GENERAL A.Do a complete RISK ASSESSMENT with the crew before undertaking any towing evolution. B.Communicate with the towed vessel’s crew who may have important information necessary to complete a successful mission
GENERAL C.Should I Tow? What is the WX condition? What is the gross tonnage? Am I experienced to tow in the conditions? Will the vessel’s casualty effect towing? Is the construction of the D/V sound?
GENERAL What is the number of POB on the D/V? Should all or some of the POBs be removed? How does the vessel ride in the sea conditions you may encounter? Are all POBs wearing PFDs? Has the operator every been towed by the Coast Guard before and how was it done?
GENERAL Does the D/V have the proper fittings for towing? Is the D/V capable of emergency signals to attract your attention in the event of radio failure?
GENERAL D.Caution: Do not let a preceived need to engage in a towing mission override a complete, honest Risk Assessment process that emphasizes personal safety.
GENERAL E.Change: The dynamics of a towing situation continuously change from the time pre-towing preparations begin until mooring at the conclusion of the mission. Think ahead, what could change and how would you handle the change?
GENERAL F.Training: Realistic towing training based on standardized techniques, critical analysis, and mission debrief will contribute to risk management and the development of a towing risk management plan.
FORCES IN TOWING STATIC FORCE A.Inertia: The tendency of a vessel at rest to stay at rest. The more mass (displacement) a vessel has the more inertia it has and the harder it is to get it moving.
FORCES IN TOWING B.Moment of Inertia: Occurs when a towed vessel resists turning to change heading. The larger the vessel, the more resistance there will be in turning. Unless necessary due to immediate danger, DO NOT attempt to start towing ahead and change direction at the same time. Start slowly on the initial heading of the tow if possible.
FORCES IN TOWING C. Caution: When towing vessels of equal or greater mass, the capacity and capability of the towboat will be strained. This requires slow and gradual changes of speed and direction. Attempt to start towing on the initial heading to gradually overcome the tow’s inertia. Even when underway, the tow will resist turning.
FORCES IN TOWING DYNAMIC FORCES A.Dynamic forces occur once the towed vessel is moving. They are based on the towed vessel’s characteristics (shape, displacement, arrangement, and rigging), the motion caused by the towing vessel, and the effects of waves and wind.
FORCES IN TOWING A.Momentum: Once a vessel moves in a straight line, it wants to keep moving in a straight line. B. Angular Momentum: Once the towed vessel’s heading begins to change, it wants to keep changing in the same direction.
FORCES IN TOWING D. Frictional Resistance: As a vessel moves, the water in contact with the hull moves as it is dragged. The greater the under-water area of the vessel the greater the frictional resistance. This keeps a steady tension in the towing rig and is managed by speed. Higher speeds cause higher friction and more strain.
FORCES IN TOWING E.Form Drag: The size and shape of a towed vessel can help or hinder. A deep draft vessel takes more effort to change direction than a fine, shallow (planning) hull. Deep draft towed vessels may be able to help offset form drag by using its rudder.
FORCES IN TOWING F.Wave Making Resistance: A surface wave forms at the bow while the hull moves through the water. The size of the bow wave increases as speed increases and generates resistance to movement of the boat. CAUTION: Do not tow any vessel above it’s hull speed.
FORCES IN TOWING G. Wave Drag: Depends on the wetted surface area of the hull and the amount of freeboard exposed to wave action. In heavy seas this can cause the tow to stop and transfer a heavy strain to tow rig. In head seas the towing vessel can control this with speed and angle. In following seas speed up and slow down to keep tension on towline.
FORCES IN TOWING H. Spray drag: Provides resistance to the tow increasing shock load. I.Wind Drag: Can cause shock loading and have a bad effect on the towed vessel’s motion and stability.
FORCES IN TOWING J. Buoyancy Response & Gravity Effects: A towed vessel’s bow may react to a wave by pitching up, or by sub-marining. Buoyancy response to following seas may cause tow to yaw 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 may cause severe shock- loading.
FORCES IN TOWING K. Combination of Forces & Shock-Load Rarely do you deal with only one force acting on a tow. Shock-loading may cause severe damage to both vessels and overload a tow rig to the point of failure. It may also cause momentary loss of directional control by either vessel and could capsize smaller vessels.
FORCES IN TOWING TO COUNTER-ACT SHOCK LOADING: Place vessel In-Step Lengthen the towline Change course Deploy drogue Reduce towing speed Adjust towing speed
FORCES IN TOWING COMBINATION OF FORCES Inertia* Momentum Form Drag* Wave Drag Wind Drag Movement of Inertia Angular Momentum Frictional Resistance Wave Resistance
FORCES IN TOWING Shock-Loading dangers: 1.It can cause damage to tow rig and fittings. 2. It can break the towline and cause “Snap- back”! 3.Can swamp or capsize the tow.
