Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 28-05-2013, 03:34   #16
Registered User

Join Date: Feb 2012
Posts: 2,441
Re: In defence of the sheet bend

Bash

You are surely having us on, taking the piss, 'haffing ze leetle choke', winding us up, trying to catch us out, no?

In the immortal words of John McEnroe (sp?)

"You cannot be serious !!!"
__________________

__________________
Andrew Troup is offline   Reply With Quote
Old 28-05-2013, 04:05   #17
Registered User

Join Date: Feb 2012
Posts: 2,441
Re: In defence of the sheet bend

Evans

As I think I've said, it's hard to apply the conventional wisdom about knot strengths and security when adapting a traditional bend to join a rope to a sling.

Especially strength evaluated over time, when subjected to snatch loads...

It would be interesting to devise a test rig, but I'm not about to do that. Not just now, anyhow ... I think it's possible to get an informal idea of security simply by tying the various options but leaving them relatively loose (hopefully to a similar degree in every case) then rhythmically jerking the line and closely observing the behaviour (and counting the jerks before the knot comes completely undone).

I seem to recall that's how Ashley initially evaluated security, and it was doing that which initially alerted me to the single sheet bend not being particularly secure in the traditional role.

Paul Elliott's ingenious adaptation of the Carrick Bend certainly looks to me more secure than a single sheet bend.

One trouble with Carrick Bends is that gurus of knot-tying have variously described it as at one extreme 'the nearest thing to a perfect bend' (Ashley) down to "Although often assumed to be strong, it is in fact only about 65% efficient" (Budworth)

The problem I have with it, in the usual role for bending two lines together, is that it can be tied several wrong ways (although only two, I imagine, in Paul's example) and these wrong ways are much less secure.

This is made considerably worse by the unfortunate fact that it is often wrongly depicted, even in books but especially on the www...

It's hard for me to gauge how it would compare, security wise, with a double sheet bend, and how it would compare in long-term snubbing, 'fatigue' strength wise, with either a single or double sheet bend.

As I have said previously, it's not safe to extrapolate from their behaviour when only one of the two 'legs' of the sling is loaded, ie the loading for which they were intended.

And the other game changing element is, of course, new materials and constructions, making conventional wisdom an even more unreliable guide...

I have found a double sheet bend exceptionally secure when adapted to a webbing sling of the type show in the photo, but I'm indebted to Paul for showing me that, contrary to what I had thought, it's not the only option.

Putting a twist in the loop to make a Carrick work is a stroke of genius, I reckon...
__________________

__________________
Andrew Troup is offline   Reply With Quote
Old 28-05-2013, 04:23   #18
Registered User

Join Date: Feb 2012
Posts: 2,441
Re: In defence of the sheet bend

Bash

I realise my post was ambiguous: when I said "You cannot be serious"

I was referring to your commending the reef or square knot to our attention, for the purpose of joining two ropes together for the purposes of withstanding load.
__________________
Andrew Troup is offline   Reply With Quote
Old 28-05-2013, 04:44   #19
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: In defence of the sheet bend

I have never used it in the application you suggest, but I can see a potential problem in that the sheet bend can be a difficult knot to untie after a heavy load.
__________________
noelex 77 is offline   Reply With Quote
Old 28-05-2013, 06:06   #20
Moderator
 
Seaworthy Lass's Avatar

Cruisers Forum Supporter

Join Date: Oct 2008
Boat: Aluminium cutter rigged sloop
Posts: 12,807
Re: In defence of the sheet bend

Andrew, no need to defend the sheet bend as a useful general knot.
Yes, it is the easiest bend to tie.
Yes, it is reasonably secure when lines are of similar diameter and not slippery.
Yes, it can be used to tie a line to a fixed loop.

There is, however, a need to defend it for the purpose you have illustrated.
It is not as secure when lines are of a different diameter (and then you want the 'fixed' loop to be the heavier line, not the webbing).
Just as a bowline can, a sheet bend can loosen and undo when the load on it decreases (not sure if it would do so sufficiently with a snubber as the boat springs forward, but why risk it).
It is not as secure as some other bends.

The Carrick bend seems superior to me if you wanted to use a knot for this purpose:
The knot will not loosen when the load decreases.
It is suitable for lines of different diameter.
It can also be attached to a loop as Paul has pointed out.
It can be untied after a heavy load.

Athough not as quick as a sheet bend, it is no slower than a double sheet bend (takes about 5-6 seconds) and is not difficult to tie given a little repeated practice.

