Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 30-12-2011, 12:49   #1
Registered User
 
PamlicoTraveler's Avatar

Join Date: Aug 2008
Location: Depends
Boat: Cabo Rico
Posts: 771
Images: 17
Tying lines together - Strength loss?

OK engineers and technical types...

I have a 200 foot 5/8 Nylon line for a Sea Anchor. I want to have a longer line than that and should probably have more like 400 feet. Since the 5/8 takes a fair amount of space I am thinking of adding 200 feet of a Dyneema 3/8 line with a breaking strength of >15,000 lbs.

I realize Dyneema has no stretch, but the 200 feet of Nylon 3 strand will take care of that.

Two questions.....

1.) what is the best know to secure two lines together so they don't come apart?.... Two bowlines?

2.) What percentage of strength is lost by connecting the two lines. Assume both lines have the same original breaking strength to begin with.
PamlicoTraveler is offline   Reply With Quote
Old 30-12-2011, 14:02   #2
Moderator Emeritus
 
roverhi's Avatar

Join Date: Aug 2005
Location: Carlsbad, CA
Boat: 1976 Sabre 28-2
Posts: 7,505
Send a message via Yahoo to roverhi
Re: Tying lines together - Strength loss?

A sheet bend will work but Dyneema and other super ropes are much more weakened by sharp bends in knots, and slippery so they don't like to hold knots than 3 strand or double braid dacron or nylon. A knot that may work to join the lines is tieing a granny knot with each line around the other line. You tie the granny knots and then slide the knots together. Not a very good description and I couldn't find an illustration on line. Believe it's illustrated in Toss's 'Rigger's Apprentice'.

I'd splice an eye with thimble into the Dyneema. Dyneema is super easy to splice, hardly harder than tieing a knot. Then tie the nylon line onto the Dyneema with a bowline. Except possibly in a tow by a much larger vessel, lines almost always part from chafe, not exceding the strength of a knotted rope.
__________________
Peter O.
'Ae'a, Pearson 35
'Ms American Pie', Sabre 28 Mark II
roverhi is offline   Reply With Quote
Old 30-12-2011, 14:23   #3
Registered User
 
delmarrey's Avatar

Join Date: Mar 2003
Location: Philippines in the winters
Boat: It’s in French Polynesia now
Posts: 11,371
Images: 122
Re: Tying lines together - Strength loss?

You could splice in a thimble to the ends of each and use a shackle between the two, or thimble thru thimble into each other. With Synthetics, knots tend to brake right next to the knot when under lots of stress (no stretch at that point).
__________________
Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........
The measure of a man is how he navigates to a proper shore in the midst of a storm!
delmarrey is offline   Reply With Quote
Old 30-12-2011, 14:37   #4
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 10,054
Re: Tying lines together - Strength loss?

Quote:
Originally Posted by delmarrey View Post
You could splice in a thimble to the ends of each and use a shackle between the two, or thimble thru thimble into each other. With Synthetics, knots tend to brake right next to the knot when under lots of stress (no stretch at that point).
I believe I have seen manufacturers recommend cow-hitching the spliced lines rather than using thimbles; the cowhitch eliminates chafe by eliminating movement, and the thimbles can shift under a cyclic load. However, in this case I wonder if the high-tech line could cut through the polyester (or rather present a sharp radius), resulting in a lower value? I wonder if this has been tested? Certainly, the high-tech line should be the one with the cow-hitch, for this reason and several others.

Definitely splicing, and I'm not a big splicing fan. However, this is a perfect splicing application.
__________________
Gear Testing--Engineering--Sailing
https://sail-delmarva.blogspot.com/
thinwater is offline   Reply With Quote
Old 30-12-2011, 15:09   #5
Registered User
 
Ziggy's Avatar

Join Date: Apr 2008
Location: U.S., Northeast
Boat: Currently boatless
Posts: 1,643
Images: 2
Re: Tying lines together - Strength loss?

Quote:
Originally Posted by roverhi View Post
A sheet bend will work but Dyneema and other super ropes are much more weakened by sharp bends in knots, and slippery so they don't like to hold knots than 3 strand or double braid dacron or nylon. A knot that may work to join the lines is tieing a granny knot with each line around the other line. You tie the granny knots and then slide the knots together. Not a very good description and I couldn't find an illustration on line. Believe it's illustrated in Toss's 'Rigger's Apprentice'.

I'd splice an eye with thimble into the Dyneema. Dyneema is super easy to splice, hardly harder than tieing a knot. Then tie the nylon line onto the Dyneema with a bowline. Except possibly in a tow by a much larger vessel, lines almost always part from chafe, not exceding the strength of a knotted rope.
What roverhi said, but instead of a bowline, use a "figure eight follow-through."

Figure 8 Follow Through | How to tie the Figure 8 Follow Through | Climbing Knots

Keep in mind that any knot weakens the rope, but figure eight does retain about 70% of the original strength and is very secure.
__________________
... He knows the chart is not the sea.
-- Philip Booth, Chart 1203
Ziggy is offline   Reply With Quote
Old 30-12-2011, 15:51   #6
Registered User
 
Artif's Avatar

Join Date: Jan 2011
Posts: 267
Re: Tying lines together - Strength loss?

Personally if I were to tie dyneema to anything I would use a triple fishermans knot.
Its very slippery and many knots will pull through.
However spliced eyes would be the first choice.
Artif is offline   Reply With Quote
Old 30-12-2011, 17:59   #7
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,441
Re: Tying lines together - Strength loss?

