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Chapter 19

Towing

Even though towing is a routine task for tugs, it is still one of the most dangerous operations Army mariners must perform. The practice of good seamanship is necessary to prevent endangering the crew, tug, or tow. The tug master is responsible for the entire operation, but the boatswain and leading seaman are responsible for preparing, making up, and rigging the tow. You should know how to make up a tow, the different types of tows, and how to assemble and rig for the different types of tows. This chapter is intended to improve your knowledge of these procedures.

TYPES OF TOWS

  19-1. The use of tugs and their connection to the tows can vary. The following are some basic configurations:
 
  • Single tug, single unit tow.
  • Single tug, multiple unit tow.
  • Multiple tug, single unit tow.
SINGLE TUG, SINGLE UNIT TOW
  19-2. 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.
  19-3. 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.
  19-4. 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
  19-5. This consists of one tug and several tows. The connection and makeup of the tows can vary. The following are the three versions 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
  19-6. 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.
  Note: When a multiple tug, single unit tow is to be made up, the senior tug master is in charge and is responsible for the tow and its makeup.

DESCRIPTION OF TOWING EQUIPMENT

  19-7. All deck crew members should know the basic terminology of towing gear, its function, and what to check for in safety and rigging procedures.
TOWLINES
  19-8. Most of the towlines used today are made up of either nylon or one of the new synthetic polyester fiber lines. Based on size and weight, they provide great strength. If properly cared for, they will last for a long time. Usually wire rope and chain are used for deep sea tows. Nylon or synthetic fiber towlines are used in inland waters and coastal tows.
NAMES OF TOWLINES
  19-9. Towlines may be called spring line or towing line, bowline or backing line, stern line or turning line, and bow breast line (see Figure 19-1).
STERN TOWLINES
  19-10. The description given here is for typical towlines that are used for stern tows over long distances and in heavy weather. For a deep sea tow you may carry as much as 2,100 feet of 2- X 6- X 37-inch high-grade, galvanized plow steel, fiber-core wire rope. Wire rope is primarily used for long distance ocean tows. For short coastal or light displacement tows, you may carry 2,400 feet of 7- to 9-inch circumference nylon towline. Refer to Appendix D for the use, maintenance, precautions, and life expectancy of both wire and nylon towlines.


Figure 19-1. Display of Towlines

CAPSTAN
  19-11. Power capstans are provided on the deck of a tug for taking a strain on line-towing hawsers. The capacity, characteristics, speed, and location vary from ship to ship.
  Note: Towlines should never be made fast on the capstan or a cathead.
CHAFING GEAR
  19-12. Chafing gear is used to prevent wear. It is additional protective material that is placed over and around a line or wire rope to protect it from damage through rubbing.
  19-13. Old fire hose cut into 4- to 6-foot lengths and then split lengthwise makes excellent chafing gear. It is wrapped around the hawser or towing cable to protect it from wear due to constant rubbing (Figure 19-2). Chafing gear can be made up of the following:
 
  • Old canvas and burlap wrapped around and secured to the towline at the point of chafing.
  • Four- to six-foot lengths of old fire hose split and then wrapped and secured around the towlines.


Figure 19-2. Chafing Gear

  19-14. A towline chafing plate for wire rope is used for making an oversea tow. These chafing plates are 2 1/2 feet long.
FLOUNDER PLATE (BALE PLATE)
  19-15. This is a triangular steel plate used as a central connecting point for the tows, bridles, and towline.
BRIDLES
  19-16. Tows to be towed astern are to be fitted with bridles. Although chain is the preferred type of bridle, wire rope may also be used. One safety rule that must be followed when making up the bridles is that the length of each leg of the bridle must be at least one and one half times the width of the tow. For a barge with a beam of 50 feet, each bridle leg would be at least 75 feet long.
RETRIEVING LINE
  19-17. This is a wire rope or fiber line that is connected to the flounder plate and usually led to the tow. The retrieving line should be longer than the distance from the tow to the flounder plate. This prevents it from taking any load. The legs of the bridle form two sides of an equilateral triangle. An imaginary line between the towing padeyes or bitts on the tow forms the triangle base.
PENDANTS
  19-18. Made up of either wire or chain; pendants are used to connect the towline to the bale. A wire pendant is usually fitted with a "hard" splice on one end and a "soft" splice on the other.
PLATE SHACKLE
  19-19. This type of shackle is preferred by personnel experienced in towing on the high seas because it will not work loose like a screw-pin shackle (Figure 19-3). However, for long tows, the threads of the shackle bolts should be peened over or the bolts welded in place.

