TYPES OF TOWS
The use of tugs and their connection to the tows can vary. The following are some basic types:
Single tug, single unit tow.
Single tug, multiple unit tow.
Multiple tug, single unit tow.
SINGLE TUG, SINGLE UNIT TOW
This consists of a tug and tow. Several methods are used in connecting the tug and tow. The single leg and bridle or stern tow is used for long distance towing in open waters. The alongside or hip tow is used where maximum control and maneuverability are required.
The single leg and bridle is made when the towing ship passes the towline, which is shackled to a flounder plate at the apex of the bridle. Each leg of the bridle consists of chain or wire rope passed through the bow chocks and secured on the tow’s deck to padeyes or bitts.
Towing alongside (hip tow) is most often used in congested waters. Towing alongside offers excellent control, it is not recommended for the open ocean. For alongside towing, the tug generally secures to one side of the tow with her own stern abaft of the stern of the tow to increase the effect of her screw and rudder. The side chosen depends on how much the towing ship must maneuver with the tow.
SINGLE TUG, MULTIPLE UNIT TOW
This consists of one tug and several tows. The connection and makeup of the tows can vary. The following are the three used for towing astern:
Christmas Tree rig (for long distance in open ocean towing).
Honolulu rig (for short distance towing).
Tandem rig (for congested waters where control is required).
MULTIPLE TUG, SINGLE UNIT TOW
It may be desirable to use more than one tug for only one tow. Greater power, increased towing speed, and better control may be obtained in a multiple tug tow. This type tow is generally used in towing large ships, deep-draft, large-displacement dry docks, or deep-draft barges.
