US20040011275A1

US20040011275A1 - Collapsible kayak

Info

Publication number: US20040011275A1
Application number: US10/134,308
Authority: US
Inventors: Murray Broom
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-04-26
Filing date: 2002-04-26
Publication date: 2004-01-22

Abstract

A flexible skin 3 is fitted over a framework 20 that includes a plurality of longitudinal stringers 50-58 running the length of the bottom and sides of the kayak. Each stringer 50-58 is assembled from several elongate segments 80-85 held together by an internal shock cord. Transverse formers 10-13 separate the stringers to define the hull outline and are releasably fixable to the stringers. Bow and stem formers 10, 13 are fixed in a manner allowing them to slide longitudinally, thereby laterally spreading and tensioning the stringers 51-58. Flexible tension members 73, 74 provide longitudinal bending strength and assist in shortening the framework 20 for assembly. A block 21 inserted in a joint 30′ between adjacent segments of a stringer provides a means for locking the segments in a telescopically extended position, for expanding the framework longitudinally.

Description

TECHNICAL FIELD

The present invention relates to collapsible kayaks having a flexible outer skin covering a skeleton frame.

BACKGROUND ART

Some of the better-known types of collapsible kayaks are assembled from disconnected stringers and formers which are joined together with latches and clamps to form a relatively loose framework. The skin is usually one piece, having bow and stem-shaped pockets and a central upper opening adjacent the cockpit structure. The opening receives the two halves of the framework, sometimes separately, which halves are then rigidly connected together inside the skin. In some designs a tensioning means stretches the skin around the framework. Commonly the stress in the skin provides a reaction to force on the framework and is an integral structural part of the kayak, without which the kayak frame has insufficient rigidity.

Such designs of kayak when disassembled result in a large number of disconnected pieces, including easy to lose small pieces. They require a considerable time to assemble, and require skill and care in following the instructions. Whilst such a kayak has the advantage of being collapsible for fitting in a confined space, these structures are usually not designed primarily for easy carrying, for example in a backpack, since they are rather bulky and heavy.

As noted, the looseness of the framework or its structural rigidity remains a problem in the prior art. If a paddler sits in the middle of an otherwise empty kayak, a lack of rigidity causes the ends rise out of the water creating more rocker and making the kayak easy to turn, but conversely difficult to maintain on a straight course. Limited flexibility is an advantage but too much flexibility is a disadvantage.

One method of reducing this flexure has been to use an inflatable air bladder system, however this adds further weight and complication to the assembly procedure, and necessitates bringing along a pump.

Another approach to improving the structural integrity has been to use more secure connectors. This approach has led to some improvements, though at the expense of added weight.

It is an object of the present invention to provide an improved collapsible kayak which is lightweight and may be simply and quickly assembled.

It is a further object of the present invention to address the foregoing problems.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a collapsible kayak having an internal framework and a hull, the hull comprising a water impermeable flexible skin, the framework comprising:

bow and stem members;

a plurality of stringers connected between the bow and stem members and running the length of the bottom and sides of the kayak, each stringer being assembled from a plurality of elongate segments;

a plurality of transverse formers approximately conforming to the transverse outline of the hull, each former being releasably connectable with each stringer;

at least one of said formers being an end former slidably connected with each stringer for laterally spreading the stringers; and

fixing means for fixing each end former longitudinally with respect to the stringers.

Each slidably connected former is located near a longitudinal end of the framework and is adjustably held toward the respective end of the framework, thereby laterally spreading the stringers.

The segments of the stringers are interconnected by a sliding engagement in the longitudinal direction. Each joint between adjacent segments of a stringer includes: a hollow axial spigot fixed at the end of a first segment; an axial recess at the end of a second segment for telescopically receiving the spigot, and an elongate resilient member fitted internally between the two terminal segments for retaining the segments together.

At least one block is used for insertion in the joint between adjacent first and second segments to fix the first and second segments in a telescopically extended position. This allows the length of the stringers to be extended after the framework has been placed inside the skin, thereby longitudinally tensioning the skin. It will be appreciated that although preferably blocks are used, various alternative means may be used for locking two telescoping segments in an extended position, such as detents, clamps etc.