TOWING EQUIPMENT A. Towline: Have faked out on deck or otherwise ready for easy deployment. Regularly inspect for: cuts, chaffing, flattening (from excessive loading), fusing (from excessive loads), or snags IF ANY OF THE ABOVE – DO NOT USE The tow rig is only as strong as it’s weakest link! (If a tow rig uses a ¾” nylon towline with a 1 ton rated shackle, the tow rig is limited to 1 ton!) Have towline faked out and ready for easy deployment, see next slide:
TOWING EQUIPMENT B. Pendant: A short length of towline used between the towed vessel and towline. It is used to prevent wear on the towline. This could be 1/2 of a bridle.
TOWING EQUIPMENT C. Bridles: Inspect regularly with towline. 1.Use “Y” bridle when both legs can be rigged to exert an equal pull on the hull. 2. Should be long enough to clear all obstructions on the deck and meet forward of the bow.
TOWING EQUIPMENT 3.Keep the bridle legs long enough to keep the angle of the legs under 30 degrees. 4.The legs must be long enough to reduce the towed vessels yaw. 5.Protect with chaffing gear as necessary. 6. Used to center tow behind towboat and/or to clear obstructions on stern of towboat.
TOWING EQUIPMENT D. Heaving lines: Light weight,75 to 100 feet long. Cotton line works well (wet before using) The end should be lightly weighted for throwing. Suggest having more than one Attach a small snap on the standing end for quick attachment to the tow rig.
TOWING EQUIPMENT Heaving line and ball Float Line Always yell “HEADS UP” before throwing Always throw over the target (BOAT)
TOWING EQUIPMENT G. Dock lines: Have sufficient dock lines to moor your vessel while you have another vessel in an alongside tow. H. Fenders: Have enough fenders to properly protect both vessels while in an alongside tow and for docking with the side tow. Use the largest size you can store. Have one large extra fender.
TOWING EQUIPMENT I.Skiff Hook: A snap hook that is used to attach a towline to the towing eye on smaller boats that do not have suitable deck cleats. The skiff hook attaches to the end of a pole (boat hook) for reaching the towing eye of a D/V. The towing eye is one of the strongest attachment points on a boat but is extremely hard to reach for connecting and disconnecting the towline.
TOWING PROCEDURES Throughout the entire towing evolution, communications between the coxswain and crew is absolutely necessary for a Safe and efficient operation.
TOWING PROCEDURES A.Notification: Get as much information as possible/needed before getting underway. Assign this duty to one of the crew. Write all information down. Develop a full understanding of the situation. Make a conscious decision to “Accept” or “Not Accept” the mission. B.Brief the crew.
TOWING PROCEDURES C.Evaluate the conditions with the crew. D.Navigate safely to the scene: Operate at a safe speed at all times. Keep a constant awareness of position and area hazards. Stay aware of the distressed vessel’s position and condition.
TOWING PROCEDURES E. Communications with D/V: 1.Keep in radio contact on a regular basis and give an ETA. 2.Advise POBs on D/V to don PFDs. 3. Get details of D/V’s deck layout 4.Ask for any important information. 5.Determine if anything has changed.
TOWING PROCEDURES 6.Ascertain any sense of heightened urgency. 7.Inform the D/V that once on scene you will observe conditions and make final preparations before setting the tow.
TOWING PROCEDURES NOTE Once on scene don’t allow D/V to become endangered while waiting for POB to put on their PFDs. Take action to remove POBs from danger or from the D/V.
TOWING PROCEDURES F.Perform On-Scene Assessment: 1. Evaluate the location and any abnormal conditions of deck fittings. 2. Confirm the number of POBs. 3. Note any unusual conditions that would affect towing, (loose gear, rigging, etc.)
TOWING PROCEDURES 4.Decide if you should place crew on D/V or remove any POBs from the D/V. 5. Decide whether to tow or not. 6.Do you need a bridle on the D/V? 7.Will a drogue be needed for the tow? 8.Brief both crews of intentions.
TOWING PROCEDURES G.Determine the approach: Crossing the “T”, parallel or back-down. H. Determine method for passing tow rig I.Brief both crews J.Determine the “Danger Zone” K.Determine the “Maneuvering Zone” L.Determine the “Optimum Position”
ASTERN TOWING A.Maneuver: Your vessel so crew can maximize use of the best deck area for passing the tow rig. Bow or stern into the seas. This will provide the most vessel control and visibility for the coxswain, while station keeping a safe distance from the D/V. Plan a safe “Escape Route” for emergency.
