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The Xiao Qinghe shipyard launched a tank barge with marine airbags on January 20, 1981 and it is known as the first use of marine airbags.
This kind ship launching method has the advantages of requiring less permanent infrastructure, risk, and cost. The airbags provide support to the hull of the ship,air bags rolling motion take a vessel launch into water, thus it is arguably safer than other options like sideways launching.
Based on the ship shapes, the ship may be launched, using air bags, by either end launching type or side launching type
There are three ways to arrange air bags when using the end launching type. They are (1) linear arrangement (see Figure A.1), (2) staggered arrangement (see Figure A.2), and (3) two-lines arrangement (see Figure A.3). As for which arrangement to use, it will depend on the ship’s width and the length of the air bags.
When the ship’s width is not greater than the effective length of the air bags,
the linear arrangement shall be selected
When the ship’s width is greater than the effective length of an air bag and less than the effective length of two air bags, the staggered arrangement shall be selected.
When the ship’s width is greater than the combined effective length of two air bags,or for special ship such as catamaran HSC or split hopper barge, the two lines arrangement shall be selected.The distance between the near ends of two air bags is greater than 0,2 m.
For small flat-bottom ships, side launching method may be utilized (see Figure A.4)
Air bags shall meet the requirements of ISO 14409>
According to the weight of the ship being launched, the quantity of the air bags needed for this operation shall be calculated in accordance with Formula (1):
N is the quantity of air bags used for ship launching;
K1 is a coefficient, in general, K1 ≥ 1,2;
Q is the weight of the ship (ton);
g is acceleration of gravity (m/s2), g = 9,8;
Cb is the block coefficient of the ship being launched;
R is the allowable unit bearing capacity of the air bags (kN/m);
Ld is the contact length between the bottom of the ship and the body of the air bag at the midship section (m).
For ship shifting, 2 to 4 additional air bags shall be made ready and available.
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