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Marlinespike - Rope Safe Working Load

Knowing the maximum safe working load for line can help prevent accidents and tragedies. You should never stress a line anywhere near its breaking strength. As line is spliced, stretched, wears, is subjected to sustained loads, shock loads, loads of many times the recommended working load, subjected to great heat or ultraviolet light for long periods of time it will continually loose some of its strength. Each line should be inspected prior to using it in extreme load conditions and if chafe, excess dirt, cut or worn strands, stiffness or hardness are found the line should not be used.

Important: Do not allow anyone to stand in line with, or within 45 degrees on either side, of a line under tension. Should the line part, the recoil force may cause serious injury.

Safe working load is generally thought of as no more than 1/5th of a line’s breaking strength. Said another way, the breaking strength should be five times the weight of the object the line is going to hold. You are not expected to memorize the tables below but you should remember this 5 to 1 safety rule. You should always choose a line with its intended safe working load in mind. The American Boat and Yacht Council has published charts of safe working loads for various types of line and are outlined below.

American Boat and Yacht Council Safe Working Load (in pounds)
3 strand twisted line and single braid line

Diameter

Circumference

Manila

Nylon

Dacron

Polypropylene

1/4

3/4

120

182

182

213

5/16

1

160

281

281

232

3/8

1 1/8

216

407

407

459

1/2

1 1/2

424

704

704

714

5/8

2

704

1144

1100

1054

3/4

2 1/4

864

1562

1375

1445

7/8

2 3/4

1232

2200

1980

1955

1

3

1440

2750

2420

2380

American Boat and Yacht Council Safe Working Load (in pounds)
Double braided line

Diameter

Circumference

Nylon

Dacron

1/4

3/4

420

350

5/16

1

680

560

3/8

1 1/8

960

750

1/2

1 1/2

1630

1400

5/8

2

2800

2400

3/4

2 1/4

3600

3000

7/8

2 3/4

5300

4800

1

3

6260

5600

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