Anchors and Anchoring Notes PDF

ANCHORS AND ANCHORING  WHY DO WE ANCHOR ? Protection of boat from storm Provide rest for the crew Dock space not available in a harbour If engine get failure then to maintain sustainability of boat in water an anchor get used. Things to look for when selecting an anchor Wat...

ANCHORS AND ANCHORING  WHY DO WE ANCHOR ? Protection of boat from storm Provide rest for the crew Dock space not available in a harbour If engine get failure then to maintain sustainability of boat in water an anchor get used. Things to look for when selecting an anchor Water depth Bottom type (clay, sand, mud, rock, boulders, weeds) – Clay, sand and mud provide the best anchoring substrates – Rock shelves, boulders and weeds are the worst substrates Protection from predicted winds, protection from prevailing winds and currents or tides Size of anchorage, for room to swing  ANCHOR PRINCIPLES Two general categories of anchors: 1. Heavy weights Used for stationary objects like navigation bouys 2. Anchors that dig into the bottom Used on vessels and combine weight and ability to dig into the substrate PARTS OF AN ANCHOR  TYPES OF ANCHOR 1. A/P or Fisherman’s anchor: Non-burying type, with one arm penetrating the seabed and the other standing upright It has a good reputation for use in rock, kelp, and grass, but is unlikely to be any more effective than a good modern design and its holding power to weight ratio is among the worst of all anchor types The primary weakness of the design is its ability to foul the cable over changing tides Fig. - Fisherman's Anchor 2. Danforth Anchor The stock is hinged so the flukes can orient toward the bottom The design is a burying variety, and once well set can develop an amazing amount of resistance. Its light weight and compact flat design make it easy to retrieve and relatively easy to store Fig. - Danforth Anchor 3. CQR/Plough Anchor Generally good in all bottoms, but not exceptional in any. It has a hinged shank, allowing the anchor to turn with direction changes rather than breaking out, and also arranged to force the point of the plough into the bottom if the anchor lands on its side. Fig. – Plough Anchor  Bruce/Claw Anchor Claw-types set quickly in most sea-beds and although not an articulated design, they have the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force. Claw types have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding power to weight ratio and generally have to be over-sized to compete with other types. Fig. – Claw Anchor  Capstans and Windlasses (They help to operate anchor from boat) Capstan Windlass Used on traditional vessels Pathfinder: Bars attached allowing – Pawl-rack system, two handles crew members to turn the are pumped back and forth capstan Playfair: – Gear system, handles are attached and wound in a circular motion  What is Scope Scope = Length of Anchor rode / Depth Scope = 9 / 3 or 3 to 1 Scope = 21/ 3 or 7 to 1 Depth 21 Fathoms 3 Fathoms 9 Fathoms  Catenary www.tensiontech.com An anchor rode is not just a straight link between the bow and the anchor. If you could swim down alongside it, you would see it start from the bow at a fairly steep angle, then slowly flatten out until it blends smoothly into the bottom. Having a lot of sag in the rode reduces shock loads and helps keep the anchor dug in by reducing the angle between the rode and anchor.  How do you know how much anchor rode to put out? Stopping for a swim – 3:1 scope Stopping for the day – 5:1 scope Anchoring for the night – 7:1 scope These are rough estimates – If you were expecting a storm with high winds you might want a 10:1 scope – What should you be concerned about when you have that much scope?  Chain Markings Fathoms Marking One One red mark Five One white mark Ten One black mark Fifty One blue mark Example: 22 fathoms would be two black marks and two red marks What would 67 fathoms be?  Dropping the Anchor As you come into an anchorage your watch officer will yell “Stand by up forward” The bosun or PO will yell “Aye standing by” When the watch officer and Captain have decided where to anchor they will yell “Let go and veer to x fathoms” Bosun will respond “Aye x fathoms” The star will be loosened all the way allowing the gypsy to spin The anchor will drop very quickly until it hits the bottom Do not have hands or feet in the way, they will get mangled  Anchor Watch Many ways to monitor the movement of the vessel at night – Alarms can be set on the depth sounder, GPS or radar to show a change in the boats position, bearings can be taken to points on land – Trainees will be instructed to monitor the chain (lean over the side and feel if the chain is skipping over the bottom), wind speed, wind direction, and electronic instruments if directed. All observations must be recorded in the log book They must wake their watch officer if things change They must stay awake They must wake the next people for anchor watch  Why do Anchors Drag? Not enough scope Anchor rode is fouled around the anchor Wind direction/tide has changed Bottom does not allow the anchor to hold (eg boulders, shale/limestone shelves, weeds etc)   Kedging Kedging means using the anchor to move the boat Anchor is rigged on a line and the ships boat is used to move the anchor into position Anchor is dropped and is hauled on by the crew on board the vessel. – Used to move a vessel when there is no wind – Used to manoeuvre a vessel in tight quarters (eg leaving the wall in port)  Using Multiple Anchors Bow and stern anchor – Used in confined anchorages where you don’t want to swing at all Two bow anchors – Used where you have tides http://www.pangolin.co.nz/jetsam/view_article.php?idx=8  Sea Anchors Used during a storm Set from the bow or stern Keeps bow or stern into the wind/waves. From the stern it slows you as you run from http://freepages.genealogy.rootsweb.ancestry.com/~fassitt/kenealy/kenealy2a.html the storm What if you don’t have a sea anchor?