Ships – Displacement-type hull – Multiple hulls
Patent
1996-03-18
1997-12-09
Swinehart, Edwin L.
Ships
Displacement-type hull
Multiple hulls
114126, B63H 1902, B63B 112
Patent
active
056948786
DESCRIPTION:
BRIEF SUMMARY
ART FIELD
The present invention relates to a semi-submerged catamaran which comprises a relatively thin and long submerged body to exhibit an improved speed characteristic but of which the susceptivity of motion at stoppage is nevertheless suppressed.
BACKGROUND ART
Generally, semi-submerged catamarans comprise at least two submerged bodies which are normally immersed in water, a strut mounted in a standing position on respective submerged bodies, and a hull part normally maintained above the water surface.
As one of means for improving the speed characteristic of semi-submerged catamarans of the mentioned type, it is conceivable to design the submerged bodies to be relatively thin and long.
If the submerged body is excessively elongated, however, the natural period of pitching tends to be so short that the possibility of resonance between wave and motion of the catamaran is increased. Also, as a result of the submerged body being thin or slender, the configuration the submerged part comprising the struts and the submerged bodies is no longer within the category of so-called "waveless configurations" which are regarded as not undergoing influences of waves.
Thus, even with semi-submerged catamarans which are generally accepted as being desirable with respect to the motion characteristic, the susceptivity of motion at stoppage tends to be relatively large if the submerged bodies are extremely elongated.
Then, it is also conceivable to limit the elongation of the submerged body so that the submerged body does not fall outside the category of the "waveless configuration", but a difficulty comes out then to do with the designing and building.
It further is conceivable to size up the existing stabilizing fins, but in this case the added resistance of the catamaran tends to be too large. Also, stabilizing fins are usually movable, so that if they are increased in size, this gives rise to a problem that a size-up has to be made of for example an actuator for driving the stabilizing fins.
Moreover, the stabilizing fins and the center of gravity of the catamaran are not largely spaced from each other, so that even if the size of the stabilizing fins is increased, pitching at stoppage of the catamaran cannot be effectively suppressed.
DISCLOSURE OF THE INVENTION
The present invention has been made in order to obviate the above indicated difficulties and problems, and the primary object of the invention is to provide such a semi-submerged catamaran of which the speed characteristic is improved as a result of an elongation of its submerged bodies and yet the susceptivity of motion at stoppage is considerably suppressed.
That is to say, the present invention consists in a semi-submerged catamaran which comprises at least two submerged bodies, a strut mounted in a standing position on respective submerged bodies and a hull part supported by the struts at a position above the water surface, and which is characterized in that it further comprises motion preventing fins fixed in a submerged part on the bow side and/or a submerged part on the stern side of the catamaran.
The submerged part termed herein refers to such a part of the catamaran which comprises a submerged portion of respective struts and the submerged bodies and which normally immersed in water.
Attributable to the above described structuring, even in connection with such a semi-submerged catamaran of which the submerged body is relatively largely elongated to attain an improvement in or relating to the speed characteristic, it is possible to increase the damping power and greatly reduce the susceptivity of motion, particuarly pitching, of the catamaran at stoppage.
Preferably the length of the motion preventing fins is 5 to 20% or, more preferably. 7 to 15% of the length of the semi-submerged catamaran.
Also, the width of the motion preventing fins is preferably 10 to 1,000 mm or, more preferably, 100 to 500
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a front elevation of a semi-submerged catamaran pertaining to the present invention;
FIG. 2 is a
REFERENCES:
patent: 3063397 (1962-11-01), Boericke, Jr.
patent: 3817199 (1974-06-01), Schirtzinger
patent: 4174671 (1979-11-01), Seidl
patent: 4763596 (1988-08-01), Yoshida
patent: 4986204 (1991-01-01), Yoshida
patent: 5301624 (1994-04-01), Hall et al.
Mitsui Engineering & Shipbuilding Co. Ltd.
Swinehart Edwin L.
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