Emergency anchor line extension

[Cruisingscotts]

Knots in a anchor road......has to be a better way. For three strand nylon I thought a eye splice was 90%. Does not seem like it would make a difference as far as finishing the end in whipping a back splice or eye splice provided it will fit thought the hole. Kind of leads to something I have contemplated. A little drift....I have a all chain rode as primary. It has a length of dynemma securing the end inside the locker long enough to come up past the windlass in the event I need to dump the road. I have been converting to softies for my halyards etc. and thought that might be a good application to extend a chain road in a hurry, IE trying to fetch up in the deep on a lee shore. Lock wired Crosby shackles would be great but slightly more time consuming. A 14mm softie has a swl of 15000 and would fit through t a 1/2" chain link.


Any thoughts?

[glenn.225]

Just to add a little difference of opinion here, but I think I would use a double fisherman's knot. Although it can be harder to untie when heavily loaded I believe it is ultimately among the strongest of knots along with the double figure 8 for joining ropes. And this would be key in this situation.

[StuM]

Originally Posted by GregoryK

Why would you knot 3 strand? A long splice wouldn't take all that long and won't weaken your anchor line by 50%. You could even do a couple of extra tucks for added security.

Evans tested the Zep at around 58% in Dacron double braid. I don't know of any tests in 3 strand

(and that's 58% of rated strength, not safe working load. Since RS is generally a large multiple of SWL, I'm not overly worried about that - I just make sure I don't exceed SWL)

[Wotname]

Another vote for Zep

In the past, my goto knot for the OPs application would have been the double sheet bend but CF has made wiser a little while ago and now I use the Zeppelin bend exclusively in these situations. Heck, I even use the Zep for joining temporary electric fencing in the paddock!

[sartorst]

Carrick bend because I can tie it but will practice the zeppelin

[Wotname]

Originally Posted by sartorst

Carrick bend because I can tie it but will practice the zeppelin

Carrick is OK but the Zep is a million times easier to undo, especially if it has been heavily loaded.

[Spindrift NH]

I'd probably use a double fishermans knot, rock climbers use it to connect two climbing lines together and trust their lives on it.
But really, by extending beyond 7:1 scope are you really going to gain enough to justify extending to what? 9:1, 10:1?

[Greggegner]

Any knot you add creates a weak point. Also you have all the scope you need. I believe you will get minimal benefit from a longer rode. Take the time and check the set and chafe guard...


Greg S/V Sweet Dreams
Pearson P385 out of Racine Wisconsin

[estarzinger]

mmmm . . . . there are very strongly diminishing returns to scope beyond 5:1. You are in 20-30' with 200' of rode already out. I would say that probably knotting on rode will do more harm than good - don't do it at all with any knot.

There are probably several other things you can do for much better effect. Dive on your anchor. Set a second anchor on that second rode. Make sure you have terrific chafe protection.

If you don't have a second anchor for that second rode, I would be tempted to place it as a second parallel rode on the one anchor (rather than in 'series' as the OP suggested). I would consider that because #1 adding scope will not accomplish much here, #2 rode chafe is probably the greatest vulnerability and a second rode in parallel provides a backup if the first chafes, #3 you could adjust the lengths of the two rodes so the second helps absorb the highest shock loads.

If you must join those two lines. Splicing will be preferred. It 'would depend' on specific circumstances but I believe splicing in a length of chain would often be preferred (for a couple reasons). The regular 3 strand tuck splice is pretty easy.

But if you can't splice for some reason . . . as to knots . . . .the key factor is that this knot is going to see a lot of cyclic surge loading. the line is going to be stretching a lot back and forth. I think I would whip (or sew) the tails down. There is very little knot testing on really stretchy rope in high cycle loading (climbing is all about one cycle). I honestly don't know which knot would be best stand up to this particular application - you want one that does not build up heat inside and does not saw at itself. I would not worry at all about how easy a know is to untie in this situation (just expect you will need to cut it). Probably all 'the usual suspect' would be ok, but I really don't know which would be 'best'.

[SVTwilight]

Is the Zeppelin bend stronger than a sheet bend, i.e. Swl and knot integrity? I use a double sheet bend in most cases of joining lines, but I have never used a Zeppelin so I am interested in a comparison from someome with experience with both.

[estarzinger]

^^ I have tested them extensively and yes the Zep is stronger and slips less.

I think the zep is easier to tie 'wrong' than the sheet bend . . . but if you tie the zep enough that problem goes away.

BUT . . . typical knot strength testing is done with a slow 'static' pull, which is unlike the OP's case - where the knot is more likely to be damaged by heat effect than just pure pull loading.

[a64pilot]

Originally Posted by Spindrift NH

But really, by extending beyond 7:1 scope are you really going to gain enough to justify extending to what? 9:1, 10:1?

That's what I'm wondering, there has to be a point of diminishing returns, and even I'd assume a point to where adding more actually is worse.
But what's that point?

[Clivevon]

This test report on relative knot strengths was interesting:

http://itrsonline.org/wordpress/wp-c...hards.2004.pdf

Double Fishermans Knot gets my vote, at up to 80% of the breaking strain of the rope.

half inch nylon sounds awful thin - I carry 2 coils of 50 metre x 18mm 3 strand nylon for this job on my 36 ft boat, (about 17,500 lbs total loaded displacement) just in case. Never used it, but its not been a problem to have it tucked away.

We also have full anchoring kit and an electric windlass for our English Channel cruising ( CQR 45lb anchor on bow roller with 50m x 10 mm chain & 40m x 18mm Nylon Octoplait. Bruce 33lb anchor in cockpit locker with 16m x 8mm chain & 30m x 14mm nylon Octoplait warp, plus a spare Danforth, chain & rode, I guess in case I lose or have to leave an anchor ) so the extra rope would really be for a hopefully never situation - or a towrope if need be.

Have had 30 knots at anchor but no more, fortunately. Other people dragging was the real problem.

[BobH260]

There is a good illustration of the angular effect of increased scope here,

Anchor Scope Illustrated Photo Gallery by Compass Marine How To at pbase.com

Bob

[Cheechako]

Originally Posted by GregoryK

Why would you knot 3 strand? A long splice wouldn't take all that long and won't weaken your anchor line by 50%. You could even do a couple of extra tucks for added security.

I was wondering the same thing, but his parameters said "the end is whipped". I assumed he didn't want a splice. But yeah, a simple splice doesn't take long if you are not picky.


That Zep looks just like two grannies together!