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Old 09-28-2019, 03:04 PM   #1
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Moring lines/storm prep

Just wanting a sturdy system for mooring lines, thinking ahead to the next hurricane/storm. Have learned about as much as I can on shackle sizes and types, thimbles, G4 vs BBB chain, working/breaking loads, etc. Planning on the following for my everyday system which would be added on to in a storm. Trying to make sure it all sounds reasonable and fits/works ok. I think it does...

5/8" 3 strand nylon dock lines, breaking strength 8,900 lbs.

4' of G4 3/8" chain, breaking strength 11,600 lbs. 4 pieces- chain around 2 cleats on concrete bulwarks for stern lines. Chain on 2 pilings off bow port/starboard that will be free to rise/fall with tides.

7/16" Cosby 209A shackles, load capacity 2.6T or 5,200 lbs.

I believe the thimbles will fit in the bow side of the shackles ok. Not sure if the chain, both ends coming from being wrapped around the cleat, will fit together on the shackle pin. Together they measure the same width as the jaw opening.

Going to use the G4 chain as I don't think 1/2" BBB will fit through the opening between the legs of the cleats. The G4 gives me more than enough strength with less thickness. The weakness in all of this is the shackles but I don't think I can get a larger size through the 3/8" chain.

Any comments/suggestions appreciated. I think I may have reached a whole new level of over thinking...
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Old 09-28-2019, 05:22 PM   #2
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Make sure whatever you're going to tie the lines and chain to, cleats/windlass, is mounted so it can't fail.
My current boat's previous owner had the windlass rip loose. Now it's tied into the main hull structure.
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Old 09-28-2019, 05:35 PM   #3
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I have been following these sailors for awhile, they are experts in just about everything sailing related..Here is a storm prep entry...

https://youtu.be/pQ3J0Kl3_DA
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Old 09-28-2019, 07:41 PM   #4
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Thanks. I'm tying off to the 6 standard issue Grand Banks cleats on board. More worried about keeping the boat from backing up in a blow. We are stern in the slip and well protected on 3 sides. Only the north which the bow faces is open. Have 10" cleats embedded in the top of the concrete bulkhead off the stern. Only pilings to tie to off the bow.

I just want to make sure that the size of what I am using is reasonable and fits. If could get my hands on a 7/16" shackle and some G4 3/8" chain locally I could just try it all on for size at the dock. However, can't seems to find them at WM or BOW so thought I'd ask before I order.
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Old 09-28-2019, 08:30 PM   #5
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Years ago I liked to tie somewhat loose. Thought I’d just let the fenders do their job. Worked well until I went to Juneau.

When I lived there in the 70’s I got acquainted w the Taku wind. There is a huge ice field above Juneau at about 3000’ and east. The cold air on the glacier at times comes rushing down the mountains right into downtown Juneau and Harris boat harbor. Almost lost my boat w it’s loose tie-up. Since then I generally tie boats tight. And extra tight in high winds.
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Old 09-29-2019, 02:32 AM   #6
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Years ago I liked to tie somewhat loose. Thought Id just let the fenders do their job. Worked well until I went to Juneau.

When I lived there in the 70s I got acquainted w the Taku wind. There is a huge ice field above Juneau at about 3000 and east. The cold air on the glacier at times comes rushing down the mountains right into downtown Juneau and Harris boat harbor. Almost lost my boat w its loose tie-up. Since then I generally tie boats tight. And extra tight in high winds.
Roger that, Willy, tie it tight, and center of the slip.
Loosely tied vessels will move enough to put some incredible snap loads on lines and cleats. Tied up tight like a spiderweb is the way I do it. No short lines, long spring lines both sides, crossed stern lines.
Vessels tied to the dock and reliant on fenders seem to get lots of damage when fenders fail or get squeezed up above the pier.
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Old 09-29-2019, 09:57 AM   #7
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Tied tight seems like the right way to go as long as the lines have a way to rise and fall with the tides/surge but you don't mention what you used to cover this. Chains on pilings or some other method??
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Old 09-29-2019, 10:11 AM   #8
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Except for big storms or Taku/Willawa winds...the best rule of thumb is tight for floating docks loose for fixed stocks....

