Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having fluid channeling or entrapping configuration
Reexamination Certificate
2000-03-16
2001-05-29
Sotelo, Jesus D. (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having fluid channeling or entrapping configuration
C114S171000
Reexamination Certificate
active
06237522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a bottom structure of a personal watercraft (also called a PWC) in which very small concave or convex portions are provided on a bottom surface of the personal watercraft to enhance running performance and to reduce rolling of the watercraft.
2. Description of the Related Art
FIG. 13
shows an example of a hull shape of a conventional personal watercraft. The personal watercraft has a bottom surface
50
having a substantially V-shaped cross section. The bottom surface
50
is provided with a plurality of longitudinal strips
51
. A rear part of the bottom surface
50
which forms a planing face of the personal watercraft is a smooth plane in a longitudinal direction of the bottom.
With the above-mentioned shape of the bottom surface
50
, however, running performance such as accelerating performance, speed performance is limited due to fluid frictional resistance to water on a water contact face of the bottom during planing. Furthermore, if the water contact face of the watercraft varies between a right side and left side, a difference in dynamic outer forces received from the water flow on the right and left water contact surfaces is generated by repeated separation and sticking of the water on the right and left water contact faces. The difference in dynamic forces creates a difference of dynamic lift forces on the right and left side of the personal watercraft. Due to the difference between right and left dynamic lifts, repetition of small rolling is generated on the watercraft so that an uncomfortable feeling is sometimes given to a rider.
It is a main object of the invention to reduce frictional resistance to the water flow during the running of the personal watercraft, thereby enhancing the running performance.
SUMMARY OF THE INVENTION
In order to achieve the above-mentioned object, a first aspect of the invention is directed to a bottom structure of a personal watercraft in which a concavo-convex face having any one of small concave and convex portions for drawing air from an outside of a watercraft is formed in a part of a water contact face on a bottom surface of the personal watercraft during planing. The concavo-convex face can be formed by grooves, projections, dimples, rough surfaces, and the like.
According to the above-mentioned structure, the air drawn into the concavo-convex face from the outside of the watercraft separates a water flow from a part of the bottom surface of a personal watercraft, to reduce frictional resistance to the water in the bottom surface so that running performance can be enhanced.
A second aspect of the invention is directed to the bottom structure of a personal watercraft according to the first aspect of the invention, wherein at least one pair of concavo-convex faces are provided apart from a longitudinal centerline of the watercraft to a side in laterally symmetrical positions with respect to the longitudinal centerline.
According to the above-mentioned structure, the concave-convex face positioned on the right and left of the watercraft relieves an imbalance of the right and left dynamic forces received from the water flow which is caused by the repetition of separation and sticking of the water flow from and to the hull bottom. Consequently, the rolling caused by the imbalance can be reduced.
A third aspect of the invention is directed to the bottom structure of a personal watercraft according to the second aspect of the invention, wherein the concavo-convex face is formed in an outside portion of a rear part of the bottom surface of the watercraft.
The above-mentioned structure has a function as described below. The outside portion of the rear part of the bottom surface is a portion where the water line usually passes during the planing, and a water contact area varies according to the rolling of the watercraft. Therefore, when the watercraft is inclined to the right side or left side by the rolling, the area of the concavo-convex face is increased on the downwardly inclined side of the water contact faces. With this structure, the increase of the dynamic lift can be prevented on the downwardly inclined side, because the dynamic lift on the concavo-convex face caused by the separation of the water flow from the bottom surface is small. As a result, the rolling of the watercraft can be reduced still further.
A fourth aspect of the invention is directed to the bottom structure of a personal watercraft according to any of the first to the third aspect of the invention, wherein the concavo-convex face has a plurality of longitudinal grooves extended in parallel with the longitudinal centerline of the watercraft.
According to the above-mentioned structure, the water flow in a transverse direction of the watercraft is turned rearward by the longitudinal grooves formed on the concavo-convex face. Therefore, a speed component in a running direction is increased. Correspondingly, the dynamic lift is increased so that the water line is lowered. As a result, the water contact area of the watercraft is reduced. Consequently, the frictional resistance in the bottom surface of the watercraft is reduced. Thus, the running performance can be enhanced still further.
These objects as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.
REFERENCES:
patent: 3363598 (1968-01-01), Mortrude
patent: 4702188 (1987-10-01), Harilainen
patent: 5199373 (1993-04-01), Mardikian
patent: 5351642 (1994-10-01), Ackerbloom
patent: 3-126786 (1991-05-01), None
patent: 4-119292 (1992-04-01), None
patent: 5-139369 (1993-06-01), None
patent: 7-17476 (1995-01-01), None
patent: 7-277267 (1995-10-01), None
patent: 8-268377 (1996-10-01), None
patent: 9-267793 (1997-10-01), None
Fujii Hisashi
Kiyohara Kanji
Maruyama Haruyoshi
Nakashima Takehiro
Sugawara Takeshi
Kawasaki Jukogyo Kabushiki Kaisha
Marshall O'Toole Gerstein Murray & Borun
Sotelo Jesus D.
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