IMPROVED HULL FOR KAYAK

HELD OF THE INVENTION

The present invention relates to boat hulls, and specifically to a new hull for kayaks.

BACKGROUND OF THE INVENTION A conventional kayak is generally symmetrical in hull form when viewed bow to cockpit and cockpit to stern and situates a cockpit in the center or slightly aft center of the craft, and centrally of port and starboard sides. Specifically, a conventional hull is generally symmetrical in keel line extending fore and aft when viewed in side elevation of the hull. When water borne, the kayak has a generally symmetrical waterline extending bow to stern. The wetted area of the hull as well as the shape of the hull (both fore to aft and port to starboard) is the same for the portion of the craft extending from bow to cockpit, as for the portion extending from cockpit to stern. The keel line at bow and stern is normally in the water when underway. The result is a stable craft, centrally balanced from bow to stern with center of buoyancy at the cockpit, easily propelled by oar, and with the craft rotating about the cockpit in turning maneuvers and encountering water resistance over substantially the entire length of the hull. A paddler in the cockpit in turning the craft with an oar applies a turning moment to the entire wetted surface from stem to stern.

Conventional single occupant kayaks and similar watercraft are characterized in location of the cockpit in the middle section of the hull equidistant from bow and stern. For example, Broadhurst US Pat No 4660490 discloses a watercraft comprising a hull construction useful for recreation and water sports and having a cockpit

indentation located on the top part of the hull. The Broadhurst cockpit is located within the middle section of the hull within an area that is from about 25-30% of the length aft of the bow to about 60-65% of the length aft of the bow. Such middle section location of a cockpit is required in order to maintain proper level trim of the watercraft. Moreover, Broadhurst desires a keel line rise from middle section to bow of about 2 to 4 times the keel line rise from middle section to the stern. A middle section cockpit, then, is essential in realizing a keel line rise toward the bow as

^' desired by Broadhurst. Moreover, the Broadhurst watercraft may have a fin positioned on the bottom part of the hull located from about 75 to 85% of the length of the hull aft of the bow. Accordingly the aft section of the hull must be in the water to utilize the fin, a condition assured by cockpit location in the middle section of the hull.

US Patents No 6612252 to King and No 6736084 to McDonough both disclose single occupant kayaks with cockpits in the middle section of the hull. US Design Patent No D332774 to Arcoutte is directed to both single and double occupant watercraft. In both single occupant and double occupant versions of Arcoutte, the cockpits are located centrally of a midpoint of the craft.

A conventional kayak then is a lightweight craft with symmetrical hull, cockpit located in the middle section of the hull, easy to propel manually, having water borne stability characterized by a wetted area extending bow to stern, and having a slow and predictable maneuvering capability.

The present invention provides a single occupant kayak characterized in being a stable craft, easily propelled by oar, and faster and highly maneuverable in comparison to conventional kayaks.

SUMMARY OF THE INVENTION

The present invention is directed to a highly maneuverable single occupant kayak formed of a hull having a cockpit situated forward of the hull mid-point between bow and stern, a hull section aft of the cockpit situated at or above the water line of the craft and having little or no wetted area, and a flat or generally horizontal keel plate extending from bow to stern. The keel plate extends along a keel line defined by convex curvature forward and concave curvature aft. The keel line convex-concave curvature is characteristic of the kayak according to the invention with an aft section at or above the water line. A kayak according to the invention with a paddler aboard has a waterborne trim with bow out of the water, center of balance at the cockpit, and with the aft section of the craft out of the water. The kayak is characterized in a fore-to-aft keel line having a forward convex curvature and an aft concave curvature. This keel line curvature has the effect of locating the water line forward and locating the rear portion of the kayak above the waterline to achieve high maneuverability of the craft.

The kayak according to the invention is also characterized in having an asymmetric hull as indicated by a length-to-girth fineness ratio constituting a parameter for defining transverse hull shape at stations aft of the bow. Length-to- girth ratio provides a metric for locating cockpit and center of balance with reference to kayak length overall (LOA) and with respect to hull midpoint between bow and stern.