Preferably the formers include segment-shaped connectors for connection with the stringers, each connector having a cylindrical inner surface for engagement with a corresponding outer surface of the stringers, whereby the opening at the mouth of the connector is less than the diameter of the stringer allowing the stringer to be entered thereinto in the radial direction and retained by a snap-fit.

The framework includes bow and stern members which are releasably connectable with the stringers. The framework further includes at least one forward deck stringer and at least one aft deck stringer supporting the deck of the kayak. A forward stringer is connected to the bow member and terminates proximate a forward end of a cockpit opening and an aft stringer is connected to the stem member and terminates proximate an aft end of the cockpit opening. The forward and aft deck stringers also provide additional stiffness for longitudinal bending.

The cockpit opening is reinforced by webbing fixed around the lip thereof. A coaming formed around the cockpit opening from the material of the deck skin, a rim of the coaming comprising a sleeve for receiving a removable coaming-reinforcing rod.

The framework includes two pairs of identical formers spaced in the longitudinal direction, the first pair comprising bow and stern end formers, the second pair comprising cockpit formers. The cockpit formers define the maximum lateral dimensions of the framework and in the disassembled state a bow or stem former can be nested inside a cockpit former.

Two longitudinal tension members are provided, each symmetrically held in locating fixtures on either side of the longitudinal centreline of the framework. The longitudinal tension members may be employed to reduce the length of the framework before it is inserted into the skin, and thereby laterally spread the stringers, although this is not necessary. After the framework is positioned inside the skin the load in the longitudinal tension members may be adjusted to fix the rocker of the kayak.

The skin includes longitudinally extending closures extending between the forward end of the skin and the cockpit opening, and the aft end of the skin and the cockpit opening respectively.

The kayak may be collapsed into a bundle adapted to be readily carried in a backpack, where the maximum linear dimension of the bundle is less than 1 meter. Straps fixed to at least the cockpit formers are provided for laterally tensioning the skin. Optionally, the kayak may be single or double kayak.

