Knots -v - Splices

[whisper]

I've read on many occasions that a knot in a rope will reduce the breaking strain by around 1/3rd. Today, for the first time, I discover that alledgedly splices will do the same. This has somewhat pissed me off as I've spent some money and a lot of time lately on learning some of the splices.
What's the point of splicing an eye if it will be just as weak as a knot and the knot can be done in seconds ? Please convince me that I've not been wasting my time.

 

[Shakey]

Blimey! A splice, if done properly, should be as strong if not stronger than the original rope. An eye splice is the trickiest splice to perform IMHO 'cos unless you are practiced you always think that you've put the third strand under the wrong one!

Anyway, what do you mean by knots? Knots is speed. Surely you mean bends and hitches? /forums/images/graemlins/smile.gif

Seriously though, I have also heard that 'knots' in lines damages them, I think it's nothing to do with the knot it's more to do with the collection of salt within the knot, the crystals will build up and chafe the rope ultimately resulting in the rope breaking.

Or summat like that.

 

[Rick]

Whisper,

Your investment in splicing is not wasted. While an eye-splice in 3 strand nylon may have similar strength to a bowline in the same material, the splice is king with exotics and braided lines. New England Ropes did some testing IIRC where they found the average BS of a bowline in Spectra versus a splice was 85% less.

 

[Guest]

From what I have read in books on knots and splices, the strength of knots varies with both the material and the knot:-

Blood knot, as use in nylon fishing lines- close to 100% of line,

Bowline, in synthetic rope- as low as 54%.

Buy some fids, and learn to splice braid on braid--strong and neat.

 

[Cobra25]

A knot reduces strength by 50% a splice by -30%

 

[trouville]

I do both, mainly bowlines but in spring when the decks walm the sea crystal clear, and the motor boat jetski lot are sking, i try to splice an eye as it looks good, i also renew the decorative bits on the boat hook bucket and so on,still im not sure about the strength of my splices.
I was told by someone that really could splice that a GOOD splice wont weaken the rope at all, but a bad splice (mine) will, and looking closly at mine verses a really good one im sure thats true,but i dont really want to spend the time needed to be truly good.Even so my splices have never failed and look good to the majority!!

 

[duncan]

sorry for the tangent but a blood knot is nowhere near 100%.

it's a strangulation knot and as it comes under strain it damages the line it is tightning up on - especially damaging on soft lines like nylon etc.

50% would be a good working guide in it's basic form - an that is for a well tied knot!

you should get better strength in most boating lines as friction will 'snag' most knots preventing the full pinch effect on the line for most laid lines - however for those non stretch slippery suckers we love for halyards etc the same enemies will apply - tight turns and the pinch.

 

[snowleopard]

any join in a rope will reduce its strength. a splice causes less distortion than most 'knots' so will reduce the strength less.

different knots reduce strength by different amounts, depending on whether they kink the rope or just grip it. for the most part in sailing the breaking strength of a rope is irrelevant, it's the stretch that causes most problems.

in climbing the breaking strain is critical so knots tend to be designed to maximise that. a classic example is the double fisherman's knot for joining loops which effectively eliminates kinks in the loaded part of the rope.

technically all 'knots' on a boat are either bends or hitches, a true knot is tied in the strands of a rope, not the whole rope, for example wall, crown, matthew walker.

 

[Vascojc]

Going to the route of the problem, why does a line break?

How many people have had lines break and why?

I would guess not many have had the line fail at a knot or a splice, much more likely they have parted where there has previously been some wear or chafe in the line or it has been led over a poor/sharp lead!

 

[jeanne]

Most ropes are over-sized to be comfortable to handle, and so their strength is way above the normal load. This makes the whole discusion a bit too theoretical. I know how to do splices in three strand rope,but not braid on braid, so thats what I do, and I´ve never been let down by one. I have been let down by the knots I have made, so the answer is clear to me.

 

[Rohorn]

Hi....I'm a bit leary of eyesplices, because they put a lot the wear onto one piece of the rope, i.e., the inside of the eye. Take the case of mooring lines onto the bow-cleats of a boat. Very convenient to just loop them on, but I prefer to make a turn or two and figure of eight onto the cleat, varying the length each time, avoiding local wear. Lasted over five years now. Putting a piece of plastic tube in an eye-splice doesn't help much. I've had eye-splices (professionally done, not mine) disintegrate over a relatively short time.
Cheers....R

 

[geoffatstanpit]

Mike Golding might disagree!

Geoff

 

[duncan]

whilst I agree with your theory I would disagree in practice because (most) people will make a mooring line with a loop out of significantly (2 sizes up) line than warps to be made off properly on a cleat.

In my case the lines I carry are 14mm but the fixed lines on my berth are 18mm with longish eyes spliced into them.

I don't think it's inappropriate to make up new lines every couple of years either, especially in the smaller sizes, as exposed lines do deterioate.

 

[graham]

I couldnt agree more about replacement every few years. It is frustrating to see boats moored near yours tied up with manky frayed old lines.

Re the strength of eyesplices ,I was taught that you can increase the strength of an eye splice by tapering the strands in the splice by doing the first 3 tucks with the full strand then doing a couple more with half the fibres in each strand cut out for each tuck. I hope my explanation makes sense?

I use eye splices for mooring ropes for the simple reason they look better.Strength isnt an issue as we mostly use oversize stuff anyway .

 

[Guest]

A splice is far kinder on the rope .... kinder on fittings etc.

A good splice done properly should actually be better than a knot .... in some cases as near to 10% loss .... but that would be foolhardy to rely on such high figure.

No you have NOT wasted time or effort .... they look good, and by jolly they do you good !

 

[Guest]

NO SPLICE OR HITCH will impart greater strength to a rope than original construction .....

Knots suffer increased friction and strain on the rope - which is why SWL is quoted so low.
Splice is in keeping with construction and still using friction to hold it - suffers less from strain and detriment to the rope .... it looks far better anyway than a hairy tattered knot !!!

 

[Alastairdent]

Where do seizings fit into this? I'd have thought they would be as strong as a splice, if done properly.

 

[Capt_Marlinspike]

You are right well made seizings should not reduce the strength of the rope at all.
Alan Alderson
Internation Guild of Knot Tyers