How does splicing affect strength?
Why would you ever use a knot when you can splice?
Why open the door when standing on your feet when you can also open de door while standing on your head ?
So the answer to your question is simple. If using knots is sufficient, then why invest extra effort to make a splice in a 2-stage dyneema line (mantle and core) ?
2-stage dyneema is cheaper then D12 and other non-core spliceable line and the outer mantle protects the dyneema fibres in the core better; this is good for long term use.
Basically, using knots is easier, cheaper, faster and more durable in the long run.
Why use a splice where a knot is sufficient ?
Wouter
You forgot an important trade on line vs wire. Line does not form little
meat hooks
to tear up your hands when strands break.
perhaps we have over complicated this for a new guy... <img src=
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because it is prettier? we all like a bit of bling on our boats too!
simon
Okay,
How effective is bling-bling up near the hound fitting ?
And how do the splice guys hold de handle up ?
The loop with a knot avoids the need for a timble on the lower end of the trapeze line.
Wouter
No at all, a splice guarntees 90 to 100% of the breaking load. The breaking load reduction of a knot depends on the rope material. For Dyneema it is said to be around 80% reduction, hence 20% of your breaking load are still usable.
If you have a 500kg breaking load trap line, you can still use 100kg on it, which should be sufficient.
Dyneema creeps about 5%, but if you pre stretch the rope (e.g. with the main sheet) you can solve this problem. After this 5%, I didn't notice any creep on the trap lines. Some suppliers deliver pre stretched ropes as well.
Cheers,
Klaus
Splices are prettier and reduce windage, obviously <img src=
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Seriously though, ropes can sometimes get caught behind knots so thats another reason to splice.
No at all, a splice guarntees 90 to 100% of the breaking load. The breaking load reduction of a knot depends on the rope material. For Dyneema it is said to be around 80% reduction, hence 20% of your breaking load are still usable.
If you have a 500kg breaking load trap line, you can still use 100kg on it, which should be sufficient.
I can't say that I find any justification for these claims in my personal experience.
After a capsize I easily put 100 kg on the line, yet I have never broken one.
Also a splice ONLY get's a high breaking load fraction when ALL parts of the loop are prevented from bending to a radius less then 7 times the line diameter. In effect, if you don't use thimbles in all spliced loops then the wrap around any object will reduced the breaking strength of the spliced loop to much less then 90%.
But we can do numbers on these things as much as we want, fact of the matter is that using knots is sufficient on a 3 mm 500 kg mantle-core dyneema line as proven by myself (90 kg in the nude) overy 7 years now. With me are several others who have done the same to their traplines. The theoretical data needs to be in agreement to that. Having only 20% break strength left doesn't appear to satisfy the real life experience.
Added to this is my cascaded downhaul setup where the later stage is experiencing 300-400 kg load and also using knots to secure it to the blocks. Again, you have good knots (with a high fraction of breaking strength left after knotting) and bad knots. I learned alot when I was still active with stunt kites. Good knots are : Double figure 8 knot, fishermans hitch, sheet bend and the bloodknot. With these you can do everything and not loose more then 50% of the breakstrength in the worst case scenario due to the knot itself.
But my best advice is to learn and remember the
double figure 8 knot
this is truly a good knot. Has the lowest break strength reduction in my opinion, makes very tidy/smooth knot and makes fixed loops. Won't come undone when shook about untensioned like the sheet bend sometimes does.
Wouter
No at all, a splice guarntees 90 to 100% of the breaking load. The breaking load reduction of a knot depends on the rope material. For Dyneema it is said to be around 80% reduction, hence 20% of your breaking load are still usable.
If you have a 500kg breaking load trap line, you can still use 100kg on it, which should be sufficient.
I can't say that I find any justification for these claims in my personal experience.
After a capsize I easily put 100 kg on the line, yet I have never broken one.
Also a splice ONLY get's a high breaking load fraction when ALL parts of the loop are prevented from bending to a radius less then 7 times the line diameter. In effect, if you don't use thimbles in all spliced loops then the wrap around any object will reduced the breaking strength of the spliced loop to much less then 90%.
But we can do numbers on these things as much as we want, fact of the matter is that using knots is sufficient on a 3 mm 500 kg mantle-core dyneema line as proven by myself (90 kg in the nude) overy 7 years now. With me are several others who have done the same to their traplines. The theoretical data needs to be in agreement to that. Having only 20% break strength left doesn't appear to satisfy the real life experience.
