Kawasaki Apple Slot
Kawasaki has developed "Kawasaki Apple Slot" for the connections between the longitudinals and transverse webs.
The new structural design is such that the conventionally fitted stiffeners on the transverse webs have been replaced by special apple- shaped slots for the connections between the transverse webs and longitudinals which exist in the hull structures in very great numbers (abut 20,000 in a double hull VLCC).
These stiffeners have been a cause of stress concentration at their connection parts, and various designs, such as soft-shaped toe or back bracket, have been used to relieve the stress concentration. Thus, the structure around slots are complicated and require considerably troublesome works such as quality control of the connections between the stiffener and longitudinal, the boxing welding of stiffener toe, etc. These were, how- ever, based on the conception that "stiffeners are necessary". In a reverse conception of dispensing with the stiffeners and providing a means to compensate for it, Kawasaki has solved the problem and achieved the excellent structural performance.
The new hull structure is about 25% smaller than the conventional type double hull structure in the number of structural members.
This will greatly contribute to improve the quality of welding work because automatic welding can be more widely applied to this simple hull structure.
This new structure is also applicable to many types of ships other than tankers.
