Towing Evolutions

^{References
OPNAVINST 5100.19 series, Navy Occupational Safety and Health (NAVOSH)
NAVEDTRA 14343, Boatswain’s Mate Manual
S9086-TV-STM-010/CH-581, Naval Ships’ Technical Manual, Chapter 581, Anchoring
S9086-TW-STM-010/CH-582, Naval Ships’ Technical Manual, Chapter 582, Mooring and Towing
SL740-AA-MAN-010, US Navy Towing Manual}

^{Towing Hawsers
Wire Rope Hawsers
Wire ropes are used for towing hawsers aboard ships such as tugs, ARS, T-ATF, and other ships that are designed specifically for towing. However, for emergency tows, wire rope is limited to aircraft carriers and submarines.}

How long is the wire rope towing hawser on aircraft carriers?

-150 fathoms
-100 feet
-900 fathoms
-200 feet

One fathom equals ____ feet?

- 1ft
- 12ft
- 6ft
- 3ft

6ft

<sup>Synthetic Towing Hawsers
Polypropylene
Polypropylene hawsers are the only hawsers that will float. They are used when floating the hawser to the tow is required.

Nylon

Nylon hawsers are the strongest type of hawser when they are dry. However, nylon loses strength when wet and becomes weaker than polyester. The Navy is phasing out nylon as a hawser and replacing it with polyester.

Polyester
Polyester hawsers are not as strong as nylon when dry. However, polyester exceeds nylon in almost every category when wet.</sup>

^{Hawser Construction
Nylon Rope
Nylon rope has good strength, elasticity, and resistance to weather. It is available in braided and plaited construction for towing applications.
Nylon loses 15 percent of its strength when wet, but regains that strength after drying out.
Eight-strand plaited rope provides ease in inspecting and splicing and does not rotate.
Double-braided rope is acceptable, but less desirable because it is more difficult to splice. This line is non-rotational. Double-braided ropes also have a firm, round cross section that provides a maximum bearing area.
This results in more gripping surface and a reduction in wear by dispersing heat and abrasion over a larger area.}

^{Hawser Construction
Polyester Rope
Polyester rope can be as strong as nylon rope, depending on the type of construction, but it does not have the stretch and elasticity of nylon rope.
Polyester rope does not have the wet-strength loss that nylon does. Polyester rope is also available in braided and plaited construction for towing applications.
Twelve-strand polyester, either plaited or double-braided, is the recommended type of rope to be used for new construction ships that are equipped with synthetic fiber rope towing hawsers.
Twelve-strand, single-braided rope provides ease in inspecting and splicing, is non-rotating, and has maximum bearing surface.}

<sup>Hawser Construction

Wire Rope
Wire rope is also used for towing hawsers. However, for emergency towing, its use is limited mostly to aircraft carriers and older submarines. The wire rope hawsers that are used for emergency towing are the 6 X 37 class type, Improved Plow Steel (IPS) galvanized.
Spring lay 6 x 3 x 19 rope is used in harbor towing by service craft. This type of wire rope is more flexible than other wire rope, but not as strong. It is stronger than fiber rope of the same diameter.
Spring lay 6 x 3 x 19 rope is made of six main strands, laid around a fiber core. Each main strand consists of three fiber strands and three preformed steel wire strands of 19 wires each, laid alternately around a fiber center.
The fiber portion provides a cushion for the wire strands and results in a rope having good flexibility and elasticity.</sup>

^{Bitt
A bitt is a strong post that is used for belaying, fastening, and working ropes, hawsers, and mooring lines. Bitts are normally used in pairs and are named according to their use.}

^{Towing Chocks
A stern chock, usually located on the centerline, is used when towing another ship. It is the aftermost chock that is used as a fairlead for the chafing chain and towing hawser.
When the ship is being towed, the bow chock (sometimes called a bullnose) is the forwardmost chock and is used as the lead of the towing gear.}

<sup>Chafing Chain

A chafing chain is a length of chain lead from the towing hawser to the attachment point (padeye) on the towing ship.The length of chain led out from the bow ranges from 5 to 45 fathoms (30 to 270 feet).</sup>

^{What is the length chaffing chain that is let out from the bow?}

<sup>Chain is used primarily to provide a catenary to the towing hawser for keeping the ships in step and to withstand chafing. What is the scope of chain used for this purpose?