This collapsible kayak is intended primarily for ease of carrying and assembly, and avoids the large number of different parts in the prior art kayaks, by providing common interchangeable parts as well as eliminating small easy to loose fasteners etc. It is lightweight, compact and can be quickly assembled. The longitudinal tension members assist with assembly and provide means for varying the longitudinal bending stiffness of the framework.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: [0027]
FIG. 1 is a side elevation of the skeleton framework of a preferred embodiment of the kayak of the present invention; [0028]
FIG. 2 is a transverse section through a preferred embodiment of the kayak of the present invention; [0029]
FIG. 2[0030] a is a detail from FIG. 2;
FIG. 3 is a pictorial view of a preferred embodiment of the kayak of the present invention; [0031]
FIG. 3[0032] a is a scrap section through the coaming of FIG. 3;
FIG. 4 is a longitudinal elevation with cutaway section of the joint between the stringers of a preferred embodiment of the kayak of the present invention; [0033]
FIGS. 5[0034] a and 5 b are side and end elevations respectively of a block for use in joint between the stringers of a preferred embodiment of the kayak of the present invention;
FIG. 6 is a side elevation of a joint between the stringers using the block of FIGS. 5[0035] a and 5 b;
FIG. 7 is an elevation of a fore or aft member of a preferred embodiment of the kayak of the present invention; [0036]
FIGS. 8[0037] a and 8 b are details of the connection between the member shown in FIG. 7 and a stringer of a preferred embodiment of the kayak of the present invention;
FIGS. 9[0038] a and 9 b are plan and elevations respectively of a section of the framework showing the installation of a seat of a preferred embodiment of the kayak of the present invention;
FIGS. 10[0039] a and 10 b are is a simplified longitudinal elevation and plan view respectively, showing tension members of a preferred embodiment of the kayak of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Referring to the drawings FIGS. 1 and 3, a [0040] kayak 100 according to the illustrated embodiment of the present invention includes a framework 20 and a resilient water impermeable hull skin 3. The framework 20 includes a plurality of full-length stringers 51-58 connected between a bow member 1 and a stem member 2, a plurality of transverse formers 10-13 separate the stringers to define the shape of the hull. Additional deck-supporting stringers 59, 60 are connected between the bow member 1 and former 11 and between stem member 2 and former 12, respectively. Not a structural part of the framework, but also illustrated in FIG. 1 are closed cell foam nose pieces 9 connected to the bow and stem members 1,2. These nose pieces 9 may either be fixed to the inside of the skin 3 or, alternatively they may be inserted into the skin 3 together with the framework 20 upon assembly. These resilient nose pieces 9 define the form of bow and stem and reduce wear and the possibility of damage to the skin where it is most vulnerable.
All the stringers [0041] 51-60 are assemblies of tube sections, preferably made of a pultruded carbon fibre reinforced epoxy material, having a high strength-to-weight ratio. The stringers 51-60 are comprised of tube segments 80-84 of varying lengths which are connected by joints 30 described in greater detail with reference to FIG. 4. The maximum length of each segment is approximately 1 meter. The joints 30 allow the stringers 51-58 to be folded into bundles when disassembled. The joints 30 are staggered longitudinally to avoid local weaknesses in the structure and they are positioned remotely from the formers 10-13 to avoid interference with the installation or adjustment of the formers 10-13. Opposing ends of each full-length stringer 51-58 and one end of each deck stringer 59,60 are fitted with an end connector 40 for releasable engagement with the bow member 1 or stern member 2. The end connector 40 is described in greater detail with reference to FIGS. 7 and 8.
Referring to FIGS. 2 and 2[0042] a, the transverse formers 10-13 are preferably formed from nylon or a like flexible and resilient material. Nine partially cylindrical recesses 14 in the formers 10-13 accept the stringers 51-60 therein with a snap fit. The chord length C (or the mouth) of the recess 14 is smaller than the diameter of the stringers 51-60 tube and the resilience of the material is sufficient that the stringers 51-60 may be manually inserted into or removed from the recess 14, in which they are otherwise retained. Also fixed to the formers 10-13 is a locating indentation 70, 71 for engagement with the flexible longitudinal tension members (not shown), more fully described with reference to FIGS. 10 and 11. Each former 10-13 is thus located laterally relative to the stringers 51-58. The snap fit between the formers 10-13 and the stringers 51-60, however permits sliding relative movement, allowing longitudinal position of the formers to be readily varied. Optionally, other means of releasably and slidably interconnecting the formers to the stringers 51-58 can be used. The end formers 10 and 13 are sufficiently flexible to maintain engagement with the stringers 51-58 as they converge toward the ends of the kayak.
