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 TB 55-1900-232-10
board splaying is commonly done on barges and the technique has been successfully applied to twin-ruddered ships and
floating dry-docks. All such rudder or skeg movements should be made in moderation to obtain optimum towing
performance with aluminum increase in drag.
3-5.4.4 Location of Attachment Point.
A point of bridle entry into the tow may be selected to offer an optimum angle, and thus eliminate or reduce excessive
yaw or sheer. Care must be taken to prevent towline chafing, and to ensure that a fairlead is sufficiently robust. As an
example, the LST 1179 Class requires either a bridle or an off-centerline pendant because of the bow doors Towing is
per-formed through a mooring chock on the side. These ships tow quite steadily with a very slight sheer. Care must also
be exercised to ensure equal leg lengths on the bridle rigs, to avoid generating a sheer problem with the tow.
3-5.4.5 Propellers. A locked propeller will create a larger drag than a free-wheeling propeller, thereby resulting m
reduced towing speed. However, the additional drag in the stern due to a locked propeller may decrease the tendency of
the vessel to sheer off from the intended track. Refer to Paragraph 3-27.2 for information on preparing the propellers for
tow
3-5 4.6 Steering Tug. The addition of an operational ship astern of the tow can offer effective steering control of the tow
The trailing ship can use its engines and rudder to maintain a light tension on the line to the tow. Following steering
orders from the tow ship, it can assist in keeping the tow from sheering off.
3-5.4.7 Sea Anchor or Drogue. An object towed from the stern of a tow will create a drag that acts to resist yawing
motions. Nets, anchor chain, line, wire, kite anchors, mine-sweeping gear and a wide variety of other drogues have been
used as stabilizing devices on small tonnage or shallow draft ships, especially those with fine hull forms. Care should be
taken to prevent snagging of the drogue in shallow water.
3-5.4.8 Bridle vs. Single Lead Pendant. Certain hull forms are more conducive to being towed by a single lead pendant
Submarines and ships with bulbous bows or forward sonar domes tow better on a single pendant than on a bridle.
3-5.5 HEAVY WEATHER. Long ocean passages rarely offer opportunity to plan a tow schedule that can guarantee
favorable weather. Seasonal storms and sudden, unexpected weather can cause difficulty for both the tug and tow.
Hurricanes, or typhoons, are the most dangerous and destructive of all storms. Advice on actions to take in the event of
such storms is contained in Chapter 18 ofKnight's Modern Seamanship (Ref. 13)
Steps to take upon receiving warning that a tow may encounter a hurricane include the following:
a. Determine the relative locations and tracks of the tow and the hurricane in order to best plan a course to avoid at least
the dangerous semicircle.
CAUTION
Running before the sea and wind can cause difficulty in steering and in keeping the tow astern or in the desired
position. The tug may be pooped or the tow may tend to overtake the tug. The overtaking will reduce the
tension in the towline and cause an increase in the catenary which may also cause the towline to snag on the
bottom or bring the tug and tow to collision. The recommended course of action is to head into the weather
and maintain steerageway, increase hawser scope and, as long as there is enough searoom, tolerate a negative
speed over the ground. There is no reason to slip the tow unless the towing ship is in danger of grounding.
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