It may not be rocket science, but it's still science.
Punted on it in the end though, principally because as oldgringo points out it is operating outside of the design box, in particular the stresses on the interlocks where you attach the hammock are completely different. In "normal" use the cord is under tension on both sides of the interlocks and there is compression on the splice. In this application the force is on one side of the interlocks, there is no compression, we're relying on the interlock to work as a jam and not slip. In the absence of any engineering data on the holding power of the arrangement, I backpedaled and put in diamond knots instead of these interlocks. My intuition is that this will degrade less than an overhand or smaller knot but that could just be a bit of vapor in my noggin. With cord rated at 1800 lbs, even degraded by 50% by knots, that's plenty strong. And it will break before it slips.
I get kinda conservative when it comes to what is holding me up 2 feet off the ground. YMMV
I'm no expert, I've just done a fair amount of reading about ropes. In looking at where the strength of a locked Brummel, it comes from the bury not the lock. The purpose of the lock is to keep the bury from sliding while not under load, think about the way a whoopie bury works.
I think GrizzlyAdams has a great idea with the diamond knots. If you look at the test data from the soft shackles you can see that it works excellent with amsteel. The only down side it that it eats up a ton of rope.
Ultimately you have to do whatever you're comfortable with. Just try to make sure you understand the risks when you start trying to invent new ways of doing things. Not saying invention is bad by any means, it just carries risks.
This may be a dumb idea, but couldn't you just do a series of continuous loops chained together using the locked brummel and bury method? There wouldn't be a bunch of knots to bulk it up. It probably wouldn't take much more Amsteel vs a series of diamond knots would it? Has this already been bandied about and I missed it? You could put some stitches through the bury for extra security too.
Interesting...the two buries on a cord link will run to at least 6-8 inches together though, a diamond knot doesn't use that much, nor for that matter does a triple fisherman's knot (but the cord link is more aesthetically pleasing).
But why link the loops together at all? How about a simple chain of links connected by interlooping, just like the metal ones...that will ensure that for the links carrying the load, it will be split evenly on both sides of the link. If you physically connected the links and didn't get the placement just right, just one side would carry the load, the shorter of the two sides between two connection points.
That was what I was trying to describe. Continuous loops linked like chain links. I didn't describe it very well. I threw the brummell and bury idea in a weird place in that post!
OK, this is what I've gleaned from the replies so far-
I've used locked brummels, not splices.
A bury is designed to hold a load in line with the bury through constriction.
Brummels are only designed to hold a bury in place, not lock or hold a load.
Have I missed anything?
The continuous loop chain would work, though I'm yet to learn how to make them.
Not sure what a diamond knot is but sure I can do so with a quick search.
What about a series of individual fixed loops with an appropriate tail length buried in to the main line in the direction of pull?
Trouble is there's no way to have and keep the load on both strands.
I thought of burying a series of eyes. Cute, but only if the spacing is the length of the bury, say 6" apart. Otherwise the buries overlap. So, maybe you don't bury, but instead rely on Shoemaker's splices and lots of stitching to be sure the spliced in eyes don't slip under light load conditions.
I last night started with 30" cord with eye splices at both ends running between hammk ring / shackle and 'biner. Length started with it quadrupled, so 7.5", then shortened to 6 lengths and 5", then 8 lengths and 3 3/4", then 10 and 3".
You could bury and stitch a series of 2" loops of light line (as they will always be used doubled. I'd stitch them for security, then larks had them in a daisy chain, with a larks head always on the bury.
This idea may have been mentioned but here's my thought. Make a fixed eye at the end for attachment to the hammock and a second at the other end that has a 7 inch eye. Take a second piece of amsteel and make a 7 inch fixed eye with 13 inches of tail. Then bury the tail into the "spine of the first loop and repeat for the desired length. You would then have a loop every foot or so to put on a marlin spike hitch. The buries would be stitched.
I do not see a way to get them closer as the recommended stitched bury is 3 fids. For 7/64 1 fid is 2 inches, so the bury is 6 inches.
I decided to try out one of the apps on my Windows 8 tablet PC and draw a picture to show what I'm talking about.
Last edited by Mouseskowitz; 05-11-2012 at 22:52. Reason: Forgot the stitching