Patent Application
20080011215
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The watercraft 100 is a foam-stabilized or air-stabilized watercraft 100 having a rigid hull 110. The hull 110 includes a generally V-shaped bottom 118. The angle that the hull bottom 118 forms (with respect to horizontal), referred to as the dead rise angle, is generally steeper near the bow 111 of the hull 110 than in the stemward portion 113 of the hull 110. The hull 110 is preferably a planing hull, wherein at higher speeds the bow of the hull lifts out of the water, decreasing thereby the hydrodynamic drag. Sides 116 (only a small portion of one side 116 is visible in
External stabilizing members 112 are mounted to the hull sides 116. Although the stabilizing members 112 are disposed on both the port and starboard sides of the watercraft 100 and sometimes referred to separately, it will be appreciated that the stabilizing members 112 may be formed together, or assembled as an integral unit. The stabilizing members 112 preferably extend along the entire length on either side 116 of a rigid hull 110.
The stabilizing members 112 are similar to the foam stabilizing members 12 described above wherein the foam stabilizing members 12 are generally D-shaped in cross-section with a relatively flat portion disposed against the sides 16 of the watercraft. However, the stabilizing members 112 define oppositely disposed performance enhancing fins 130 that extends along a curved, forward portions of the stabilizing members 112. The fin 130 is sized and positioned to take advantage of the hydrodynamic forces generated as the watercraft 100 is underway, as discussed below, and are preferably curved to be approximately uniformly distant from the hull side 116.
The stabilizing member 112 is preferably formed from plastic foam, which may be coated with or otherwise encapsulated in a harder plastic shell, or more preferably covered and retained in a flexible membrane. A currently preferred membrane is formed from a polyurethane-coated polyester tube. Although foam stabilizing members 112 are preferred, it will be readily apparent that the present invention may also be practiced in watercraft using an air-bladder type stabilizing member.
The stabilizing members 112 are attached to the sides 116 of the watercraft 100 in any convenient manner. The attachment mechanism disclosed in the previously incorporated U.S. Pat. No. 5,870,965, also by the present inventor, is believed to be particularly advantageous because it does not require that any hardware penetrate the rigid hull 110. The stabilizing members 112 are sized such that the lower inboard edge of the stabilizing member 112 is disposed above the hard chine 120, and therefore a lower portion of the hull sides 116 are not covered by the stabilizing members 112.
As discussed above, prior art outboard stabilizing members generally have a relatively smooth, cylindrical or curved lower surface, or at least a so-called non-trip chine, wherein the lower surface does not include any sharp angles. In the present stabilizing member 112, in contrast, the lower surface of the stabilizing member 112 includes an elongate fin 130 that projects from the lower surface, and extends generally from a location near the front of the stabilizing member 112 rearwardly. If the stabilizing member 112 is formed from a polymeric foam, for example, the fin 130 may be formed as an integral part of the stabilizing member 112. Alternatively, the stabilizing fin 130 may be formed as a separate component, perhaps from a different material, and attached to the stabilizing member 112.
Although it is contemplated that the elongate fin 130 could extend along the entire length of the stabilizing member 112, in the preferred embodiment shown in the FIGURES the fin 130 extends from near the front of the stabilizing member 112 along a portion of the stabilizing member 112 that curves about the front of the hull 110, extending along approximately 30-50% of the length of the stabilizing member 112. The height of the fin 130 is tapered, gradually increasing from a minimum thickness at the forward end 132 of the fin 130, to a design height at an intermediate location, and maintaining the design height to the aft end 134 of the fin 130. Of course, the fin 130 may gradually taper along the trailing edge, if desired.
