Emergency Towing

Safety is always the most important concern when towing. Every towing activity is potentially dangerous. The safety of the crew and the crew of the towed vessel is more important than property, and the primary responsibility in any towing situation is to maintain safety. Towing is a complex evolution. A safe and successful outcome hinges on crew professionalism, ability, and teamwork.

Every boat crewmember is responsible for identifying and managing risks. Towing mishaps can be prevented by honestly evaluating risks involved in every step of any towing evolution. Communicating with the towed vessel’s crew may provide important information necessary to complete a successful mission is essential and help make a risk assessment. Do not let a perceived need to engage in a towing mission override a complete, honest risk assessment process that emphasizes personnel safety.

The dynamics of a towing situation continuously change from the time pre- towing preparations begin until mooring at the conclusion of the mission. All crewmembers must stay fully aware of the constantly changing situation at any given time during a towing evolution. It is important that each crewmember knows what goes on in the surrounding environment and how things change. Crew awareness should be reinforced through communication: commenting on what is believed to be happening and involving the towed vessel’s crew. The “outside” view could provide information on things not visible from the towing vessel. When clues indicate that situational awareness is being lost, a decision must be made whether or not to continue with the towing evolution. A decision takes the form of action/reaction and communication. Everyone in the crew has a responsibility in the decision-making process.

Realistic towing training based on standardized techniques, critical analysis, and mission briefing and debriefing will contribute to risk management and the development of a towing risk management plan. All crewmembers must contribute to risk management planning.

Boat crews must understand the forces, or types of resistance, which act on the towed vessel and how to handle the resistance safely. They are the same forces that affect all vessels, but a distressed vessel is limited in how it can overcome them. The towing vessel must provide the means to move the towed vessel. The towline or tow rig transfers all forces between the two vessels. Boat crews must learn to recognize the different forces and each of their effects individually to effectively balance and overcome them when they act together.

Static forces cause a towed vessel to resist motion. The displacement or mass of a towed vessel determines the amount of force working against the vessel. The assisting vessel must overcome these forces before the towed vessel moves. Inertia and the moment of inertia are two different properties of static forces that cause resistance in towing vessels.

In this case, inertia is the tendency for a vessel at rest to stay at rest. The more mass a vessel has (the greater its displacement), the harder it is to get it moving.

The moment of inertia occurs when a towed vessel resists effort to turn about a vertical axis to change heading. The larger the vessel, the more resistance there will be in turning the vessel. Unless necessary in a case of immediate danger, an attempt to tow a distressed vessel ahead and change its heading at the same time should not be used (see Figure 3-1). Both inertia and the moment of inertia will be involved in the resistance of moving the distressed vessel, which can cause potentially dangerous situations and greater resistance for towing. Both of the vessels, as well as their fittings and the towing equipment, take much less stress and strain when the two forces are conquered individually.

[Illustration in the handbook: Figure 3-1 — Static Forces]

Overcome the effects of static forces by starting a tow slowly, both on the initial heading or when changing the towed vessel’s heading. A large amount of strain is placed on both of the vessels, as well as their fittings and the towing equipment, when going from dead-in-the-water to moving in the desired direction and at the desired speed. Extreme caution should be used when towing a vessel of equal or greater mass than the assisting vessel. In such situations, the assisting vessel strains the capacity and capability of its equipment, requiring slow and gradual changes.

To start the tow on the initial heading, perform the following procedures:

To change the towed vessel’s heading, perform the following procedures:

Dynamic forces occur once the towed vessel is moving. They are based on the towed vessel’s characteristics (shape, displacement, arrangement, rigging), the motion caused by the towing vessel, and the effects of waves and wind (see Figure 3-2).

[Illustration in the handbook: Figure 3-2 — Dynamic Forces]

line. The greater its displacement or the faster it is moving, the harder it is to stop or change the vessel’s direction.

Once the vessel’s heading begins to change, it wants to keep changing in that same direction. The faster the towed vessel’s heading changes, the harder it is to get the tow moving in a straight line. The towed vessel’s momentum will gradually increase with towing speed. Momentum in a straight line will resist effort to change the towed vessel’s direction and will tend to keep the towed vessel moving when tension in the towing rig is decreased. When changing directions, the towed vessel will develop angular momentum while the vessel’s heading is changing. Towing force opposite the swing may need to be applied before the towed vessel achieves the desired heading. The key to dealing with momentum is to anticipate how momentum will affect the towed vessel’s motion and apply an offsetting force early and gradually.

As a vessel moves, the layer of water in immediate contact with the hull moves. Due to friction between water molecules, the layers of water close to the hull try to drag along. The vessel appears to move “through” the water. This attempt to drag water alongside takes energy. As speed increases, this action becomes “turbulent.” This turbulence takes additional energy, and more speed requires even more power. Frictional resistance will constantly affect the tow, normally keeping some steady tension in the towing rig. Since the shape and wetted surface area of the towed vessel will not change, frictional resistance is managed with towing speed. Higher towing speed causes higher frictional resistance and more strain on the towing rig. Frictional resistance also varies with hull shape. Greater underwater (wetted) surface area causes greater frictional resistance. Hull appendages, such as propellers, shafts, skegs, keel, and rudders contribute to wetted surface area and frictional resistance.

Form drag plays a large role in the ability to control changes in the towed vessel’s movement. Different hull shapes react to motion through the water in different ways. The shape and size of the towed vessel’s hull can either help or hinder effort to move in a straight line, when changing heading, and motion changes in response to waves due to buoyancy. The less water a hull shape has to push out of its way, the easier it will move through the water. A deep-draft, full-hulled vessel takes more effort to move than one with a fine, shallow hull. A large amount of lateral resistance, spread evenly over the length of the hull, will hinder effort to change a towed vessel’s direction, but will help offset angular momentum in steadying up on a desired heading. A towed vessel may be able to help offset form drag by using its rudder. It is not always safe to tow a planing hull type of vessel above planing speed. Going from displacement speed to planing speed, or back, can decrease the towed vessel’s stability and cause it to capsize. Also, wave drag (even one large wake) could slow the hull down to displacement speed and cause a severe “shock-load” as the towed vessel tries to get back on plane.

A surface wave forms at the bow while the hull moves through the water. The size of the bow wave increases as speed increases, causing the wave to create resistance for the bow to be pulled or propelled through the water. Boat crews should keep in mind the different hull types of maritime craft, including the towing vessel. In any towing evolution, the boat crew must be able to recognize a vessel’s hull type, as well as its critical capabilities and limitations. Dependent on the type of hull, towing vessels must be careful not to tow a vessel faster than the design speed of its hull. Refer to Table 3-1 on page 3-57 for a discussion of towing speeds. “Shock-load” or “shock-loading” is the rapid, extreme increase in tension on the towline, which transfers through the tow rig and fittings to both vessels.

The frictional forces of wave drag, spray drag, and wind drag act on the hull, topsides, superstructure, and rigging. They all have a major effect on the motion of the towed vessel, and the transfer of forces to and through the towing rig. These constantly changing forces all vary with the towed vessel’s motion relative to the environmental elements and are directly related to the towed vessel’s exposure to them. These forces can add up and cause shock-loading. Wind and wave drag also cause a distressed drifting vessel to make leeway, which is motion in a downwind direction.

Wave drag depends on the “normal” wetted surface area of the hull and the amount of freeboard exposed to wave action. Wave drag has a large effect on the strain of the tow rig.

(01) In large seas, be aware of: a) Combination of wave drag and form drag could overcome the towed vessel’s forward momentum and cause the towed vessel to stop and transfer a large amount of strain to the tow rig. b) Shock-load could damage a vessel’s fittings and part the towline endangering both vessels’ crews. (02) In head seas, be aware of: a) Towing vessel can only control the effect of wave drag by the speed and angle that the towed vessel encounters the waves. b) Limiting speed and towing at an angle to the seas to prevent them from breaking over the bow of the towed vessel. (03) In following seas, be aware of: a) Wave drag causing the towed vessel to speed up as the crest approaches, increasing speed to keep tension in the towing rig, and reducing speed as the crest passes.

Spray drag also provides resistance to the tow. The spray from a wave could slow the towed vessel and increase the amount of shock-loading. Spray drag could also adversely affect the towed vessel’s motion by imparting a momentary heel, pooling on deck or in the vessel cockpit, and in cold weather form ice, and thus decrease stability.

