Ship stability analysis during launching from longitudinal sloping slipway by pneumatic airbags

The changing forces acting on a ship during launching from a longitudinally sloping slipway can be divided into four stages: the 1st stage – from beginning of ship movement until the launching runners or the ship’s aft end contacts the water; 2nd stage – from the end of 1st stage until the ship begins to float off the ways; 3rd stage – from the end of 2nd stage until the ship paces the slipway threshold and is fully afloat; 4th stage – from the end of 3rd stage until comes to a full stop. The biggest danger for a ship during the launch is the end of stage 2 and the beginning of stage 3, when tipping is possible as the ship rotates around the slipway threshold; also as the ship pivots on the slipway’s threshold there are large concentrated forces imparted on the forward section of the ship due to pivoting pressures (the difference between the mass of the ship and launching devices and the rising buoyancy). This paper presents, for the first time, a new analysis method of taking into account the possibility of a tanker tipping during launching on pneumatic airbags. Launching calculations and diagrams for both the traditional and pneumatic airbags launching are presented along with a comparative analysis of the two launching methods. The analysis showed that during launching using pneumatic airbags, float off begins earlier than during a traditional launch. This earlier float off does not increase the risk of tipping but does increase the pivoting pressure due to the increased buoyancy from the airbags.


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  • Accession Number: 01707793
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 29 2019 2:36PM