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 TB 55-1900-232-10
CHAPTER 2
ELEMENTS OF TOWING-SHIPS AND HARDWARE
SECTION I
2-1 INTRODUCTION
This chapter introduces the technology and equipment involved in towing operations. Included are brief
discussions of the tows, towing ships and towing systems involved in the operation. Detailed data on
operations and on the design and selection of towing systems and components are contained in subsequent
chapters and the appendices. Through- out this manual the terms "tug" and "towing ship" are used
interchangeably.
SECTION II
2-2 TOWS
2-2.1
TYPES OF VESSELS. The types of vessels which may require towing include the following:
a. All Navy combatant ships-ranging in size from small patrol boats to large aircraft carriers
b. Non-combatant vessels-ranging from targets to large fleet oilers and other supply ships.
c. Non-ship vessels-ranging from small barges to large floating dry-docks
CAUTION
The craft listed in Table 2-1 are representative of vessels requiring special
consideration. Evaluation of stability characteristics, material condition of the hull,
equipment on board, operational requirements and other applicable considerations
must be made on any craft before towing. Only under extreme emergency
situations should open-ocean towing be attempted when the tow is not considered
seaworthy.
Hulls not considered seaworthy for open ocean tows should be transported as deck cargo or on board a floating
dock, submersible vessel or LSD-type ship. Table 2-1 provides a partial list of tows which are not
recommended for open ocean towing, along with supporting rationale as to why they do not qualify
2-2.2
TOWING SERVICES. The conditions under which towing must be attempted depend to a large
degree upon the principal missions of the Navy at the particular time. Wartime towing can be essentially
worldwide and will often include combat zones as well as the supply routes to these zones. The weather
environment can range from tropical to polar and local specific weather conditions can range from dead calm to
tropical cyclones or Arctic ice storms. Towing can also vary from routine, well-planned activities to time-critical
emergencies such as rescue or salvage towing.
2-2.2.1 Routine Towing. Routine Navy towing includes a wide variety of activities such as harbor work and
many classes of offshore or open ocean towing. The vessels towed in routine point-to-point ocean tows include
barges, special work craft and ships of various classes being towed to repair bases or to reserve fleet areas.
Included in the routine-tow category are target towing and other special projects such as towing oceanographic
instrumentation plat- forms and R&D operations.
2-2.2.2 Emergency Towing. Navy emergency towing consists almost entirely of escort, rescue and salvage
missions Much of this towing is performed by ships that have been specifically designed and built for such duty.
However, nearly every class of U.S Navy ship can tow and be towed in an emergency. See Chapter 3 for data
on "Tow and be Towed." Ships not specifically equipped for towing can make use of anchor chains, wire
straps, mooring lines or necessary combinations of these items. A proper catenary will ensure some spring in a
wire towline; slow speed will minimize dynamic loads developed between the towing ship and the tow
Therefore, the towing
2-1
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