The kayak according to the invention has a substantially reduced wetted area as compared to conventional kayaks of the same length, enables a paddler to

operate the kayak with greater leverage particularly in maneuvering the craft, and is characterized in being a faster and more highly maneuverable craft.

OBJECTS OF THE INVENTION

An object of the invention is to provide a new and improved single paddler kayak hull faster and more highly maneuverable than conventional craft.

Another object of the invention is to provide a kayak hull having a substantially smaller wetted area enabling a faster vessel of high maneuverability.

Another object of the invention is to provide a kayak with cockpit situated forward and a rear hull structure with minimal water resistance while underway. Another object of the invention is to provide a kayak hull with flat keel plate between bow and stern to provide a high performance kayak.

Another object of the invention is to provide a kayak hull with curved keel line between bow and stern including convex curvature forward and concave curvature aft to provide a high performance kayak. Another object of the invention is to provide a kayak having a hull shape in which the wetted area is situated over the forward two-thirds section of the hull with the rear hull section having minimal wetted area to provide a kayak of exceptional maneuverability and speed.

Another object of the invention is to provide a kayak in which the cockpit is located ahead of kayak midpoint and in which a rudder is positioned at the stern so as to provide high mechanical advantage between turning force applied by a paddler in the cockpit and the rudder for turning of kayak.

Another object of the invention is to define a kayak by length-to-girth ratio at stations along the length of the kayak, and to define location of the cockpit with

reference to that ratio so as to make available the advantages of the kayak to those skilled in the art.

Another object of the invention is to provide a kayak having a fore-to-aft asymmetric hull with a length-to-girth ratio lowest forward of kayak longitudinal midpoint.

Another object of the invention is to provide a kayak having a fore-to-aft asymmetric hull with cockpit located where length-to-girth ratio is lowest among length-to-girth ratios for equidistant stations along the entire kayak length.

Other and further objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for detailed description to enable those having ordinary skill in the art to which the invention appertains to readily understand the invention and is shown in the accompanying drawing in which:

Figure 1 is a side elevation a kayak according to the invention.

Figure 2 is a plan view of the kayak of Figure 1.

Figure 3 is a bottom view of the kayak of Figure 1.

Figure 4 shows the fore to aft curvilinear contour of the bottom plate of the kayak of Figure 1.

Figures 5-13 are section views of the kayak hull taken along lines 5-5 through 13-13 respectively of Figure 1.

Figure 14 is a fragmentary side elevation view showing a rudder mount for the kayak of Figure 1.

Figure 15 is a plan view of the rudder mount of Figure 14.

Figure 16 is a side elevation view of a kayak according to the invention showing a keel line with convex curvature forward and concave curvature aft.

Figures 17 and 18 are side elevation and plan views respectively of the kayak of Figures 1-16 with eleven equidistant stations marked 0-10 along kayak length from bow to stern for determining length-to-girth ratio at each station.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to drawing Figures 1-3 a kayak 10 according to the invention comprises hull 12, deck 14, cockpit 16 and steering gear 18.

The hull comprises an elongate watertight structure having starboard and port sides 12a-b and bottom 12c contours characterized in defining a wetted area of the hull over approximately the forward two-thirds portion of the hull. The water line WL (and wetted area) of the hull is indicated by dash line in Figure 1 extending from a point WLF aft the bow to a point WLA aft the cockpit. The water line extends from forward point WLF located a distance from the bow of approximately one-tenth of the length-over-all (LOA) of the craft, to aft point WLA a distance from the bow in a range of approximately two-thirds to three-quarters of LOA of the craft.

When the kayak is water borne with a paddler aboard the center of buoyancy CB is well forward of the mid-point MP of the length-over-all of the craft and is located at the cockpit approximately amid forward two-thirds portion of the hull.

The aft one-quarter to one-third portion (from stern) of the hull is at or above the water line of the craft having little or no wetted area, and presents little or no turning resistance when a paddler maneuvers the kayak.