Wind drag can cause shock-loading and have a bad effect on the towed vessel’s motions and stability. A steady beam wind can cause list and leeway, while a severe gust can cause a threatening heel. List, heel, and leeway may cause the towed vessel to yaw. A headwind increases tow rig loading in a direct line with the towed vessel while the towed vessel crests a wave, causing shock- loading.

Boat crews should develop a feel for the towed vessel’s initial and reserve buoyancy characteristics, overall stability, sea keeping, response to the prevailing environmental conditions, and the response to being towed. Though a distressed vessel may seem stable and sound at rest, its response once in tow could be to capsize. A towed vessel’s bow may react to an oncoming wave by pitching skyward, or by “submarining.” Buoyancy response to following seas could cause the towed vessel to yaw excessively or gravity may cause it to gain speed and “surf” down the face of a wave. Once making way, a vessel’s buoyancy response or the effect of gravity in a seaway may cause severe shock loading.

During a towing evolution, the boat crew rarely deals with only one force acting upon the tow. The crew usually faces a combination of all the forces, each making the situation more complex. Some individual forces are very large and relatively constant. Crews can usually deal with these safely, provided all towing-force changes are made gradually. When forces are changed in an irregular manner, tension on the tow rig starts to vary instead of remaining steady.

Even in calm winds and seas, a towing vessel can encounter a large amount of frictional resistance from form and wave drag when towing a large fishing vessel with trawl lines fouled in its propeller and net still in the water. The tow rig and vessel fittings will be under heavy strain, and the tow vessel engine loads will be rather high, but the tow proceeds relatively safely. If suddenly the net tangled and caught on an unseen obstacle, this new “force” acting through the tow rig could immediately increase stress to a dangerous level. This shock-load could part the towline or destroy fittings. (In the example above, the prudent solution would be to make a “safe” tow by recovering the net or marking it and letting it loose before starting the tow.) Though this example began as a safe and steady tow, a single unexpected incident could have caused a very dangerous situation. Boat crews should always keep in mind that some degree of shock-loading can occur during any tow evolution. Shock-loading may cause severe damage to both towing and towed vessels and overload a tow rig to the point of towline or bridle failure. Shock-loading could also cause momentary loss of directional control by either vessel and could capsize small vessels.

Because of the potential dangers, the tow vessel must use various techniques to prevent or counteract shock-loading, or reduce its effect.

Towlines are usually 2-in-1 (double-braided) nylon, two to four inches in circumference. Length can be up to 900 feet. Nylon instead of other synthetic fiber cordage should be used for a good combination of strength and stretch (elongation and elasticity). The Auxiliary is not required to use double-braided nylon for towing and will use a variety of types and sizes of towlines. Refer to line manufacturers guidelines for recommended sizes for various circumferences of towline. Do not tow beyond the vessel’s design limits by simply increasing towline size. If the towline’s breaking strength exceeds the limits designed into the vessel’s fittings and structure, damage and structural failure may result. The towing vessel’s construction, power, size, and fittings determine towline size (circumference). The proper towline will allow a vessel to tow up to its design limits. The towline will part before damage occurs to a vessel’s fittings, structure or hull. Each Coast Guard boat type has an equipment list that specifies towline length and size. Towlines will usually have an eye spliced into the tow end. Towline length and size will vary on other vessels due to design limits and available space. Offshore or in heavy weather, a towing vessel may need 500 feet or more of towline to keep a towed vessel in step and to minimize the effect of shock-loading.

Towline is stored typically on a tow reel with the bitter end secured to the reel with small stuff. The line will lie evenly on the reel. More importantly, to quickly slip (release) the towline in an emergency, the small stuff can be cut with a knife, and the bitter end runs free. When putting new cordage in service as a towline, an eye should be spliced at both ends. This will allow an “end- for-end” switch before part of the towline is beyond useful service. Many tow reels have mechanical advantage (hand crank, gear train) or electric motors to ease towline retrieval. These devices are only to retrieve a slack towline. Crewmembers should not try to take any tension with these devices. The tow reel should be inspected frequently for easy rotation and adequate lubrication. Unless slipping the towline in an emergency, keep at least four turns of towline on the reel. Paying out the entire length can result in loss of both tow and towline.

Safe and efficient towing requires an undamaged, serviceable towline. Whenever any towline damage is found or suspected, crewmembers must remove or repair the damage. If removing damage shortens the towline to less than serviceable length, then the towline should be replaced. Remaining usable sections of a discarded towline can be used for bridles, alongside lines, mooring lines, etc. Units shall use applicable ALMIS MPC for towline condition or inspection. Inspect towlines on a regular basis to detect damage from:

(01) Cuts. (02) Chafing. (03) Flattening. (04) Fusing (caused by overheating or over-stretching). (05) Snags. (06) Hardening (heavy use will compact and harden a towline and reduce its breaking strength).

If a towline shows any of these characteristics, it must not be used as a towline.

It is not always possible, appropriate, or safe to attach a towline from the stern of a towing vessel to a single point on the bow of a distressed vessel. For instance:

(01) The distressed vessel’s deck layout may not have a single direct run through a bull nose. (02) There might not be a sampson post or centered bitt. (03) The towline might be too large for deck fittings. (04) Deck fittings may be improperly mounted, rotted or corroded where they attach to the deck.

In these cases, a pendant or bridle should be rigged. The pendant or bridle forms part of the tow rig, leading from the eye or thimble of a towline to the appropriate location(s) or deck fitting(s) on the towed vessel. Towing pendants and bridles are made of double-braided nylon or Kevlar. The two most common rigs are a pendant and a bridle. Auxiliary facilities will have a variety of pendants and bridles, not necessarily constructed of double- braided nylon or Kevlar. When possible, pendants and bridles should be used with breaking strength equal to or greater than the towline.

A pendant is used to reduce wear and chafing at the towline end (particularly the eye and its splice). A pendant must be long enough so the towline connection is clear of obstructions on the towed vessel (see Figure 3-3).

[Illustration in the handbook: Figure 3-3 — Pendant]

A bridle or “Cats Paw” is used when both legs can be rigged to exert an equal pull on the hull of a distressed vessel, and is preferred for heavy weather towing (Figure 3-4). A bridle provides the best results where a towed vessel deck fittings (chocks and cleats or bitts) are not right at the towed vessel’s bow (as a bullnose), or where obstructions (bulwark or rigging) on the bow prevents a pendant or towline from making a direct lead back to the towing vessel. Use the following list as a guideline for attaching a bridle for towing:

(01) Use a long bridle when the best attachment points for the towed vessel are well aft to either side of the deck, but maintain a fair lead forward to reduce chafe. (02) Remember that the amount of tension on each bridle leg increases with the size of the angle between the bridle legs. (03) Keep the legs of the bridle long enough so the angle of the legs stays less than 30°. (04) The legs must be long enough to reduce towed vessel yaw. (05) Protect bridles with chafing gear when necessary. (06) Use thimbles in the bridle leg eyes where they meet. (07) When shackled to the towline, remember to mouse the shackle pin.

A bridle is also used by towing vessels without centerline towing capability or with transom obstructions (outboard motors or rigging). The bridle is attached to fittings in a manner to clear the obstructions. Again, bridle leg lengths must be equal to share the strain of the tow.

[Illustration in the handbook: Figure 3-4 — Bridle/Cats Paw]

Safe and efficient towing requires undamaged, serviceable pendants and bridles. Crewmembers should inspect pendants and bridles on a regular basis to detect damage and to ensure bridle leg lengths are equal. For nylon pendants and bridles, the towline condition and inspection list provided in B.1.b. Towline Condition and Inspection should be used. Inspect towlines, pendants, and bridles after each tow and whenever shock loading has occurred.

A towline is too heavy to cast more than a few feet. In rough weather or when impossible to get close enough to throw a towline to a distressed vessel, a heaving line should be used to reach the other vessel. A heaving line is a length of light line used to carry a larger line between vessels.

In most cases, a heaving line or float line will be used to make the initial pass to the vessel in need of a tow. To pass a towline with a heaving line, one end of a small line is attached to the end of the towline and the other end is cast to the other vessel’s crew. The lighter line is used to pull the towline across the distance between the vessels. Sometimes, multiple lines are used as heaving lines.

