to break the Prussiks.

Yes, although my point was only a "for instance" and was not made as an exclusive. Always options, the simplest probably being to just vector the main.

[MichaelXYZ]

Just curious, why is cordage not good for a Mariner?

[Rescue 2 Training]

I would suspect that there is not enough friction from the strands of cordage running over each other. That said, testing has shown that a mariner's with webbing can have too much friction and fuse some of the strands of webbing together.

Also, I'm not even sure that the illustration you posted is actually even a mariner's. While it might work to transfer the tension of a single person load. I'm guessing that it doesn't pass the BCCTR Belay Competency Drop Test. The gold standard for belay devices and their associated load release hitches.

[jdcalamia]

Looks lie a half-assed version of a BC and Hoakie Hitch. Parts of both, but not complete. Also no munter, which lends to less friction when letting it out.

[MichaelXYZ]

This you tube shows the knot as above. http://www.youtube.com/watch?v=6PSlFodqGJs
Did not realize I was doing it wrong all this time. I would not think a munter would work to well with webbing. I guess I will have to do more reading on the Mariner.

Thanks

[Rescue 2 Training]

While I don't use a Mariners, this is how I know to tie it. There is no Munter in it.

[jdcalamia]

If I'm going to use one, it's most likely a 3:1 RRH. Quick and easy to tie. Anymore though I'm using the ID or MPD, so much easier. Like Eric said a set of fours should be a staple just in case.

[MichaelXYZ]

The MPD would be nice, but I don't think our Dept is willing to fork out $650. per pop.

[FiremanLyman]

If I'm going to use one, it's most likely a 3:1 RRH. Quick and easy to tie. Anymore though I'm using the ID or MPD, so much easier. Like Eric said a set of fours should be a staple just in case.

We stopped carrying the Mariner's hitch all together, using a radium or a jigger (mini block and tackle, don't know if "jigger" is a national term) in our systems for transfering loads. Our TTPB always has a radium in it.

[MichaelXYZ]

We stopped carrying the Mariner's hitch all together, using a radium or a jigger (mini block and tackle, don't know if "jigger" is a national term) in our systems for transfering loads. Our TTPB always has a radium in it.

Do you know the reasons for this? Just wondering the thinking for the switch. Our training officer seems pretty confident using the mariner.
After all, a RPM system is defined as Rack, Pulley, Mariner.

[jdcalamia]

I can't speak for Drew, but the popular reason seems to be the results of the BCCTR Belay Competency testing. Potential for fusing under shock-load. It is slightly more equipment intensive (3 carabiners instead of 2). Could be an issue for some areas. The RPM comes from out west, California I believe. Anymore when I teach I just replace the "M" with an "L" for load releasing hitch. No need to limit everyone's options simply by using an acronym. The basics are essential to know, but with modern technology and innovations, if you can't afford the MPD the Petzl ID is a less expensive more viable option. If I remember correctly, the BC and the Radium scored the best in all 9 areas examined out of the 30 (34?) some LRHs tested. If you have to use an LRH instead, use one of these, they have proven themselves. Also, since you are newer in your career don't get caught up in thing such as acronyms and one way of doing things. That's the beauty of technical rescue, there are many acceptable ways to accomplish the same task. You're doing the right thing by throwing your thoughts out here, this place is full of great educated and experienced members willing to share their expertise!