- 5 to 45 feet
- 30 to 270 feet
- 5 to 45 fathoms
- 30 to 270 fathoms</sup>

^{Chain Stoppers
Chain stoppers are used in groups of two or more to secure the ship’s anchor chain. They eliminate the strain on a windlass, which would otherwise be caused by towing loads
The pelican hook is used if the tow must be dropped in an emergency. Another detachable link connects the other end of the turnbuckle to a shackle that attaches to a padeye welded to the deck.
Towing chain stoppers are the same as housing chain stoppers, except the housing chain stoppers have modified eyebolts that accept a locking plate and cotter pin.
The locking plate prevents the chain stopper turnbuckle from backing off when subjected to the shock loading of the towing hawser. No turnbuckle is used on the pelican hook aft.}

^{Pear-Shaped Detachable Link
A pear-shaped detachable link is used to connect a small fitting or chain to a larger fitting or chain.
Three different pear-shaped detachable links will satisfy all normal chain connection requirements.}

<sup>Shackles
Shackles are U-shaped metal fittings that are closed at the open end with a pin. They are used to connect wire, chain, and similar components.
There are two types, two grades, and three classes of shackles. Of these twelve categories, only four can be used as towline connectors:

Type I Anchor Shackles
Grade A – Regular
Class 3 – Safety Bolt and Nut
Type II Chain Shackles
Grade A – Regular
Class 3 – Safety Bolt and Nut
Type I Anchor Shackles
Grade B – High Strength
Class 3 – Safety Bolt and Nut
Type II Chain Shackles
Grade B – High Strength
Class 3 – Safety Bolt and Nut</sup>

Chain Detachable Links
A detachable link is used to join shots of anchor chain. The Navy uses a C-shaped link with two coupling plates, which form one side and the stud of the link

^{Flounder plates
A flounder plate is a triangular steel plate to which bridle legs are connected. it is sometimes called a fish plate or a bridle plate.}

<sup>End Fittings for Towing Hawsers
All synthetic lines end with hand-spliced eyes, and a variety of end fittings are used on them to protect the line from chafing.
The recommended end fittings for towing hawsers, which are made of synthetic rope (nylon and polyester), are shown below in their order of preference:

1. Towing thimble
2. Rope connector
3. Thimble and link
4. Rope coupling</sup>

^{NATO Towing Link
A NATO towing link is a special link to facilitate connection of the towing rig with ships of other nations. The towing ship passes its NATO link to the towed ship.}

^{What is the breaking strength for the US Navy NATO standard towing link?}

^{Towing Messenger
The primary purpose of the messenger is to lessen the load on the heaving line when it is raised out of the water. The towing messenger is made up of 50 fathoms of 21-thread or 1/2-inch nylon line, spliced into 100 fathoms of three-inch nylon line using a long splice to create a taper from the 1/2-inch line to the three-inch line, for a total length of 150 fathoms (900 feet). Connect a messenger that consists of approximately 100 fathoms (600 feet) of three-inch circumference line (or four-inch circumference line for a ten-inch circumference or larger hawser) and 50 fathoms (300 feet) of 1 1/2-inch circumference line to the outboard end of the towing hawser. Fake down the towing hawser messenger clear for running fore and aft. Lead the free end of the messenger through the stern chock.}

^{What is the primary purpose of the towing messenger?}

^{Supervisory Positions
Safety Officer
The Safety Officer ensures towing evolutions are conducted safely and observes closely for any safety violations, which could result in a mishap.
Rig Captain
A Boatswain's Mate Chief (BMC) or Boatswain's Mate First Class (BM1) is in charge of ensuring the rigging and passing of the towing hawser are conducted properly and safely.
Line Captain
A BM2 or BM3 is in charge of ensuring that line handlers properly handle the lines and maintain good seamanship on deck during the towing evolution.}

^{Communications and Handling Positions
Riggers
Riggers are on station for connecting and disconnecting the towing hawser line and messenger line as well as for performing any other tasks deemed necessary.
Phone Talker
The telephone talker's duty is to relay orders and information between the towing station and the bridge.
Line Handlers
Line handlers are used to pull on the lines that will bring the towing hawser and messenger line aboard.}

^{Required Special Positions
Engineer
The Engineer acts as the capstan or towing winch operator during the towing evolution. The Engineer watches for any abnormal condition which may occur.
Line Gunner
A Gunners Mate (GM) is on station to shoot the line throwing gun, which passes the shotline to the ship to be towed. This allows the towing messenger to be pulled across.
Corpsman
Towing evolutions are dangerous evolutions and there is a risk of personnel injury. A Corpsman must remain in the immediate area to provide first aid, if required.}

<sup>What items of safety gear are required for crew members preparing a tow rigging involving synthetic towlines? Choose all that apply.

- Gloves
- Hard hats
- Loose clothing
- Life preservers
- Safety shoes</sup>

<sup>You are the Rig Captain during a towing evolution. The Safety Officer asks you if your personnel are allowed to use gloves while handling rope. What do you tell the Safety Officer? Choose all that apply.

- Gloves must be worn when handling wire rope that is not moving under load.
- Gloves may be worn when handling wire rope while it is moving under load.
- Gloves may be worn when handling synthetic towlines.
- Gloves must be worn when handling messengers</sup>

When wire rope is used in towing operations without a towing engine, the towing hawser must have a scope of at least what length, especially for long tows and in heavy weather?