HANDLING TOWLINES

  19-20. Three ways can be used for making up when towing alongside or towing astern. When towing alongside, towlines can be made up as a single towline or the towline can be doubled up. The method used will depend on the situation.
SINGLE-LINE LEAD
  19-21. When leading out a towline, lead it out between the towing bitts and make the eye fast to the bitt on the tow that is nearest to you. Then take in all the slack and secure the line with figure eight or round turns.


Figure 19-3. Small Plate Shackle

DOUBLING UP A TOWLINE
  19-22. In this method (see also Figure 19-4) the eye splice of the towline is put over one of the bitts on the tug, and the bight of the line is then led around the bitt on the tow. The bitter end of the tow line is made up on the same bitt as the eye. The bitter end is lead from the outboard side, and one or two round turns are taken on the bitt, making a figure eight of the line on the bitts.
 
  • Doubling the lines gives added strength.
  • When releasing the tow, you slack off on the line, cast off the eye from the bitt on the tug, and take in the line. This eliminates the need of having to put an individual aboard the tow to release the line.
RIGGING A STERN TOWLINE
  19-23. To rig a stern towline, the towing hawser should be faked out in the fantail of the tug (Figure 19-5). This will ensure that the hawser will pay out without becoming fouled. The eye of the hawser is led back over the top of the "H" bitt, over the shoulder of the horn, and back through the legs of the bitt (Figure 19-6). Then the hawser is payed out. When you get close to the point where you are going to secure the tow, take a full round turn and cross the line back onto itself. Then take two or three additional round turns before you figure eight the line on the bitts, and finish it off with two or three turns on the arm of the bitt.


Figure 19-4. Doubling-Up Towlines


Figure 19-5. Hawser on Fantail


Figure 19-6. Leading the Hawser
Over the "H" Bitt

  WARNINGS:
  1. ALWAYS FACE YOUR WORK.
  2. NEVER STEP OVER A LINE LYING ON THE DECK. EITHER LIFT IT UP AND WALK UNDER IT, OR STEP ON TOP OF IT AND CROSS OVER. NEVER STRADDLE OR STEP IN THE BIGHT OF A LINE.
  3. WHEN TOWLINES ARE COMING UNDER OR ARE UNDER A STRAIN, WORK FAST. GET THE TURNS OR FIGURE EIGHT ON AS QUICKLY AS POSSIBLE. WHEN SURGING OR SLACKING OFF ON A LINE THAT IS UNDER STRAIN, KEEP YOUR HANDS CLEAR OF THE BITTS.
  4. KNOW WHERE THE FIRE AXE IS LOCATED.

TOWING ALONGSIDE (HIP TOW)

  19-24. For tugs working inside harbors and for towing short distances or in confined areas where constant control is required, towing alongside or the hip tow is the preferred method. A hip tow can be made up on either the port or starboard side of the tug (see Figure 19-7). There are various ways of making up a hip tow; however, some standard requirements must be met.


Figure 19-7. Making Up a Hip Tow

TOWLINES
  19-25. Three lines should be used: the spring line, the bowline, and the stern line. For large or heavy tows, you may want to double up on the towlines and also use a bow breast line. Before the tug goes out to make up for a hip tow, the towing lines must be inspected and made ready. Inspect the lines for signs of severe chafing and the eyes and the eye splices for fraying or breaks. Check the towlines for wear and breaks. If you find a line damaged or one that you have doubts about, point it out to the boatswain or mate. When selecting the lines to be laid out, the usual procedure is that the best line is used for the spring line. This serves as the towline and takes the greatest strain. The second best line is used for the bowline, and the third best line is used for the stern line. The lines are then faked down (they are laid out so that they are free of kinks and obstructions). They can then be paid out rapidly when they are needed.
DETERMINING WHICH SIDE TO MAKE UP TO
  19-26. The tug secures to one side of the tow with her own stern abaft of the stern of the tow. This will increase the effect of the tug's screw and rudder. The side chosen depends on how much the tug must maneuver with the tow.
  19-27. If all turns are to be made with the tug's screw going ahead, she will be more favorably placed on the outboard side of the tow--the side away from the direction toward which the most turns are to be made.
  19-28. If a sharp and difficult turn is to be made under headway, the tug should be on the side toward which the turn is to be made. Here she is properly placed for backing to assist the turn, because as she slows, the tow's bow will turn toward the side the tug is on.
  19-29. If a turn is to be made under no headway, the tug is more efficient on the starboard side of the tow. When the tug backs to turn, the port send (side force) of her screw will combine with the drag of the tow to produce a turning effect greater than that which could be obtained with the tug on the port side.
  19-30. The best position for a long back in a straight line is to have the tug on the port side. Then the drag of the tow tends to offset the port send of the backing screw.
SECURING THE TOWLINES
  19-31. The towing line or spring line, usually a 6-inch (or larger) hawser, is led from the forward towing bitts on the tow side of the tug to the aft set of bitts on the tow. This line is secured first. Then the tug eases ahead with her bow turned in to take out all of the slack.
  19-32. Next the bowline or backing line is paid out over the outboard side of the bow stem or king post and lead to a bitt on the forward end of the tow. Once the bowline is secured on the tow, all the slack is taken in and the bowline secured. This will bring the tug into proper position, slightly bow-in to the tow. When backing down, the bowline becomes the towline.
  19-33. The stern line or turning line is lead from the tug's stern to the outboard side of the tow's stern. The purpose of this line is to keep the tug's stern from drifting out. The three lines, when properly secured and made taut, will make the tug and tow work as one unit.
  Note: If for some reason the stern line cannot be fair led and secured to the outboard side of the tow, it is then secured to the inboard bitt on the stern of the tow.
  19-34. A fourth line (optional), the bow breast line, can also be used for greater control when making up to a heavy tow. Check all the lines to ensure that they are as taut as possible. Perform this by easing the tug gently forward, then aft, to see that all the towlines are secure. The tug and the tow should be made up as a single unit.
 

