Why spectra for bridge hammock suspension?
I'm starting to thing I need to dive in an make myself a bridge hammock. I've been reading some of the tutorials and posts and spectra seems to be very popular for suspension. My question is why?
I have some of the 2.8mm spyderline from west marine, I know it has a stiff hand and really holds knots. Where as my single braid dyneema is a little limper and kind of slick. I'm guessing vectran would be even more so but haven't handled any to know first hand.
Of course having purchased both of these I also know how much less expensive the spyderline is and any of the dyneema single braids.
So the question is, does spectra enjoy the popularity it does because of its physical properties or its price?
Quick answer: Both.
Originally Posted by Merganser
Have used Spyderline and still have a couple hundred feet. Use it for some tasks, but given a choice between a double braid and a single braid, I'll pick the single braid.
Also, if you want to try/use the new spliced suspension methods using the UCR or the whoopie sling, single braid is sooooooooo much easier.
Now there are places where the polyester sheath of the double braid Spyderline is the best choice - namely those situations where the abrasion is a real problem.
For the suspension, abrasion isn't really a problem with the right suspension so the the polyester sheath isn't really necessary.
Also, when taking the hammock down, I want the suspension ropes to make the smallest bundle possible. That dictates single braid. The double braid Spyderline is just to rigid to yield the smallest bundle.
Also, as regards the spectra/dyneema vs vectran debate: We have both and like both for the right situation. I like the almost zero creep of the vectran. But the susceptibility of vectran to abrasion is really bad. I like the small Figure 9s for the tarp ridge line and the vectran is showing very serious abrasion after only 2 or 3 uses. This was true with knots also and I was hoping that it would be better with the Figure 9s. For this reason we are phasing out our use of vectran and staying with dyneema.
I'll just mostly echo what TiredFeet said, although my use of Vectrus doesn't involve Figure-9's or most knots for that matter (marlin spike hitch, and now UCR or whoopie sling at which it excels). Exceptions are the bowline and sheetbend but the bowline is not tied/un-tied nor is the sheetbend in my use, and I've not noticed any abrasion there, or where the loop of the bowline drops over a marlinspike hitch toggle.
The price differential between spyderline and Vectrus is approximately a factor of two, and the Vectrus is stronger by approximately a factor of two also. With no creep, and a much better strength around small radii (or so the vendors claim...) My finances are fortunately flexible enough so that a price difference of $0.25/ft for the 25 feet or so that I use for a hammock's suspension doesn't factor into the decision.
But the right tool for the right job. The vectrus doesn't hold some useful knots under tension---the alpine butterfly for example. It seems to do best when hitched in some way, or not tied at all, as in the UCR and whoopie slings.
my $0.05 for what it is worth
Last edited by GrizzlyAdams; 08-16-2009 at 22:13.
This whole whoopie sling thing is new to me. It looks pretty slick. I would seem to me though that you'd limit your range (by about half) over using an SMC ring because the position of the adjustment is fixed whereas with the SMC ring its movable. Am I right about this or am I misinterpreting how this is used?
Assuming the same length of cord used for the two suspensions, yes, that's correct. At its maximum extension, the whoopie sling gives you slightly less than 1/2 the length of the cord, because it doubles back.
Originally Posted by Merganser
The UCR does not have this particular issue.
One end is fixed, the closed or locked end eye. The other end is adjustable, your range of adjustability depends on how long your original rope is. The rope maintains much of its original strength in a whoopie. Knots are notorious for diminishing the original strength. Buckles and rings rings have been mentioned here as also wearing the rope prematurely, especially in the pinch point of rings.
The whoopie has been reported to maintain a higher percentage of original strength, ( some say 90% or better). I'm not a mathlete, I'll take their word for it.
They are simple to build, lightweight, and if you dont like them, you can simply undo the whoopie and the rope is undamaged.
The first one or two can be difficult to build and the right tools make the job a breeze. They only work with braided hollow core rope i.e., polypropylene, like amsteel, or similar.
The most important step is to make sure you "milk" the adjustable section to ensure the weave is smooth and taught. If not, it will slip.
Grab some rope and try one out, they are cool.
Ambulo tua ambulo.
Equivalent strength rope is 1/3 the weight of webbing. So even using twice as much rope, the Whoopie sling is going to be lighter than webbing.
Also, it is a lot less bulk.
For the whoopie hitch it is obvious to me that there is tension on entire cord, including the adjustment section. I see how that would be secure and not slip. With the UCR its not so obvious.
Examples I've found of the UCR show it wrapped around the tree. I've always been a fan of straps for that to reduce damage to the tree (I use strap + marlin spike + cord). Does that still work? Can you just attache one end of the UCR (presumably the short end through which the longer one is treaded) to the marlin spike? It seems like it should be able to slip.
This does work, although slippage is possible. You can forestall that by putting a slippery half hitch in the bury rope, at the end of the UCR that is taking the tension, creates a "jam" that keeps the bury line from slipping through.
Originally Posted by Merganser
I've used a UCR made of vectrus 4 nights so far, and lots of ins and outs in the yard. With that cord it seems pretty reliable. For reasons unknown, in my experience, it slips more on 1/8" Amsteel blue.
I'm currently using and SMC ring with a buntline hitch (like you show in your really nice video). I don't really care so much about eliminating the weight of the SMC ring I just want to avoid damage to my cordage. The buntline jams up a bit and I could see it getting abraded when I pull it apart. That's what's appealing about the slings. Does the half hitch with a UCR do less damage to the cordage than the buntline hitch that I use on my SMC ring (ala your amazing video)? I could see the UCR being easier to release since you could just pull it back and eliminate the friction and that might be easier on the cordage.
Originally Posted by GrizzlyAdams
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