- 100 fathoms
- 200 fathoms
- 1,200 feet
- 600 feet

<sup>Towing Procedures for the Towed Ship

1. Stopping off the anchor
2. Preparing the anchor chain
3. Rigging the hawser
4. Adjusting the catenary
5. Completing the rigging</sup>

<sup>Towing Procedures for the Towing Ship

1. Connecting the pelican hook to the towing padeye
2. Connecting the chafing chain to the pelican hook
3. Connecting the towing hawser to the chafing chain
4. Faking down the hawser
5. Attaching the NATO towing link
6. Connecting the towing hawser messenger to the hawser, then faking the messenger down fore and aft
7. Stopping off the lead line messenger on both port and starboard sides
8. Passing the lead line messenger to the towed ship
9. Paying out the towing hawser messenger and hawser</sup>

<sup>Stopping Off the Anchor
The following table describes the steps to stop off the anchor for ship being towed:

1. Place a chain stopper port or starboard of the anchor chain to be used, securing it in the hawsepipe.
2. Apply the anchor windlass brake.
3. Pass a pinch bar through the chain, letting the bar rest on the lip of the chain pipe, or pass a preventer through the chain to prevent the chain from backing down into the chain locker.
4. Place a preventer on the anchor to back up the stopper.</sup>

^{Hawsepipe
A heavy casting through which the anchor chain runs from the deck, down and forward through ship’s bow plating}

<sup>Anchor Windlass


The machine used to hoist and lower anchors</sup>

<sup>Preparing the Anchor Chain for the Towed Ship
The following steps describe how to prepare the anchor chain for the ship being towed:

1. Break the anchor chain at the detachable link, inboard of the swivel on the outboard swivel shot.
2. If power is available, roust forward the desired length of chain through the bow chock using the anchor windlass. If power is not available, the chain will have to be rousted forward manually.
3. Shackle the towing chain stopper to the designated towing padeye on the forecastle, then stop off the anchor chain after the tow is properly adjusted.</sup>

<sup>Preparing and Rigging the Hawser
1. Fake out the towed ship’s hawser on the forecastle of the deck for clear running fore and aft, prior to connecting it to the anchor chain.
2. Use the towing ship’s messenger to haul the towing hawser from the towing ship on board through the bow chock.
3. Connect the messenger to the towed ship’s hawser, which is secured to the end of the anchor chain. If the towed ship’s hawser is not to be used, connect the towing ship’s hawser to the anchor chain.
4. Normally, the towing ship provides the messenger during towing evolutions. It is a good practice for the towed ship's messenger to be on deck in case it is needed.</sup>

<sup>Completing the Rig

To take the strain on the towed ship's anchor chain, perform the following:

1. Set the brake on the wildcat.
2. Pass and equalize the chain stoppers, one outboard and one inboard of a detachable link.
3. Disengage the wildcat</sup>

You are conducting a towing evolution. The tow is underway, and you notice that the ships are out of step. You need to adjust the catenary and complete the rig.

Put in order

A- Pass the chain stoppers.
B- Disengage the wildcat.
C- Cast off the chain stoppers.
D- Pay out or haul in enough chain to crest when the towing ship crests.
E- Engage the wildcat.

<sup>Towing Signals

One short blast</sup>

<sup>Towing Signals

Two short blasts</sup>

<sup>Towing Signals

Two short, one prolonged blast</sup>

<sup>Towing Signals

Two short, one prolonged blast</sup>

<sup>Towing Signals

Two prolonged, five short blasts</sup>

<sup>Towing Signals

Two prolonged blasts</sup>

<sup>Towing Signals

One short, two prolonged blasts</sup>

<sup>Towing Signals

One prolonged, two short blasts</sup>

<sup>Towing Signals

Three short blasts</sup>

<sup>Towing Signals

Two prolonged, one short blast</sup>

^{Towing Signals
Three groups of five short blasts}

<sup>Towing Speeds

Towing speeds depend upon the size, type of tow, and weather and if the towed vessel can provide any assistance with its own screws. Under good weather conditions, what is the speed a vessel can be towed at ?</sup>

<sup>The following procedural steps are used when rigging a Williams target tow sled for towing. Place the steps in the correct sequence, then select CHECK to review your answers.

A- Shackle the pendant to the non-rotating main synthetic towline.
B- Shackle the synthetic bridle to the inboard sides of the catamaran hulls.
C- Shackle a 30-foot pendant of synthetic line to the flounder plate or joining shackle.
D- Join the sled's two bridle legs to either a joining shackle or a triangular flounder plate</sup>

<sup>How can the target be made up to the towing ship for tows that begin at the target’s berth? Select all that apply.

-Bow-to-stern alongside
-Bow-to-stern aft of the towing ship
-Bow-to-bow alongside
-Bow-to-stern forward of the towing ship
-Stern-to-bow alongside</sup>