- Question and Answers
- Ship Construction
marinetales September 7, 2020
Oil tankers have a lesser freeboard than general cargo ships of the same LBP. They are considered to be safer ships for following reasons- 1. They have much smaller openings on the main deck. 2. They have greater subdivision 3. The cargo of oil has generally more buoyancy than the bulk cargo or general cargo 4. They have more pumps to quickly control the water ones in case of an bilging or flooding incident 5. Cargo oil has a permeability off about 5% compared to grain cargo/bulk cargo which has a permeability of about 50-60% 6. Oil tankers have greater GM values
marinetales May 13, 2021
Container ships are highly subjected to torsional moments because of their very large hatch openings. This leads to even higher warping stresses at the corners of the openings due to lack of torsional rigidity. The upper part of the double hull in such ships is fitted with torsion box. Torsion boxes are fitted with welded joints on the side shell as on the deck plating which prevent the torsion produced by twisting.
marinetales August 27, 2020
Lightening holes are used to access the tank in ford/aft/athwartship direction. They also reduce the overall weight of the plates and gives strength to the overall design through the grid structure
marinetales June 16, 2021
Transverse thrust describes the imbalance from the water flow about a propeller causing a vessel to pay off to one side or another. Mostly affects the vessel when operating astern propulsion.
marinetales August 23, 2020
The allowable limits of Shearing Force and Bending Moments are the values which the structure of the ship is designed to take. The Ship’s capacity to bear SF and BM depends upon its sectional properties (differs from ship to ship). This capacity of the ship to take sheer and bending moment varies from one longitudinal location to other. These values are stated in the Stability Booklet of the vessel and depends upon the Classification Society Rules which lays down such requirements. The values of SF/BM are in Newton-Metre and is defined on a scale of 0% to 100% on loadicator. A ship will always have some value of stress so the value can never be 0%. But in any case it should never exceed 100%.