good paracord usually has 7-strands.
good paracord usually has 7-strands.
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Hi all. I've been quite intrigued by all the recent talk about splicing, in part because I've seen some reference single digit decreases in rope strength. I took a look at Samson Rope's splicing page, specifically the (pdf) instructions for making a whoopie sling using 12-strand AmSteel.
According to Samson, "Whoopie Slings have a break strength of 60% of the published average ROPE break strength". Any idea why there's such a large discrepancy? Where have people come across the aforementioned single digit estimates?
From what I've gleaned from this thread, the difference is in whether the splice is a 'locked brummel' as in the pdf you referenced or a burried brummel (maintaining >90% of the rope strength), shown in this paper:
The burried brummel needs to be locked stitched.
Last edited by Scratch; 07-06-2009 at 07:54. Reason: Add clarification
Real 550 cord has 7 strands inside the sheath. I've seen "parachute cord" at Walmart and others that has the same kind of sheath but no strands inside...it wasn't a braid or anything, but looked about like a strand of synthetic insulation. It was plenty strong to use as accessory cord but I wouldn't trust it to hold 550 lbs. It did stretch like 550 cord though.
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With the whoopie sling, you can't really avoid the abrupt transition. I think Frawg or Tee Dee has some good pics showing a failure of the whoopie sling from a recent post. I think he determined it was because the stopper knot at the tail end pulled tight before the bury engaged. My suggestion is if you need the comfort of adding a stopper knot, you do it further down the line and not right at where the tail exits. Lastly, make sure you "milk" the buried section to engage the splice before loading it. Low loading conditions cause these splices to not perform correctly.
This "Toggled Suspension System" post was my reply to nacra533's question, which was prompted by the pics from my first UCR test in in this post. My final conclusion (in this post) was that the hitch in the running end of the constrictor section functions like the lock in the locked brummel under light loading.
The failure was in the UCR, btw; haven't seen this happen with my whoopie slings.
Bear in mind that my thoughts were just speculation from a non-professional. Validation / correction from a pro would be much appreciated.
Last edited by Frawg; 07-06-2009 at 11:07. Reason: tightened a few loose ends :LOL:
I'd like to toss out a 'Thanks' to everyone that had input into this suspension method. I've been following the various threads that lead to this, and have been tinkering with the different methods discussed. Well done!
Because the first post of this particular thread was so detailed, I've gone ahead and made it a sticky for the suspension forum.
*Note - I changed the title, also, because this method isn't Blackbird specific*
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I to have been following the whoopie sling / UCR threads with much interest. I made my "splicing needle" today. It was constructed from an 18" zip tie. I cut the locking end of the zip tie and then folded the end over to form a eyelet loop and used super glue secure everything. Tonight I will dig through my gear, find my Amsteel blue, and start making my first set of Whoopie Slings.
Thanks to all who have been experimenting with this method and special thank to SloBro for posting these simple instructions.
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Does anyone see a reason aircore plus from BPL won't work. I think it has 8 strands. It is what I have on hand and the Mrs. has me on a tight budget right now.