If you are talking about bare 12-plait dyneema, there is absolutely no excuse for even thinking about knotting it. It is extremely slippery and doesn't like small radius bends, so knotting is a non-starter. However, as others have said, eye splicing is dead easy, retains nearly 100% of its strength, and won't slip under load.

A quick review of the manufacturers website info will likely set you straight.

Cheers,

Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
Jim Cate is offline   Reply With Quote
Old 30-12-2011, 18:10   #8
Registered User
 
PamlicoTraveler's Avatar

Join Date: Aug 2008
Location: Depends
Boat: Cabo Rico
Posts: 771
Images: 17
Re: Tying lines together - Strength loss?

Thanks all...Sounds like an eye splice is needed. At least on the Dyneema, and then a bowline to the eye with the 3-strand.
PamlicoTraveler is offline   Reply With Quote
Old 30-12-2011, 18:14   #9
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Ohio
Boat: Now boatless :-(
Posts: 11,580
Images: 4
Quote:
Originally Posted by PamlicoTraveler
Thanks all...Sounds like an eye splice is needed. At least on the Dyneema, and then a bowline to the eye with the 3-strand.
If you aren't going to splice I would consider anchor bend or double fisherman knot for tying two different sized lines together in a towing type situation.

I use the double fisherman all the time. It's the first to go to after the basic 4 (square, figure eight, bowline and clove hitch). Well maybe after the truckers hitch...

Here' a cool link for knots - http://www.animatedknots.com/knotlist.php
__________________
Relax Lah! is SOLD! <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 30-12-2011, 18:16   #10
Registered User

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,855
Re: Tying lines together - Strength loss?

If worried by strength loss, why not use a stronger rope in the first place?

Maybe you can splice eyes over thimbles and then use a big shackle to connect the two lines?

They say splicing does not reduce line strength as much as tying does ...

b.
barnakiel is offline   Reply With Quote
Old 30-12-2011, 18:25   #11
Registered User
 
Ziggy's Avatar

Join Date: Apr 2008
Location: U.S., Northeast
Boat: Currently boatless
Posts: 1,643
Images: 2
Re: Tying lines together - Strength loss?

Quote:
Originally Posted by PamlicoTraveler View Post
Thanks all...Sounds like an eye splice is needed. At least on the Dyneema, and then a bowline to the eye with the 3-strand.
Again--don't use a bowline. It's not very secure for critical applications. Figure eight to an eye splice on the dyneema is much better.
__________________
... He knows the chart is not the sea.
-- Philip Booth, Chart 1203
Ziggy is offline   Reply With Quote
Old 30-12-2011, 18:37   #12
cruiser

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 5,030
Re: Tying lines together - Strength loss?

Quote:
Originally Posted by PamlicoTraveler View Post
OK engineers and technical types...


2.) What percentage of strength is lost by connecting the two lines. Assume both lines have the same original breaking strength to begin with.
From memory most loose up to 50% of breaking strain, think a fishermans bend looses least. Can't find the destruction test data though.
conachair is offline   Reply With Quote
Old 30-12-2011, 19:26   #13
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,077
Images: 6
Re: Tying lines together - Strength loss?

Eyesplice the end of the nylon.
Eyesplice the end of the Dynema (or polyester line which is really chafe resistant) making the eye large enough to easily pass the whole bundle of Dynema through the eye.
Pass the Dynema eye through the nylon eye then the bundle through itself.
Pull tight, this forms what looks line a balanced square knot between the two lines.
Strength will be about 100% because there is double the line for each one to take strain up to each splice as long as eacheye splice is good.
According to Brion Toss this type of join has been tested close to 100% and, as such, I have been using this technique to join lines for years now with no failure(s).

It is super easy to join and remove lines this way. I have a basket of 500 ft of line that I pass through the eye (big enough for the basket) to join long anchor lines.
__________________
"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
Rick is offline   Reply With Quote
Old 30-12-2011, 19:51   #14
Registered User
 
Ziggy's Avatar

Join Date: Apr 2008
Location: U.S., Northeast
Boat: Currently boatless
Posts: 1,643
Images: 2
Re: Tying lines together - Strength loss?

Rick: I agree--that is the best solution.
__________________
... He knows the chart is not the sea.
-- Philip Booth, Chart 1203
Ziggy is offline   Reply With Quote
Old 30-12-2011, 20:10   #15
Registered User
 
jackdale's Avatar

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 6,252
Images: 1
Re: Tying lines together - Strength loss?

Quote:
Originally Posted by Ziggy View Post
Rick: I agree--that is the best solution.
+ another 1
__________________
CRYA Yachtmaster Ocean Instructor Evaluator, Sail
IYT Yachtmaster Coastal Instructor
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Storing Lines SVNeko Construction, Maintenance & Refit 2 30-09-2011 22:59
Reefing Lines Always Ready ? nv5l Deck hardware: Rigging, Sails & Hoisting 14 16-08-2011 15:26
Dock Lines on Avon 340 RIB ? twistedtree Auxiliary Equipment & Dinghy 6 03-08-2011 07:09
Want To Buy: Jack Lines and Harness for 38' trimming out Classifieds Archive 0 10-06-2011 10:46

Advertise Here


All times are GMT -7. The time now is 22:52.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.