Question

If you are using a double braid rope that has a breaking strength of 8,600 pounds, how much can safety be liftedonce a knot is tied in the rope?

a. 860

b. 2,000

c. 1,500

d. 650

Answer 1

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 should always choose a line with its intended safe working load in mind

Working loads, often called working load limits (WLL), are calculated by dividing the rope minimum
breaking strength (MBS) by the required safety factor (sf).
WLL = MBS ÷sf

=8600/5 = 1720

= 2000

While a knot reduces rope strength, a knot can be a convenient way to terminate a
rope for attachment to other hardware/equipment. The tight bends that occur in the knot result in
strength loss. With some knots, ropes can lose up to 50% of their strength. However, this number
can be higher or lower based on rope construction and fibers used. It is vital to take into account
the reduction in strength by the use of knots when determining the size and strength of a rope to
be used in an application. Whenever possible, spliced terminations should be used to maximize the
rope strength for new and used ropes.