A heaving line is made of light, flexible line with a rubber ball or a monkey’s fist at the throwing end. A heaving line must be in good condition, at least 75 feet long, and free of rot or weathering (see Figure 3-5). The bitter end of a heaving line is attached to the towline with a clove hitch, bow line, small carabiner, or snap hook. Slip clove hitches may work best in very cold weather because they are easier to untie. The longest heaves are cast downwind, but this may not always be possible. The throw should be targeted above the center of the vessel so the thrown line crosses over the deck and avoids breaking glass or injuring people. Always yell “heads up” before throwing a heaving line or ball. They can cause damage to property or personnel.

[Illustration in the handbook: Figure 3-5 — Heaving Lines]

To reach a vessel beyond the range of a heaving line or in an inaccessible position, a buoyant synthetic line may be floated from upstream or upwind. One end is tied to a ring buoy or float, the other end to the towline, and the float line is thrown downstream in the direction of the distressed vessel. The current or wind will carry the float line toward the other vessel. This method is only effective if the wind or current can get the float within range of the other vessel.

Chafing gear protects towlines, bridles, and pendants from wear caused by rubbing against deck edges, gunwales, bulwarks, chocks, taff rail or tow bars.

Layers of heavy canvas or leather can be tied with small stuff to the towline, bridle, or wire rope at contact points to prevent chafing damage. Sections of old fire hose also work well as chafing gear, or commercially available products may be used. Crewmembers must make sure the chafing gear stays in place for the duration of the tow.

Thimbles are designed to equalize the load on an eye of a line and provide maximum chafing protection to the inner surface of the eye. On double- braided nylon, thimbles made specifically for synthetic lines (see Figure 3-6) must be used.

[Illustration in the handbook: Figure 3-6 — Thimbles]

Fittings are attachments or fair lead points on vessels for towlines, anchor lines, and mooring lines. Many fishing and sailing vessels have other attachment points for standing and running rigging that could also provide tow rig attachment points or fair leads. For towing, attachment points and fair leads designed for horizontal loads should only be used. Common fittings include bitts (mooring and towing), cleats, bollards, and sampson posts. Chocks, tow bars, and taff rails act as fair leads redirecting or supporting the towline. Pad eyes, turning and snatch blocks, winch drums, capstans, and windlasses should also be considered as attachment points or fair leads on a towed vessel. Trailerable boats usually have an eyebolt or eye fitting at the bow for an attachment point.

The following regular inspections should be conducted of towing vessel fittings:

(01) Check for cracks, fractures, rust, corrosion, wood rot, fiberglass core softening, or delamination. (02) Inspect surfaces that are normally hidden from view, particularly backing plates and under-deck fasteners. (03) Tow bars are subject to high vibration and may loosen or cause stress fractures around their foundations. (04) Ensure working surfaces are kept free from paint and relieve any surface roughness. A smooth working surface reduces wear, friction and chafing on lines.

The typical skiff hook has a quick-release safety buckle and snap hook clip that can be attached directly to the boathook handle (see Figure 3-7). Skiff hook assemblies are commercially available. Do not over-stress a skiff hook. Never use one for any operation that exceeds the stress load of towing small, trailerable boats. Use extreme care when removing a skiff hook from a trailer eye fitting. Even at a dock, crewmembers risk injury from vessel movements.

[Illustration in the handbook: Figure 3-7 — Skiff Hook]

Perform the following procedures to use a skiff hook:

A drogue is a device that acts in the water similar to how a parachute works in the air. The drogue is deployed from the stern of the towed vessel to help control the towed vessel’s motions. Coxswains and boat crews must familiarize themselves with the operating characteristics and effectiveness of available drogues, training with and testing drogues under various conditions to learn drogue capabilities. The time to learn about a drogue is before one is needed to deploy.

While trailing a drogue from the towed vessel is not common, it may be useful when a distressed vessel has lost rudder control. Normally drogues are not deployed when well offshore but rather inshore where greater control of the towed vessel is required. If necessary to tow a vessel with large swells directly on the stern, it may be more prudent to alter course or lengthen the towline rather than to deploy a drogue. Drogues are typically used when the tow is shortened as in preparing to tow into a bar or inlet. With a short hawser and large swells on the stern, the drogue is deployed to prevent the towed vessel from running up the stern of the towing vessel or “surfing” down the face of a wave. The drogue keeps a steady strain on the towline reducing shock-loading.

The idea of the drogue is to provide backward pull on the stern of the towed vessel so that the wave will pass under the boat. It is important to match the size of the drogue to the towed boat, its deck fittings, and its overall condition. Larger, well-constructed cone drogues can exert a very large force on a boat’s transom so the towed vessel’s stern must be carefully examined. Different-sized drogues are used for different conditions and different vessel sizes. A modern style drogue (Figure 3-8) is a synthetic material cone, with the pointed end open. Drogues may have a ring in the base of the cone (the leading edge) to which attaches a four-part bridle. The other ends of the bridle connect to a swivel, which in turn, connects to a line made fast to the stern of the towed vessel. The towed vessel “tows” the drogue. Drogues sometimes have another line (dumping line) attached to the tail end for retrieval. A large drogue can cause stress that will damage a boat. For a boat, the larger the drogue used, the slower the towing speed must be. A slight increase in speed causes a tremendous increase in drogue tension.

[Illustration in the handbook: Figure 3-8 — Modern Drogue Types]

To inspect and prepare the drogue gear, perform the following procedures:

Auxiliary facilities are not required to carry drogues. Determine the fittings to which the drogue will connect, how to make the connection, and how much line to deploy before sending it to the tow. Always ask about backing plates, fitting sizes, and strength of materials involved. Be cautious if an attachment point cannot be seen. Rely on experience and judgment.

Perform the following procedures to pass the drogue:

Unless a crewmember from the towing vessel goes aboard the towed vessel, the towed vessel crew must carry out the following procedures. Provide them guidance and direction as needed.

Perform the following procedures to rig the drogue for deployment:

Perform the following procedures to deploy drogue when vessel is being towed astern:

Drogue use does not justify towing through breakers. When in doubt, stay out.

Because a tripping line is not recommended, several alternate recovery methods are available. If recovery is not properly set up and controlled, a drogue may become fouled on the tow, a buoy, or other object. Perform the following procedures to shorten up and recover the drogue:

Perform the following procedures to store the drogue:

Alongside lines, fenders, and general hardware account for other equipment that may be necessary to employ for towing evolutions.

At some point during a tow, the towing vessel most likely will need to tow the distressed vessel alongside or moor to the towed vessel. The towing vessel will usually need a combination of lines to allow for vessels of different size.

The boat equipment list specifies number, length and size of alongside lines for vessel type. Stowage and weight considerations will guide other vessel types.

Alongside lines must be kept in the same condition as towlines and bridles (see B.1.b. Towline Condition and Inspection).

Fenders are portable rubber, synthetic, or foam devices that protect a hull when maneuvering in close proximity to other vessels, docks or pilings. Fenders have either eye(s) or a longitudinal hole for attaching lines. They can be spherical, cylindrical, or rectangular prisms. Fender size varies greatly, and the appropriate size should be used depending on the situation. Fenders that will keep space between vessel hulls or rub rails and hulls should be used.

Fenders should be used whenever there is the possibility of a hull making contact with another object. They should be strategically placed to account for different hull shapes (maximum beam, tumble-home, flare) or appendages (rub rails, spray rails, trawl rigs, platforms). Never use hands or feet to fend off another object (pier, boat, buoy). This could result in serious physical injury. Always use a fender!

Because vessels are shifted around by water, fenders may need to be moved for best effectiveness, even after strategic placement. Most vessel crews are too small to have a dedicated fender tender; therefore, the need should be minimized beforehand.

General hardware for use in towing includes shackles, snap hooks, carabiners, swivels, and other items, that should have the following characteristics:

(01) These items must be made of strong, low-maintenance materials. (02) They must be easy to connect and disconnect or open and close by all crewmembers. (03) All hardware should resist distortion. (04) Shackles need a large enough opening to easily cross an eye or thimble. Captive-pin (safety) shackles should be used wherever possible. The pin should be attached to the shackle with a lanyard to prevent pin loss.

