Tham khảo tài liệu 'lesson 3-other seakeeping performances(2)', ngoại ngữ, anh văn thương mại phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lesson 3-Other Seakeeping Performances 2 Roll and Pitch When floating on water or sailing at sea vessels will roll or pitch owing to wave motions as well as the influence of wind current and propeller. The fatal results of excessive roll and pitch are as follows 1. First the ship upsetting arising from excessive inclination due to roll. 2. In the next place the hull structure damage because of sharp roll and pitch as well as the violent movement of bulk cargoes or even worse the hull might break. 3. Still next the affection on the propulsion plant i. e. the increase of water resistance and the reduction of speed by reason of roll and pitch. 4. Then the affection on proper operation of various kinds of machines and instruments. 5. Last of all the hard working condition which causes the crew to be seasick. Therefore we have to take roll and pitch into our consideration during the design stage for they are closely related to the whole seakeeping performance. As you know the roll period is greatly concerned with the initial metacentric height and in some degree stability is contrary to roll. It seems to be strange that violent roll as many people might think is not derived from poor stability. So far different stabilizing units have been invented and found wide application to decreasing roll and pitch. Common stabilizing units now in practical use are bilge keels stabilizers and wing buoyant tanks. Fig. stabilizer Floodability Floodability states the ability for a vessel to keep afloat with sufficient floatability stability and other seakeeping performances in case one or several compartments are flooded. Should sea damage take place reserve buoyance would be the principal condition to keep a vessel afloat. With the help of the watertight bulkheads and decks which separate the inside of hull into a number of compartments and spaces reserve buoyance enough is to be retained so that the intake of sea water may be confined to the damaged compartment without water .