But, given that all knots are slower to undo than the loop of a soft shackle (a critical factor I feel) why would you want to knot the snubber on at all instead of using a soft shackle on the loop? Or have I misunderstood you?

By the way, the Carrick and sheet bend share much in common visually (see photo). Don't let the loose ends of the line looking as though they end up on opposite sides in the photo of the sheet bend fool you - this is how the line will move as the knot is tightened.
In this photo Carrick bend is at the top, sheet bend below:
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	118
Size:	123.9 KB
ID:	61429  
__________________
"The cure for anything is salt water: sweat, tears or the sea." Isak Dinesen
"To me the simple act of tying a knot is an adventure in unlimited space." Clifford Ashley
Seaworthy Lass is offline   Reply With Quote
Old 28-05-2013, 06:33   #21
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: In defence of the sheet bend

Quote:
Originally Posted by estarzinger View Post
OK, for the specific application I was doing today, what is the best knot? I have a spliced loop in 1/2" dyneema and I want to join a piece of 11mm climbing line to it. It can be 'permanent' . I don't have to untie this. Ideally I think I would put a splice in the climbing line and cow hitch the two splices together . . . but lets say that I can't splice the climbing line. Then what is the best way to join the end of the climbing line to the spectra loop? I used a double sheet bend, but it sounds like perhaps there are better higher strength knots for this.
Buntline or anchor bend?

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 28-05-2013, 07:23   #22
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: In defence of the sheet bend

I always remember a time when I was six, I had convinced my Mum to let me take the dingy and run the shore lines. Of course I ran out of length in my first line and I couldn't remember how to join the other line... The first knot I tied came undone on the first tug to my everlasting shame. Since then I have been a big fan of sheetbend's

I normally tie one like a bowline, it's much quicker and I can do it in the dark.

I prefer the double sheet bend. Much more secure and easier to untie, but Pauls carrick bend looks interesting.

On a side note I used to have access to a test bed and I did a few tests on climbing rope knots. The results surprised me, with a double fishermans bend failing before a single fishermans bend and an alpine butterfly knot. It seemed like the heat generated by the slippage through the double fishermans bend could not escape fast enough and the rope melted, breaking in the middle of the knot. Maybe this could be a downside to the double sheet bend or any bulky knot?

Cheers

Ben
__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 28-05-2013, 07:36   #23
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: In defence of the sheet bend

Quote:
Originally Posted by Bash View Post
Ah. You probably grew up as one of those kids who called it a "reef knot."

Same thing. Still superior to a sheet bend for similar-sized lines.
Ha, I was always taught not to use a reef knot for joining lines together, as it was very easy to capsize and have the whole thing collapse and was inclined to slip. The sheet bend was for similar sized lines and the double sheet bend was for different sized lines.

The carrick bend was for joining wire to rope, or large hawsers that you wanted to lead around a warping drum...

But I could be persuaded otherwise by some good evidence
__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 28-05-2013, 08:12   #24
Registered User
 
Delfin's Avatar

Join Date: Aug 2010
Location: Anacortes, WA
Boat: 55' Romsdal
Posts: 1,390
Re: In defence of the sheet bend

Quote:
Originally Posted by estarzinger View Post
OK, for the specific application I was doing today, what is the best knot? I have a spliced loop in 1/2" dyneema and I want to join a piece of 11mm climbing line to it. It can be 'permanent' . I don't have to untie this. Ideally I think I would put a splice in the climbing line and cow hitch the two splices together . . . but lets say that I can't splice the climbing line. Then what is the best way to join the end of the climbing line to the spectra loop? I used a double sheet bend, but it sounds like perhaps there are better higher strength knots for this.
Would not a double zeppelin bend work just ducky? Leave the bitter ends long and whip them to the standing part if you're feeling nautical?
__________________
http://delfin.talkspot.com
When stupidity is a sufficient explanation, there is no need to appeal to another cause.
- Ulmann's Razor
Delfin is offline   Reply With Quote
Old 28-05-2013, 08:13   #25
Registered User

Join Date: Jan 2010
Location: Narragansett Bay
Boat: Able 50
Posts: 3,055
Re: In defence of the sheet bend

Quote:
Originally Posted by Andrew Troup View Post
Hopefully eventually someone will come along and read the post, rather than the title....

