WO2006125445A1

WO2006125445A1 - A kayak

Info

Publication number: WO2006125445A1
Application number: PCT/DK2006/000297
Authority: WO
Inventors: Jim Hartvig Andersen
Original assignee: Struer Kajak A/S
Priority date: 2005-05-27
Filing date: 2006-05-29
Publication date: 2006-11-30
Also published as: EP1726522A1

Abstract

A kayak (10) comprises a deck or a top part (14) including a manhole, and a hull or bottom part (12) defining a stem or leading edge and a stern or trailing edge, the deck (14) being joint to said hull (12) . The hull defines a specific overall length, a maximum width and a maximum frame, and has a centre of buoyancy located behind the centre of said hull, such as at a position at a distance constituting 51 - 53 %, such as 51 - 52 %, preferably approximately 51.5 % of said specific overall length from said stem or leading edge. The hull further defines a prismatic ratio larger than 0.6, such as 0.6 - 0.70, e.g. 0.62 - 0.68, preferably 0.63 - 0.66, most preferably approximately 0.64, or a prismatic ratio of 0.60 - 0.61 ; 0.61 - 0.62; 0.62 - 0.63; 0.63 - 0.64; 0.64 - 0.65; 0.65 - 0.66; 0.66 - 0.67; 0.67 - 0.68; 0.68 - 0.69; 0.69 - 0.70, preferably approximately 0.63 - 0.64 or 0.64 - 0.65.

Description

A kayak

The present invention relates to a kayak or more particularly to a kayak being a competition kayak fulfilling the requirements defined by the International Canoe Federation.

According to these requirements, a kayak may constitute a one-rower kayak, a two- rower kayak or a four-rower kayak. The kayak generally comprises a hull and a deck, which may be made of separate components which are then joined together or may be made as an integral structure from natural materials such as veneer, preferably mahogany veneer as used by the applicant company. Alternatively, the hull end or deck may be made from polymer material such as plastics materials or fibre, e.g. glass fibre or carbon fibre reinforced plastics materials as the hull may be handmade as a glass fibre reinforced structure or alternatively be cast in a mould.

According to the requirements defined by the International Canoe Federation, a one-rower kayak must have a minimum weight of 12 kg and may have a maximum length of 5.2 m and a maximum width of 42 cm. Similarly, a two-rower kayak must, according to the requirements defined by the International Canoe Federation have a minimum weight of 18 kg and a maximum length of 6.5 m and a maximum width of 42 cm. The four-rower has, according to the requirements defined by the International Canoe Federation a minimum weight of 30 kg, a maximum length of 11 m and a maximum width of 42 cm.

Generally, kayaks such as one-rower kayaks, two-rower kayaks and four-rower kayaks used for competition have been made as structures developed empirically by the craftsmen building the kayaks manually from veneer or glass- or carbon fibre reinforced polymer material.

Since the dimensions and the weight of a kayak intended to be used for competition purposes are strictly limited, any improvements which may be of the outmost importance as to the success of the rower or rowers in a competition, any improvements need to be based on entities different from weight, length and width. In the general technical field of ship building, certain technical parameters have been used for at least several decades, namely on the one hand the centre of buoyancy and also the prismatic ratio. The centre of buoyancy defines the centre at which the force generated by the buoyancy of the ship or in the present context, a kayak, is acting as the kayak is submerged in the water by the weight of the rower or the rowers in combination with the weight of the kayak, as the water level defines a perimeter at the outside of the hull of the kayak. It is contemplated that the location of the centre of buoyancy has importance as to the ability of the kayak to be rowed fast through the water, since the location of the centre of buoyancy influences the outer surface geometry, which is of the highest importance as to obtaining of a laminar flow along the sides of the hull rather than the generation of whirls, eddy currents or swirls.

The prismatic coefficient is also, according to the teachings of the present invention, of the outmost importance as to the obtaining of a fast ship or in the present context, a kayak. The prismatic coefficient is defined as a ratio between the actual volume displaced by the hull below water level and the prism generated by the generator being the major frame of the hull within the maximum length from stem to stern of the ship, or in the present context, the kayak.