As seen most clearly in the front view of
The fin 130 provides significant performance advantages to the watercraft 100, and in particular provides a righting moment to reduce heeling during low-speed turns, and generally softening the during other operating conditions. The inventor's current theory regarding the reasons for the improved performance will now be discussed, to aid the reader in understanding the hydrodynamics of the improvement. When the watercraft 100 is underway, displaced water flows over and about the hull 110 as the watercraft is propelled through the water. In particular, the V-shaped hull bottom 118 forces water upwardly and rearwardly generally along the hull surface. The upward flow will generally be greatest where the dead rise angle is largest. When the fin 130 is at or near the surface of the water, for example during relatively low-speed turns (when the planing hull is not significantly lifted out of the water) this flow produces a high-pressure region in the channel defined between the hull side 116 and the fin 130, generating a lift or upward force on the hull 110. This high-pressure region will tend to counter the tendency of the watercraft 100 to heel during turns and is particularly effective during hard or drastic low speed turns or maneuvers, providing a more stable ride. The fin 130 uses the dynamic pressure from the relative motion of the hull 110 to generate an upward force that acts against the tendency of the boat to heel during the turn.
It is also an advantage to form the fins 130 from a polymeric foam material, for example the material used for making foam stabilizing members. The fins may be formed integrally with the stabilizing members 112. The fins 130 will therefore be pliable and compressible, reducing the risk of damage, for example from minor collisions with flotsam, docks, and the like.
It will be appreciated also that it is desirable that the fins 130 do not extend downwardly beyond, or at least not significantly beyond, the hard chine 120. The pressurization in the channel between the hull 110 and the fins 130 will not be significant below the chine 120, and it is desirable that the fins 130 not contact the water surface during high speed operations, for obvious reasons.
It is believed that the fins 130 also disrupts the laminar flow of water interacting with the hull 110 and the stabilizing member 112, increasing the local turbulence, further reducing the tendency of the watercraft 100 to heel. The combination of these phenomena act against the tendency of the watercraft to heel excessively, allowing a rapid turn to occur in a safe manner, and reducing the chance of capsizing the watercraft 100 or of taking water over the side.
In addition, these same hydrodynamic effects assist in creating what is known or referred to as a ‘softer ride’. During operation of the watercraft, at any speed through chop or wakes, the pressurization or lift generated about the fins 130 help to reduce the physical impact of the hull 110 onto the water as it crosses through chop or otherwise disturbed water. The pressurization in the channels between the hull sides 116 and the fins 130 is believed to act as a sort of shock absorber in such conditions.
Referring again to the FIGURES, it is contemplated that the fin 130 may be formed integrally with a foam stabilizing member 112, for example in an extrusion process, or physical shaping process such as cutting or otherwise removing material. Alternatively, the fins 130 may be attached directly to the stabilizing member 112, for example as an insert that penetrated into the stabilizer or by direct adhesion thereto.
Alternatively, a rigid or semi-rigid stabilizing member cover may be formed comprising a generally cylindrical portion that is sized and adapted to fit over, and engage, a conventional stabilizing member and having a fin extending generally downwardly therefrom. The stabilizing member that engages the stabilizer cover may be a foam member, an air bladder, or a combination thereof. The fin portion of such a cover may be formed as a hollow, substantially rigid portion or may be a solid fin, for example formed from a polymeric foam or the like. The stabilizer cover may attach to the stabilizer in any number of ways, as are well known in the art, including attachment with mechanical attachment mechanisms such as removable bolts, straps, or rivets, or by use of an adhesive, for example.
It will be appreciated that the particular size, shape and length of the fin 130 may be tailored to a particular hull for optimal results, or a more generic fin may be utilized that is applicable to different hull shapes. It will also be appreciated that the fin 130 may extend at an angle from the stabilizer, other than perpendicularly therefrom, depending on the particular application. Although a fin 130 having a generally rectangular cross-section is shown in the FIGURES, it is contemplated that the fin cross section may be alternatively shaped. For example, the bottom surface of the fin 130 may be oriented such that the surface is substantially parallel to the water when the watercraft heels far enough for the fin to engage the water surface.
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
This application claims the benefit of U.S. Provisional Patent Application No. 60/811,523, filed Jun. 6, 2006, the disclosure of which is hereby expressly incorporated by reference in its entirety, and priority from the filing date of which is hereby claimed under 35 U.S.C. §119.
| Number | Date | Country | |
|---|---|---|---|
| 60811523 | Jun 2006 | US |