When using general hardware, crewmembers should be sure to:

(01) Keep all hardware clean and lubricated. Inspect hardware after each use. (02) Be particularly cautious of hardware that has been shock-loaded. (03) Immediately replace any hardware that is distorted, spreading, excessively worn, or stripped.

The amount of effort put into preparing ahead of time will pay off with safer, easier execution of the tow. Throughout the entire towing evolution, open communication between the coxswain, boat crew and towed vessel is absolutely necessary for safety and repeat backs should be used.

When notified of a towing mission, the coxswain takes the following procedures as common practice:

The coxswain is ultimately responsible for mission execution, so the tasking should only be confirmed in view of vessel and crew capability. If tasking exceeds vessel or crew capability, particularly if not an actual distress case, the coxswain’s concerns should be made clear. Vessel towing limits, maximum range, sea-keeping, crew fatigue, etc. are all essential considerations to assess and manage potential risk. Keep a brief (plastic clipboard and grease pencil) written record of critical information. Include vessel information (length, type, displacement, disability), number of persons on the boat, position, and

NOTE

environmental conditions. A written record allows the crew to concentrate on task completion without having to later rely on memory for needed facts. Repeating information over the radio is frustrating and distracting. As information changes, update your records and notify your unit.

The coxswain shall brief the crew as follows:

Boat crews shall evaluate conditions for a tow as follows:

The only way to perform the tow is get there safely. A sense of urgency should never affect judgment. For safe operation and navigation, the following precautions apply:

Contact should be made with the distressed vessel, if possible. Communication shall be as follows:

Equipment shall be prepared for the tow as follows:

Once on-scene, use the following procedures:

During the period of pre-tow, on-scene analysis is when crew experience and judgment on both vessels must mesh. Discuss concerns before directing action. The distressed vessel’s crew may have information that the towing vessel’s crew does not. The easiest way to get the big picture may be by circling the distressed vessel, if possible. A method to check drift rate of the distressed

NOTE

vessel is to maneuver the towing vessel onto the same heading as the distressed vessel and stop astern of it. If the distance between the vessels increases, one vessel has a higher drift rate. Note the different angles or aspects the towing vessel and the towed vessel hold towards the winds and seas. The only time the drift rate and aspect will be exactly the same is if the vessels are exactly the same.

Crewmembers should visualize the tow in progress, given all the factors identified in the on-scene assessment. This may help identify any special considerations. Elements of the tow rig should be appropriately sized for the specific distressed vessel (i.e., a 3-inch towline with eye might not fit through a bow chock or around a cleat of a 25-foot boat).

NOTE

Pass equipment (pump, drogue, etc.) and transfer personnel before making the approach to transfer the tow rig.

Though optimal to make an approach from downwind and down sea, the drift and aspect of the distressed vessel may determine the approach. Vessels with a large superstructure forward or outboard-powered engine will tend to lay stern-to the wind. A vessel with deep draft and low superstructure will generally lie broadside to the seas. Of course, there are many positions in between. The approach to a vessel drifting down wind and down sea, “stern to” the wind and seas will be different from the approach to a vessel lying “beam to.” The usual approach by a boat to make a tow is with the bow into the seas. Once the coxswain has determined how to make the approach he/she shall inform the crew, specifically telling them:

(01) From which side to pass the tow rig (or equipment). (02) When (in what relative position of the two vessels) to pass the tow rig. (03) Whether to use a heaving line.

Perform the following procedures when briefing the distressed vessel:

Limit the content of this briefing to information the distressed vessel needs to know before the tow begins. Once hooked up and in tow, there will be opportunity to pass additional information.

The most common towing technique is to tow the distressed vessel from astern of the rescue vessel.

Before starting the approach, an imaginary danger zone is established around the distressed vessel and the approach is made from the outside. The size of a danger zone depends upon conditions and the arrangement of the distressed vessel. The poorer the conditions, the larger the danger zone (Figure 3-9).

NOTE

A boat crew’s teamwork, communications, and experience are key to a safe, successful approach.

[Illustration in the handbook: Figure 3-9 — Danger Zones]

The on-scene assessment gives the knowledge of how conditions affect both vessels. Knowledge and experience with the towing vessel’s handling and maneuvering should allow to overcoming conditions and putting the towing vessel in a safe position for the crew to pass the tow rig.

Safe distance keeps you out of the danger zone. It gives your crew time to pass the towing rig. It minimizes stress levels and increases situational awareness. Safe distance is different for each operator. You may have to close to get a heaving line across in heavy weather, but regain that safe distance before attempting to pass a towline.

Optimum position is the position taken by the rescue vessel which allows the crew the safest opportunity to pass the towing equipment to the vessel to be towed. Optimum position provides better vessel control, while keeping appropriate distance from the distressed vessel and maintaining a safe escape route in case of an emergency.

[Illustration in the handbook: Figure 3-10 — Optimum Position]

Maneuvering Zone is a 90-degree arc; 45-degrees forward and 45-degrees aft of your tow bitt. It is a guide to keep you in optimum position and allow you to safely maneuver the boat. Staying in the maneuvering zone keeps you out of the danger zone and gives you a way out if you encounter problems while station keeping. Use the heaving line, your towing bitt, and the disabled boats attachment point as a reference. Coxswains need to keep their attention divided between the disabled boat and the seas. Coxswains will rely heavily on their crew to assist them with all aspects of the evolution.

[Illustration in the handbook: Figure 3-11 — Maneuvering Zone]

Optimum position is when the towing vessel provides the safest opportunity to pass the towing equipment to the vessel to be towed. Optimum position provides better vessel control, while keeping appropriate distance from the distressed vessel and maintaining a safe escape route in case of an emergency. Perform the following procedures to maneuver to this optimum position (Figure 3-10):

Actual maneuvering techniques vary from vessel to vessel and are mastered by practice and experience. Actual station keeping techniques also vary as the specific wind and sea conditions affect the specific distressed vessel.

The following procedures apply for station keeping:

Once optimum position (Figure 3-12) is maintained, the tow rig may be passed as follows:

While passing and connecting the tow rig, and transitioning to stern tow, use loud and clear communication between crewmembers and coxswain to prevent accidents. Whenever the coxswain

NOTE

directs an action, a crewmember must take that action and reply that the action has been taken. Whenever a crewmember advises the coxswain of status or action, the coxswain must acknowledge same.

[Illustration in the handbook: Figure 3-12 — Optimum Position for Passing the Tow Rig]

When passing the rig in calm conditions (no heaving line), the following procedures apply:

When passing a rig using a heaving line the following procedures apply:

NOTE

It takes practice to cast a heaving line properly. Adapt technique to conditions for a safe and successful result.

When casting a heaving line, the following procedures apply:

Opening and closing maneuvers are used to maintain optimum position and a safe distance while staying inside the maneuvering zone. These procedures are performed prior to passing the towline. A coxswain must use power consistent with the environmental conditions and timely and deliberate throttle inputs to achieve the desired results. Opening maneuvers consist of opening by pivoting or opening by backing. Closing maneuvers consist of closing by pivoting or closing by quartering. The following procedures are often used for opening and closing maneuvers: The towing transition occurs once the towline is secured to the disabled vessel and the rescue craft maneuvers to pay out the towline to the desired length to take the vessel into stern tow. In heavy weather it can be one of the most hazardous periods. The coxswain must leave the safety of the maneuvering zone to put the tow behind while the crew is paying out towline. Some basic rules of transition are:

(01) Communicate with the crew. (02) Begin the transition in optimum position (Figure 3-10). (03) Take the time necessary. (04) Get distance between the boat and the disabled vessel. (05) Try not to tow the disabled vessel until paying out the desired amount of towline. (06) Pay out the towline while in the trough or quartering the swell to reduce surging of the towline.

Methods of tow rig connection (Figure 3-13) generally available are:

(01) Tow rig to fittings. (02) Tow rig to trailer eye.

Though deck fittings should be checked during pre-tow procedures, do not hesitate to stop the connection if something is wrong. If necessary, recover the rig and transfer a crewmember to the distressed vessel to physically inspect the fittings.