When considering the prismatic ratio, one would readily think that a low prismatic ratio would provide the fastest kayak and to the knowledge of the applicant company, the prior art competition kayaks have been built with a prismatic coefficient of the order of 0.5 - 0.55, possibly somewhat larger, however, lower than 0.60.

It has through computer simulations been demonstrated that a larger hull. i.e. a hull having a larger prismatic ration, i.e. a prismatic ratio larger than 0.60 performs better than a hull having a lower prismatic ratio, such as a prismatic ratio lower than 0.55. It is contemplated that the faster performance of the kayak implemented in accordance with the teachings of the present invention having a prismatic ratio larger than 0.60 is based on the fact that the larger hull provides larger continuous surfaces of the hull allowing the water to flow in laminar flow along the sides of the hull rather than separating from the hull and generating whirls, eddy currents or swirls. It is to be emphasised that the above explanation of the improved performance of the kayak implemented in accordance with the teachings of the present invention and having a prismatic ratio larger than 0.6 is entirely speculative and the present invention is therefore by no means limited to this contemplated explanation.

According to the present invention, a kayak is provided comprising a deck or a top part including a manhole, a hull or bottom part defining a stem or leading edge and a stern or trailing edge, said deck being joint to said hull, said hull defining a specific overall length, a maximum width and a maximum frame, said hull having a centre of buoyancy located behind the centre of said hull, such as at a position at a distance constituting 51 - 53 %, such as 51 - 52 %, preferably approximately 51.5 % of said specific overall length from said stem or leading edge, and said hull defining a prismatic ratio larger than 0.6, such as 0.6 - 0.70, e.g. 0.62

- 0.68, preferably 0.63 - 0.66, most preferably approximately 0.64, or a prismatic ratio of 0.60 - 0.61 ; 0.61 - 0.62; 0.62 - 0.63; 0.63 - 0.64; 0.64 - 0.65; 0.65 - 0.66; 0.66

- 0.67; 0.67 - 0.68; 0.68 - 0.69; 0.69 - 0.70, preferably approximately 0.63 - 0.64 or 0.64 - 0.65.

As discussed above, the fairly large prismatic ratio provides most surprisingly, an improved kayak as compared to a conventional kayak having a prismatic ratio lower than 0.60 or in most case, lower than 0.55, possibly due to the above explanation. The location of the centre of buoyancy, also according to the teachings of the present invention, provides an improvement in the performance as to the speed of the kayak as compared to prior art kayaks, since the location of the centre of buoyancy in combination with the prismatic ratio generates the sufficiently large outer surfaces of the hull providing the maintenance of laminar flow along the sides of the hull at a high speed, such as a speed of approximately 6 m/s.

According to computer simulations performed during developing the kayak according to the present invention, it was demonstrated that the kayak implemented in accordance with the presently preferred embodiment of the hull structure having a prismatic ratio of 0.64 and a centre of buoyancy located 51.5 % along the overall length of the hull was 2.9 % faster than the kayak produced by the applicant company. Although an improvement of 2.9 % may seem fairly low, it has to be realised that the figure has to be compared to a competition situation in which an improvement by 2.9 % of a kayak as compared to a prior art allows the improved kayak to reach the goal after 1000 m, approximately 29 m or equivalent to AVz lengths of a two-rower kayak before the prior art kayak.

The kayak according to the present invention is preferably implemented in accordance with the above-mentioned requirements defined by the International Canoe Federation as a one-rower-, a two-rower- or a four-rower kayak.

The maximum frame of the hull defines below water level a configuration deviating from a semicircular configuration of the same area as the configuration of the maximum frame, which maximum frame defines a central bend defining angle of 120° - 160°, such as 130° - 140°, e.g. approximately 140° and defines a maximum reduced by approximately 7 - 15 %, such as 8 - 12 %, e.g. approximately 10 % as compared to the radius of the semicircle and further define a maximum width at water level exceeding the diameter of the semicircle by at least 20 %, such as 20 - 25 % or 25 - 30 %, such as approximately 28 %. The configuration of the maximum frame is as will be understood, of the outmost importance as to the stability of the kayak, since a configuration identical to a semicircle inevitably causes a completely unstable kayak, which was readily tilt over, although the semicircle constitutes the geometrical configuration having the minimum line of contact with the water provided the area of the frame is specified. As distinct from different kinds of ships or boats, a kayak may not include a keel and therefore, the configuration of the major frame and also the frames of the hull are of the outmost importance as to the stability of the kayak.

