Rigging a hammock with constrictor ropes (UCR's)...

[ZA206]

Hey, TeeDee --

Thanks a lot for the kind words, but especially for the update on your system. Your article is what got me started on this line of experimenting, so we've got the makings of an infinite loop here.

It dawned on me today that there has to be tension on both ends of the outer, constricting, section -- at least for this slippery line. ZA206's UCR experience suggests the other approach can certainly work if the line's coefficient of friction is high enough. I really wish that approach had worked for me, because it would have required less line overall.

Side note - I wonder how friction hitches would hold with an underlayment of thin rubber, e.g., a piece of inner tube from a bike tire.

Cool stuff; the beat goes on...

Chuck

Yea Chuck.... that's the only downside of the Whoopie arrangement is all the extra rope involved. I was able to develop and test the UCR's for my original application and they work fine for that b/c there is a different loading arrangement on the contstrictor section when used with climbing sticks. As you found out though, in a setup like hammock suspension, the first 6"-8" of the constrictor is the only part of the constrictor that "bites" into the static line. Since I use 1/4" rope, it was do-able with a simple back locking half hitch... I never got any movement. When used with climbing sticks, there is no need for the locking half hitch, as the tree itself compresses into the constrictor and makes the entire constrictor bite into the static line. Wierd how it turned out working like that, but it did.

I think you guys are on the right track with the skinny Amsteel and a whoopie arrangement. I'm getting ready to order a Clark NX250 and will probably rework it's suspension with a whoopie, a beener and a hugger on each end. That will be secure and lightweight.

FYI... all the eye loops on my UCR's are locked Brummels b/c I needed the low load stability of the eye loop for my UCR's. I also think the locked brummels looked alot better and gave a more finished and professional look.

-ZA

[Frawg]

ZA, thanks again for originating this thread, and to Acer for suggesting the whoopie sling. It was the last 'letter' I needed in the alphabet soup of ideas I've picked up here from Risk, Jeff, TeeDee, HC4U, Grizz, et al. I'm finally on a track that suits me.

Best,

Chuck

[PuckerFactor]

No problem! I'd say we're the pioneers of the best ultralight suspension system, and we'll start seeing a lot of people picking up on it. Maybe?... *crickets chirping* Now that I've dialed in on what I want in a hammock, it's time to start sewing!

Later,
Acer

[TiredFeet]

Thanks for the informative post. I read somewhere else on the web that the strength of splices comes from the buried portion. One series of posts I read somewhere, one person tested various splices with and without the bury and confirmed that. He also learned something else that was interesting: when burying the end, e.g., for an eye splice, taper the end. In his experiments the rope always broke at the end of the bury when the end hadn't been tapered. He theorized that the abrupt change in diameter at the non-tapered end weakened the rope at that point. He also pointed out that Brian Toss has been saying what you said below, that the strength comes from the bury.

The "brummell" is a type of splice that uses a bury. The buried section is called the "bury". The strength of all of these "bury" type splices is in the buried portion. Other things like whipping, sewing, weaving (brummel), or locked brummell are only to improve the low load characteristics of the splice.

Brummell and locked brummell are two different types of splices. Many people argue over terminology, they also argue over the strength. Check out forester sites or rigger sites, plenty of debate. These are the descriptions I use, but others argue.

Locked brummell - strength is in the bury, not in the locked part. This splice is NOT as strong as a plain buried splice. It looks like it is stronger but it is not.
http://www.neropes.com/SPL_12Strand_...ceBrummel.aspx

An easier method if you have both ends available is to put the working part through the standing part, then the standing part through the working part, bury the working part, like in the Samson directions for a Whoopie Sling.

Brummell -Strength is still in the bury
This is the one most of you are familiar with. Weave the working end through the standing part 2 or 3 times then bury the working end. Samson and others have good directions on this type. Usually just called a 12 strand eye splice.

A properly done 12 strand Class II (spectra/dyneema) eye splice retains 97% or better of the line rating, provided proper taper, bury length (72 diameters)etc. Brummells may fail at high load.