[Illustration in the handbook: Figure 3-13 — Bridle and Trailer Eyebolt Tow Rig Connection]

The attachment point(s) for a tow rig must be sound. Towing places a tremendous strain on deck fittings, especially in rough conditions. On the distressed vessel, bow bitts, forward cleats and Samson posts will usually provide the best attachment points. Fittings secured to a deck with through bolts and backing plates or those secured to the keel or structural framing should always be used. Other fittings, such as pad-eyes or capstans, may also provide solid attachment points. Unless the towing vessel puts a crewmember aboard the distressed vessel, the towed vessel crew is responsible for these actions. A good brief to the distressed vessel will address each item, but in the rush to get things set up aboard the distressed vessel, the crew may forget important steps. The towing vessel crew must closely watch, and advise when necessary. Transfer of people between vessels is not a common practice. Whenever this is considered, it must be conducted with extreme caution for the safety of people on both vessels. Avoid connecting the towline to an off-centerline fitting on the towed vessel. Use a bridle for an equal amount of strain on both sides of the bow.

When ensuring a fair lead, the following procedures apply:

When making fast to fittings, the following procedures apply:

[Illustration in the handbook: Figure 3-14 — Towline Connection Showing Bridle Angle]

Where necessary, when installing chafing gear the tow rig should be protected from abrasion or chafing, particularly if the rig takes a sharp turn at chocks or comes close to contact with any obstructions.

On smaller, trailerable boats, the trailer eye is frequently the sturdiest fitting available to attach a tow rig. Attaching a towline to the trailer eye is a dangerous technique. It requires the towing vessel to maneuver very close to a distressed boat and requires crewmembers to extend themselves over the side between two vessels, or under the flared bow sections of the distressed boat. To reduce risk in connecting the tow rig to the trailer eye, use a skiff hook.

A skiff hook with a quick-release safety buckle and snap hook clip is in common use. Manufacturer instructions should be reviewed for its proper use. The skiff hook requires the following procedures:

Do not use a shackle to directly connect a towline to a trailer eye. This requires crewmembers to get too close under the bow of the distressed vessel.

When moving away, the following procedures apply:

Once the distance allows clear movement of a tow the towing vessel can be maneuvered to allow a smooth pay-out of the towline. As tension increases in the towline, static forces will be felt as the tow rig tries to move the towed vessel. Transitioning is the initial test of strength and performance for the tow rig and connections. Each towing vessel will react uniquely to this initial resistance. The pivot-point distance, propulsion and steering, and size difference between towing and towed vessels and weather will determine how the towed vessel will react. Actual maneuvering techniques are mastered through practice and experience. Minimize surge and shock-loading. Gradually come to a pay out course. Rapid movements or changes in direction increase the risk of:

(01) Fouling the towline in propellers or on deck fittings. (02) Shock-loads. (03) Loss of towline control.

The boat crewmember must have complete control of the towline. Too much towing vessel headway may cause the crewmember to lose control of towline tension, and the towline will start to run out. Crews risk injury from a running towline, with the possibilities of injuring their hands and arms in the tow bitt, tow reel, or in bights of line faked on deck. If the towline starts to run, reduce speed immediately. The crewmember working the tow bitt should regain control of the towline after the line stops running.

Paying out towline should be continued until the initial amount of towline scope is satisfactory.

Once the desired scope of towline is deployed, the coxswain directs the crew to make up the bitt. Forward motion should be slowed enough to slack the towline, and then the proper turns can be applied. Do not attempt to make up the bitt with a strain on a towline. This increases risk of injury by catching hands, fingers, and arms between the bitt and the towline.

The towing watch has a critical responsibility. In addition to the crewmember assigned, it is a collateral duty for all other crewmembers. The condition of the vessel in tow and the towline must be constantly monitored. Refer to Towing Watch on page 2-24 for further information on tow watch responsibilities.

The best course to safe haven is not always the shortest distance. A course that gives the best ride for both vessels should be chosen. At times, the vessels may have to tack (run a zigzag type course) to maintain the best ride. A firm understanding of the dynamic forces in towing help to ensure a safe tow.

The following instructions and information that will apply to each step of the tow astern should be shared with the towed vessel:

(01) General safety (PFDs, staying clear of tow rig, tow rig chafe, location of crew). (02) Equipment (pumps, drogues). (03) Steering (whether to man helm or lock rudder amidships, whether to steer on towing vessel stern). (04) Route to take, expected weather and seas, destination, ETA. (05) Lighting, sound signals. (06) Communications (primary/secondary radio frequencies, times of status reports). (07) Emergencies (breakaways, signals).

If drogue deployment is necessary, (i.e., to counteract a jammed rudder or other condition), the drogue should be deployed while barely making way before increasing speed to the planned towing speed (see PART 1 CHAPTER 3 Section C Standard Towing Procedures for more information).

Once underway with a tow astern, a proper length of towline should be maintained as discussed in Combination of Forces and Shock-Load of this chapter. Gravity causes a “dip” or downward sag (known as catenary) to form in the middle of the towline as it is lengthened. This catenary acts as a natural shock absorber for a tow rig and is a major factor in counteracting shock- loading (Figure 3-15).

[Illustration in the handbook: Figure 3-15 — Scope of Towline with Catenary]

The tow should be kept in step at a proper distance behind the towing vessel. When the towing vessel is on a wave crest, the towed vessel should also be on a wave crest several waves astern. If the towing vessel is riding up the back of a wave while the tow is sliding down the wave face, the towline slackens. When the towing vessel starts to slide down the wave face into the trough, as the towed vessel starts to climb up the back of a wave, the towline becomes taut shock-loading the tow rig. If an adjustment is not made, control of the tow may be lost. To prevent this from occurring, the towline scope should be increased to get the tow in step. An increase or decrease of your vessels speed may also help. Other measures to consider include:

(01) Altering course to increase the angle of the tow to the waves (to approximately 45°). (02) Deploying a drogue. In really confused seas, drogue deployment could help by preventing the towed vessel from surfing down the face of a wave.

Sometimes conditions make staying in step impossible. In such cases, the techniques above and reduction of speed should be used to counteract shock- loading.

The tow is said to yaw when it veers to one side or the other. Yaw can be caused by trim (including list, heeling or rolling, or by a bow-down attitude), rudder problems and wave action. Severe yawing is extremely dangerous and, if not corrected, may cause one or both vessels to capsize. Yawing also places tremendous strain on deck fittings and connections. Ways to reduce or minimize towed vessel yaw include:

(01) Change towline scope. (02) Adjust trim (more easily done on a smaller vessel) to raise the bow or counteract list. (03) Decrease speed or alter course to reduce effect of waves and wind. (04) Deploy a drogue (particularly to overcome rudder problems). (05) Use a bridle.

Crewmembers should keep close watch on the action of the tow and immediately report any unusual movements to the coxswain. If yawing cannot be reduced or controlled, it may be prudent to heave to until sea conditions improve or the source of the yaw is corrected. Currents can cause a relatively constant or gradual offset of the towed vessel from the towing vessel’s

NOTE

intended track or heading. Do not mistake this for yaw. (See “Compensating for Current,” later in this chapter.)

A safe and comfortable towing speed maximizes towing efficiency. Damage, sinkings and loss of life have occurred as a direct result of towing too fast. Maximum safe towing speed is based on the vessel’s waterline length and hull shape, but wind and sea conditions could dictate a much slower speed. The following formula shows how to calculate maximum safe towing speed:

(01) S = Maximum towing speed (hull design speed) (02) Ss = Maximum safe towing speed (03) Lw = Square root of length at waterline (04) S = 1.34 x Lw (05) Ss = S - (10% x S) a 10% reduction in the maximum towing speed

For example, to determine a safe towing speed for a boat that has a 36-foot waterline length, the following calculations apply:

(06) S = 1.34 x Lw (07) S = 1.34 x (square root of 36) (08) S = 1.34 x 6 (09) S = 8.0 knots (10) Ss = 8.0 - (.1 x 8.0) (11) Ss = 8.0 - .8 (12) Ss = 7.2 knots

If it is possible to tow fast enough to get the vessel up to the maximum towing speed (hull design speed), the strain and stress of the tow can be reduced for both vessels. Often, due to weather, seas, and other conditions, a hull will not be able to be towed fast enough to take advantage of its design. While it is tempting to tow some vessels at higher speeds, in most cases – after performing risk management and factoring in conditions such as weather, seas, boating traffic and safe speed – it is recommended to tow all vessels using the safe towing speed calculation. Table 3-1 lists the recommended maximum towing speed for all vessels. Due to safety concerns, never try to tow a hull faster than the hull design speed. Above hull speed, the vessel will try to ride up on its bow wave, becoming unstable and, in extreme cases, capsize. Also, wave drag (even one large wake) could slow the hull to displacement speed and cause a severe shock- load in the tow rig as the towing force tries to pull the towed vessel back on plane. In response to this shock-load, the towed vessel could plow its bow into another wave and swamp or capsize. Do not overlook the effects of wind and seas on determining safe towing speed. Though conditions can change during a long tow, be particularly careful when transition takes place in relatively protected waters. What may have been a safe speed during transition before could become dangerous for the towed vessel once it gets out of the lee of a headland, wharf, or large vessel.

