What size dock lines for a 13,000 pound boat?

[Rockinar]

What size dock line would be good for a 13,000 pound boat? I know this will kinda depend on the boats cleat size, just wondering what an average would be good as far as strength.

[Don C L]

I'd use 5/8" nylon. Where are you? Do you have a lot of surge and/or chance of major storms coming through?

[GordMay]

Not directly responsive, but, perhaps, useful:

Design Loads for Deck Hardware ➥ https://www.cruisersforum.com/galler...r&imageuser=79

WLL for Anchor Rodes ➥ https://www.cruisersforum.com/galler...r&imageuser=79

[tkeithlu]

Ditto on Don C L. I wouldn't use less than 1/2" nylon on any boat, and I use 3/4" nylon for a 65,000 pound boat. Came through hurricane Michael just fine.

[EmeraldCoastSailor]

I have a similar situation (6 tons) and researched it once. 1/2" seems like the right size so there is a adequate stretch combined with enough strength. I use 1/2" for springs and 5/8" for stern and bow lines just to be a little over in terms of strength. If a storm is forecast I add lines.

[TrentePieds]

Rockinar said: "What size dock line would be good for a 13,000 pound boat? I know this will kinda depend on the boats cleat size, just wondering what an average would be good as far as strength."

Well, no - it doesn't depend on cleat size :-) It's the other way about! You determine what tensile strength you need to keep your boat secured in her slip. THEN, when you've looked up the tables to see what kind and diameter of line you need to attain that tensile strength, you determine from that chosen diameter the size of your cleats.

As a general rule for cleats: Bigger is better. Within reason.

Having determined the size of cleat, you must now consider if the means of attaching the cleat to the boat can handle both the tension and the sheer to which the cleat will be subject.

But a 13K boat is only a baby so don't overthink it. In a finger slip in a marina, 1/2" is plenty. Slip a "snubber" (a rubber "shock absorber") onto each mooring line so when the boat moves in her slip, sudden (and therefore destructive) tensioning of the lines is prevented.

Use horn cleats for mooring lines and learn to belay them correctly.

Mooring lines are the SHIP's gear. Not the marina's. Take your mooring lines with you when you depart the marina, and when you enter a slip or come alongside anywhere, get secured, then tidy up so each mooring line has just enuff length to belay on the marina's cleat or bullrail and the excess length is taken on deck and there "cheesed" down neatly.

TrentePieds

[dadster3]

I replaced all my dock lines with 1/2" double braid. They are soft and easy to work with, but still can be difficult where you have multiple lines on a single cleat, as in spring lines. The three strand nylon (5/8 & 3/4) that were replaced were just too hard to tie & untie, especially after they had stiffened up from use. You're in a marina, and the likelihood of storm level stress is minimal to non-existent on a day to day basis. I did use some heavier 3-strand a couple of years ago when it seemed we might get some serious weather from a hurricane remnant, but nothing came of it. It is unlikely that you will be surprised by weather so extreme as to compromise 1/2" lines. Oh, BTW, my boat is 15,000 lbs.

[sinnerman]

I have a 10,500 (empty weight) 30 ft sailboat. And use 1/2" lines.

I use 3- strand nylon which has the most "stretch" (which you want as it absorbs shock loads).

They also have braided nylon lines which are less stiff and therefore easier to handle (and more $$).

I add some 5/8" backups (spring lines) when hurricane season arrives.

Guides:

https://www.westmarine.com/WestAdvisor/Dock-Lines

https://www.defender.com/pdf/Defende...-Selection.pdf

https://www.boatus.com/expert-advice...sing-docklines

Cheers

[thunderhoof]

I bought a length of 5/8 inch Nylon 12 strand single braid to make a set of dock lines. The advantages are: relatively inexpensive, easy to splice ( basic core to core with lock stitches), good shock absorbing (some springiness) and a soft, easy to use feel. Some folks add a wear-resistant jacket over the cleat loop which is not necessary in most situations.

[Pegu Club]

Originally Posted by Don C L

I'd use 5/8" nylon. Where are you? Do you have a lot of surge and/or chance of major storms coming through?

In agreement here, we use 5/8” dock lines on our Bristol 29.9, we are located on Long Island Sound, near New London CT, we head south/ Bahamas for the winter, although this winter we are in sunny SoCal,

Fair winds,

[zstine]

I think 5/8 will be too big and will not have enough stretch. Tartan recommended 5/8 for my 19,000lb, 41ft boat. so a 13,000 boat I'd go a size or 2 smaller, 9/16" or 1/2". This is not a "bigger is better" type situation. Chafe is what kills line. A 1/2" lie is plenty strong as long as you don't chafe through.

[Cheechako]

On that light a boat it will be dictated more by what's comfortable to handle I suppose. 5/8" nylon would be nice if the cleats will accommodate it, but 1/2" is plenty.

[HankOnthewater]

I think posts #6 and #11 are spot on. And the comments that many others made: protect from chafe !!! The stretchier the rope is, the more chafe it will have when going over the gunnels etc.

I agree that 1/2" (12 mm) suffices when using nylon, and that 5/8" in nylon might not give enough stretch.

Another variable to be taken into account is if the marina/pen/berth/slip is subject to waves, and how protected it is from prevailing winds.

Again when very protected, 12 mm might be fine, when exposed go one size higher to 14 mm (is that 9/16"?), again in nylon. When in an exposed location, check backing plates, or increase them and maybe also size of bolts and cleats.

When using silverrope (poly-ethylene 3 strand) use 5/8" or 16 mm to start with and 18 or 20 mm (3/4") in exposed areas.

When using nylon, no need to use rubber snubbers.

When in a permanent pen/berth/slip, splice eyes in the ropes at the correct length, that speeds up the docking process, much more secure, and takes up less space on a cleat.

[Adelie]

Anchoring and dock loads are size dependent.

When a wave hits 2 boats of the same size but differing weights it imparts the the same momentum to each.
So the lighter boat experiences higher acceleration but decelerates more quickly as the lines tighten and the loads a similar.

[KP44]

Originally Posted by Don C L

I'd use 5/8" nylon. Where are you? Do you have a lot of surge and/or chance of major storms coming through?

Ground tackle and cleats are second only to your hull in importance. They will keep you safe when everything else fails.

Always size your cleats and your lines for storm conditions. As someone told me, "Cleats are never too large during a storm." (I replaced all the 8" cleats on my boat with 15" cleats.)
Replace stock cleats with larger, if needed. It is a worthwhile project. Make your lines large enough to be comfortable in your hands.
At 6 1/2 ton; 1/2" is good, 5/8" is right - and 3/4" lets you sleep soundly in any conditions.