In the presently preferred embodiment of the kayak according to the present invention, the maximum frame defines a level below water level, at which level the configuration of the maximum frame is identical to the semicircle, which level constitutes 55 % of the maximum depth of the configuration of the maximum frame below water level. It is contemplated that the fairly deep location of the correspondence between the actual configuration of the maximum frame and the semicircle is of importance as to the stability of the kayak.

In accordance with alternative embodiments of the kayak, the kayak includes a rudder position behind the stern or trailing edge, or alternatively a rudder being an underlying rudder. According to the requirements defined by the International Canoe Federation, the overall length requirements of the competition kayak also includes the rudder and therefore, the rudder is preferably an underlying rudder.

The fulfilment of the requirement characteristic of the present invention of positioning the centre of buoyancy behind the centre of the hull, is readily obtained by locating the maximum frame at a position behind the centre of the hull and further behind the centre of buoyancy. Dependent on the actual configuration of the kayak which is developed on the basis of the two criteria characteristic of the present invention, and also the configuration of the maximum frame in a computer simulation programme, the individual frames are readily obtained.

As a conventional kayak, the hull preferably includes a pointing stern or alternatively, the hull may, according to a different configuration, have a planar stern.

According to the teachings of the present invention, the kayak is developed for providing laminar flow along the sides of the hull and to cause the laminar flow to be preserved until a position behind the trailing edge or stern of the kayak, which position is located approximately 0.5 - 1 m behind the stern or trailing edge. It is believed that the elimination of any whirls, eddy currents or swirls along the front and/or the rear part of the hull, i.e. the part before or after, respectively, the maximum frame, improves the speed capacity of the kayak.

The present invention is now to be further described with reference to the drawings, in which

Fig. 1 is an overall perspective and schematic view of a first and presently preferred embodiment of a kayak according to the present invention constituting a two-rower competition kayak,

Fig. 2 is a vertical sectional view of the major frame of the first and presently preferred embodiment of the kayak shown in Fig. 1 and also showing the cross sectional configuration of the kayak, Fig. 3a is a schematic view illustrating in a vertical view and a top view the stem of the first embodiment of the kayak also shown in Fig. 1 ,

Fig. 3b is a vertical sectional view along the line 3B-3B in Fig. 3a of the frame of the first and presently preferred embodiment of the kayak, Fig. 4a is a view similar to the view of Fig. 3a of the central part of the first and presently preferred embodiment of the kayak also shown in Fig. 1 , Fig. 4b is a vertical sectional view similar to the view of Fig. 3b along the line 4B-4B in Fig. 4a, also showing the seat for one of the rowers,

Fig. 5a is a view similar to the views of Figs. 3a and 4a illustrating the rear most part of the first and presently preferred embodiment of the kayak, and Fig. 5b is a vertical sectional view similar to the views of Figs. 3b and 4b along the line 5B-5B in Fig. 5a.

In Fig. 1 , a two-rower competition kayak is shown designated the reference numeral 10 in its entirety. The kayak 10 comprises a bottom part or hull 12 and a top part or deck 14, which according to the technique developed by the applicant company are produced separately from veneer or mahogany and shaped in a evacuation chamber into the intentional configuration of the bottom part and top part, respectively, and glued together by means of adhesive, preferably epoxy. After several operations of scraper grinding and polishing, the two parts are joint together into the composite structure shown in Fig. 1.