ASTERN TOWING B. Rough seas: In rough seas make approach with bow or stern into the prevailing forces. (if it works in rough seas it will work in any seas) (NOTE: IF THE SEAS ARE TOO HEAVY AND YOU ARE TAKING ON WATER OVER YOUR STERN, YOU ARE IN SEAS TOO ROUGH FOR YOU!)
ASTERN TOWING C. Approach: – Make approach at the slowest speed possible while maintaining steerage. – Stop in optimum position and pass the tow rig with a heaving line (At coxswain’s command). – (Coxswain MUST let the crew know before making correcting maneuvers so that they can safely tend lines.)
ASTERN TOWING D. Opening & closing: Use opening and closing maneuvers to maintain optimum position. Act before a problem develops. (NOTE:) Maneuver as required but it is preferable not to maneuver when lines are over (except the heaving line).
ASTERN TOWING E.Passing the tow rig: (Include drogue if it is needed.) In calm conditions the rig may be passed by simply handing it over or by use of a boat hook. Practice using a heaving line for moderate or heavy seas.
ASTERN TOWING 1. To pass the heaving line: If cotton heaving line wet it to make it more flexible and to minimize tangling. Take 2/3 of the heaving line coil into the casting hand and the reminder in the other. Check if area is clear of obstructions.
ASTERN TOWING Advise the coxswain when ready (“I have a shot”) Coxswain will give command “Take your shot” Call out to the D/V “Heads up” Cast so the heaving line falls across the D/V’s deck. Tell the coxswain when casting
ASTERN TOWING If not successful, quickly retrieve the heaving line and prepare a second line or attempt. Repeat steps 2 through 7 until successful
ASTERN TOWING 2. Keep coxswain advised on tow rig transfer: a.“TOW RIG AWAY” b.“TOW RIG IN THE WATER” c.“TOW RIG ON D/V” d.“TOW CONNECTED” e.“D/V CREW SECURED”
ASTERN TOWING F.Connecting the tow rig: 1. Monitor crew of D/V to follow directions 2. Towline clear of any gear on deck 3. Chaffing gear 4. Under railing 5. Not pulling against railing or stanchion
ASTERN TOWING 2.Connect to cleat or the “Towing Eye”. If using the towing eye use extreme caution in bringing the vessels together. (Not safe to do in rough seas) If using deck fittings, be sure they are in good condition. Don’t hesitate to put crew aboard to check out conditions.
ASTERN TOWING 3.Have crew of D/V return to cockpit area after securing towline 4.Slowly open distance between boats and manually adjust length of towline. (Crew and Coxswain should be in communication constantly during this process.) (Line in water, Tension coming on line, under tow)
ASTERN TOWING 5.Have your crew take a working turn on bitt/cleat before there is a strain on towline. 6.After length is set (Maintain a catenary in tow rig) make up line on bitt/cleat.
ASTERN TOWING A.Start tow slowly and if possible, in the direction the D/V is pointing. B.Set “tow Watch” and maintain COMMS with the D/V. C. Slowly bring tow onto desired heading D.Watch for “YAWING” or any other problems with the tow.
ASTERN TOWING E. Maintain catenary while towing F. Keep tow in step and tow at safe speed G. If yawing: straighten helm of D/V or, If O/B or I/O raise it’s lower unit or, adjust the trim on D/V (Move POBs) or, decrease speed or, change angle into waves or wind or, deploy a drogue from D/V.
USE OF A DROGUE H. Drogues are used behind a tow to slow it down and give stability. It acts much like a parachute. It’s deployed from the stern of the towed vessel. A traditional drogue is a canvas or a synthetic cloth cone open on both ends.
USE OF A DROGUE With a short hawser and large swells on the stern, the drogue is deployed to prevent the tow from running up the stern of the towboat as it keeps tension on the towline preventing the tow from “surfing down the face of a wave.
USE OF A DROGUE The drogue should have about 200 feet of line (marked every 50 feet) attached to the bridle swivel using a shackle. Pass the drogue directly to the D/V and watch the crew ready the drogue rig. Use centerline attachments or bridle unless compensating for a jammed rudder.
USE OF A DROGUE A second light line should be attached to the smaller end of the drogue for ease of drogue retrieval. Start the tow moving slowly, then deploy the drogue. Once it sets, increase speed while the towed vessels crew observe the rig.