As is common practice, the formers [0043] 10-13 are shaped to allow the skin 3 to deform inward in use without interference by the formers 10-13, thereby maintaining the continuity of the hull shape at the point where the former 10-13 is inserted and permitting smooth laminar flow on the outside of the skin 3. This feature also reduces damage to the skin 3 when it is forced inwardly by an object against the framework 20.
Referring to FIG. 3 the [0044] upper deck 4 of the skin 3 has a cockpit opening 5 to receive a kayaker, which for assembly and disassembly of the kayak 100 may be further opened out by releasing zippers 6 and 7, to open fore and aft longitudinal slits respectively. Preferably the lower surface 8 of the skin 3 can be of transparent urethane film and is joined to the upper deck 4 along a line intermediate the topmost full- length stringers 51 and 58 and the stringers 51 and 52 (FIG. 2). Preferably the deck 4 is of a lightweight polyester film bonded along its edge to the material of the lower surface 8. In the preferred embodiment illustrated, the fore and aft portions of the skin are also locally reinforced with capping pieces 15, 16 of tough abrasion resistant material such as urethane. Optionally additional reinforcement may be provided at other points inside or outside the skin 3 (not shown) as is desired. The resilient nosing 9 (see FIG. 1) is shaped to conform with the inside of the bow and stem capping pieces 15, 16.
Referring to FIGS. 3 and 3[0045] a, the cockpit opening 5 has a coaming 33 adapted to receive a spray skirt (not shown) to seal around the kayaker. Two sleeves 34, 35 extend around longitudinally opposing sides of the opening 5 and receive coaming reinforcing rods 36, 37 which are connected by joining pieces (not shown) at their intersections 31, 32 to form a relatively stiff rim.
The [0046] lower surface 8 of the skin 3 is tensioned by straps (not shown) that may be manually tensioned. A first end of each strap is fixed to the formers 11 and 12 and a second end is bonded or otherwise fixed to the lower surface 8 on each side of the kayak 100. Optionally other means of tensioning the skin 3 may be employed.
The construction of joint [0047] 30 for connecting each of the tube segments 80-84 is described with reference to FIG. 4. Each joint 30 includes a hollow spigot 85 at one end of the tube segments 80-84. The spigot 85 is received and retained in the axially opening cavity portion 86 at the end of an adjacent tube segment. Axial passages run through each of the tube segments 80-84. An elongated resilient member 87 extends through the passages of each of the tube segment to resiliently retain the tube segments 80-84 together. The resilient member 87 is fastened at one end of the first segment and terminated at the opposite end of the final segment. With this construction, when one spigot 85 of a tube segment 80-84 is telescopically received in the cavity of the adjacent tube segment 80-84, the resilient member retains these tube segments 80-84 in this relationship. The resilient member 87 is sufficiently flexible so that the tube segments 80-84 can be separated and folded into a side-by-side relationship when disassembled. In this manner a separate ferrule is not required and the outer surfaces of the adjacent tube segments 80-84 are essentially flush at each joint 30, reducing the risk of damage to the skin 3.
Preferably the [0048] resilient member 87 is a shock cord. Alternative means to permit the folding and biasing together of the tube segments 80-84 can be also used, such as using a separate tension spring means at each joint 30.
FIGS. 5[0049] a, 5 b and 6 illustrate a block 21 that is used to extend the length of the stringers 51-58. The block 21 has inner and outer cylindrical faces 22 and 23 respectively and opposing planar ends 24, 24′. A fixture 25 on the outer surface is provided for fastening eight blocks 21 (e.g. by a length of chord 26) being one block for fitting to each of the eight stringers 51-58. FIG. 6 illustrates a joint 30′, which for example is formed between tube segments 80 and 81, the joint being like joint 30 (FIG. 4) but preferably having a longer spigot 85 to provide a more substantial extension. For convenience, the joints 30′ are positioned toward one one of the kayak, with the ends of the stringers 51-58 being colour coded to ensure their correct orientation. The block 21 is captured between the annular face 180 and the annular shoulder 181 and held in position by the tension in the resilient member 87 which biases the segments together. The inner face 22 is complementary to the outer cylindrical face of the spigot 85 and the block is installed with the fixture 25 on the inner side of the framework, opposing the skin 3.
Referring to FIGS. 7, 8 and [0050] 8 a, the end connector 40 is fitted to opposing ends of each stringer 51-58 (and to one end of stringers 59 and 60) for releasable engagement with the bow member 1 and stem member 2. The members 1, 2 include slots 63 to receive the end connectors. The connector 40, includes a transversely elongated head 41 fixed to a cylindrical stem 42, the head 41 and stem 42 are sized to enter the slot 63, whereby rotating the connector 90 degrees makes the connection in the known manner. Alternatively other releasable connection means may also be employed.