It is to be realised that the first and presently preferred embodiment of the kayak according to the present invention shown in Fig. 1 is a two-rower kayak complying with the international requirements of the International Canoe Federation as the kayak has to comply with a maximum length requirement and a minimum weight requirement. According to these international standards, a one-rower kayak has to weigh at least twelve kg and must at the most have a length of 5.20 m. Similarly, a two-rower kayak must have a minimum weight of 18 kg and a maximum length of 6.50 m. For the four-rower competition kayak, the requirements are similarly a maximum length of 11.00 m and a minimum weight of 30 kg. It is to be understood that the maximum length requirements also include the rudder, which is therefore, as is illustrated in Fig. 5b, implemented as an underlaying rudder rather than a rudder positioned at the rearmost end of the hull. The maximum width of the hull is 42 cm.

The two-rower kayak shown in Fig. 1 includes two manholes defined by two manhole rim parts 16 and 18, respectively, and each of the two rowers are in the intentional position within the kayak sitting on fixed seats 20 and 22, respectively.

According to the teachings of the present invention as defined in the appending claims and discussed in the description above, the hull of the two-rower kayaks shown exhibits a prismatic coefficient higher than 0.6, preferably higher than 0.62, such as 0.64 and has a centre of buoyancy located behind the centre of the hull, i.e. at a position closer to the stern or the trailing edge as compared to the stem or the leading edge of the hull. It has been established through computer simulation that a position around a relative distance from the stem or leading edge constituting approximately 51.5 % of the overall length of the hull from the stem or leading edge or at least 51 % provides a maximum efficiency at the maximum speed of the kayak, which in terms of a two-rower kayak is a speed of approximately 5-6 m/s, such as 5.5-5.9 m/s. The computer simulation has demonstrated that a two-rower kayak following the above two requirements relating to the prismatic coefficient and the location of the centre of buoyancy provides an increase in speed as compared to a cenventional two-rower kayak produced by the applicant company of 2.7 - 2.9 % in a 1000 m race equivalent to a distance of 27 - 29 m or 4 - 5 lengths of the two-rower kayak. It is contemplated that the fairly large prismatic coefficient in combination with the location or position of the centre of buoyancy allows the water at the maximum speed of the hull to establish a laminar flow along the sides of the hull, in particular at the front part of the hull until the maximum frame and possibly also along the rearmost part of the frame providing a virtual elongation of the hull of 0.5 m - 1 m, at which position behind the stern or trailing edge of the hull the water flow establishes whirls, eddy currents or swirls, which however, due to the distance behind the hull do not influence the performance of the hull and in particular do not slow down the kayak.

According to a particular feature of the kayak shown in Fig. 1 , which feature is also evident from the below figures 3a, 4a and 5a, the top part or deck 14 has a rounded edge part joining the basically planar or horizontal top wall to the vertical side wall joint to the lower part or the hull 12. It is contemplated that the rounded configuration of the top part or the deck 14 establishes lower wind friction, in particular relative to winds coming in from the side, as compared to conventional kayaks having sharp cut edges joining the planar horizontal top surface to the vertical side walls of the hull.

The location of the centre of buoyancy behind the centre of the hull is evidently established by providing the maximum frame at a location behind the geometrical centre of the hull, which major frame in the presently preferred embodiment of the two-rower kayak shown in Fig. 1 is located at a distance of 4.150 m from the stern or the leading edge of the hull. Consequently, the major frame is located at a position around a relative distance from the stern or leading edge constituting approximately 63 % - 64 % of the overall length of the hull.

In Fig. 2, a vertical sectional view is shown illustrating the configuration of the major frame of the hull and also illustrating a semicircle having the same cross sectional area as the cross sectional area of the major frame below the water level when loaded with two rowers having a weight of 75 kg each. From Fig. 2, which illustrates the major frame in a dimensionally stable presentation similar to the views of Figs. 3a - 5b below, the following dimensions H1 , H2 and H3 may be measured (M =7.2; H2=6.5; H3=4.0) from which the following ratio H2/H1 is 0.90 constituting the reductions of the depth of the hull as compared to the semicircle 24 and the ratio is H3/H1 is 0.55, which ratio defines the relative depth of the hull at which the hull becomes narrower as compared to the semicircle 24. Further from Fig. 2, the dimensions W1 , W2 and W3 may be measured (W1=9.1 ; W2=7.1 ; W3=6.2) on the basis of which dimensions the ration W1ΛΛ/2 constituting the relative widening of the hull as compared to the semicircle 24 at the water level is calculated constituting 1.28 and also the ratio W1/W3 being 0.68 defining similar to the ratio H1/H3 the relative depth of widening of the hull as compared to the position at which the hull becomes wider as compared to the semicircle 24.

