In the most recent high wind event, we had another dock line break and nearly lost a boat to the fierce winds.

If you are currently relying on some old ski rope, shoe string, clothes line, or dental floss, or even marine grade dental floss, you are taking a chance of not only damaging your boat, but your neighbors’ boat and possibly the dock itself.

You, the Owner, are ultimately responsible for all damages incurred.

Consider the following when mooring your boat. When followed, these guidelines provide parameters to properly secure your boat and prevent a boat break away.

  • Size of the dock Line:
    Your dock line should have 1/8″ of diameter for every 9′ of boat with a minimum size of 3/8″. This means a 20′ boat should use 3/8″ lines. A 40′ boat should use 5/8″ line.
  • Number of Dock Lines required:
    At a minimum, you should have one bow line, one stern line, and two spring lines. You don’t always need to use two bow/stern lines, but you should have them on board regardless, because there will likely be a time when you do need them. When you’re expecting heavy/stormy conditions, consider doubling up your lines.
  • Type of Dock Line Required:
    It is recommended that your dock line must be nylon rope. Polypropylene degrades quickly in the sun, doesn’t have the level of stretch needed, and has a low breaking strength so it is generally a bad choice. Dock lines most commonly come in three weave types:

Three-stranded, braided and double braided. There are subtle differences between these three types of lines listed below, but ultimately, any of these types makes an adequate dock line.

  1. Three-strand: Abrasion resistant, stretches more, easier to splice less expensive.
  2. Braided Nylon: Stronger, easy on the hands, looks good.
  3. Double Braided Nylon: Strongest, easy to handle, abrasion resistant and controlled elongation, looks good.

Dock Lines Lifespan and Care (and Tricks Making them Last Longer)

Most dock lines are quite durable, and you may get several years of use out of them before you see any deterioration in performance. You should wash your lines with a simple brush and hose every few months to prevent build up on the lines. However, even with proper care, lines tend to get ‘gunky’ over time, and many boaters elect to replace their lines every 2-3 years.

Dock lines are also prone to some stiffening from repeated dampness and drying out. To reduce the stiffness, a popular sailor’s trick is to place the dock lines in a pillow case and wash them in the washing machine with a healthy dose of fabric softener.

Dock Line Accessories: Snubbers and Chafe Guards
There’re also several accessories you can use with your dock lines. The most popular are line snubbers and chafe guards. A line snubber help absorb the shock from agitated lake conditions, reduce wear and tear on your lines and reduces the stress put on deck and dock cleats.

Congratulations if you made it to the end of this message. Sorry, there is no prize for doing so except perhaps you may have learned something new or were reminded to practice what you already know.

Joel Leach
Harbor Master
Grand Lake Sailing club

References
https://www.anchoring.com/blogs/anchoring/how-to-choose-the-best-size-of-dock-lines-