Page 35 - Randy Penn Everything Knots Book

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THE EVER YTHING KNOTS BOOK

to understand how the properties of the rope you choose to use
affect your application. Some ropes have a very specific application,
while others are general-purpose. Not all ropes can be used cor-
rectly and safely for any activity. When you choose your rope, con-
sider its properties and how they apply to your particular needs.

Strength under Strain
You need to know the strain that an application will place on
the rope and whether this strain will be steady or variable. A steady
load is one where the tension will remain constant, such as when
binding something that will not shift or suspending something that
will not move. Here the strength needed can be as easy to deter-
mine as just looking at the weight that is being lifted. However, if
the load will not be steady, the strain on the rope will be higher
and more difficult to determine.
A shifting load can increase the strain on a rope and can lead
to shock loading. You can try to prevent shock loading by securing
the load to prevent it from shifting, but sometimes shock loading
cannot be avoided and must be accounted for in determining the
strength of the rope needed. The less stretch a rope has, the
stronger it has to be to resist shock loading; a rope with more
stretch can absorb more of the energy of the shock, and therefore
doesn’t need to be as strong.

ALERT!

One way to deal with shock loading is to use a rope strong
enough to provide for a margin of safety. When rope is too
weak for the sudden load it receives, a number of problems
may occur. The rope may break, it may be weakened due to
strain, and any knots that were tied in it may overheat or even
melt as a result of the friction caused by being rapidly
tightened. Also, if a fitting the rope is secured to is not strong
enough, it may break free and fly through the air like a missile.

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