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Old 06-27-2017, 02:39 PM   #1
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Dock Line - Rookie Mistake

I’m thinking I may not be the only one who’s tried this – might save somebody else some trouble.

I set up my stern dock lines using 5/8” three strand nylon about 4 years ago. I thought I was pretty thorough in examining my lines, but clearly not thorough enough. Put replacement dock lines on the “to do” list for this summer, before the throat of hurricane season. Nothing visually bad, but they’re getting a little long of tooth.

When I initially installed the lines, I had 1’ eyes spliced in. In each eye I installed an appropriate size thimble, held in place with tie-wraps placed well clear of the thimble throat. So the line goes through two eyes screwed into the piling to keep the line at the correct elevation on the piling, The running (boat) end goes through the thimble to provide a low friction bearing surface.

Because I don’t know why, I wound up with galvanized thimbles. Knowing that galvanizing produces a pretty rough surface, I Dremel’d the interior (running side) thimble surfaces to a smooth to the touch finish.

TS Cindy came in last week while I was out of town. Sustained 30-35 for a day or so with gusts 40-45. No big deal. I routinely tie up with 8 lines – 2 bow, 2 stern, 2 aft springs, 2 forward springs. I was therefore perplexed when a marina buddy called me to advise he had retied my stern because one line had parted. Only did a little rub rail damage.

Examination showed that the thimble had finally worn through line and it finally had enough and parted. After recovering the line, discovered that the thimble, while for the most part polished by the friction of the line continually shifting, also had some newly revealed rough spots in the surface. If you look carefully at the thimble picture, you’ll see a few black spots – that’s actually black nylon deposits.

Here’s the question: Given that the slip is set up such that I need to wrap the line around the piling and it is a “permanent” line, how best to minimize friction at the running end to loop/thimble interface? I can make up some sort of chafing gear, but my experience looking at other peoples is that it doesn’t last well. There is an array of 316 stainless forged thimbles that appear ultra-smooth and low friction. Additionally, there are nylon and other synthetic thimbles out there.

Any suggestions appreciated. And if you have a thimble setup, you might wish to look hard at the condition of the line at/near the wear point with the thimble. Like I didn't.
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Old 06-27-2017, 03:01 PM   #2
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I used washing machine hose and make a big loop around the pile. That hose has smooth inner surface and ten years after installing for full time FL use the line inside was like new.
A big loop spread the load over a larger surface avoiding the friction melting you experienced.I don't bother with spices either just a bowline with the tail half hitched to the loop.
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Old 06-27-2017, 03:43 PM   #3
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Would it be easier to tie the line to the pilings? movement will lead to chafe. Even a smooth ss thimble in that setup will chafe a line eventually.

one and a half turns or a clove hitch around a piing with 2 half-hitches to finish it off won't chafe at all.
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Old 06-27-2017, 04:39 PM   #4
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Bayview - thanks, and you've reminded me that I've done similar in the past. Duh! I need to check out washing machine hose - would have thought it's too stiff to bend. Why not this time with enough extension that the hose will pass through the thimble?

The problem I have with knotting the line is strength reduction. I'm going a good ways back to my climbing days - I recall a bowline was figured to reduce the line assembly tensile strength by about a third. Some knots more. I need to research that. May be different with today's materials, although I think 3 strand nylon is pretty much 3 strand nylon, then and now.
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Old 06-27-2017, 04:57 PM   #5
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Quote:
Originally Posted by sbu22 View Post
Bayview - thanks, and you've reminded me that I've done similar in the past. Duh! I need to check out washing machine hose - would have thought it's too stiff to bend. Why not this time with enough extension that the hose will pass through the thimble?

The problem I have with knotting the line is strength reduction. I'm going a good ways back to my climbing days - I recall a bowline was figured to reduce the line assembly tensile strength by about a third. Some knots more. I need to research that. May be different with today's materials, although I think 3 strand nylon is pretty much 3 strand nylon, then and now.
I like Shrew's suggestion above about the clove hitch around the piling. That avoids the weakening knot issue.
Also, you problem was heat, not the strength of the line. Therefore even if you do use bowline, it will work fine.
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Old 06-27-2017, 05:07 PM   #6
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I just run a line aound the piling and back to the cleat on the boat.

We have tides of 4 feet average, 6 foot moon tide s and a bit bigger on storm tides.

To keep them about the right height on the piling, a nail with a length of line keeps it from getting caught too low.

Easy to adjust or remove.
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Old 07-08-2017, 09:15 PM   #7
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Go down to Arabi Sling and Rigging, in da parish, and have Big Lou make you a 3" strap with eyes on each end to wrap around pilings, then run rope through eyes.
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Old 07-08-2017, 10:45 PM   #8
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Great idea - Thanks, Kart
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Old 07-09-2017, 10:26 AM   #9
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How about instead of a thimble just splice in a big, 3'-4' diameter eye. Easy to drop or toss over a piling.
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Old 07-09-2017, 11:26 AM   #10
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Currently, Hamilton Marine has a sale, or at least VERY good pricing on Yale 8 Brait ( Plait). I bought a 600 foot spool of 1/2" for $399. Breaking strength about 8300lb working load (as ah recall) 1500-1800lb. Great stuff. I now have 8 50ft mooring lines and 2- 100ft lines. Dockmaster or I determine at the last minute to swap sides I am ready.
While I was at it I got 70 feet of 3/8 for a monkey fist heaving line. NO eye splices, loops from bowline only on the mooring lines. I lasso or boathook or hand to Dock Walker a loop and politely ask, "Please loop that cleat, piling and so forth" then control of lines are on the boat.

For my home port mooring I use whatever I come across. Mostly Sampson braid and I leave them behind. The high class 8 plait is reserved for traveling.
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Old 07-09-2017, 02:15 PM   #11
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atbu: I should have said washing machine drain hose
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