The bottom 12c or keel of the kayak is a transverse flat, elongate curvilinear plate extending from a point near the bow to a point near the stern. Section views Figures 5-13 show a flat transverse keel plate at each station where these views are taken. Figure 4 shows the elongate curvilinear keel line 12d traced by the keel plate. As shown in Figures 1 and 4, the bottom plate extends in a curvilinear contour downwardly and aft from the bow reaching a low point adjacent the center of buoyancy and then gradually rising toward the stern. As the bottom plate rises and extends aft, it draws near to the water line such that aft section of the hull presents a diminishing wetted area. In a preferred embodiment of the invention as noted above, the section of the hull aft of the forward two-thirds portion of the hull has negligible wetted area. The keel line 12d comprises a complex curve of convex and concave portions. As a result the aft hull section encounters negligible water resistance. A flat bottom has the effect of lifting the craft and aiding maneuverability of the kayak in providing a lower turning resistance than encountered in a conventional transverse curved bottom of the craft.

The keel line 12d is further defined with reference to Figure 16 as comprising a forward convex curve section 12h and an aft concave curve section 12i. The location of convex 12h and concave 12i curves is determined as follows. A first line s-t extends between a point s at the juncture of stern and bottom plate to a point of tangency of the line s-t with keel line 12d. The tangent point is indicated by letter t. A second line b-t extends between a point b at the juncture of bow and bottom plate to the tangent point. Both lines s-t and b-t as well as kayak longitudinal axis x-x' (Fig 18) lie in a vertical plane. It is to be observed from below the hull that the forward

segment 12h of keel line is convex with respect to the line b-t and the aft segment 12i is concave with respect to the line s-t.

Tangent point t therefore defines a point of transition of the keel line from convexity to concavity. Keel transition from forward convex to aft concave curvature is an aspect of the present invention in achieving kayak maneuverability by bringing the aft section to a position at or above the water line while the forward convex curvature is waterborne for buoyancy of the kayak. The point of transition t is near the kayak midpoint, i.e., just aft the cockpit, as seen in Figures 1 and 16.

As best shown in Figures 1, 2, 17 and 18, the cockpit is situated ahead of the length-over-all midpoint MP (also designated as Station 5 in Fig 1) of the kayak so that its burden when water borne is located at or near the center of buoyancy CB of the craft. In this location of the cockpit, the paddler is located centrally of the wetted area, i.e., that area of the hull below water line WL shown in Figure 1.

The cockpit is fitted with an ovate cowling or spray skirt 16a having an upper flange 16b for receiving a waterproof shroud (not shown) normally used with kayaks. The cowling contour rises from rear to front to shed any water splashing over the deck forward of the cowling. The cockpit forms opening 16c (Figs 2, 8 and 18) through the deck accommodating a paddler in sitting position with legs extending forward in the usual manner for kayaks. The deck 14 covers the hull in a watertight joint extending the full perimeter of the kayak. The transverse contour of the deck is shown section views Figures 5- 13. The deck contour ahead of the cockpit is convex to aid in shedding water, and comparatively flat 14b aft the cockpit.

Figures 5-13 show pronounced chines 12d and 12e at the joints of bottom plate 12c and starboard 12a and port 12b sides. In addition each of the starboard and port sides have pronounced chines 12f and 12g (Fig 3) extending along the sides of the hull from bow to stern.

5 The stern of the kayak is fitted with steering gear 18 (Figures 14 and 15) conventionally used for such craft, including mounting hardware 18a, and rudder blade 18b operable by means of lines 18c-d extending to the cockpit and controlled by paddler^ feet. The rudder may be moved to a stowage position when the kayak is removed from the water (dash lines in Figure 14) and held by retaining bracket o 18e fitted to the deck.