USE OF A DROGUE To avoid fouling drogue lines: Slow or stop the tow and have the towed vessel recover the drogue. Run a “dumping” line from the drogue to the stern of the towed vessel (suitable for large drogues that drain slowly).
ASTERN TOWING I.Shortening the tow: 1. Select a safe area 2.Brief both crews on planned action. 3.Determine new towline length 4.Reduce speed and take off way slowly 5.Break towline from bitt/cleat
ASTERN TOWING 6.Back as crew keeps line out of screws 7.When at desired length, make up line on bitt/cleat 8.Resume tow in direction of D/V heading
ALONGSIDE TOW Always do in calm protected waters. A.Determine which side to tow from: Consider side of dockage Consider your visibility Consider location of fittings on each vessel Consider the type of approach (free or back- down) Consider which vessel will be against the dock.
ALONGSIDE TOW B. Prepare alongside tow lines C. Position fenders to protect both boats D. Prepare dock lines and have boat hooks ready E.Note direction of wind and current and consider their effect on mooring F.Always connect Line #1 first then #2.
ALONGSIDE TOW G. If necessary you can then start towing in a forward direction only. H. Connect line #3 and then #4 if used. I. Adjust fender position or use a “Walking” fender as necessary.
ALONGSIDE TOW J.Tighten lines as follows: While going forward and turning away from the tow, tighten lines #3 and/or #4. Go in reverse to tighten lines #1 and #2 or while in forward turn into the tow.
ALONGSIDE TOW CAUTION: Keep all body parts out from between boats. Always place the eye of a line on the D/V so that adjustments can easily be made from towing boat. You may have to place crew aboard the D/V as a lookout
MOORING ALONGSIDE TOW A. It is easier to moor into the prevailing force and on the lee side of dock. B.Use only enough speed for steerage C.Use a lookout to call range and bearing to dock and objects or other traffic.
MOORING ALONGSIDE TOW D. It is easier to turn toward the tow in forward. To make a turn away from the tow consider going in reverse. You can make a very sharp turn in reverse. E.If possible, place the larger of the two vessels against the dock. F.Secure D/V to the dock
MOORING ALONGSIDE TOW G. Gather required information for reports. H.Break tow I. Report “Tow secure” per local policy. J. Get underway
TOWING PRECAUTIONS A.Have all POBs on D/V don PFDs. Furnish if necessary. Don’t jeopardize POB or vessel safety waiting for POBs to don PFDs. B.Remove POBs when necessary C.Cast heaving lines well over D/V so line falls across D/V’s deck. D.Monitor conditions of the tow rig.
TOWING PRECAUTIONS E.Establish and maintain D/V COMMS F.Monitor any sea-water on D/V G.Monitor conditions of POBs on D/V H. Keep clear of tow rig (SNAP-BACK) I. Keep tow rig attachment points low and near the centerline
TOWING PRECAUTIONS J. Do not attach tow rig to lifeline, stanchions, grab rails, or ladders. K. Do not attach lines to cleats that are only held by screws. L. Avoid using lines provided by the D/V M. Avoid using knots to join tow-lines N.Use two crew if possible to tend lines
TOWING PRECAUTIONS O.Tend a towline by hand until secured to D/V then secure on coxswain’s command. P.Only use figure-eight cleat hitches on cleats with NO weather hitch. Q.Crew should keep clear of towline.
TOWING PRECAUTIONS R.Crew should not cross arms but change hands when handling lines. S.Keep towline clear of prop and rudder. T.Use chaffing gear as needed. U.Avoid towing boats over 50% larger. V.Tow at a safe speed for conditions. W.Avoid sudden maneuvers.
TOWING PRECAUTIONS X.Consider a drogue to reduce yaw. Y.Have helm of D/V manned and have D/V steer at stern of towboat if needed.
TOWING PRECAUTIONS Z.Keep towed boat in trim, consider: 1. Condition of D/V (damage, taking on water, etc.) 2. Structural design of D/V 3. Cargo 4. Number and location of POBs
TOWING PRECAUTIONS WARNING Overloading astern, or along either side of the centerline, may swamp or capsize a tow!
TOWING PRECAUTIONS AA. Maintain a diligent tow watch. All crew should be assisting in this. AB. Bridle breaking strength should be equal to or greater than towline. AC. If possible, do GPS and chart work at dock
TOWING PRECAUTIONS AD. If there is a possible need for a pump or drogue, pass before start of tow. AE. Coxswain/Crew should inspect the tow rig before it is connected.