TOWING RIGS

MODIFIED CHRISTMAS RIG
TANDEM RIG

HONOLULU RIG

CHRISTMAS TREE RIG

TOWING IN TANDEM
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
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. 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
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. The Honolulu rig allows independent connection of the two tows. Disconnecting and control are readily workable.

CHRISTMAS TREE RIG
In this method, all of the barges tow from a single towing hawser. This is done by means of pendants shackled to flounders (sometimes called bale or fishplates) inserted in the towing hawser.

MODIFIED CHRISTMAS TREE RIG
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

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.

ALONGSIDE TOWING

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. There are various ways of making up a hip tow, here are some standard things to keep in mind.

Making Up a Hip Tow
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 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 operator. 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
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.

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.

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 placed for backing to assist the turn, because as she slows, the tow’s bow will turn toward the side the tug is on.

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.

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
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.

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.

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.

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 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. The tug and tow seldom pitch in the same manner. When both start pitching 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 operator. In that case, a lookout is stationed aboard the top who keeps the operator informed of activity and hazards in the blind area.

BASIC TOWING

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.

BASIC TOWING #5

If you are taking a disabled vessel in tow at sea and the weather is good you should not have any problem. The lines are run and secured as you would any vessel that you are towing. The towing vessel starts ahead slow on the course that the disabled vessel happens to be heading and uses every precaution to prevent a jerk on the line. Before changing course, you should wait until both ships have way and are moving steadily with a good tension on the tow line.

In bad weather, towing should not be made unless circumstances make it necessary. The running of lines in a heavy sea is a lot more difficult, especially if the vessel to be towed is unable to assist by placing herself in a good position. In really heavy weather, it would be necessary to proceed so slow that little or no time would be lost by waiting for the weather to get better.
Disabled vessels lie in different positions relative to the wind,it depends on the size and position of the superstructure, the trim. If there is more superstructure for­ward than aft, the vessel will lie with the wind from abaft the beam to astern. Vessels with more superstructure amidships will lie with the wind abeam, and those with superstructure aft, such as tankers, will lie head into the wind. All vessels make leeway and, if lying at an angle to the wind, headway or stern way of 1 to 3 knots. Vessels down by the head tend to head into the wind, and vice versa.
If a tug with a deckhouse forward and a flat stern is the towing vessel, she should approach downwind and just clear of the bow, except when the vessel to be towed lies head into the wind. In this case, the approach of the tug is still downwind but just ahead of the vessel, using the engines to keep her position and clear.

Here is how a towing operation might go. It will be assumed that one vessel is going to tow another and that the weather is rough, but not rough enough to make towing impracticable. The disabled vessel will be lying with the wind and sea abaft the beam. You should have some means of communications with the other vessel. The first line to be run will be a light one by which the heavier ones can be hauled across. There may be special circumstances when it will be desirable for the disabled vessel to run lines, but under ordinary circumstances it is more convenient for the towing vessel to run them. Once the first line is across, the heavier lines are run and made fast to the anchor cable of the vessel to be towed. A good length of cable is paid out 20 to 45 fathoms is none too much for heavy work and the line made secure on both ships. Chafing gear is used wherever it is needed. And when all is ready, the engines are started ahead as slowly as possible and stopped the moment the line begins to get tight. Then a few more turns are made and so on until the inertia of the tow is overcome and both ships are moving slowly with a steady tension on the line. The revolutions are then increased little by little and the course changed gradually. When the tow is finally straightened out and moving steadily, the speed is worked up to that at which it is best.
After settling down to a steady rate of towing, the lines should be exam­ined, the strain divided as evenly as possible, chafing gear renewed wherever necessary, etc. crew should be stationed night and day to watch the lines on both ships, with axes and unshackling tools ready for slipping.