CAUTIONS:

  1. When securing these towlines, remember; NEVER secure the line so that it cannot be thrown off quickly and easily.
  2. Areas of the harbor subject to wave action should be avoided whenever possible. The tug and tow seldom pitch in the same tempo. When both start pitching out of harmony, the lines take a heavy strain and may part. When equipped with a rudder the tow assists in steering. Size and loading of the tow may obstruct the view of the tug's conning officer. In that case, a lookout is stationed aboard the top who keeps the conning officer fully informed of activity and hazards in the blind area.
SHIFTING THE TOW TO THE OTHER SIDE
  19-35. Occasionally it may be necessary to shift a tow from one side to the other. One method of doing this is shown in Figure 19-8.
TOWING TWO BARGES ALONGSIDE
  19-36. Two barges may be towed alongside. Figure 19-9, shows the makeup for alongside tow.

TOWING ASTERN (INLAND WATERS)

  19-37. There are many variations of a stern tow. Different towing materials are also required. Some factors that must be considered in planning for a stern tow are as follows:
 
  • Whether the tow is being made in inland waters, bays, coastal waters, or overseas.
  • Weather and sea conditions.
  • Size and horsepower of the tug.
  • Size of tow.
  • Number of tows involved.


Figure 19-8. Shifting a Tow From One Side to the Other


Figure 19-9. Towing Two Barges Alongside

SHIFTING THE TOW FROM ALONGSIDE TO ASTERN
  19-38. Shifting usually is necessary when a tug is to tow a barge from port to port. The tow is taken alongside within the harbor and shifted astern outside. The shifting procedure is simple. The towing hawser is connected to the towing bridle before getting underway. Outside the harbor, the lines used for towing alongside are cast off, allowing the tow to drift away from the tug. Then, by slowly accelerating and carefully altering course and judiciously paying out the towing hawser, the tug gets underway with the tow and comes to the required course.
  Note: When towing astern, you have limited control over the forward motion and turning of the tow. For this reason, stern tows are made in open waters. The longer the towline the less control you will have.
TOWING LINES
  19-39. When towing in inland waters, the towing hawser is usually made up of nylon or other polyester line. For their size, the lines are lightweight and have tremendous strength. They are easy to handle. For inland waters, the length or scope of the stern towline is relatively short. Seldom will it ever be longer than 600 feet. The area in which you are towing and the master's desire determine the length.

19-40. Due to their relatively light weight, synthetic fiber towlines will float when they lie in the water. When a strain is taken on the line, it will rise up out of the water and stretch out. When using synthetic fiber towing lines there will be no catenary or dip in the towline. As the strain of the tow increases, the towline stretches out like a rubber band. As the line stretches, it will reduce its diameter by as much as 30 to 40 percent. Then the tow surges forward towing actually consists of pulling by jerks. Then the cycle starts over. The greatest danger in using synthetic fiber towlines is that if the line should part when under strain, it will snap back its full length like a bull whip. The force of the snapback is tremendous depending on the strain that the line was under at the time it parted. There is no set pattern on how the line will whip back. It may snap back directly on itself or it may whip from side to side. There is no way to tell what it will do. If you see a synthetic fiber line under strain parting or beginning to part--DO NOT RUN--just fall flat down on the deck.