As shown in Figures 1, 2, 16 and 17, the cockpit is located ahead of the midpoint MP and near to the center of balance CB which is located at a point distant from the bow equal to approximately 40% of LOA. The remaining distance (approx 60% LOA) between cockpit and rudder constitutes a moment arm providing high5 mechanical advantage for turning force (arrow TF, Fig 2) applied by a paddler with oar in the cockpit and directed by the rudder 18b at the stern for turning the kayak. High maneuverability of the kayak results from the rear portion of the hull being at or above the water line, the wetted area being situated over the forward two-thirds of the hull, and the cockpit being forward of the kayak midpoint for high mechanical o advantage of turning force applied there by the paddler.

The kayak hull according to the invention is asymmetrical in that the hull form ahead of the midpoint is substantially different from the hull form aft of midpoint. This asymmetry is directly perceived by comparing Figure 1 with Figures 5-13. Figure 9 is a section view at midpoint, with Figures 8, 7, 6 and 5 showing hull forward

sections and with Figures 10-13 showing hull aft sections. The perimeters p of hull forward sections are considerably larger than perimeters p of hull aft sections.

More specifically, hull asymmetry is defined by means of a length:girth (l/g) ratio for each of Stations 0-10 of Figures 17 and 18. An l/g ratio is length over all of a kayak divided by perimeter or girth at each station. L/g ratio provides a defining parameter for indicating fineness of hull sections fore and aft, for location of the cockpit, for location of the center of balance, and for location of the cockpit in relation to the center of balance. For ease of reference with respect to a plurality of l/g ratios, the hull may be described as asymmetric comprising a hull shape forward of the midpoint defined by a first length-to-girth ratio set, i.e., l/g ratios for Stations 0-5, and another hull shape aft of the kayak midpoint defined by a second length-to- girth ratio set, i.e., l/g ratios for Stations 5-10.

Girth measurements are taken transversely of the outer surface of the kayak along the perimeter p (Figures 5-13) of a plane normal to longitudinal axis x-x' (Fig 18) of the kayak. Adjustment is made at Station 4 to factor out the effect of the cockpit cowling. The resultant Station 4 measurement is along perimeter p and along dash line p' (Fig 8).

L/g ratios for adjacent stations, e.g., Stas. 3, 4 and 5 are an index of the volume of the hull at such stations, and are useful in comparing hull volume in respect of other stations, e.g., adjacent stations 6, 7, and 8. In an asymmetric hull, l/g ratios therefore designate and distinguish that section of the hull where the cockpit is located from other sections of the hull.

Figures 1, 17 and 18 respectively are side elevation and plan views of a kayak according to the invention. Figures 17 and 18 are marked with transverse stations 0-

10 equally spaced along the length of the kayak with Station 5 being kayak midpoint MP. As is clear from Figure 1, Stations 1-9 correspond to section views of Figures 5- 13. It is to be observed that the cockpit is situated through the deck ahead of Station 5 and between Stations 3 and 5. It is also to be observed that the center of balance is at Sta. 4.

The overall length (I) of a kayak and the girth (g) at each station are measured for computing an l/g ratio for each station. The kayak measured 15 feet, 8 inches LOA and has substantially the following l/g ratios.

Ua Table N ⁰ I

Station l/q ratio

0 28.9

1 7.5

2 4.4

3 3.4

4 3.1

5 3.2

6 3.6

7 4.4

8 6.3

9 11.8

10 26.3

The bow section of the kayak may be said to be the forward 20% of the craft

(Sta. 0-2); the midsection the next 40% aft the bow section (Sta. 3-6); and the stern section the remaining 40% of the craft (Sta. 7-10). In like manner, the bow section has an l/g range of 28.9 to 4.4; the mid section an l/g range of 3.4 to 3.6;

and the stern section an l/g range of 4.4 to 26.3. It will be understood that lower l/g ratios of the midsection correspond to the center of balance of the kayak being located at the cockpit (i.e., Station 4), and being forward of the longitudinal midpoint (i.e., Station 5) of the kayak. The cockpit is located between Stations 3 and 5 where l/g is 3.4 (Sta. 3), 3.1 (Sta. 4), and 3.2 (Sta. 5). In accordance with the invention, therefore, the cockpit lies ahead of the kayak mid-point, lies in a zone (Stations 3-5) with an l/g ratio in a range from about 3.1 to 3.4, and lies at the center of balance of the kayak. When the l/g ratio at each Station of the kayak is considered, it is observed that the cockpit is situated among Stations having the lowest l/g ratios. It is also to be observed that the lowest l/g ratio occurs at Station 4 at the center of balance. (See Hg. 1).