BASIC TOWING #4

Securing the Line on the towed ship on board the tow, the hawser is usually secured to the anchor cable, there are a lot different conditions and some other plan will be used. Use a short length of chain to take the chafe in the chock if the anchor cable is not used. If the anchor cable is used, the hawser is secured or shackled to it and the cable veered away to the desired length; the windlass brakes are then set up and springs or chain stoppers used to take the real strain of towing. You should have a shackle between the windlass and the point at which the springs or chain stoppers are secured and to keep tools at hand for unshackling if it becomes necessary to let go in an emergency. The tow should not be let go in this way, except in case of extreme emergency, because the line weighted with a length of heavy anchor cable would sink immediately, hanging as a dead weight from the stern of the towing vessel. In this position, it would be very hard to handle and in danger of fouling the propellers. This is only when the tow is a vessel of some size and is towing by her anchor cables. When a large ship is towing a small one, it is evident that the natural way of casting off is for the tow to let go, leaving the line to be handled by the large ship.

BASIC TOWING #3

In securing the towline, you must keep in mind of letting go in an emergency. In letting go, it is desirable to have a break in the line near the stern. It would be advisable to have a shackle connecting two parts of the line at or near this point, together with some arrangement like a pelican hook for slipping. The possible whip of towlines and bridles when these are released at any point may be overcome by the use of preventers.
If the towing ship is comparatively large and has a chock at the stern, the line should be brought in through it. It is a good plan to use a short length of chain for the lead through the stern chock, shackling it outside to an eye in the end of the towing hawser and inside to a towing bridle. The chain through the stern chock takes the chafe but by its flexibility does away with the dangerous nip that might be thrown into the wire if the tow was to take sheer on the quarter.
Where the chain is not used for taking the chafe in the stern chock, the towline must be fully protected by chafing gear in the form of a pudding. The stiffness of this pudding reduces the sharpness of the nip; without the pudding, the nip would be thrown upon the towline from time to time by the sheering of the ships. Manila should be wormed, parceled, and served. Canvas, hides, burlap, and old rope should be used on wire towlines.
If the strain is not too heavy, one pair of bitts may be used to secure the towing line.
When one pair of bitts is not strong enough, the line can be taken to as many as three sets of bitts. To divide the strain, it is advisable to take one turn around the first set, two around the second, and three around the third.
If pelican hooks are used for letting go, the strain is taken on the hook, relieving the shackle so that it can be disconnected and the towing hawser slipped. This arrangement, with the pelican hook taking the steady strain of towing, offers the quickest emergency release.
If pelican hooks are not used, a strap may be attached to the wire or chain outside the shackle and a heavy purchase hooked to the strap and taken to a winch. In letting go, the strain is taken by the winch long enough to disconnect at the shackle, and then the strap is cut. A preventer must be used to prevent a dangerous whip upon letting go.

There are some conditions under which it is convenient to use a span on the towing ship. Its two parts are brought in through the quarter chocks. This makes it easier for the towing ship to steer, and this advantage may become important in cases where a small ship is dealing with a heavy tow. If the line leads from a chock directly over the rudder, it binds the stern in such a way that it can swing. A large ship can take care of this situation by the power of her steering gear, assisted if necessary by the propellers, but a small ship with a heavy tow and the line leading through the stern chock will steer very sluggishly if she steers at all. Tugs fitted for towing have their bitts well forward of the rudder to allow the stern to swing; the fittings abaft the bitts allow the line to sweep freely across from one quarter to the other.
Spans may be made up of chain, wire, or line. Plans must be made for letting them go quickly in emergencies.

A convenient plan is to bring the tow line in through a quarter chock and bend a hawser from the other quarter to it at such a point outside that the two parts shall form a span of good length. This plan has the advantage that by letting go the second line we get rid of the span at once and have to deal only with the tow line itself.