TOWING ASTERN (OPEN SEA)

  19-41. Deep-sea towing places many more requirements on the deck crew members of the tug. Now we are talking of much heavier towing gear, a variety of equipment, and the added requirements for assembling the towing gear.
  Note: The tug master is responsible for determining the size and length of the towing gear to be used. The mate is responsible for obtaining this equipment. The boatswain and crew must be familiar with it and know how to assemble and rig for the different types of stern tows.
INSPECTION OF TOWING EQUIPMENT
  19-42. Before assembling the towing rig, the mate and boatswain will inspect each item of equipment. If there is any doubt of its serviceability, REPLACE IT! If there is a question of size, for safety's sake, go to the next larger size. Remember, if anyone of these items fail you at sea, you stand the chance of losing the tow and even the life of a crew member.
SCOPE OF HAWSER
  19-43. When underway, the tug and tow should be "in step"; that is, meeting and riding over the crests of waves at the same time (see Figure 19-10). Otherwise, the towline is alternately slack and taut, causing heavier than normal stresses. You can easily adjust the scope or length of the hawser when you have a towing machine. However, if you do not have the machine, it is almost impossible to make an adjustment. If you have the tow's anchor chain shackled to the hawser, you can let out or heave in the chain and hawser with the windlass.
  19-44. The scope of a hawser should be long enough to provide a good catenary, but not to the extent of having the towline drag on the bottom if in shallow water. A catenary absorbs shocks. The scope of the hawser should be no less than 200 fathoms to provide a good shock-absorbing catenary when towing a large vessel. You should not put stress on a towline to the extent of lifting it out of the water, but you can increase the catenary by reducing the tug's speed.


Figure 19-10. Keeping a Tow in Step

HAWSER WATCH
  19-45. A hawser watch must be posted on the after deck to keep tow and gear under constant observation. Instruct the crew member, on watch, to immediately report the following:
 
  • Too much tension is on the towline.
  • The tow is not weathering properly.
  • The bridles or other gear fail.
PREVENTIVE MAINTENANCE
  19-46. The bos'n is responsible for maintaining the towing cable or line, bridles, and other gear efficiently at a minimum expense. Begin by having the cable or line properly wound and stowed. Then as rusted surfaces appear, have them scraped with wire brushes and then oiled. If the towline is a cable, oil it at least once a month. After each use, have it washed down with fresh water and then oiled. Greasing the rail at the stern reduces friction. Using chafing material at points where the cable contacts the tug, tow, and bitts reduces wear and tear.
  19-47. In addition to chafing gear, continued monitoring of the towline's condition is necessary and important. Stern rollers and other fairleads must be properly lubricated and all possible points of line wear offered a fairlead. Canvas, hose, line, wood, or other materials should be used for chafing gear as required. Chafe must be eliminated or reduced on board the tow and the tug as much as possible. Continued paying out and retrieving of the towline can cause excessive chafing. Freshening the nip and lengthening or shortening the tow wire should be done every few hours in moderate weather and more often during heavy seas.
  19-48. The towline must be checked periodically for a fairlead and chafing. Points of chafe must be protected. Appropriate lubrication and wearing surfaces should be placed so as to eliminate towline-to-hull contact.

TOWING IN TANDEM

  19-49. When towing more than one barge astern, it is referred to as tandem towing. In a pure sense, tandem means one behind the other. Within the tandem rig are three other methods called the Honolulu rig, Christmas tree rig, and Modified Christmas Tree rig.
TANDEM RIG
  19-50. In this method, the tug is connected to the first tow. The first tow connects to the second, and so on if additional units are towed (see Figure 19-11). The intermediate hawser, connecting the first tow to the second, must be streamed and allowed a proper catenary depth. The surging action must be eliminated between tug and first tow and between first tow and second tow.
HONOLULU RIG
  19-51. In this method, the first tow is connected to the main tow wire. The second tow is connected, with an auxiliary tow wire, to the bitts on deck (see Figure 19-12). The Honolulu rig allows independent connection of the two tows. Disconnecting and control are readily workable.
CHRISTMAS TREE RIG
  19-52. In this method, all of the barges tow from a single towing hawser (see Figure 19-13). This is done by means of pendants shackled to flounders (sometimes called bale or fishplates) inserted in the towing hawser.
MODIFIED CHRISTMAS TREE RIG
  19-53. In the modified Christmas Tree rig, all of the tows are towed from a common flounder, but the last barge will tow as a separate unit (Figure 19-14).


Figure 19-11. Tandem Rig


Figure 19-12. Honolulu Rig


Figure 19-13. Christmas Tree Rig


Figure 19-14. Modified Christmas Tree Rig

  Note: Christmas Tree rigs are preferred for multiple tows. They are stronger and any one unit can be taken from the tow at anytime without disrupting the whole tow. The assistance of another tug is usually required to break up the Christmas Tree rig before entering port.

 

 

 

 

 

 

 

 

 

 



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