The l/g ratio range for the aft section rises rapidly corresponding to the increasing fineness of hull lines approaching the stern clearly apparent in Figure 17, and in Figures 1 and 9-13. A kayak according to the invention may be further defined by l/g ratios as comprising a bow section with an l/g ratio of 4.4 to 28.3; a cockpit section with an l/g ratio of 3.1 to 3.4; and an aft section with an l/g ratio from about 3.6 to 26. It is to be further noted that the aft portion of the kayak situated at or above the water line, i.e., Stations 7-10, has an l/g ratio of 4.4 to about 26.3. In another embodiment, a kayak with a LOA of 18.5 feet has substantially the following l/g ratios taken at Stations as designated in Figures 1, 17 and 18: l/α Table N ⁰ 2

Station l/q ratio 0 31.7

1 8.5

2 5.0

3 3.8

4 3.6 5 3.7

6 4.2

7 5.1

8 7.2

9 13.5 10 44.4

In this embodiment, the cockpit is situated in that section of the kayak where l/g ratio is less than 4, and where the Stations of the kayak ahead and aft of the cockpit have l/g ratios greater than 4. In this embodiment, the bow section has an l/g range of 31.7 to 5.0; the mid section an l/g range of 3.8 to 4.2; and the stern section an l/g range of 5.1 to 44.4. It will be understood that lower l/g ratios of the midsection correspond to the center of balance of the kayak being located at the cockpit (i.e., Station 4), and being forward of the longitudinal mid- point (i.e., Station 5) of the kayak. The cockpit is located between Stations 3 and 5 where l/g is 3.8 (Sta. 3), 3.6 (Sta. 4), and 3.7 (Sta. 5). In accordance with the invention, therefore, the cockpit lies ahead of the kayak mid-point, lies in a zone (Stations 3-5) with an l/g ratio in a range from about 3.6 to 3.8, and lies at the center of balance of the kayak. When the l/g ratio at each Station of the kayak is considered, it is observed that the cockpit is situated among Stations having the lowest l/g ratios. It is also to be observed that the lowest l/g ratio occurs at Station 4 adjacent the center of balance. (See Rg. 1).

The l/g ratio range for the aft section rises rapidly corresponding to the increasing fineness of hull lines approaching the stern clearly apparent in Figure 17, and in Figures 1 and 9-13.

A kayak according to the invention may be further defined by l/g ratios as comprising a bow section with an l/g ratio of 5.0 to 31.7; a cockpit section with an l/g ratio of 3.6 to 3.8; and an aft section with an l/g ratio from about 4.2 to 44.4. It is to be further noted that the aft portion of the kayak situated at or above the water line, i.e., Stations 7-10, has an l/g ratio of 5.1 to about 44.4.

In still another embodiment, a kayak with a LOA of 11.0 feet has substantially the following l/g ratios taken at Stations as designated in Figures 1, 17 and 18:

l/α Table N ⁰ 3

Station l/q ratio

0 17.6

1 5.6

2 3.3

3 2.4

4 2.1

5 2.1

6 2.5

7 2.7

8 3.9

9 7.0

10 18.9

In this embodiment, the cockpit is situated in that section of the kayak where l/g ratio is 2.4 or less, whereas the Stations of the kayak ahead and aft of the cockpit have l/g ratios greater than 2.4.