Tides and wakes are the wild-cards.... Depending on how large, they can garner all sorts of differences of opinion.
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Old 09-29-2019, 10:26 AM   #9
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If tied to non-floating points, longer lines will allow you to keep them tighter. Less relative length change as the boat changes height as well as more stretch. So tricks like stern lines run across, long spring lines, etc.
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Old 09-29-2019, 11:46 AM   #10
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If you have that luxury, not all places allow for really long lines....unless a storm is coming and emergency preparations are required.

Large tidal range dictates enough slack as necessary.
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Old 09-29-2019, 01:35 PM   #11
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If you have that luxury, not all places allow for really long lines....unless a storm is coming and emergency preparations are required.

Large tidal range dictates enough slack as necessary.
True in my case. I'm ok on the stern as I cross them and they have enough length to handle rise/fall. Springs are quite long and no issue there. Problem is the bow. Pilings are 19' wide and my boat is 14' beam. I have about 7' from hawse to piling on each side, not very much. To make it worse I dock the boat "sticking out" a little to keep my swim platform away from the concrete bulkhead. That puts the hawse pipes at less of an angle from the pilings. I need to lose the nervousness of being close to the concrete. that would help some.
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Old 09-29-2019, 04:50 PM   #12
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5/8" 3 strand nylon dock lines, breaking strength 8,900 lbs.

4' of G4 3/8" chain, breaking strength 11,600 lbs....

7/16" Cosby 209A shackles, load capacity 2.6T ...

... The weakness in all of this is the shackles but I don't think I can get a larger size through the 3/8" chain.

Any comments/suggestions appreciated. I think I may have reached a whole new level of over thinking...
The weakness in all this IS NOT the shackle.

Rope break strength 8900# reduced by putting a knot in it or a splice.
Chain breaking strength 11,600 doubled around the cleat to shackle equals 23,200#
Crosby 7/16 steel alloy shackle 36,000# minimum breaking strength. FYI Crosby uses a 6:1 factor of break strength to Working Load Limit.
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Old 09-29-2019, 05:17 PM   #13
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The weakness in all this IS NOT the shackle.

Rope break strength 8900# reduced by putting a knot in it or a splice.
Chain breaking strength 11,600 doubled around the cleat to shackle equals 23,200#
Crosby 7/16 steel alloy shackle 36,000# minimum breaking strength. FYI Crosby uses a 6:1 factor of break strength to Working Load Limit.
Thanks. Forgot about that. I was looking at the WWL of the shackle only, 2 2/3 tons or 5,333 lbs. So, to even everything up, I should upgrade to Dyneema or some such 5/8" dock lines. Shouldn't be more than $1,000 for dock lines!
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Old 09-30-2019, 11:13 PM   #14
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Thanks. Forgot about that. I was looking at the WWL of the shackle only, 2 2/3 tons or 5,333 lbs. So, to even everything up, I should upgrade to Dyneema or some such 5/8" dock lines. Shouldn't be more than $1,000 for dock lines!

A splice will reduce the strength of the line by 10%. I would not use dyneema for the lines as you lose stretch. If you think you need the increased strength, upside the 3 strand.
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Old 09-30-2019, 11:30 PM   #15
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My experience is that the three strand stretches way too much. Great for anchor rode but it can stretch something like 20 percent of length before yield. I found that lines as long as possible to allow for surge but then use heavy 3/4 double braid. And for a reall hurricane double or triple lines all double braid but in a way to distribute forces as the wind directions change through the hurricane
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Old 10-01-2019, 12:25 AM   #16
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A splice will reduce the strength of the line by 10%. I would not use dyneema for the lines as you lose stretch. If you think you need the increased strength, upside the 3 strand.
I was kidding about the Dyneema. I have additional 5/8 and 3/4 lines to add as needed and cleat space allows. Just trying to figure out the best way to attach to the pilings I have.
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