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Whether you are tied up at your permanent slip or are securing your boat in a transient slip, selecting and using the correct dock lines for the task can be daunting. There are simply too many choices and some work better than others. Let’s simplify this process by comparing your options in terms of materials, construction, size, and length.

Materials

Dacron

Dacron can be seen in some fashion on most sailing vessels. While it comes in many color patterns, it does not stretch and therefore does not make a good dock line.

Polypropylene

Polypropylene is inexpensive and it floats. It is because of these characteristics that poly line is often used for watersports such as waterskiing and well as for towing rafts and dinghies. It will stay afloat and away from your prop. It is also very slippery to work with and difficult to splice. Most polypropylene has a low breaking strength and because it is so cheap, it may also have poor-quality control.

Nylon

One material that stands out as being particularly excellent for dock lines is nylon. Nylon has four qualities that make it the best for dock lines.

   1. Elasticity

Nylon stretches and is elastic. It will absorb the sudden stress and strains caused by the environment. Nylon doesn’t tighten suddenly. It dissipates sudden loads by stretching. It will stretch about 15% of its length at about 20% of its breaking strength. Think of it as a shock absorber for your boat. This means less stress, wear and failures off your deck hardware.

   2. Strength

Nylon is very strong. For example, a 5/8” double braided nylon dock line can have a breaking strength of 13,500 pounds. This makes it perfect for the stresses of holding a boat to the dock in inclement weather. 

   3. Resistance to exposure

Nylon is resistant to damage from environmental stressors such as ultraviolet radiation, chemicals, and fuel. This provides peace of mind and longevity of your dock lines and boat security. 

   4. Economical price

Nylon is relatively inexpensive. It is not as cheap as polypropylene, but very close and it’s overall benefits add up to the right purchase. 

Construction

Nylon line comes in both braided and three-strand construction options:

Braided

Braided nylon dock lines are constructed with a braided inner core and smoothly woven outer jacket. Braided lines are generally stronger than three-strand lines in terms of breaking strength and abrasion resistance. From an aesthetics standpoint, braided lines look and feel great. They wrap neatly around cleats and coil down perfectly on the fiberglass deck of your boat. Braided line’s ability to flemish and coil nicely gives your boat that “attention to detail” look.

Braided line can be a good choice for tying up in your home dock. On the flip side, braided lines tend to snag on everything from wood pilings to concrete or wood docks, and it’s because of this that they do not make the best choice for keeping on your boat while you are visiting transient slips.

Three-strand

Three-strand nylon is the most practical and ideal choice for dock lines. It is made up of many smaller filaments that are wound into three primary strands that form one solid line much like steel cable. Three-strand line is easy to splice. It is less expensive and has more stretch than braided line. Three-strand lines also tend not to snag on pilings or docks as much as braided lines.

Size

Choosing the correct size line for your boat is much more important than selecting the biggest size. Although a larger diameter line will take longer to chafe through, it also becomes less elastic. Most of the pre-spliced “dock line in a box” will have sizing charts. The line diameters shown in the chart should deliver both a sufficient strength and elasticity needed for your boat size.

Length
For your home slip, cut and splice the lines to length to suit the tidal range or expected water level changes. Every boat should have two stern lines and two bow lines equal to the length of the boat. This gives you flexibility in a variety of conditions. For spring lines, carry two lines equal to 1.5 times the length of your boat.

Dock Line Maintenance

Once you have purchased your dock lines, remember to inventory and inspect the lines at least once a quarter, before and after violent storms, and any time you suspect chaffing may have occurred. Also retie the lines an inch or two in or out so that the lines will not rub or chafe at the exact same spot. Repair or replace suspect lines when needed – it is a cheap form of insurance.

If you have any questions regarding dock lines and which type is the right fit for your vessel, feel free to reach out to anyone on the Yachts360 team. We would be happy to discuss your dock line questions.