non-mechanical rope grab, 3/4" stable braid?

[Ghillie]

Any suggestions on a rope grab for 3/4" stable braid? Used on at least 3:1 mech. advantage.

Sizes and what hitch?

I am trying to get set-up on a new porty to "winch"/pre-tension rigging lines, I have some ideas but want a fresh set of eyes and experience.

Fred

 

[Ghillie]

Standard 3-wrap prusik it is.

Does anybody use a 3:1 or 5:1 to take the slack out of rigging lines while using a porty?

 

[Bermie]

I use a 'Z rig' on my 9/16" stable braid to pre tension a pulling rope. It gives me 3:1.

Two lengths of 10mm braided prussic cord, I use distel hitches, and two pulleys allows you to take up a lot of slack and not have it run back when you let go.
It is also adjustable during the pull if you need to take more slack.
If you search Z rig there has been some discussion on it, not sure if it is entirely suitable for what you want to do, using a porty?

 

[treemandan]

Pics? what are you trying to accomplish? A brake/ safety catch? or something to bite and pull?

 

[Ghillie]

Pics? what are you trying to accomplish? A brake/ safety catch? or something to bite and pull?

This is a picture out of the port-a-wrap instructions.

I want to replace the mechanical ascender with a friction hitch (rope grab).

I don't have the 3/4" stable braid as of yet, so when I buy the rigging rope, I was going to purchase cord or rope of the appropriate size to attach this system to take the slack out of the line once everything else is set.

 

[Ghillie]

I use a 'Z rig' on my 9/16" stable braid to pre tension a pulling rope. It gives me 3:1.

Two lengths of 10mm braided prussic cord, I use distel hitches, and two pulleys allows you to take up a lot of slack and not have it run back when you let go.
It is also adjustable during the pull if you need to take more slack.
If you search Z rig there has been some discussion on it, not sure if it is entirely suitable for what you want to do, using a porty?

Thanks Bermie, that gives me an idea of what I need.

I am familiar with z-rigs, just never attached one to anything bigger than 1/2" static kernmantle.

I have 11mm dynamic kernmantle that I think I will try before I purchase anything else.

I have never used a distel hitch (in fact I'm going to look it up after this posts). Why do you use this over the a standard prusik hitch?

 

[Slvrmple72]

Ghillie, to answer your question the distel hitch tends itself more easily then a regular prusik. If you set it up with a pulley with cheek plates when the rope is tensioned the distel will break free more easily when it gets pulled into the cheek plates and then like the regular prusik it will grab hold of the line when you stop pulling on it. With enough pulleys and prusik knots you can set up some incredible mech. adv. Next step would be something like a hobbs or grcs. I use a prusik on my flipline and a distel on my climbing line. The distel is so much easier. IMO better than the Blakes Hitch and very much like the Michoacan/Martin hitch. What are you working on? Inquiring minds want to know.-Kevin

 

[Ghillie]

Kevin, not really working on anything specific. Just outfitting myself to be able to handle a a variety of scenarios.

Last year I tried out a partnership with a well established business in the area. I mainly worked with a boom truck and aerial. We did use a Hobbs a couple of times.

Long story short, I decided against a partnership with anyone.

Now, I am expanding my own capabilities without draining the bank account.

I would love to have a Hobbs or GRCS but the portawrap with a piggybacked mech. adv. system seemed the best bang for my buck.

I want to be able to take as much slack out of the rigging when blocking down on removals and be able to lift around 1000# if absolutely needed.

I guess I should have gone into more detail in my first post. I was interested in finding out from those who have used 3/4" rigging what their preferred hitch was, what cordage they used and anything else they have learned from experience.

I was also wondering at what point hitches (such as the distel) would slip on the host rope, ie. your 5:1 mech. adv. with one ground worker should be able to produce 1000# of pull. Would the distel tied with 11mm on 3/4" stable braid slip before all of that pull was transfered to the host rope?

I know what I am picturing in my head is not translating well.

I know that tandem 8mm prusiks will slip at around 1000# on 1/2" static kernmantle. A Gibb's or similar mechanical rope grab will desheath the same rope at around 1500#. Using prusiks in that situation is a safety measure so that you don't overload the syatem and cause failure. Kind of acts like a shock absorber.

With the increase WLL of the 3/4" rope and other components, I want to be able to take full advantage of the capabilities of pulleys and mech. advantage.

Back to your post, so you are saying the distel doesn't need to be tended as much as the prusik as far as dressing and setting and it releases easier after loading?

Fred

 

[Norwayclimber]

How about trying what we in norwegian call a "french prussik". It's easy to place, and it can be released while tensioned. Backsides are that it's not quite as stable as a normal prussik, and you will have to make adjustments to the prussikcord in length and wraps to optimize it's function.

 

[Bermie]

Ghillie, to answer your question the distel hitch tends itself more easily then a regular prusik. If you set it up with a pulley with cheek plates when the rope is tensioned the distel will break free more easily when it gets pulled into the cheek plates and then like the regular prusik it will grab hold of the line when you stop pulling on it. With enough pulleys and prusik knots you can set up some incredible mech. adv. Next step would be something like a hobbs or grcs. I use a prusik on my flipline and a distel on my climbing line. The distel is so much easier. IMO better than the Blakes Hitch and very much like the Michoacan/Martin hitch. What are you working on? Inquiring minds want to know.-Kevin

What he said! Very easy to tend with the pulleys
I don't use a prussik anywhere in my setups, I have found the distel and VT much better.

 

[Ghillie]

Thanks guys and gal, I will have to give those hitches a try.

Is there "rule of thumb" on what ration cordage to host rope that grips best?

From Bermie's example 10mm on 14mm (9/16") = 71%

From my example 8mm on 12.5mm = 64%

So I would want to try cordage in the 60-70% range of my host rope?

 

[TheTreeSpyder]

Something that seats well, is strong enough for purpose, and can take some heat. Generally might go more polyester(for less stretch), dbl. braid (or high tech) for strength, 2 sizes smaller than host line at least. these will have 2 bent legs to the host load line's single straight.

Prussiks are fair. i've climbed up and rode a 5x1 down some, then reached in and maid it an 8x1 to finish. Also pushed up cams and prussiks with bladeless polesaw etc. especially when couldn't get Porty set real low. A few times, we mounted a block where Porty would go and Porty on another close by low anchor. Then, you can extend rig far (horizontally across yard), but can't get as much bodyWeight into the multiplier of the rig.

For, lighter lifting and control we'd do the horizontal rig above or we've even mounted Porty to truck, lifted, then chocked truck and lowered load. Here a low block is good too, so that as truck pulls, it's rear end doesn't get 'lighter' from the upward angle to higher load support. If the load is too much for prussik, lift with non prussik line, lower with other line.

 

[Ghillie]

I had considered the low block and horizontal pull to facilitate longer travel of the mech. advantage rig, but I hadn't considered using the truck as an anchor or to lift with. That broadens my possibilities.

I agree with nylon (dynamic kernmantle) not being the most ideal. That was kind of the underlying question to my original post. Appreciate the input on everything.

 

[TheTreeSpyder]

Of curse we could get into trouble with truck like that, and lifting usually implies less shock loading than just as an anchor. The extra line to truck does give some more dampening though. 1 Ton truck on solid ground with weight in back (for traction) pulling a 3:1 rig, gives some power!