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SABOT. Standardized Auxiliary Boat Operations Training Ninth District - Eastern Region COMO. Lew Wargo, Sr. DSO-OP/CQEC 15 April 2014 GENERAL TOWING. SABOT. GENERAL TOWING. REFERENCES. Coast Guard Addendum to the National Search and Rescue Manual (NSS), COMDTINST M16130.2(series)
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SABOT Standardized Auxiliary Boat Operations Training Ninth District - Eastern Region COMO. Lew Wargo, Sr. DSO-OP/CQEC 15 April 2014 GENERAL TOWING
SABOT GENERAL TOWING
REFERENCES • Coast Guard Addendum to the National Search and Rescue Manual (NSS), COMDTINST M16130.2(series) • Auxiliary Operations Policy Manual COMDTINST M16798.3 (series)
REFERENCES • Boat Crew Seamanship Manual, COMDTINST M16114.5(series) Chapter 17 • Auxiliary Boat Crew Qualification Guide, COMDTINST M16794.52(series) • SABOT Job Aid (Section H)
GENERAL A. Do a complete RISK ASSESSMENT with the crew before undertaking any towing evolution. B.Communicatewith 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 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 NOTattempt 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 • Dynamic forces occur once the towed vessel is moving. They are based on thetowed 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 • Momentum:Once a vessel moves in a straight line, it wants to keep moving in a straight line. C. 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 • 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: Should be light weight and 75 to 100 feet long. Cotton clothes line works well. Wet cotton line before using. The end should be weighted for throwing but not enough to cause damage or injury. 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
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. 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. Do you need a bridle on the D/V? 6. Decide whether to tow or not. 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”