Reality is: 1/8 spectra is good for 2000#, 7/64" a little less, you can/should use a locked brummell and be fine. I use locked brummells almost exclusively on sailboat rigging because I need the low load performance more than the true rating of the line. Unless you are hanging at VERY little sag, you'll never get close to the breaking limit on the line.

You all and a little trig taught me: A 30 degree angle doubles the Tension on the line. In other words, if you weigh 200#, there is 200# in each line because there are 2 lines. Steeper angles mean less tension, more horizontal mean a lot more tension. Tension=1/2 Weight/sin(hanging angle off horizontal)

[nacra533]

E.g., I'm curious about the wear characteristics. I've noticed my line getting a little fuzzy; how long will it maintain its strength, and are there any telltale danger signals to look for? Thanks again for chiming in!

Cheers,

Chuck

Wear characteristics... Depends on application. Spectra and dyneema will fuzz a little, especially as UV starts to degrade them. It is normal, but each little piece of fuzz is a broken strand. My normal application is much different. Ex. If a line on a boat breaks, I come in last (or more last than normal) in the race. If a hammock line breaks, you fall. Spectra does very well with chafe and UV resistance. Many of my lines stay exposed to the sun for at least year or more. They also see loading more close to their rating combined with chafing from running through blocks under high load. For example, the 1/8" Amsteel downhaul can see up to 1500# if you really crank on it with a 16:1 purchase. A good line inspection prior to each hang in is called for. If you notice significant degradation or wear, replace it. A little fuzzy is obviously some level of degradation/wear because it was not made fuzzy to start with. A lot of words to say if you use common sense and are conservative, you should be fine. Spectra is the cheapest line I purchase and is so easy to splice, I don't think twice about changing it out and I buy it 100'+ at time. (Some of the lines can go in the $2.50 / foot range.)

[nacra533]

... In his experiments the rope always broke at the end of the bury when the end hadn't been tapered. He theorized that the abrupt change in diameter at the non-tapered end weakened the rope at that point...

Exactly. That is where the stress is concentrated. If you dig a little deeper; in the eye, the load is 1/2 because it is shared by both halves of the eye. In the bury the load is carried by a section with double the diameter (line in a line)... At the transition between bury and single line you have a shrinking diameter and full load. If not tapered, you have an abrupt diamter change and full load which concentrates the stress.

...He also pointed out that Brian Toss has been saying what you said below, that the strength comes from the bury.

I said it BECAUSE Brion Toss said it. He is a well known expert rigger.

I am not a professional rigger, but have devloped some understanding and skills using info from Toss and many other riggers and arborists/foresters.

[Frawg]

Wear characteristics... Depends on application. Spectra and dyneema will fuzz a little, especially ...

Thanks for taking the time to post all of that. That's just the sort of info I was looking for -- good facts with some insight added. I've got more line on order now so I can start with a fresh setup; sounds like it should be good for several months, if not a year or more.

Cheers!
Chuck

[TeeDee]

...

I said it BECAUSE Brion Toss said it. He is a well known expert rigger.

..

Didn't mean any insult or anything. I was just trying to reinforce what you wrote.

[nacra533]

Didn't mean any insult or anything. I was just trying to reinforce what you wrote.

I didn't take it that way. I should have been more clear. I was trying make sure I gave Toss the credit he deserves because much of what I have learned, I picked up from books or articles he has written or posts he has made on his forum. In other words, I am merely a parrot, repeating techniques that others more experienced than I have developed.

No worries.

[Frawg]

I wanted to follow up in this thread some results I've reported in the Toggled Suspension System thread.

In a nutshell, I was able to make a working UCR using 7/64 AmSteel Blue.

I did three things that make a difference:

• use a longer bury (I'll be making them 6 fids long from now on),
• lengthen the running end of the constrictor section, and
• use that extra bit of line to tie a slippery half hitch over the standing part of the static line.

This adds friction to the constrictor section and the slippery half hitch acts like a drag instead of a stopper.

ZA, thanks again for offering this bit of design. My hopes have now been realized.

Chuck