Patent Application
20080156249
The present invention relates to a small watercraft and, more particularly to a reinforcement structure of a spray strip portion provided on a hull of the small watercraft, and a manufacturing method thereof.
Small watercraft (e.g., PWC) are in some cases provided with a spray strip portion at a front portion of a hull or a bow. The spray strip portion is also called a chine or a spray deflector formed to improve sea kindliness. The spray strip portion is typically a protruding portion formed by curving and protruding outward a part of the hull and by extending it in a longitudinal direction of the hull. One to four spray strip portions are provided on both sides of the hull at different vertical positions.
The spray strip portion is manufactured in such a manner that FRP sheets impregnated with thermosetting resin or the like are stacked to conform in shape to a mold (female mold) of the hull having grooves corresponding to the spray strip portions and are pressed from downward to upward using a roller or the like every time an FRP sheet is stacked, to avoid uneven heating of the spray strip portion in a thermal hardening process.
In this process, the roller falls into the groove portion of the spray strip portion and reduces the thickness of a bottom region of the groove portion, whereas a region immediately above the thinned region is made to have a larger thickness. This results in a hull cross-sectional shape in which stress concentration is likely to occur on the groove portion. Such stress concentration tends to occur particularly on the spray strip portion located higher whenever a front bottom portion of the hull hits on the water surface while skipping on the water surface, thereby decreasing stiffness of the hull.
In addition, as described above, non-uniform thickness may cause the spray strip portion to be unevenly heated and may adversely affect a quality of a product if it is directly thermally hardened.
The present invention has been developed under the circumstances, and provides a reinforced spray strip structure of a small watercraft and a manufacturing method thereof.
According to a first aspect of the present invention, there is provided a small watercraft comprising a hull formed to have a substantially uniform thickness by using reinforced fibers impregnated with resin, the hull including a curved portion formed by protruding outward and curving a part of the hull; and a filling material filled in a groove portion on an inner side of the hull which is created by forming the curved portion.
In such a construction, the hull which is not substantially susceptible to stress concentration and is stiff can be provided.
The curved portion may be a spray strip portion formed on a bow of the hull.
The groove portion filled with the filling material may define a smooth curved line together with an inner surface of the hull around the groove portion.
The curved portion may include a plurality of curved portions. In this case, the smooth curved line may extend over a plurality of groove portions on the inner side of the hull which are created by forming the plurality of curved portions.
The smooth curved line may be a circular-arc curved line.
According to a second aspect of the present invention, there is provided a method of manufacturing a spray strip portion of a small watercraft, comprising: forming a hull to have a substantially uniform thickness by using reinforced fibers impregnated with resin and protruding outward and curving a part of the hull to form the spray strip portion; thermally hardening the hull provided with the spray strip portion; and filling a filling material in a groove portion on an inner side of the hull that is created by forming the spray strip portion.
In such a construction, the hull which is not substantially susceptible to stress concentration and is stiff can be provided. Further, since the filling material is filled into the groove portion after the spray strip portion is formed, uneven heating of thermosetting resin in a thermal hardening process will not occur, and therefore, a quality of a product will not be degraded.
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like reference numerals indicate similar elements and in which:
Hereinafter, a small watercraft of the present invention will be described with reference to the accompanying drawings.
A seat 15 is mounted over a region extending from a center region to a rear region in a longitudinal direction of the deck 12, and is configured to be straddled by an operator. A bar-type steering handle 16 is attached to a portion of the deck 12 in front of the seat 15.
In this embodiment, the hull 11 includes four spray strip portions 20 (20A, 20B, 20D, and 20D) at a portion forward of the steering handle 16. The spray strip portions 20 are disposed at different vertical positions, and are arranged in the order of the 20A, 20B, 20C, and 20D from above.
As used herein, the term “spray strip portion” is one example of a “curved portion.” The term “curved portion” includes the above mentioned chine, spray deflector, and other portions, and is, of course, applicable to other similar construction of the body of the watercraft.
It is advantageous that the filling material 22 is made of a material which forms a hull body (e.g., thermosetting FRP) or a similar material, in order to improve stiffness of the entire hull. But, this is merely exemplary and a bond (urethane based bond, bonding agent or other bond), putty, and others may be used. As the bond, the bond used to join the deck 11 and the hull 12 may be used so that the body 13 is manufactured easily. In addition, by using flexible bond, the hardened bond advantageously well conforms to a deformed shape of the hull 12 and does not substantially peel off from the hull body. Furthermore, by using quick-drying putty, a manufacturing time can be reduced.
As can be seen in
Next, with reference to
In this embodiment, the hull is manufactured by a hand lay-up method, but may alternatively be manufactured by other methods such as a SMC method or a spray-up method.
In this process, the roller may in some cases fall into the groove portions 201a, 202a, 203a, and 204a of the spray strip portions 20 and reduce the thickness thereof, while regions located immediately above the thinned regions are made to have a larger thickness. This results in a hull cross-sectional shape in which stress concentration is likely to occur on the groove portion. Accordingly, in step S2, as shown in
At this time, the filling material 22 may be thermally hardened when the thermosetting FRP is used as the filling material 22. By thus carrying out the thermal hardening process at two stages, the product quality of even the spray strip portions 20 which may have uneven thickness are not degraded, and hence the hull 11 that is stiff and is not substantially deformed can be manufactured. In a case where the bond, adhesive, or the like is used as the filling material 22, it is dried and hardened directly or after its temperature is increased.
Alternatively, the FRP sheet may cover the filling material 22 from above and may be hardened together with the filling material 22.
As shown in
Such stress dispersion is effectively achieved by forming the continuous curved surface over the plural spray strip portions 20.
Although the present disclosure includes specific embodiments, specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of features, functions and elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims and whether broader, narrower, equal, and/or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
