Strake Structure and Method for Building Bonded Lapstrake Boats

Abstract

An improved method for building a lapstrake boat 240 includes an improved strake structure 152 having a wide rabbet 182 running the length of said strake's lower edge 164 and inside face and having a selected rabbet width which defines a joint overlap region with a bond receiving gap 210. The strake's rabbet width is preferably three times the plank's thickness 180 along most of its length but may taper. A plurality of temporary tie receiving holes 220 are bored through the thickness of the strake, and entirely within the rabbet segment of the strake for coaxial alignment with adjacent holes 224 in the adjacent strake. Adjacent strakes 150, 152 are aligned and tied together so that the wide rabbet segment 182 in the bottom edge of one adjoining strake 152 overlaps and is tied to a selected surface area on the outside face of the adjoining strake 150.

Description

This application is a continuation of and claims priority to International Application No. PCT/US2014/061713, filed on Oct. 22, 2014, entitled “Improved Strake Structure and Method for Building Bonded Lapstrake Boats,” which claims priority from U.S. Provisional Application No. 61/894,300, filed Oct. 22, 2013, entitled “Improved Strake Structure and Method for Building Bonded Lapstrake Boats”, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates, in general, to methods for building boats, and more specifically to the construction of lapstrake planked boat hulls and to improved methods of construction of such hulls.

Discussion of the Prior Art

Traditional methods for building wooden boats include a procedure known as lapstrake planking, a method which has been used for thousands of years. Like most wooden boats, lapstrake boats are built of planks, or strakes, which comprise the boat's hull. In lapstrake construction, each strake overlaps and is fastened to the outside face of the strake below. In other planking methods, the strakes are joined edge-to-edge, But many boat builders favor the lapstrake method of building because it results in a boat that is less expensive and faster to build than one built with other traditional methods. Many boat owners also favor lapstrake construction for its aesthetic qualities, light weight, and lower construction costs. In addition, lapstrake hulls are known to deflect water downward and thereby provide a “drier ride” than other hull types.

Lapstrake boat hulls are most often built over a strongback and molds as illustrated in commonly owned U.S. Pat. No. 6,142,093, entitled “Method For Building Lapstrake Boats”, the entire disclosure of which is hereby incorporated herein by reference. The “strongback” is a frame to which are attached molds that define the cross-sectional shape of the hull. This frame and mold structure forms the upside down shape of the hull. In this method, individual strakes are shaped so as to cover the molds and then the strakes nearest the keel are attached to the molds. A bevel, or angle, is cut in the edge of each strake and the next adjacent strake is attached to the first using mechanical fasteners and/or glue. The remaining strakes are sequentially attached in this manner until the hull is completed. Upon completion of planking, the hull is removed from the frame. Permanent frames, bulkheads, and other components may be incorporated into the molds and are removed from the strongback frame as part of the hull. Alternately, the frames, bulkheads or other components may be added to strengthen the hull after it is removed from the mold.

There are several disadvantages to the foregoing method:

(a) It is time consuming and costly to construct a strongback and molds for each type of boat built; often, as much time is required to build the strongback and molds as to assemble the hull;

b) The shape of each strake is determined by holding it against the molds. Each pair of planks, one for the port and one for the starboard side, are individually shaped and fit to the molds. This is a time consuming and exacting process demanding substantial skill on the builder's part; and

(c) A rolling, or constantly varying, bevel must be cut in the edge of each of the strakes. This method is time consuming and exacting, and it requires considerable skill on the part of the builder.

