船舶与海洋工程英语

船舶与海洋工程英语内容摘要：

he ship is. This length is known as the length of the extreme point at the after end to a similar point at the forward end. This can be clearly seen by referring again to Figure 1. In most ships the length overall will exceed by a considerable amount the length between perpendiculars. The excess will include the overhang of the stern and also that of the stem where the stem is raked forward. In modern ships having large bulbous bows the length overall LOA may have to be measured to the extreme point of the bulb. A third length which is often used, particularly when dealing with ship resistance, is the length on the waterline LWL. This is the distance measured on the waterline at which the ship is floating from the intersection of the stern with the waterline to the length is not a fixed quantity for a particular ship, as it will depend upon the waterline at which the ship is floating and upon the trim of the ship. This length is also shown in Figure 1 . 7 Breadth The mid point of the length between perpendiculars is called ‗amidships‘and the ship is usually broadest at this point. The breadth is measured at this position and the breadth most monly used is called the ‗breadth moulded‘. It may be defined simply as the distance from the inside of plating on one side to a similar point on the other side measured at the broadest part of the ship. As is the case in the length between perpendiculars, the breadth moulded dose not represent the greatest breadth the breadth extreme is required (see Figure 2 ). In many ships the breadth extreme is the breadth moulded plus the thickness of the shell plating where the strakes of shell plating were overlapped the breadth extreme was equal to the breadth moulded plus four thicknesses of shell plating, but in the case of modern welded ships the extra breadth consists of two thicknesses of shell plating only. The breadth extreme may be much greater than this in some ships, since it is the distance from the extreme overhang on one side of the ship to a similar point on the other side. This distance would include the overhang of decks, a feature which is sometimes found in passenger ships in order to provide additional deck area. It would be measured over fenders, which are sometimes fitted to ships such as cross channel vessels which have to operate in and out of port under their own power and have fenders provided to protect the sides of the ships when ing alongside quays. Depth The third principal dimension is depth, which varies along the length of the ship but is usually measured ant amidships. This depth is known as the ‗depth moulded and is measured from the underside of the plating of the deck at side amidships to the base line. It is shown in Figure 2(a). It is sometimes quoted as a ‗depth moulded to upper deck‘ or ‗depth moulded to second deck‘, etc. Where no deck is specified it can be taken the depth is measured to the uppermost continuous deck. In some modern ships there is a rounded gunwale as shown in Figure 2(b). In such cases the depth moulded is measured from the intersection of the deck line continued with the breadth moulded line. Other features The three principal dimensions give a general idea of the size of a ship but there are several other features which have to be considered and which could be different in two ships having the same length, breadth and depth. The more important of these will now be defined. Sheer Sheer is the height of the deck at side above a line drawn parallel to the base and tangent to the length of the ship and is usually greatest at the ends. In modern ships the deck line at side often has a variety of shapes: it may be flat with zero sheer over some distance on either side of amidships and then rise as a straight line towards the 8 ends。 on the other hand there may be no sheer at all on the deck, which will then be parallel to the base over the entire length. In older ships the deck at side line was parabolic in profile and the sheer was quoted as its value on the forward and after perpendiculars as shown in Figure 1. So called ‗standard‘ sheer was given by the formulae: Sheer forward (in) = +20 Sheer aft (in) = +10 These two formulae in terms of metric units would give: Sheer forward (cm) =+ Sheer aft (cm) =+ It will be seen that the sheer forward is twice as much as the sheer aft in these standard formulae. It was often the case, however, that considerable variation was made from these standard values. Sometimes the sheer forward was increased while the sheer after was reduced. Occasionally the lowest point of the upper deck was some distance aft of amidships and sometimes departures were made from the parabolic sheer profile. The value of sheer and particularly the sheer forward was to increase the height of the deck above water (the ‗height of platform‘ as it was called ) and this helped to prevent water being shipped when the vessel was moving through rough sea. The reason for the abolition of sheer in some modern ships is that their depths are so great that additional height of the deck above water at the fore end is unnecessary from a seakeeping point of view. Deletion of sheer also tends to make the ship easier to construct, but on the other hand it could be said that the appearance of the ship suffers in consequence. 9 Camber Camber or round of beam is beam is defined as the rise of the deck of the ship in going from the side to the centre as shown in Figure 3(a). The camber curve used to be parabolic but here again often nowadays straight line camber curves are used or there may be no camber at all on decks. Camber is useful on the weather deck of a ship from a drainage point of view, but this may not be very important since the ship is very rarely upright and at rest. Often, if the weather de。