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DAMAGE CONTROL, CAPSIZED VESSELS AND GROUNDING Part 2 GROUNDED VESSELS. July 2012. ROYAL CANADIAN MARINE SEARCH AND RESCUE. Grounded Vessels. Grounded Vessels. What damage? Does towing vessel have sufficient power? What is the tow gear capacity? What strong points are on casualty vessel?
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DAMAGE CONTROL, CAPSIZED VESSELS AND GROUNDINGPart 2GROUNDED VESSELS July 2012 ROYAL CANADIAN MARINE SEARCH AND RESCUE
Grounded Vessels • What damage? • Does towing vessel have sufficient power? • What is the tow gear capacity? • What strong points are on casualty vessel? • What are sea, weather and tide conditions? • What would be the stability of the casualty vessel, once afloat?
Grounded Vessels • What is the current situation - can the casualty wait for the tide to rise?
Grounded Vessels Broaching • This is where the casualty is moved by the wind and sea to go broadside to both. • If not got to quickly the sand will be scoured away and deposited midships on the lee side of the casualty, which can ultimately result in it breaking its back.
Grounded Vessels Pounding • This is where the casualty is moved vertically by the sea onto the sea floor underneath it. • The worse the conditions, and closer to afloat the casualty is the more damage will occur.
Grounded Vessels • On a falling tide some vessels (especially sailing vessels) will need shoring to prevent them from falling over, and consequent swamping on the rising tide.
Grounded Vessels • Inspect the grounded vessel to see what damage has been sustained. • If there is any doubt about keeping the vessel afloat, once free, do not tow off. • Initiate damage control as necessary. • If necessary lay out anchors to seaward to prevent situation worsening.
Grounded Vessels • Is the tide rising or falling - if rising and the vessel has not fallen over, and there is no damage, it may simply be a matter of waiting. • If the tide is falling, how much has it still to fall, and what will happened to the grounded vessel as the tide falls, and more important what will happen as the tide rises again. • If it is a sailing vessel, consider a halliard tow to get the vessel off.
Freeing Grounded Vessels • If the vessel is fast aground on a falling tide, do not try attaching a tow line and taking a run at it in the hope of pulling the vessel off. • You are likely to either damage the grounded vessel, or put your own crew and vessel at risk from a snapped tow line. • This will only work with very small dinghys or tenders.
Freeing Grounded Vessels • The first method of getting the grounded vessel off is a straight pull. • Consider using you anchor and veering down to hold your position off a lee shore. • Get the tow line or a messenger to the casualty vessel. If anchored, either line can be floated down using a buoy or scotsman. • The towline is passed and made fast to a strong point.
Freeing Grounded Vessels • Lots of tow line is paid out to maintain a good catenary. • The casualty vessel is pulled in the opposite direction from which it went on - a rising tide or high water will help.
Freeing Grounded Vessels • A second method of getting the grounded vessel off is wrenching or pulling. • The casualty vessel is pulled ahead but the towing vessel alternatively pulls from one side then the other.
Freeing Grounded Vessels • A third method is doing a bow on pull. • The rescue vessel approaches the casualty bow on. • This is for calm conditions, and keeps the rescue vessels propellers in deeper water. • The tow line is made fast on the casualty and aft of the bow on the rescue vessel to maintain ability to pivot. • Pull astern gradually.
Power Dredging or Scouring • If a casualty vessel is lightly aground on sand, gravel or mud, power dredging may work. • Have consideration on the effects of sand and mud on the bearings and cooling water system of your propulsion. • The depth of water alongside the casualty vessel must be sufficient to operate the engines.
Power Dredging or Scouring • The rescue vessel is made fast from the after tow post to strong points on the bow and stern of the casualty vessel. • Move your vessel fore and aft to achieve the necessary scouring.
Power Dredging or Scouring • The engines on the rescue vessel are put on fairly low revolutions ahead. • Over a period of time this may dredge away sufficient mud or sand to free the grounded vessel. • High revolutions are not used.
Halliard Towing • This technique is for freeing grounded sailing yachts (with a fixed keel), where the vessel is substantially afloat. This example would have to wait for tide to rise.
Halliard Towing • On arrival, ask those onboard what position they went aground, what direction they were heading in, and ascertain whether that position has changed. • Where the keel is aground, but where there is sufficient water under the side of the hull that is immersed, and the deck edge can be submerged, there is a good chance the halliard tow will work.
Halliard Towing • If there is one, pull using the spinnaker halyard, which is designed to swivel and be pulled on over wide range of angles. • A jib or main halyard has a fixed sheave and may not be happy with much side-load without damage to halliard line or sheave-box.
Halliard Towing • Initially place the rudder amidships, where not damaged. • If available, a second vessel, or even someone in the casualty’s dinghy pulling can be sufficient to provide the necessary down force. • The rescue vessel can then tow the vessel clear, astern or ahead to safety. • Tow very gently - even by hand can work.
Halliard Towing • However it should also be noted that where the halliard tow is set up forward of the athwartships line through the casualty vessel’s centre of gravity, the casualty may tend to go ahead as it comes free of the bottom.
Halliard Towing • It is suggested that the halliard tow is set up just aft of the athwartships line through the casualty vessel’s centre of gravity, as the casualty will tend to go astern as it comes free of the bottom. • This is likely opposite to the direction in which it went aground.
Halliard Towing • This technique is only for towing over a short distance to get the vessel afloat. • As soon as it is afloat in deeper water, stop pulling, take in alongside or astern tow as appropriate to safe waters, and thoroughly inspect.
Halliard Towing Any comments?
Handling a Sinking Tow • The sinking tow can pull down the stern of the towing vessel or try to capsize the towing vessel. • Cut or slip the tow when it is apparent that it is sinking, using the axe or knife. • Rescue any personnel in the water. • If sinking in shallow water, tie floating object to end of tow line, to mark vessel, and then cut line on rescue vessel side of object.
Final Thought • What would you do here?