Where and to what the tow rig is connected will also have an effect on the towing speed. Keeping in mind that the trailer eyebolt is usually a stronger connection than most deck fittings, a small craft may be towed at a greater speed if its trailer eyebolt is used instead of a weaker fitting up on deck. By connecting the towline to the eyebolt, the towline will pull the bow with more upward force compared with pulling the bow down if the tow is connected to a fitting on deck. MAXIMUM TOWING SPEEDS

[Lettered on the illustration: DISPLACEMENT AND PLANING HULL VESSEL TOWING SPEEDS]

[Illustration in the handbook: Table 3-1 — Maximum Towing Speeds]

[Illustration in the handbook: Figure 3-16 — Calculated Safe Towing Speeds]

Handling a tow becomes more of a challenge when traveling in a river, estuary or other area where tidal currents affect navigation or in areas where major coastal currents or wind-driven currents come into play. This is particularly true near inlets, bars, river mouths, river bends, and areas where currents diverge or converge. Generally, there are four conditions encountered while towing in current:

(01) Head current, (02) Tail current, (03) Cross current, (04) Combinations of currents.

To effectively deal with any of these, the towing vessel as well as the towed vessel must be navigated. One way to do this is to look at a stern tow as a single long vessel, with the propeller(s) and rudder(s) at the bow, and the pivot point at the stern. Though not a totally accurate picture, it shows that just because the towing vessel (the bow) changes direction, the towed vessel (the stern) will not immediately and automatically follow. Momentum will try to keep the towed vessel going in the original direction. Also, though the crew may frequently “crab” against the current with the towing vessel alone, now they must crab a vessel that becomes longer than the towline. “Local knowledge” becomes extremely important when dealing with current. The effect of current on vessel navigation at 12-30 knots is far less than the effect while towing at 6-8 knots. Keep overall tow length in mind. In current, even though the towing vessel may be well clear of obstructions or buoys, the tow rig and towed vessel may be set into them.

Head current is a current flowing directly against the steered course. Depending on the velocity of the current and the speed of the tow, speed over the ground may be reduced, stopped, or even reversed (Figure 3-17).

[Illustration in the handbook: Figure 3-17 — Head Current]

Regardless of speed over the ground, the tow is still moving through the water. Safe towing speed is based on speed through the water. Avoid towing a vessel above its hull speed or exceed the safe limits imposed by wind and sea conditions. If the current opposes winds and seas, the seas get steeper and break more readily. Increasing the speed through the water places excessive strain on a tow rig and deck fittings. Dynamic forces are still at work.

A head current in a “narrow” waterway poses other concerns. In a perfectly straight waterway, shallower water outside a deep channel will provide some relief, provided that the tow remains in deep enough water for safe navigation. Make sure that both the towing vessel and the tow stay in water deep enough so neither vessel grounds.

When towing in a waterway with bends and turns, the greatest current will be to the outside of the bend or turn. Accordingly, the water will be deepest on the outside. When towing around a bend, the direction of the head current acting on the towing vessel may differ from that on the towed vessel. At a bend, the towed vessel may sheer (or yaw) to the outside of the bend. In these situations, the following procedures apply:

Prevent towed vessel sheer by reducing towline length before entering narrower sections of a waterway.

Tail current is a current flowing in the same direction as the course steered. Crewmembers should remain aware of how the influence of a tail current affects both vessels. As with the head current, in general, speed through the water indicates appropriate handling procedures, not speed over the ground (see Figure 3-18).

[Illustration in the handbook: Figure 3-18 — Tail Current]

In open water, a tail current usually helps the tow along. However, when opposing the wind or seas, the tail current causes steeper waves. The steeper waves may require slowing the towing speed. The tail current should be accounted for when estimating the time of arrival. All course changes or shortening-up of the tow must be done earlier, or the current will carry the tow past the desired point. Then, considerable effort will be needed to go back against the (now) head current. Compensate for a tail current by taking early action.

As with a head current, a tail current in a narrow waterway also affects how the tow handles. A common situation develops when the towing vessel gets into an area of lesser current than the towed vessel. This often occurs near turns and bends where it appears that the shortest distance is on the inside of the bend. If there is a significant difference in the current, the tow sheers off along the axis of the current. This will possibly cause slack in the tow rig, loss of firm control, and will potentially overrun the towing vessel. To prevent this from occurring, the following procedures apply:

A cross current is a current that is flowing from either side, across the intended track. This current will require the towing vessel to adjust heading for set and drift for both vessels. At a towing speed of 7 knots, a 2-knot cross current will require a heading offset of over 15° in order to follow the intended track. In open water, this may not pose a problem, if the towing vessel adjusts properly throughout the tow (Figure 3-19). In restricted waters, suddenly encountering a cross current, such as where a longshore current crosses a harbor entrance channel, could first cause the tow to appear to veer, even though the towing vessel is the one being affected. Then, when the towed vessel encounters the flow, it will appear to veer the other way. In restricted waters, the towing vessel must adjust accordingly for the amount the cross current offsets the towed vessel from the intended track. The cross current could push the towed vessel into danger. The possibility of a cross current pushing the towed vessel into danger can be minimized through a combination of shortening tow and offsetting the towing vessel’s intended track in an up-current direction. Also, if the towed vessel is able, they should be instructed to steer into the current to compensate for the set. As an example, if a cross-current moving from right to left is present near a channel entrance, the tow should be shortened before entering and the towing vessel should be lined up to the right of the channel centerline. If unable to shorten tow, get well off to the up-current side of the channel centerline. While towing astern, if there is any crosscurrent in a channel marked by a navigational range, do not steer the towing vessel exactly on the range. Doing so could stand the towed vessel into danger on the down-current side of the channel. If the towed vessel has any problems such as steering or stability, keep the towed vessel in good water (usually the center of the channel, marked by the range). Use the towed vessel’s crew to inform the towing vessel when they are the range. Remember, when taking a vessel in tow, the towing vessel becomes responsible for its safety.

[Illustration in the handbook: Figure 3-19 — Effects of Cross Current]

Seldom will the current be dead on the bow, from directly astern, or exactly on the beam. If it happens to be that way at the moment, it may not be for very long. The marine environment is constantly changing, including the motion of currents. The general principles and specific procedures discussed above should be used to effectively compensate for combinations of currents. The surface of the water should be closely watched for evidence of current changes. A “tide line” usually appears at the leading edge of a current change or marks the difference between two different flows. A river’s color changes because of flow from another river. “Tide-rips” or bar conditions vary with the amount of current. Close attention to how current flows past a fixed object (pier, bridge support, piling) or a buoy will provide a good idea of what direction the current is heading and how fast it is moving. There is no substitute for experience and preparation. Learn the area of operations and be alert to hazards as to not be taken by surprise.

When approaching safe haven, it may be necessary to shorten the towline to safely enter an inlet, cross a bar, tow in a channel, or turn into a basin. The tow should be shortened to increase control in confined areas and in current. The towline must be slack to shorten tow. The coxswain controls the amount of slack and the direction the towline tends while the crew recovers the towline. The crew and coxswain must communicate and coordinate their efforts and actions to make the task as easy as possible without fouling the tow vessel’s propellers, rudders or waterjets. Knowing your boat and its systems is important during the towline recovery. For example, if on a boat with propellers, Towline recovery should be kept on the beam or quarter to prevent the slack towline from fouling the propellers.