FIGS. 9[0051] a and 9 b illustrate the mounting and fastening of the seat 90. The seat body is closed-cell foam construction, and includes two longitudinal sleeves (not shown) that receive the stringers 54, 55. Two attachment webs 93 are fixed to a lower part of the seat 90 each having a buckle 94 fixed thereto for engagement with a footrest assembly 95. The footrest assembly 95 comprises a transversely extending strap 97 which is looped around opposing pairs of stringers 51, 53 and 58, 56 and supports a tubular cushion 98. Opposing sides of the strap 97 are connected by longitudinally extending joining webs 96 to the respective buckles 94 fixed to the seat. It will be appreciated that with this arrangement the longitudinal load caused by the kayaker bracing his feet against the footrest assembly reacts directly against the seat 90, rather than tending to move the seat longitudinally.
Referring to FIGS. 10 and 11, the flexible [0052] longitudinal tension members 73, 74 are connected between the bow member 1 and stern member 2. The tension members 73, 73 are readily attachable to the bow and stem members 1, 2 by means of a hook and eye type connector (not shown). The tension members 73, 73 are preferably made from webbing material, but other suitable material may also be used. The tension members 73, 73 include a buckle 77 or a ratchet type device (not shown) of a known type for manually tensioning and maintaining the tension in the members 73, 74. The tension members 73, 74 sit in guides 70, 71 in each former 10-13 which separate the two tension members 73, 74. Instead of requiring the stringers 51-58 to take a tensile load, as in the prior art, the use of separate tension members 73, 74 permits a weight saving with respect to the prior art devices.
The [0053] formers 10 and 13 are fixed to the bow and stern members 1 and 2 respectively by two lockable web and buckle devices 76. Manually moving the formers 10 and 13 toward their respective ends of the kayak 100 acts to expand the framework 20 by spreading the attached stringers 51-58. The formers may then be locked in position by the locking means 76 when the framework 20 is fully expanded. Preferably the web and buckle device 76 includes quick release buckle type connector, allowing for adjustability and allowing it to be manually tensioned. Other known means of applying a tension to bias the formers 10, 13 toward the bow and stem members 1 and 2, for example a pulley member having a cam-type lock, may also be employed.
To assemble the [0054] kayak 100, the stringers 51-60 are unfolded and the segments 80-84 connected together. The bottom stringers 54, 55 are entered through the sleeves 91, 92 to fix the seat 90. The stringers 51-60 are then fixed to the bow member 1 and stem member 2 by connectors 40. Next the tension members 73, 74 are connected between the bow member 1 and stem member 2, and the stringers 51-58 are spread apart laterally while the tension in the tension members 73, 74 is increased. This tensioning action acts to shorten the length of the framework 20 sufficiently for it to be inserted into the skin 3. With the zippers 6 and 7 released, the bow of the framework 20 may be inserted into the skin 3, which is then pulled over the stem of the framework 20, or vice versa. Once the skin 3 is correctly positioned the load in the tension members 73, 74 is relaxed, allowing the framework 20 to expand lengthwise and the joints 30′ are opened sufficiently to insert the blocks 21 to further expand the framework and tension the skin. The tension members 73, 74 are then adjusted to limit the rocker of the kayak.
To complete the assembly, the [0055] end formers 10, 13 are clipped to the stringers 51-58 and pushed toward the bow and stem respectively, thereby expanding the framework 20 and the end formers 10, 13 are then fixed by the web and buckle devices 76. The formers 11, 12 are then inserted and all the stringer 51-58 are connected to them, in the manner previously described. The fore and aft deck stringers 59, 60 are then fastened. The straps (not shown) fixed to the skin for tensioning it laterally are connected to the formers 11 and 12. The seat 90 is inserted and made fast with the buckles 94, 95. After closing the zippers 6, 7 and fastening the joins 31, 32 in the coaming 33, the straps 35-0 months are tightened, stretching the skin 3 of the lower surface and the assembly is complete.
Disassembly may be performed in the reverse order to that given above. The stringers [0056] 51-60 are folded, with the segments 80-84 side-by-side, the skin 3 is also readily folded. The two smaller formers 10 and 13 nest within the larger formers 11 and 12 and the complete kayak is thus collapsed into a compact bundle, weighing less than ten kilograms.
The preferred embodiment of the invention disclosed herein is in the form of a single person kayak. It should be understood however that the invention could be applied to various watercraft, including for example a double kayak or a multi-hulled craft. It should also be appreciated that the invention is not limited to the specific hull shape illustrated herein, and that hulls of other known shapes may also be produced. Also, a greater or lesser number of formers [0057] 10-13 or stringers 51-60 may be used, and the number of segments in each stringer 51-60 may also vary.
Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof. [0058]

