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 TB 55-1900-232-10
When stopping off a synthetic towing hawser, a synthetic fiber stopper should be used.
E-6 STOPPER BREAKING STRENGTH
Ideally, the strength of the passed stopper would be equal to the strength of the tension member, thus
eliminating the stopper as the weak link in the system.
When stopping off relatively small lines such as fiber boat falls, this ideal strength condition may be achieved.
The prime factor limiting breaking strength of a large stopper is the physical size that can be manually handled
by the deck seaman. As an example, a stop- per of 1/2-inch chain can be passed fairly easily and one of 3/4-
inch chain with some difficulty. However, if one were to try to match the breaking strength of a large towing
hawser of 2- to 2 1/2-inch wire, he might come up with a stopper of 1 1/2-inch or 2-inch chain. From an
engineering point of view, the numbers would match up, but from a practical seamanship point of view the deck
force would be faced with an impossible task.
In cases of heavy rigging, the stopper indeed becomes the weak link. Thus, all personnel who are involved in a
towing hawser/stopper passing evolution must be aware of inherent dangers.
During the period the stopper is in use on the towing hawser or pendant, the Conning Officer should not
increase speed or radically change course without first notifying the afterdeck of his intention, and requesting
concurrence from the Afterdeck Supervisor that it is safe to do so. Direct communication between the deck
work area and the bridge is mandatory.
The Conning Officer should be well-versed in the use of stoppers, especially concerning their applications and
limitations.
E-7 FIBER STOPPERS
Fiber stoppers, shown in Figure E-1, are the simplest and most commonly used type of stopper.
One version, called a rat tall stopper, may be merely a length of fiber line with an eye in one end, with the
section of the stopper that is to make contact with the tension member flattened.
When using a 3-strand line, this flattening is accomplished by passing a seizing, unlaying the line and then
weaving it back together m a 3-strand braid.
In the case of double-braided line, the flattening may be accomplished by shipping the cover back and
removing a section of the core.
E-8 STOPPER HITCHES
Attaching the stopper to the tension member may be accomplished by any one of a number of methods, such
as:
a. A rolling hitch backed up with half hitches (see Figure E-1 .
b A long series of half hitches, known as a crossover or Chinese stopper (see Figure E-2).
c.
A series of crisscrosses formed by weaving the stoppers over and under the tension member (see
d. Two long series of half hitches formed by half hitching a double stopper to the hawser (see Figure E-
5).
e. Any desirable number of combination of the above.
There is no universal best stopper hitch. The decision as to which hitch arrangement to use is dependent upon
the size and composition of the line to be stopped, the size and composition of the available stoppers and the
personal.
E-2
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