Ironic that the biggest boat on our dock has the skinniest lines.  It’s a $120,000 boat, but they skimped on the lines.

No matter the size or value of your boat, the mooring lines are essential in keeping it safe at the dock.

Are we talking about ropes? Well, yes, but when aboard a boat, ropes are called LINES.

Whether you are outfitting a newly acquired antique or classic boat, or just now scrutinizing what you already have, here are some guidelines:

How thick should the line be?

Boat Length Line diameter
Less than 30 feet  use 1/2″ line
30 feet to 40 feet use 5/8″ line
40 feet to 70 feet use 3/4″ line
70 feet to 90 feet use 7/8″ line
90 feet to 110 feet use 1″ line

If your boat is heavier than average or is docked where it is subjected to excessive wind or rough water, you should choose the next larger size.  You need at least four lines.

How long should the lines be? 

Bow line and stern line should each be about 2/3 the length of your boat.

Spring lines (two) should be the total length of your boat.

If you will be going through a lock, prepare for the rise or fall with a line that will reach the mooring rings and back at the extreme.

What kind of line?

For most of our pleasure craft, nylon offers some elasticity to lessen the shock of wind or wave action. Nylon is also less damaging to the cleat or bright work. Modern double braided polyester lines now offer much the same advantages of the nylon.

Double braid is the strongest of the line structure and the easiest to splice to form the eyes at the line ends.

“You get what you pay for” is so true when you’re shopping for line. This quote comes from Rope, Inc.

“Sighting the braid”
When selecting a new piece of line, simply sight down its length as you would a plank. If you see broken yarn filaments, high or low strands, corkscrew or roll, randomly uneven yarn color or looped strands; beware!

Their Rope, Inc. website goes on with more information about what to look for in a quality line.


Tying up at the dock or in a slip with the correct lines is much simpler.  BoatUS offers this advice:

Tying up at a dock is one of those techniques that’s most elegant when it’s done simply. The trick is to get the fewest number of docklines serving the greatest number of functions. And doing that means paying attention to three things: Strong points, a good hitch, and the right combination of lines.

The best combination of docklines is typically at least one springline, plus a bow line and a stern line. If you run the bow line forward and the springline aft, you’ll limit the boat’s motion in both directions yet still allow for some motion up and down.  [BoatUS June 2015]

(Did you know that BoatUS gives a 50% discount on their membership to active ACBS members? Call ACBS (315) 686-2628 for discount code)

Another day, we’ll take a look at fenders…more essential equipment.

Headline picture above was taken by Forrest Bryant and used as a cover picture on the Heartland Classics Chapter quarterly magazine, Mahogany & Chrome.

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  1. I think not enough attention is paid to backing for cleats and fairleads…All of the above info is useless if a surge or high winds rips out these items. Disaster awaits.

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