Claims

What I claim is:

1. A collapsible kayak having an internal framework and a hull, the hull comprising a water impermeable flexible skin, the framework comprising:

bow and stern members;

a plurality of stringers connected between the bow and stern members and running the length of the bottom and sides of the kayak, each stringer being assembled from a plurality of elongate segments;

2. A collapsible kayak as claimed in claim 1 wherein each end former is positioned near a longitudinal end of the framework and said fixing means comprises an adjustable tension device connected between each end former and a respective bow or stern member.

3. A collapsible kayak as claimed in claim 1 wherein each joint between adjacent segments of a stringer includes:

a hollow axial spigot fixed at the end of a first segment;

an axial recess at the end of a second segment for telescopically receiving the spigot, and

a resilient member extending through the first and second segments for retaining the segments together.

4. A collapsible kayak as claimed in claim 3 further including locking means for engagement at the joint between adjacent first and second segments to lock the first and second segments in a telescopically extended position.

5. A collapsible kayak as claimed in claim 4 wherein a block is provided for insertion between annular faces on the first and second segments respectively to lock the first and second segments in a telescopically extended position, the block comprising an elongate cylindrical face for engagement with the outer surface of the spigot and longitudinally opposing ends for abutting each of the annular faces.

6. A collapsible kayak as claimed in claim 3 wherein the resilient member extends through each said joint and opposing ends of the resilient member are fixed to respective terminal segments of the stringer.

7. A collapsible kayak as claimed in claim 1 wherein each former is slidably connected with the stringers allowing the longitudinal position thereof to be varied.

8. A collapsible kayak as claimed in claim 1 wherein the formers include segment-shaped connectors for connection with the stringers, each connector having a cylindrical inner surface for engagement with a corresponding outer surface of the stringers, whereby the opening at the mouth of the connector is less than the diameter of the stringer allowing the stringer to be entered thereinto in the radial direction and retained by a snap-fit.

9. A collapsible kayak as claimed in claim 1 wherein single piece resilient bow and stem members are releasably connectable with the stringers.

10. A collapsible kayak as claimed in claim 1 wherein the framework further includes at least one forward deck stringer and at least one aft deck stringer supporting a deck of the kayak.

11. A collapsible kayak as claimed in claim 10 wherein said forward deck stringer is connected to the bow member and terminates proximate a forward end of a cockpit opening and said aft deck stringer is connected to the stem member and terminates proximate an aft end of the cockpit opening.

12. A collapsible kayak as claimed in claim 1 wherein the cockpit opening has a coaming formed from the material of the skin, a rim of the coaming comprising a sleeve for receiving a removable coaming-reinforcing rod.

13. A collapsible kayak as claimed in claim 1 wherein the framework includes two pairs of identical formers spaced in the longitudinal direction, the first pair comprising slidably fixed bow and stem end formers, the second pair comprising cockpit formers fixed either side of a cockpit opening.

14. A collapsible kayak as claimed in claim 13 wherein the cockpit formers define the maximum lateral dimensions of the framework and in the disassembled state a bow or stern end former can be nested inside each cockpit former.

15. A collapsible kayak as claimed in claim 1 further including at least one flexible longitudinal tension member connected between the bow and stem members for taking tensile loads induced by bending about an axis perpendicular to a longitudinal axis of the kayak.

16. A collapsible kayak as claimed in claim 15 including two longitudinal tension members, each being symmetrically held in locating fixtures in the formers on either side of the longitudinal axis.

17. A collapsible kayak as claimed in claim 13 wherein the skin includes longitudinally extending closures extending between the forward end of the skin and the cockpit opening, and the aft end of the skin and the cockpit opening respectively.

18. A collapsible kayak as claimed in claim 13 wherein straps fixed to at least the cockpit formers are provided for laterally tensioning the skin.

19. A collapsible kayak as claimed in claim 15 further including at least one block for insertion in the joint between adjacent first and second segments to fix the first and second segments in a telescopically extended position.

20. A collapsible kayak as claimed in claim 1 wherein the kayak may be collapsed into a bundle of a pre-determined size adapted to be readily carried in a backpack.

21. A collapsible kayak as claimed in claim 20 wherein the maximum linear dimension of the bundle is less than 1 metre and the weight of the bundle is less than ten kilograms.

22. A collapsible kayak having an internal framework and a hull, the hull comprising a water impermeable flexible skin, the framework comprising:

bow and stem members;

a plurality of stringers connected between the bow and stem members and running the length of the bottom and sides of the kayak, each stringer being assembled from a plurality of elongate segments, each joint between adjacent segments of a stringer including: a hollow axial spigot fixed at the end of a first segment; an axial recess at the end of a second segment for telescopically receiving the spigot; a resilient member extending through the first and second segments for retaining the segments together, and locking means for locking the first and second segments in a telescopically extended position;

at least one of said formers being an end former slidably connected with each stringer for laterally spreading the stringers;

fixing means for fixing each end former longitudinally with respect to the stringers, and

at least one flexible longitudinal tension member connected between said bow and stem members for taking tensile loads induced by bending about an axis perpendicular to a longitudinal axis of the kayak.