Boat Length Rope Diameter
  Metric Inches
Boats under 20 feet or 6 metres in length 10mm 3/8"
Boats from 20 to 30 feet or 6 to 9 metres in length 12mm 1/2"
Boats from 25 to 35 feet or 8 to 10 metres in length 14mm 9/16"
Boats from 30 to 40 feet or 9 to 12 metres in length 16mm 5/8"
Boats from 40 to 46 feet or 12 to 14 metres in length 18mm 3/4"
Boats from 46 to 54 feet or 14 to 17 metres in length 20mm 4/5"
Boats from 55 to 63 feet or 17 to 19 metres in length 22mm 7/8"
Boats from 64 to 72 feet or 20 to 22 metres in length 24mm 1"


As a general rule, the length of bow and stern lines should equal half of your boat's overall length. Spring lines should be slightly longer, approximately  two-thirds the length as your boat. Spring lines keep the boat snugly near the dock by preventing it from moving fore or aft, while allowing for the rise and fall of the tide.

Keep in mind; the position of the cleats on your boat and dock as they may affect the length of the dock line required. Always check if your boat cleats height and centre gap will accept the proposed dock line loop.

Unless your boat is unusually heavy or will be subjected to severe conditions, a bow line, stern line, and two spring lines are recommended. If your permanent slip has outboard pilings as well, you will need an additional bow and stern line.

In the case of cyclonic weather (constant winds above 50 knots), it is always recommended to double the amount of dock lines. That is 2 X bow, 2 X stern and 4 X springer. This is recommended over solely increasing the diameter of an existing dock line.

Whitsunday Discount Marine only recommends using either double braided, 3 strand nylon or 8 strand polyester for dock and mooring lines; the stretch characteristics absorb shock and will resist damaging cleats on your boat and on your dock.

Remember by increasing the diameter of a dock line, in turn reduce the wearing due to constant abrasion caused by the boats's movement in wind, tide and current.

Our nylon, poyester and polypropylene docking ropes are supplied with a 300mm loop spliced and whipped at one end. The majority of our docklines have an anti-chafing sleeve to prevent abrasion and marking the hull.



  Nylon Double Braided Polyester 8 Braid
Rope Diameter Breaking Load Kg Working Load Kg Breaking Load Kg Working Load Kg
10mm 2,000 400    
12mm 2,400 480    
14mm 3,300 660    
16mm 4,400 880    
18mm 5,000 1,000 5,500 1,375
20mm 6,500 1,300 6,910 1,725
22mm     9,910 2,475
24mm     12,140 3,025