Responding to the point raised, I used to think the sheet bend was uniquely suited to varying sized ropes, but there are better bends which are claimed to share or exceed its capabilities in this regard

I'm not familiar with Bash's 'square know' so I can't comment ;-)

What does a square know ? Now that's a thread all by itself.
__________________
savoir is online now   Reply With Quote
Old 28-05-2013, 08:22   #26
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
Re: In defence of the sheet bend

Quote:
Originally Posted by Andrew Troup View Post
Bash

I realise my post was ambiguous: when I said "You cannot be serious"

I was referring to your commending the reef or square knot to our attention, for the purpose of joining two ropes together for the purposes of withstanding load.
Slow down there, hotshot. I said that the reef knot is superior to the sheet bend when tying similar lines. Nothing more.

I wouldn't use a sheet bend in a hundred years to withstand load. At best, I'd use the knot to tie a messenger or a heaving line to a larger rope.

Any fool knows that there are better knots for general purposes than either the sheet bend or the reef knot/square knot, and that splices are generally superior to knots.

You started a thread called "in defence [SIC] of the sheet bend." I'll presume you meant "defense." So, I'm listening: defend all you want. I you want to go on attack, however, think again.
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 28-05-2013, 08:50   #27
CF Adviser

Cruisers Forum Supporter

Join Date: Aug 2009
Boat: Custom Van De Stadt 47 Samoa
Posts: 3,743
Re: In defence of the sheet bend

Quote:
Originally Posted by Paul Elliott View Post
How about this? (see attached photo):

Pretend the blue line is your dynema loop (I have looped it using a zeppelin bend, and Kleimheisted it around the hammer). Give the loop a half-twist and then tie a Carrick bend with your climbing line. The Carrick is strong and secure.
Interesting, I will have to play with that and the zeppelin. I have heard of both but never used them.

Is there data to show that either/both are stronger than a (double) sheet bend?

One challenge with this specific application is that the dyneema portion will be quite slippery . . . But I can sew the tail if necessary.
__________________
estarzinger is offline   Reply With Quote
Old 28-05-2013, 09:19   #28
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,858
Images: 4
Re: In defence of the sheet bend

Quote:
Originally Posted by estarzinger View Post
Interesting, I will have to play with that and the zeppelin. I have heard of both but never used them.

Is there data to show that either/both are stronger than a (double) sheet bend?

One challenge with this specific application is that the dyneema portion will be quite slippery . . . But I can sew the tail if necessary.
Evans, I've got no data on these knots. other than what I've read in Ashley (the Carrick), and on the web. Ashley says little about modern slippery synthetic lines. I've seen the conflicting reports on the Carrick strength that Andrew mentions, but at least in dacron / nylon lines it does seem fairly shake-proof.

I've really grown to like the Zeppelin. It's quite easy to tie (look for the "6 and 9" explanation), it holds really well, doesn't shake free, and unties after loading. In my example I could have used a Carrick to make the loop, but I now prefer the Zep. I used the Carrick to attach the climbing line to the loop because I didn't have access to both tails.

Bash, Everything I've read and personal experience tells me that the Reef Knot (Square Knot) is less secure than the sheet bend unless you set it *really* hard. And, it's impossible to set it hard if you are tying low-friction lines. It can capsize and slip if you drag it over an obstruction. If you do manage to set it, it then becomes difficult to untie. It's main advantage is that it's easy to tie under load.

The Sheet Bend is just fine with equal-diameter lines, but with unequal lines there is a best way to tie it.

The Carrick is harder to tie, but won't collapse if you drag it around a bollard or other obstruction.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 28-05-2013, 09:23   #29
Registered User
 
Dennis.G's Avatar

Join Date: May 2011
Location: Sea of Cortez and the U.P. of Michigan
Boat: Celestial 48
Posts: 750
Re: In defence of the sheet bend

I was always told to not use a square (or reef) knot to join two lines, and that it was only useful when snug against a surface (such as against boom or bunched sail material). Commonly use sheet bend.

When I worked on ski patrol we had to tie small poly ropes together all the time. We used what we called a Barrel Knot, which is also known as a Double Fisherman's knot. This is also used on monofilimant. Very solid strong knot that stays tied when flopped around. Great knot excepting for the fact that you need a knife blade to "untie" it.
Attached Thumbnails
Click image for larger version

Name:	double_fisherman_knot.gif
Views:	2993
Size:	19.5 KB
ID:	61432  
__________________
Dennis.G is offline   Reply With Quote
Old 28-05-2013, 09:24   #30
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,858
Images: 4
Re: In defence of the sheet bend

Quote:
Originally Posted by Andrew Troup View Post
Putting a twist in the loop to make a Carrick work is a stroke of genius, I reckon...
I think I'm going to put that in my signature!
__________________

__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:51.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.