So what ratio of boat weight to dock line does one use? Most charts are listed by length of boat. A half inch being rated up to 40'. But a 35' aft cabin weights more then a 35' express cruisers. I never found chart that stated use "X" amount of 1/2" lines per "Y" lbs. of vessel. If your boat is a 35', 15000 lbs express cruisers are you safe with two lines? But if you have a 35' 20,000 lbs aft cabin, does 3 surface? Im not talking proper set up, but more so proper ratio of rope strength to vessel weight. Even thug most tie up with a min of 4 lines, two of those four are normally not doing much, depending on wind. Even Chapman's does;t address this.