In Fig. 3a, the front part of the kayak is shown and as stated above.

In Fig. 3b, a vertical sectional view is shown illustrating the frame of the hull of the kayak 10 at a position 0.90 m from the stem or leading edge.

In Fig. 4a, a view similar to the view of Fig. 3a is shown illustrating the central part of the kayak illustrating the manholes of the kayak and Fig. 4b illustrates, similar to Fig. 3b, the frame of the hull of the kayak at a position 4.150 m from the stem or the leading edge.

In Fig. 5a, a view similar to the views of Figs 3a and 4a is shown illustrating the rearmost end of the kayak and in Fig 5 b, a vertical sectional view similar to the views of Figs. 3b and 4b is shown illustrating the frame of the hull of the kayak at a distance of 5.350 m from the stem or leading edge.

In the tables 1 - 9 below, reports for Hydrostatics & Stability Report for nine different embodiments according to the present invention are included.

Claims

1. A kayak comprising: a deck or a top part including a manhole, a hull or bottom part defining a stem or leading edge and a stern or trailing edge, said deck being joint to said hull, said hull defining a specific overall length, a maximum width and a maximum frame, said hull having a centre of buoyancy located behind the centre of said hull, such as at a position at a distance constituting 51 - 53 %, such as 51 - 52 %, preferably approximately 51.5 % of said specific overall length from said stem or leading edge, and said hull defining a prismatic ratio larger than 0.6, such as 0.6 - 0.70, e.g. 0.62 - 0.68, preferably 0.63 - 0.66, most preferably approximately 0.64, or a prismatic ratio of 0.60 - 0.61 ; 0.61 - 0.62; 0.62 - 0.63; 0.63 - 0.64; 0.64 - 0.65; 0.65 - 0.66; 0.66 - 0.67; 0.67 - 0.68; 0.68 - 0.69; 0.69 - 0.70, preferably approximately 0.63 - 0.64 or 0.64 - 0.65.

2. The kayak according to claim 1 , said deck including a single manhole and defining a specific maximum length of 5.20 m and a maximum width of 42 cm, and said kayak in total having a weight of minimum 12 kg.

3. The kayak according to claim 1 , said deck including two manholes and defining a specific maximum length of 6.5 m and a maximum width of 42 cm, and said kayak in total having a weight of minimum 18 kg.

4. The kayak according to claim 1 , said deck including four manholes and defining a specific maximum length of 11 m and a maximum width of 42 cm, and said kayak in total having a weight of minimum 30 kg.

5. The kayak according to any of the claims 1 - 4, said maximum frame defining a configuration below water level deviating from a semicircular configuration of the same area as said configuration of said maximum frame, said configuration of said maximum frame defining a central bend defining an angle of 120° - 150°, such as 130° - 140°, e.g. approximately 140° and defines a maximum height reduced by approximately 10 % as compared to the radius of said semicircle and further defines a maximum width at water level exceeding the diameter of said semicircle by at least 20 %, such as 20 - 25 %, 25 - 30 %, such as approximately 28 %.

6. The kayak according to claim 5, said configuration of said maximum frame defining a level below water level, at which level said configuration of said maximum frame is identical to said semicircle, said level constituting 55 % of said maximum depth of said configuration of said maximum frame below water level.

7. The kayak according to any of the claims 1 - 6, said kayak including a rudder positioned behind said stern or trailing edge or alternatively and preferably constituting an underlying rudder.

8. The kayak according to any of the claims 1 - 7, said maximum frame being located at a position behind the centre of said hull and further behind said centre of buoyancy.

9. The kayak according to any of the claims 1 - 8, said hull defining a pointing stern or alternatively a planar stern.