BASIC TOWING #2

The Towline, the longer and heavier the tow­line, the easier the towing will be. A decided dip or catenary gives the same advantage here as in the case of a vessel at anchor riding with a good scope of chain. The weight of the catenary acts as a spring, preventing tension variations from being thrown upon the towline in sudden jerks.
Wire rope is used for heavy sea towing, its advan­tages being that it is convenient for casting off, takes up small space when stowed, and does not deteriorate if properly dried and oiled before stowing.
Nylon is satisfactory for light or moderate towing. It is heavy enough to give a good dip when used in sufficient length, but it is not too heavy for convenient handling. Nylon is popular because of its resiliency, ease of handling, and long life.
For towing a small ship in rough weather and it must not be overlooked that rough weather may be encountered in almost any towing operation the full length of an 8-in. nylon hawser or a 1 1/2in. diameter wire rope will be none too much.
A point of importance in towing in a seaway is to keep the ships in step. In other words, the length of the line should be such that the ships will meet the waves and ride over them together. If the length of the line allows one vessel to be in the trough of the sea and the other on the crest, the line will slacken for a moment and then become tight with a sudden jerk, if the ships meet the waves at the same time, the tension of the line will remain steady.

BASIC TOWING #1

Alongside towing ("on the hip") is a common method of handling a barge or another vessel, docking, undocking, and transiting waterways. The tug will usually make up at the bow or the stern of the barge with its centerline inclined at an angle toward the barge to compensate for the offset position of the tug. The tug will make fast with several lines, usually a minimum of three,a head line, a spring line (also called a tow strap), and a stern line.
The operator must allow for the tug and barge to "crab" sideways a bit because of the offset position of the tug. This will vary according to the draft of the barge as well as which end of the barge is forward (with the stern forward, the tendency is less because of the skegs).
Deep-Notch Towing Pushing "in the notch" is getting to be common practice in offshore towing when weather and sea conditions are good. (The notch is the indentation at the stern of the barge into which the bow or stem of the tug fits to permit pushing.) It is probably the most efficient way for a tug to propel a barge and is faster than conventional towing since it reduces both the drag of towing gear and the barge's tendency to yaw or sheer.
Tugs and barges navigated in this fashion are suitably renforced in the area of contact and have special gear to secure them together. The tugs are also well fendered.
The deeper the notch, the more weather the tug and barge can with stand in pushing. When sea conditions are too rough, the tug will be obliged to take the barge in tow; towing gear is prepared usually in advance for this.
Since weather and sea conditions are an important factor in this type of operation, pushing is often seasonally limited.
Towing astern, the most common method of navi­gation for tug and barge units is employed in all oceans in all seasons. A tug may use either a hawser or tow cable. As a rule, hawsers are made of some synthetic fiber, nylon, other synthetic lines (such as those that float, such as polypropylene, polyethy­lene, and some blends like polydacron) are used by small tugs.
The tow hawser must be protected against chafing, either by securing a towing board to it or a piece of chain where it passes over the stern of the tug. It is shackled to a chain, wire rope pendant, or bridles secured to the bow of the barge.
Towing with a cable is much the same except that the cable is wound on the drum of a towing winch instead of secured to the tow bitts as a hawser is. On most tugs, these winches are nonautomatic and do not payout or recover cable when the load increases or decreases. Since the cable has little elasticity, a length of chain or nylon shockline is usually attached to the barge's bridle to help absorb some of the occasional heavy surge loads that the cable's catenary may not compensate for.
The tow cable must also be protected against chafing, either by shackling it to a steel spool that slides back and forth across the tow span or securing it to a metal "shoe" where it crosses the stern of the tug.

Multiple Tows are handled by oceangoing tugs. If the tug has a double-drum towing winch, the various barges are usually connected to separate tow cables and the forward barge rides over the bight of the after barge's cable. With hawser tugs, or tugs with a single drum winch, the barges are usually connected by means of an intermediate hawser. Most of the complications in multiple tows stem from the rigging and maneuvering while making and breaking tow.

Making and breaking tow are the pro­cesses involved in connecting up and getting underway with the barge, entering port, taking the barge "on the hip" or "on the head" (pushing), and docking it.
Making Tow If the barge is alongside a dock and must be maneuvered clear, the tug will usually "hip up" on the bow of the barge and connect its cable or hawser to the barge's bridle. Once the tug and barge unit is clear of the dock, the tug will drop the barge astern on a short hawser until it is clear of confined waters and then slack the cable or hawser to the desired length.