The following procedures should be performed before shortening a tow:

The following are procedures describing how to shorten the tow:

Do not back too quickly and cause a large bight in the towline that increases risk of fouling propellers, waterjets, or rudders. Backing too quickly may also create too much strain for the line handler if the towline bight leads too far forward. Once a short tow is set, the “shock absorber” effect of catenary and scope is reduced. Special care should be used to counteract shock-loading.

NOTE

In calm conditions, if not much towline was out to begin with, shortening a tow may not be necessary. It may be easier to go directly to an alongside tow.

When operating in rough conditions, the following procedures apply:

The greatest control occurs when the wind and seas are off the towing vessel’s bow while on the beam of the tow. The wind and seas will drift the tow away from the towline. Speed should be reduced to lessen the forces on the towed vessel, which in turn are transferred to the towing vessel.

This technique is very demanding and must be learned through training and experience. Throttle

NOTE

response (acceleration and deceleration) must be matched to the towed vessel’s speed. If this technique is impractical to counteract shock-loading, speed reduction and quartering the seas may be your best options.

At the safe haven, the towing vessel will either moor the towed vessel or disconnect the tow so the towed vessel can anchor or be assisted by other resources.

NOTE

If disconnecting the tow, determine beforehand whether any other part of the rig will stay aboard the towed vessel. The weight of shackles or a wire-rope bridle will increase the difficulty of towline recovery, and could pose additional risk of fouling in propellers or rudders.

The towline should be shortened up to some extent already. The towed vessel should be turned into the prevailing conditions for better control, making towline recovery easier and safer because there is less towline for the crew to recover and less towline in the water to foul propellers. It also allows the towing vessel to maintain control of a tow a little longer. Once shortened, and with the tow barely moving to allow the towline to slacken, the coxswain signals for the towed vessel crew to disconnect the rig and let it go into the water. The towing vessel crew then hauls it aboard.

When set up properly, an alongside tow allows two vessels to be maneuvered as one. This advantage is necessary when approaching a dock, mooring, or anchorage in sheltered waters, or when maneuvering in congested or restricted waters. Most of the pre-tow procedures used for towing astern described earlier in the chapter remain valid. However, some additional preparations are needed and the make-up of the tow rig and approach will be different. The tow rig configuration and approach will be more like that for mooring (see Figure 3-20).

[Illustration in the handbook: Figure 3-20 — Side Tow]

These following additional preparations apply for an alongside tow.

Do not place the towing vessel between a larger towed vessel and a lee shore or obstruction. The towing vessel may not be able to overcome the other vessel’s momentum before losing all room to maneuver.

WARNING

As with any towing approach, leave an escape route.

If the alongside tow occurs at the completion of a stern tow, the coxswain should decide if the towline will be disconnected from the stern tow (the Drop Tow method); or hauled in while still connected, and used as a bow line for the alongside rig (the Transition method). If the stern tow required a bridle, Drop Tow may be the only option to provide a fair lead for the alongside bow line. One benefit of using Transition for an alongside tow is that there is always a separate bow line attached to the disabled vessel, and returning to a stern tow is possible, should the need arise.

Crewmembers should make ready the proper size and number of lines to rig alongside, determining where the attachment points on the towed vessel will be for each line. Use of a towline as the bow line in an alongside tow leaves more line lying on deck and may be a tripping or fouling hazard. Hull match is determined by assessing how the two hulls will align alongside. In towing alongside, the tow vessel may be angled, slightly bow-in to the towed vessel, with the towing vessel propeller(s) and rudder(s) aft of the towed vessel’s transom, rudder, or outdrive(s). All available fenders should be rigged, except one for hand-tending as the tow approaches, in potential contact points. All fenders should be secured in place, using clove hitches or slip clove hitches, before bringing a tow alongside.

NOTE

Keep all lines clear of the water. The coxswain should brief the towed vessel as follows:

When making the approach, two alternatives are possible:

(01) Transition approach, (02) Drop tow approach.

With towed vessel already in a stern tow, the following procedures apply:

Show the towed vessel crew where to attach the alongside mooring lines. Perform all line

NOTE

handling at coxswain direction, just as in mooring. Always pass the eye of alongside lines to a towed vessel. Keep the working ends of the lines aboard the towing vessel to adjust or relocate as necessary.

The Drop Tow approach is made as if mooring to a pier, but the first line over will be the bow line. There will not be a spring line to check forward motion with respect to the towed vessel. The coxswain directs the crew to pass the bow line when alongside. Do not fend off boat with your feet or hands.

Once alongside, with the bow line connected, the tow should be positioned so that the towing vessel’s propeller(s) and rudder(s) or waterjets are well aft of the towed vessel’s stern. This affords best control for maneuvering in confined areas. Fender placement should be checked and adjustments made so they provide maximum protection at contact points.

If there is little or no movement from wind, seas or current, rig lines in accordance with the following procedures:

(01) Rig a stern line from the towed vessel’s stern to the towing vessel’s stern. This line holds the sterns together while setting up the “spring lines”. (02) Rig a “tow strap” (forward spring line) from the towing vessel bow or forward mooring fitting to a point aft of the beam on the towed vessel. (03) Rig a backing strap (aft spring line) from a quarter location on the towing vessel to a location forward of the beam on the towed vessel.

For maximum control of a tow, all alongside lines should be as tight as possible. Spring lines are

NOTE

tightened by crewmembers taking up slack obtained when the coxswain throttles forward and reverse, pulling first against the tow strap then backing down against the backing line.

If conditions are setting the vessels into danger (e.g., toward shoals or breakwaters) with the bow line attached, and time is critical, use the following line procedures to secure lines alongside:

(01) Rig a tow strap (forward spring line) so that once secured, the towing vessel can put headway on and move clear of any dangers. (02) With headway still on, rig a backing strap (aft spring line) and/or stern line. These will be needed to slow or control the towed vessel.

Maneuvering with an alongside tow is a challenging boat handling technique. To do it well and to do it safely requires practice and experience. An experienced coxswain will observe how winds, seas and current affect the combined tow and use these forces to the best advantage, often making the maneuver look easier than it really was.

To moor an alongside tow safely and skilfully, perform the following procedures:

When it becomes evident that a tow is about to sink, the situation should be very quickly assessed. Quick decisive action to minimize loss of life is the first priority. Once abandon ship procedures are initiated, radio communications will likely be lost. The primary action is to break the tow and rescue the people, either from the deck of the towed vessel or from the water. A sinking tow can pull the stern of the towing vessel under unless all crewmembers pay close attention to the immediate situation. There might not be enough time to disconnect the towline from the towed vessel once it begins to sink. If a tow begins to sink, all towing vessel headway is stopped. The force exerted through the towline increases the danger of the towed vessel yawing and capsizing. Every attempt should be made to have the towed vessel’s crew disconnect the towline if possible and await rescue. Be aware that the boat could become fouled in rigging or debris while attempting to rescue survivors.

Perform the following procedures to minimize danger in sinking tow:

If there were no people onboard the tow, the water is shallow (depth less than towline length), and safety permits, the towline should be paid out until the tow reaches bottom. A fender or floatable object should be tied to the remaining towline so it is visible on the surface. The floating object will mark the location of the sunken vessel for salvage later as well as recovery of the towing vessel’s towing equipment.

NOTE

For further information, see Reference (v).

Circle the vessel, watch the vessel’s movement (pitch, roll) in the seas and determine the effect of wind and current on the distressed vessel’s drift rate and lateral movement. Compare it to your own drift. Knowing the different drift rates will help determine the best approach. Evaluate the location and any abnormal condition of deck fittings. Confirm the number of persons on board. Note any unusual conditions that may affect towing procedures (i.e., loose gear, rigging, or debris in the water). Communicate any concerns to the distressed vessel and direct all personnel on the distressed vessel to put on PFDs. Decide whether to put one of your crew aboard the distressed vessel. Decide if it is best to remove the crew from the distressed vessel. Determine if an equipment transfer (drogue, pump, radio) will be necessary. After evaluating the on-scene situation and assessing the risk, decide whether to tow or not.

NOTE

When conditions warrant, pass over emergency equipment, such as pumps or radios, before taking the vessel in tow.

Before beginning the approach to the disabled vessel, the coxswain must ensure the crew and boat are prepared as follows:

In heavy weather, it may be necessary to set up the deck underway at a slow speed to give the crew a safe, comfortable ride.

