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 1/5^th 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

	AMERICAN SAILING ASSOCIATION
CERTIFICATION FACILITY