Added to this is my cascaded downhaul setup where the later stage is experiencing 300-400 kg load and also using knots to secure it to the blocks. Again, you have good knots (with a high fraction of breaking strength left after knotting) and bad knots. I learned alot when I was still active with stunt kites. Good knots are : Double figure 8 knot, fishermans hitch, sheet bend and the bloodknot. With these you can do everything and not loose more then 50% of the breakstrength in the worst case scenario due to the knot itself.
But my best advice is to learn and remember the
double figure 8 knot
this is truly a good knot. Has the lowest break strength reduction in my opinion, makes very tidy/smooth knot and makes fixed loops. Won't come undone when shook about untensioned like the sheet bend sometimes does.
Wouter
Layline.com has a line
punisher
that is a long steel I-beam, a hydraulic press, and a load meter. I don't have the exact numbers but they clearly confirm that knots definitely weaken lines more than splices.
Wouter
I think you should listen to engineering advice before basing on personal experience. <img src=
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There is no doubt that knots weaken lines. The best knot still weakens a line by 40%. Some of the worse knots weaken line by 60%. A double fisherman is a good knot that is closer to the 40% figure. I've read many scientific studies related to this. It's a fact.
Again though the failure point is usually a wear point in the line. Because after a line hits the real world you can throw all those scientific studies out the window as the real world is a very rough place.
Mike Hill
Jake,
Come on Jake, read what is actually written !
I never said knots didn't weaken lines, just that with care they weaken lines alot less then what is made out in this thread. Additionally I said splices weaken lines as well, often less then knots but nevertheless ...
Please don't make any strawman arguments of my comments.
Either that or content that I have mastered the oriental art of hovering weightlessly on my knotted trap lines that obviously can't support my weight ! <img src=
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Not to mention the telekinetic attraction I excerted on my quiver of stunt kites in a good blow fitted with 100-150 kg break strength lines, dragging my 100 kg frame and clothing through the sand and air, plowing the beach.
There are several tricks to compensate for knot weakening. After a while I was only breaking the lines on the unknotted parts and never at or even near the knots themselves. These are not high tech tricks by the way, most of them are pretty much common sense.
If you are interested the combo of a piece of line with a bloodknot and a fishermans hitch on the main line was the superior setup of all. It could be dissembled very easily even after being highly tensioned and broke a lot less then any loop, spliced or unspliced around any ring or shackle. In fact it was the bend around the ring/shackle that weakened the line the most and even significantly more then the knots ever did. Shock loadings tend to do different things to lines then high static loadings. Loops or peices of line that changed shape or angle under shock loadings often failed on my stunt kites; the
static
knots themselves didn't.
I have the very same experience with traplines where the 5 mm (2000 kg break) running trap line breaks alot more often around the little pully then the 3 mm knotted traplines themselves (I have never broken one in 7 years).
But as with all things I write, make the best of my (real life tested) comments or simply ignore them are irrelevant based on an appreciation of my persona. In teh end, I don't care either way.
Wouter
Wouter
Wouter
I guess you just answered your own question.
Geezus, Stephen !
Are you trying to be dumb or it that your natural state of being ?
He is a brainbreaker for you;
if a knot is sufficient for the job then what is the advantage of a splice that is
more
sufficient ?
Neither won't break and I can tie that knot in 5 seconds or less in any given line.
I would like to see any-one make a splice in a (attractively priced) two-stage dyneema line with a very tightly woven mantle and an extremely open weave core. Let alone do it under 5 seconds. The line I used was 2.5 times less expensive then spliceable dyneema lines like D12 and swiftcord; it also creeps less because the is less
setting
of the fibres under load.
With respect to stunt kite lines, any takers for splicing a multi threaded slippery line with a outer diameter of 1 mm ? Bring your magnifying glass and diamond pincers.
There are jobs that call for splices and there are jobs that call for knots. With regard to traplines either method will work satisfactory. When two methods lead to identical results in the important parameters then I choose the most inexpensive and easiest method. That was my point
Wouter
You are so easy to wind up.
If you want to use cheaper line and tie knots, then go a head. If I have D12, I will splice.... It does not take long.
If a splice weakens the line by 20% and a knot weakens line by 40%, then you can use lighter line with the spliced line to achieve simular results. Knowing you race a boat that is significantly over class weight and you are not concerned with being competitive, I am sure weight does not bother you anyway. <img src=
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