Another article on anchors

If you take a length of nylon, an old double-braid halyard or sheet will suffice, and run it from stern to bow you will have a roughly boat-length snubber. You could go off and buy anchorplait, but recycling old running rigging seems sensible
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Does anyone use nylon halyards or sheets?
 
I was intrigued by this

"The tested anchors (with surface area to weight ratios in brackets) were the ..... Kobra, 4.2kg (80)..... Delta, 6.7kg (61)"

and it made me look a bit further.

From the catalogues of the two anchor types, at http://www.seateach.com/Kobra-Plough-Anchors.htm and http://www.google.co.uk/imgres?imgu...a=X&ei=_lFeUvuyNYbR0QW4goHgBg&ved=0CE0Q9QEwBQ

The body part of a 4kg (where does 4.2 come from?) Kobra is 236mm max width x 310mm long. For a 4kg Delta it's 230mm wide x 304mm long (length derived by A-E as not given directly).
The body part of a 6kg Kobra is 270mm max width x 359mm long. The 6kg (where does 6.7 come from?) is 265mm max width x 351mm long.

Very crudely speaking, the body is like two triangles so the area is going to be (related to) width x length/2. The profiles are so similar that I would think the errors will be similar for both.

4kg Kobra, area 36580,ratio to weight 91 - never mind the units - (or 87 if you take it as 4.2kg)
4kg Delta, area 34960, ratio to weight 87

6kg Kobra, area 48465, ratio 81
6kg Delta, area 46508, ratio 78 or (69 if you take it as 6.7kg)

That's way different from what the article implies. The difference in area between a Kobra and Delta of the same catalogue weight, whether 4kg or 6kg, is under 5%.
What's the point of comparing ones of different sizes to give a spurious difference of 30%?
It's invalid.

It always puzzles me that some tests show the Kobra as holding significantly better than the Delta when they seem so similar. The figures in the article initially make it look as though it's because the Kobra gives much more area for the same weight (which would suggest it's much more flimsy) but a closer look does not support that.

I do find it difficult to see why the Delta is categorised as old generation and the Kobra as new generation. I would have thought they both fall in the middle!
 
Troubadour said:
why the Delta is categorised as old generation and the Kobra as new generation
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The first ever to use the term "new generation anchor" was Alain Poireaud (RIP) aka Hylas, of Spade fame, in the early 2000s; at that time according to him the one and only "new generation" anchor was his Spade, of course.
Delta and Kobra existed before the Spade, so obviously according to the the original definition they must be old generation :D

In recent years the "new generation" term spread so out of proportion that today no-one knows exactly what it means, except possibly "get rid of that old piece of metal, come on be modern and get a new one"; (btw I have one).
New generations are not what they used to be :D



add
The Kobra was originally developed as a copy of the Delta, they put the hinge just not to infringe the Delta patents, so I was told
 
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sailorman said:
Braid on braid has little stretch, so how does that work as a snubber
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It doesn't, the author is an idiot.

He also discounts the idea that three-strand stretches more than braid, because he can't find any "modern reference". I'd have thought watching a three-strand mooring line stretching under load would have been a pretty good reference, but I guess he was looking for something written down.

Pete
 
prv said:
It doesn't, the author is an idiot.
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One thing Neeves is not is 'an idiot'. No doubt he had good reasons for his words and maybe will explain them here when it is daytime in Oz. He has been conducting unique and extensive testing on many aspects of anchoring, largely recorded in Practical Sailor. It is all good stuff.
 
who says braid on braid doesnt stretch? purpose made parachute anchor rode, designed to stretch, is Braid on Braid. I have 100m of it for my parachute.
 
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geem said:
who says braid on braid doesnt stretch? purpose made parachute anchor rode, designed to stretch, is Braid on Braid. I have 100mm of it for my parachute.
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Yep, and braided dynamic climbing ropes stretch almost like bungee. The crucial part being that they're made of nylon and designed to stretch, not old sheets and halyards which are made of polyester, explicitly designed to stretch as little as possible, and then have any remaining stretch pulled out of them over the course of their useful life. It's hard to think of a worse material for an elastic snubber unless you go to wire or dyneema. Maybe the author isn't generally an idiot (I bow to Vyv's superior knowledge of him, I'd not noticed the name) but that part is a very odd suggestion to make.

My point about braid was that like-for-like (same material, same diameter, rope not designed to stretch), three-strand stretches more. That's why it hasn't been generally used for yacht halyards for at least thirty years.

Pete
 
I really don't know whether three-strand stretches more or less than braid-on-braid but I suspect it might be less. I have used a nylon braid-on-braid snubber line for many years and watched it stretching on numerous occasions.
 
The article still doesn't answer my questions of
1) Can I use a 5 kg (super new bragging type) anchor instead of my 16 kg (old out of fashion) anchor, 'cos it has 5 times more holding power?
2) How easy are the new anchors to recover after they have dug in so deep?
3) Why are super new bragging anchors so expensive?
 
vyv_cox said:
I really don't know whether three-strand stretches more or less than braid-on-braid but I suspect it might be less. I have used a nylon braid-on-braid snubber line for many years and watched it stretching on numerous occasions.
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From the rocna site
http://www.rocna.com/kb/rope

[TABLE="width: 33%, align: right"]
[TR]
[TD]When polyester line is loaded to 20% of its breaking strength, it stretches between 2.2% and 2.9% depending on construction. Double braid nylon, in same situation will stretch 5.3% and three strand nylon 10%.[/TD]
[TD="width: 20, align: right"]”[/TD]
[/TR]
[TR]
[TD="colspan: 3"]
— Dave Strauss, Samson Rope​
[/TD]
[/TR]
[/TABLE]
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GHA said:
From the rocna site:
When polyester line is loaded to 20% of its breaking strength, it stretches between 2.2% and 2.9% depending on construction. Double braid nylon, in same situation will stretch 5.3% and three strand nylon 10%.
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Should have known really I suppose. Three strand will straighten more than braid on braid under load.
 
vyv_cox said:
I really don't know whether three-strand stretches more or less than braid-on-braid but I suspect it might be less. I have used a nylon braid-on-braid snubber line for many years and watched it stretching on numerous occasions.
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Yep, cos it's nylon. Which is famous for stretching, and perfectly appropriate for use as a snubber, or mooring lines.

The article advocated using old sheets and halyards, which are designed to minimise stretch and therefore made of polyester.

Pete
 
When polyester line is loaded to 20% of its breaking strength, it stretches between 2.2% and 2.9% depending on construction. Double braid nylon, in same situation will stretch 5.3% and three strand nylon 10%.

That explains why my polyester b on b was so poor on the running rigging. Mast height is 58 ft so assuming over 50 ft of halyard I see over a foot of stretch! Rubbish for the mainsail. The new dyneema is a massive improvement.
 
vyv_cox said:
One thing Neeves is not is 'an idiot'. No doubt he had good reasons for his words and maybe will explain them here when it is daytime in Oz. He has been conducting unique and extensive testing on many aspects of anchoring, largely recorded in Practical Sailor. It is all good stuff.
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Agree the practical sailor stuff is a good, but using halyards or sheets as snubbers because they are nylon is a big error and bad advice. Hope it gets cleared up.
 
GHA said:
Agree the practical sailor stuff is a good, but using halyards or sheets as snubbers because they are nylon is a big error and bad advice. Hope it gets cleared up.
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Why is this bad advice? it all stretches better than chain so anything will act as a snubber with varying degrees of stretch
 
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