The term "stopper," as used in seamanship, describes a device or rigging arrangement that is used to tempo-
rarily hold a part of running rigging or ground tackle that is, or may come, under tension. The stopper is an
indispensable tool in a towing operation.
E-2 TYPES OF STOPPERS
There are many types of stoppers and methods of attaching them to the tension members that are to be
stopped off. Most stoppers cannot be released under load, and require the held line to be heaved in to slack
the stopper and allow its removal. On the other hand, some stoppers, such as the pelican hook and carpenter
stopper, can be released when under load.
There is no single "best" type of stopper for all situations. However, for the three basic types of tension
members-chain, fiber line and wire rope- the following is recommended:
a. Chain The attachment to a tension member should be made by means of a suitably-sized, jaw-type
chain stopper . See Figure 3-22
b. Fiber Line . Fiber line always should be stopped off with fiber stoppers
Wire Rope Stopping a wire rope can be accomplished with a carpenter stopper, Klein grip, chain
stopper or fiber stopper using Kevlar
E-3 PREVENTION OF DAMAGE
When passing a stopper, a major consideration is prevention of damage to the tension member that is being
stopped off This priority is second only to safety of personnel.
A dedicated towing ship's towing hawser is its "main battery" If the towing hawser is damaged, the ship
essentially is out of action
Properly using a stopper on a towing hawser entails considerably more than merely passing the stopper It
requires very close coordination between the Conning Officer on the bridge and the Boatswaiun's Mate in
charge of the stopper-passing evolution on the fantail.
E-4 STOPPING OFF A WIRE TOWING HAWSER
Never pass a stopper on a tension member that is under a strain greater than the safe working load of
the stopper, or on a tension member that might be subjected to a heavier loading condition while the
stopper is in place.
A properly-fitted carpenter stopper should always be used when stopping off a wire rope towing hawser. See
technical manual on carpenter stoppers (Ref. 24)
In a situation where a carpenter stopper is not readily available, the hawser can be stopped off with a chain . If
a chain stopper is selected, great care must be exercised so as to prevent damage to the hawser
E-5 SYNTHETIC LINE
In recent years synthetic fiber line has replaced virtually all large natural fiber line in the Navy. Synthetic fiber
has many good qualities, such as its superior strength and elasticity.
Its prime weakness when compared to other types of tension members is its susceptibility to physical damage .
It is very intolerant of mechanical mistreatment such as cutting by sharp objects, melting of the fibers due to
friction or abrading by rough surfaces. Damage of all three types may occur from the action of a poorly-passed