In this embodiment, the bow section has an l/g range of 17.6 to 3.3; the mid section an l/g range of 2.1 to 2.4; and the stern section an l/g range of 2.5 to 18.9. It will be understood that lower l/g ratios of the midsection correspond to the center of balance of the kayak being located at the cockpit (i.e., Station 4), and being forward of the longitudinal mid-point (i.e., Station 5) of the kayak. The cockpit is located between Stations 3 and 5 where l/g is 2.4 (Sta. 3), 2.1 (Sta. 4), and 2.1 (Sta. 5). In accordance with the invention, therefore, the cockpit lies ahead of the kayak mid-point, lies in a zone (Stations 3-5) with an l/g ratio in a range from about 2.1 to 2.4, and lies at the center of balance of the kayak. When the l/g ratio at each Station of the kayak is considered, it is observed that the cockpit is situated among Stations having the lowest l/g ratios. It is also to be observed that the lowest l/g ratio occurs at Station 4 at the center of balance. (See Hg. 1). It is to be understood that to say that the lowest l/g ratio is at, near, or adjacent the center of balance, and to say that the center of balance is at, near or adjacent a station means a location within twenty percent of station length, i.e., longitudinal length I (Rg 18) between consecutive stations. The l/g ratio range for the aft section rises rapidly corresponding to the increasing fineness of hull lines approaching the stern clearly apparent in Figure 17, and in Figures 1 and 9-13.

A kayak according to the invention may be further defined by l/g ratios as comprising a bow section with an l/g ratio of 3.3 to 17.6; a cockpit section with an

l/g ratio of 2.3 to 2.4; and an aft section with an l/g ratio from about 2.5 to 18.9. It is to be further noted that the aft portion of the kayak situated at or above the water line, i.e., Stations 7-10, has an l/g ratio of 2.7 to about 18.9.

In each of the foregoing embodiments, l/g ratios are stated as substantially the values given in Table Nos. 1-3. The term substantially for purposes of this application means plus or minus 10% of the values stated.

The forward convex curve 12h (Fig 16) of keel line has a radius ri in a range of 1.4 to 1.8, and is preferably 1.6, times the length overall of the kayak. The rear concave curve 12i of keel line has a radius r ₂ in a range of 2.7 to 3.3, and is preferably 3.0, times the length overall of the kayak.

In use, the kayak is propelled by oar in the hands of a paddler positioned forward of the midpoint of the kayak at the center of balance of the kayak and amid the wetted area of the craft. For a turning maneuver a paddler propelling the craft applies a turning force in the vicinity of the cockpit and center of buoyancy, with turning resistance confined to the wetted area such that the craft turns rapidly and with a shorter turning radius in comparison to a conventional kayak. Increased steering leverage is attained in locating mass (i.e., the paddler and forward hull) forward in the craft at an increased distance from the rudder. With the paddler applying a turning moment at Station 4, the remaining 60% of the kayak length aft of Station 4 provides a highly effective and highly levered moment arm applied to the rudder for turning the kayak. In addition, by reason of the flat keel plate and convex/concave keel line the kayak has lower wetted area than a conventional kayak and less water resistance to forward propulsion as well as turning motion of the

craft. The result is a nimble kayak that is faster and more highly maneuverable with increased steering leverage as compared to conventional craft.

The invention in one embodiment provides a kayak with wetted area extending over the forward two-thirds of the hull. Advantages of the invention may be attained in a kayak with a wetted area extending over a range of forward ninety percent to fifty percent of the hull, with a preferred range of sixty to seventy-five percent of the hull.

A kayak, with cockpit forward according to the invention, provides level wave breaking performance allowing the kayak to go through rather than over a wave. When running with waves, the asymmetrical hull design enhances the kayaks ability to hold and surf even the smallest wave. The kayak is less likely to broach when running with the waves because forward location of the cockpit provides increased mechanical advantage and increased rudder leverage.

The kayak hull design enhances the experience of sea kayaking. A paddler may encounter more water and splash, but the excitement and maneuverability is unique in kayaking.

Various changes may be made to the structure embodying the principles of the invention. The foregoing embodiments are set forth in an illustrative and not in a limiting sense. The scope of the invention is defined by the claims appended hereto.