The towing approach requires maneuvering the boat close enough to the disabled boat, maintaining that position, and providing a stable platform long enough for the crew to safely pass the towing rig. The towing approach in heavy weather is to set up down-swell of the disabled boat with the bow into the seas. When the crew is ready, the coxswain drives the boat into optimum position. It may be necessary to use more power than in calm conditions to get steerageway and make a straight-line approach. Conditions may require stopping below or above optimum position to pass a heaving line

Many factors are going to affect your decision on which towing approach to make. Some factors are discussed in the subparagraphs that follow.

In smaller sea conditions with strong winds, the stern to approach may be the better choice. In large seas or breaking seas, the bow to approach must be used to protect your crew.

Depending on many factors, the Nature of Distress may affect your approach.

Size and configuration will greatly influence your towing approach. A large vessel with high freeboard at the bow may make passing a line to the bow difficult. Many commercial fishing vessels have stabilizing outriggers that must be left down in heavy weather to prevent loss of stability. Other challenges may include the skiff with a trailer eyebolt, a ferry boat, and crowded charter vessels to name a few.

There are potential hazards in any towing evolution. Some serious potential problems that may affect your towing approach could be nets or lines in the water, rocks or shoals, outriggers and other gear, boat taking on water, logs and debris in the water.

Coxswains’ skill and experience are going to greatly affect their decisions. No two coxswains will see the situation the same or make the exact same decisions in heavy weather.

Bow must be kept square to the seas. By keeping your bow square into the sea conditions, you will maintain better control of your boat. This position gives you the safest approach, best visibility of your boat, your crew, the disabled boat, and the sea condition. Push ahead slowly without zigzagging from your down swell station keeping position and approach the disabled vessel.

[Illustration in the handbook: Figure 3-21 — Bow-to-Swell Approach]

In heavy weather conditions, your crew may be exposed to waves coming over the guwhales of the boat. This is extremely dangerous for your crew. Constant watch must be maintained when operating stern to to protect your crew and to safely pass the towline. Your vessels stern must be square into the predominate factor, this will allow you to maintain better control of your boat. Push ahead slowly without zigzagging from your up swell station keeping position and approach the disabled vessel.

NOTE

For operating parameters concerning stern-to-swell approaches, refer to the platform specific Boat Operators Handbook.

[Illustration in the handbook: Figure 3-22 — Stern-to-Swell Approach]

In a heavy weather environment you will first have to pass a heaving line. Once the heaving line is across, complete any maneuvers required and stop in optimum position. The coxswain has to determine when to pass the towline and give the command. Do not allow your crew to just send the line across before you give the command. On command from your crew, the crew of the disabled vessel hauls in the towline. Train your crew to ensure the line is attached to the disabled boat properly and will not come off the attachment point. If you are using a bridle, ensure it is attached to the boat on both sides for an even pull. There should be no turn on the bitt until coxswain gives the command. The coxswain ensures the bow is clear before giving the command to take a working turn on the bitt.

A working turn is a towline placed on a bitt that allows enough surface contact to ensure positive control of the towline. A working turn begins with a round turn placed on the bitt, and depending on the factors of the object being towed (e.g. size, weight, wind and seas) may require additional figure eights to effectively maintain control.

Towing transition is the maneuver from station keeping to towing astern. This is the most hazardous period in heavy weather. You have to move from the safety of the maneuvering zone to put your tow behind you. Take your time and don’t maneuver away during the series. Transition is when you have the greatest likelihood of surging the towline through the bitt. The following are basic procedures for transitioning:

Risk from a running towline is greatly increased in heavy weather conditions. Great care must be taken to reduce surging the towline through the towing bitt as the boats separate and are affected by the seas. Constant watch should be kept on the towed vessel and any change in trim or the way the vessel rides should be investigated immediately.

In open water, getting both boats in step will also dramatically reduce the forces on the towed vessel. Changing course to reduce wave action is often the next safest technique. This will reduce the yawing and surfing of the towed vessel. Reducing speed or changing the scope of the towline will also lessen the forces on the towed vessel, which in turn are transferred to the towing vessel. Never allow the towed vessel to overtake the towline. When approaching the coast, or nearing an inlet or bar, keeping the tow in step as water depth changes becomes very difficult. Plan to approach with seas on the quarter to reduce shock loading. The following technique should be used to maintain control and reduce the forces affecting of your tow:

While towing in open waters, it is usually safer to change course to reduce the wave action. This will reduce the yawing and surfing of the towed vessel. Getting both boats in step will also dramatically reduce the forces on the towed vessel. Reducing speed or changing the scope of the towline will also lessen the forces on the towed vessel, which in turn are transferred to the towing vessel. When approaching the coast, or nearing an inlet or bar, keeping the tow in step as water depth changes becomes very difficult. The coxswain should plan to approach with seas on the quarter to reduce shock-loading. The following techniques should be used to maintain control and reduce the forces affecting tow:

(01) Constantly adjust towing speed to prevent a tow from surfing on a wave or broaching. (02) If a large wave approaches the stern of a tow, increase towing vessel speed to keep ahead of the tow as it is pushed by the swell. (03) As a tow reaches the crest of a swell, reduce speed. (04) Avoid shock-loading the towline. Keep the towline taut. (05) Constantly watch the seas astern and the towed vessel until in sheltered waters or course is changed to reduce influence of the seas. (06) Deploy the drogue.

Staying offshore and waiting for better sea conditions may be a safer alternative if controlling the tow or the safety of the tow is in question.

Towing into heavy seas creates heavy strain on the towing vessel, the towing equipment, and the towed vessel. One of the most effective techniques to reduce strain is to reduce speed. Lengthening the towline and allowing a greater catenary will reduce the shock of the seas reducing chafing, stress on the towed vessel, and shockloading. The placement of the towline on the bow affects the ride of the disabled vessel by pulling it down and often allowing seas to wash over its bow. This can be extremly hazardous to the disabled vessel and affect its stability. Reducing towing speed might help by raising the disabled vessel’s bow and reducing the amount of water taken over the bow.

Towing beam to heavy seas will reduce shock-loading and strain on the vessels but it increases the amount both vessels will roll in the seas. Great care should be taken when towing vessels with narrow beams or large liquid storage tanks. Narrow beam boats have less stability and are prone to capsizing. Vessels with large liquid storage tanks such as live wells may experience free surface effect that will greatly effect their stability. Free surface effect is the movement of a liquid (fuel, water) to one side of a partially filled storage tank as the vessel rolls from side to side. This shifting of weight is very dangerous to a vessel’s stability.

Shortening the tow should be accomplished in open waters where there is plenty of room to maneuver. It is most often done prior to approaching an entrance to a harbor or river. By shortening the tow, control of the towed vessel will increase and make turning and manuvering in tight quarters easier. Before beginning, the coxswain takes up a course 10° to 15° off the seas with tow to windward. The wind should set the boat away from ther towline. Speed is reduced until both vessels are stopped. This should set the boat up to put bow into the seas and have the towline off of the quarter. Once the bow is square, then the command is given to break the tow bitt. Keeping the bow square to the seas back and take in the amount of line required. It may be necessary to make more than one attempt to recover the line. Extreme care should be taken to prevent the towline from becoming fouled in the waterjets/propellers.

(01) Crew Communications are extremely important. Ensure your crew can hear you and they understand their assignments. (02) Always tend the towline through the tow bitt. If you have an emergency, the crewmember can make the bitt and you can get underway again. (03) Keep towline in sight. (04) Know where your rudder is, use your Rudder Angle Indicator (RAI). (05) Make the bitt and pull ahead in case of emergency. This is your escape route. (06) Do not let the towline loop pass the recess. Excessive line in the water puts a heavy strain on your crew. Slow down and work at a pace your crew can recover the line.

Handling towing evolutions in surf is extremely hazardous. The danger involved limits this response to cases involving potential loss of life. Abandoned boats do not warrant the risk involved to boat crews or boats. Extreme caution must be taken when towing in surf conditions. Towing in surf conditions requires specific techniques and should only be attempted when removal of the crew is more dangerous than the potential dangers from towing, whether to the disabled vessel or the towing vessel, or injury to personnel.