Working With Dyneema

Ash

Active member
I was never a boy scout but it's always been my understanding that even the best knots substantially reduce the working strength of whatever they're tied into.
 

BarryO

Well-known member
You don't use knots. You splice them. It takes five minutes.
For a long-term solution, yes. I think his intention was to do a quick field repair that could be done without any of the proper tools (no way to trim the ends neatly, no fid to do a proper splice). Something that could be used for recovery that you'd cut out when you get home.
 

Red90

Well-known member
I was never a boy scout but it's always been my understanding that even the best knots substantially reduce the working strength of whatever they're tied into.
Not really. Proper knots in the correct rope don't reduce strength.
 

Red90

Well-known member
For a long-term solution, yes. I think his intention was to do a quick field repair that could be done without any of the proper tools (no way to trim the ends neatly, no fid to do a proper splice). Something that could be used for recovery that you'd cut out when you get home.
You just need a coat hanger, a bit of tape and 5 minutes. You should be practiced and have the coat hanger wire with you. Be prepared. Of course, if you are breaking ropes, you probably are not.
 

Ash

Active member
Not really. Proper knots in the correct rope don't reduce strength.
Found this interesting chart. In terms of re-joining a broken line, it looks like using a large diameter pin to couple both lengths of rope is the only way to retain any significant amount of strength if you were to use a knot.

For splices in the field, it's also a good idea to keep a length of thread to use for a lock stitch to secure everything in place. I've used safety wire with good results as well. The joint is only strong under tension (as mentioned previously, like a chinese finger trap) and has a tendency to slip during normal handling when not under a load. Using a lock stitch will prevent the splice from slipping back out, and I like to put a little collar of tape where the two sections of rope meet for a quick visual indicator.

 

rocky

Well-known member
While we are on a safety kick, if you use a winch hook, position the hook so if it slips/fails, it is thrown to the ground, not into the air.

Wire rope repair
 

BarryO

Well-known member
One thing that makes wonder is the wide disparity in synthetic rope prices. On the one hand to have high-priced stuff from the winch manufacturers themselves and from places like Master Pull. I assume they're using "real" Dyneema(R) from DSM, or another name-brand UHMwPE such as Spectra(R). I'm guessing the stuff on Amazon at 1/3 the price is some generic Chinese UHMwPE. Is is safe to use(?). Or is the high-priced stuff just jacked up due to name brand recognition?
 

Roverman2010

Well-known member
If you use the cheaper stuff I would go up in size 13mm, the cost differance is in the heat treatment. When I was working offshore seismic our big stuff was Dextron13 50mm. I did a three day course with OTS Norway as we made our own Paravane bridles. I think master pull say they use Dexron which is a good trade name, if you can't find a mention of the Dyneema fiber in the make-up who knows what it's made of.
If you are making your own splices, get a fid. A coat hanger does not cut the mustard.
 

Attachments

Red90

Well-known member
For splices in the field, it's also a good idea to keep a length of thread to use for a lock stitch to secure everything in place. I've used safety wire with good results as well. The joint is only strong under tension (as mentioned previously, like a chinese finger trap) and has a tendency to slip during normal handling when not under a load.
You interlock the splices so that they can't come apart. This eliminates the need for lock stitching.
 
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