Marine Engineering and Naval Architecture

The only meaningful way to rate anchor winch performance is by looking at what it will lift and at what speed. The two things to consider are (a) the maximum pull capability and (b) the working load of the winch. Maximum pull (sometimes referred to as stall load) is the maximum short term or instantaneous pull of the winch. Working load is generally rated at about one third of the maximum pull and is usually considered to be the load that the winch is pulling once the anchor is off the bottom. To determine your required maximum pull capability, complete the calculation below. The most useful way to rate windlass performance is by looking at what it will lift and at what speed. The two things to consider are the working load and the maximum pull capabilities of windlass. Working load is the load that the windlass is pulling once the anchor and rode are off the bottom. Maximum pull (sometimes referred to as stall load) is the maximum short term or instantaneous pull of the windlass. ...

A windlass is a machine used on ships that is used to let-out and heave-up equipment such as a ship's anchor or a fishing trawl.   An anchor windlass restrains and manipulates the anchor chain on ship, allowing the anchor to be raised and lowered by means of chain cable. A notched wheel engages the links of the chain or the rope. The windlass is mounted on a doubler plate welded to the forecastle deck. The deck girders in forecastle space is increased. The deck beams pitch distance decreased to accommodate more beams. Four round pillars at four corners of the base of windlass doubler plate connect to the main deck plating to give continuity of strength to deck. Technically speaking, the term "windlass" refers only to horizontal winches. Vertical windlasses are characterized by situating the capstan and/or gypsy above the deck and the motor and gearbox below. Vertical windlasses provide a 180° wrap of the anchor rode around the gypsy giving optimal chain control, ...

After having found the equipment numeral from previous blog , the details regarding sizes and quality  may be obtained from the rigging tables provided in these regulations. From these table , we can find the following information The Equipment Letter Stockless bower anchors number of anchor Mass per anchor (kg) Stud-link chain cables for bower anchors Total length (m) Grade and Diameter (mm) of chain CC1———— low  strength. CC2———–medium strength. CC3———–high strength Towline Minimum length (m) Minimum breaking strength (KN) Mooring Lines Number Length of each mooring ropes (m) Minimum breaking strength (KN)

The equipment number, EN, on which the requirements of equipment ship anchor are based is to be calculated as follows :- EN = K * ENc where, ENc = Δ^2/3 + 2BH + 0.1A where, Δ = moulded displacement, [t], to the summer load water line. H = effective height, [m], from the summer load waterline to the top of the uppermost deck-house, to be measured as follows: H = a + Σhi a = distance [m] from summer load waterline amidships to the upper deck at side. hi = height [m] on the centreline of each tier of houses having a breadth greater than B/4. For lowest tier, hi is to be measured at centre line from the upper deck, or from the notional deck line where there is a local discontinuity in the uppers deck. A = area [m2] in profile view of the hull, superstructures and houses above the summer load waterline, which is within the Rule length of the vessel. Houses of breadth less than B/4 are to be disregarded. In the calculation of H and A, sheer and trim are to be ign...

The equipment is therefore not designed to hold a ship off fully exposed coasts in rough weather or to stop a ship which is moving or drifting. In this condition the loads on the anchoring equipment increase to such an extent that its components may be damaged or lost due to the high energy forces generated particularly in large ships. The anchoring equipment presently required herewith is designed to hold the ship in good holding ground in conditions such as to avoid dragging of the anchor. In poor holding ground the holding power of the anchors will be significantly reduced. A good holding ground as defined by the above stated requirements are; A current  speed  of not more than  5  m/sec (max tide current  speed) A  wind  speed  of not more than  25m/sec Depth of  water ranging  between  85M and 100M . The ground should  be  sandy  or  muddy and  not  rocky A good anchoring groun...

The chain connecting the anchor to the ship is of a heavy construction with a breaking strength with much higher than required. These chain links are made heavy so that when the anchor is dropped in sea with the attached chain and the ship is in the stand still condition, the catenary so formed is deep and almost vertical, The shape of the curve formed by the chain is called a catenary. This curve is like a parabola shaped but has a different mathematical formula when compared with the parabola. It is a physical curve caused by a hanging chain supported at the ends and the total depth of the curve from  the end supports is directly proportional to the unit length of the chain. The Bower anchor is made up of two parts, the head with the flukes folded inwards and the shank. Both these parts are fitted together by a heavy and large pin fitted tightly on the head but loosely in the shank hole. The head has sufficient internal space to allow free movement of the shank to turn ...

A ships anchor is an important component, used to prevent the ship from drifting from its location due to wind and tidal currents. Generally, larger ships having two bow and one stern anchor. Anchors can either be temporary or permanent. Permanent anchors are used in the creation of a mooring, and are rarely moved; a specialist service is normally needed to move or maintain them. Vessels carry one or more temporary anchors, which may be of different designs and weights. The  anchoring  equipment of  a  ship  comprises  the  anchor, anchor  chain  and  the  windlass. Anchor chains are connected to a windlass that can either be of vertical or horizontal design. A vertical windlass is known as a capstan, and we shall describe the operation of the anchor and its components using a capstan. The capstan has a drive wheel called a gypsy that is notched to suit the forged steel chain links. The chain is fed from the capstan along ...