An alternate method of lapstrake planking is historically used in the Scandinavian countries. In this method, the hull is built without a strongback and molds; it is built right side up, and the hull shape is established by placing posts under it and by using beams wedged against the ceiling of the workshop to form the strakes. Although this method eliminates the need to build a strongback and molds, it does have other disadvantages, most notably:

(a) It requires a boatbuilder possessing substantial skill, artistry, and experience, since the overall shape of the hull is largely determined by “eye” as it is being built, rather than by the molds;

(b) A rolling, or constantly varying, bevel must be cut or planed into each strake in order to attach the next strake. This is time consuming and exacting, and it requires considerable skill on the part of the builder;

(c) The shape of each strake is determined by eye and must be fitted to the boat without the use of molds to guide the builder. Each pair of planks, one for the port side and one for the starboard side, are individually cut to fit without the aid of the molds. This is also a time consuming process demanding substantial skill on the builder's part; and

(d) In practice, this method limits the hull shapes that can be built.

A more recent method of construction, also illustrated in U.S. Pat. No. 6,142,093, is termed “stitch-and-glue construction,” and also allows building boats without strongbacks and molds. The development of computer boat design programs has made it possible to easily determine the exact shape, or expansion, of each strake, and to cut the strakes prior to building the hull. Both the two-dimensional shape (that is, the shape when the strakes are cut from wood or other flat stock) and the three-dimensional shape (the shape after the strake is bent to form part of the hull) of the strakes can be calculated.

Boats are now built without strongbacks and molds by butting the edges of the strakes and joining them with epoxy fillets and fiberglass reinforced plastic. This technique has the following disadvantages:

(a) The hull is not the lapstrake construction that is favored by many boat builders for reasons of aesthetics as well as for reasons of functionality and economy;

(b) This method demands extensive use of fiberglass and resins, which results in increased cost and increased environmental impact; and

(c) Fiberglass reinforced joints require additional sanding and finishing, particularly if the hull is to be finished with varnish or other clear coating, which many owners desire for aesthetic reasons.

A further refinement of the stitch-and-glue technique, as illustrated in U.S. Pat. No. 6,142,093, involves overlapping the strakes used in a hull design to make a lapstrake boat. In this case, flexible plastic rivets are used to hold the strakes in position, but this method has the following disadvantages:

(a) It is difficult to hold such overlapped strakes in alignment since the forces required in bending and twisting the strakes tot the desired hull shape cause them to slip prior to being bonded. The plastic rivets must flex in order to accommodate the changes in angle between the strakes as the hull is assembled, and this flexibility makes it difficult, if not impossible, to precisely align the strakes;

(b) Given the large number of strakes in some designs, the accumulated error caused by changes, or errors, in each strakes' position may result in hull shapes substantially different than those the designer envisioned;

(c) The rivets must be placed with great precision to assure the most accurate possible alignment of the strakes;

(d) The lack of accuracy in strake alignment limits this method to boats with little bend in the strakes and does not allow designs containing substantial twist in the strakes, such as might be used in powerboats with both flare and tumblehome in the hulls, for example; and

(e) The amount of overlap between the strakes may not be consistent, which is detrimental to the aesthetics of the boat.

Finally, the above-mentioned U.S. Pat. No. 6,142,093 also described and illustrated an improved “stitch and glue” method for use in building a wide range of lapstrake-type boat hulls without requiring a strongback and molds, and without the need to cut bevels on the strakes. This method, the applicant's own LapStitch™ system and method, allowed amateur boatbuilders, working from plans or a kit, to create lapstrake boats with a minimum of skill, time, and effort, as compared to traditional methods. In accordance with the described method, a two-dimensional shape is determined for each strake, using a computer program. Thereafter, the strakes are cut and a narrow rabbet is cut in the lower inside edge of each of the strakes. Holes are drilled in the strakes for receiving temporary ties away from the rabbet Then the hull is assembled without a strongback or molds and adjacent strakes are bound together using temporary ties to secure them for the bonding step.

The self-aligning nature of the narrow rabbet at the strake edge simplified assembly of the hulls with this method, but it was discovered that the narrow edges of the strakes were deformed when the ties were tightened. It was eventually discovered that the lapstrake of the '093 patent was also not as strong as might be needed for some applications, and the method had a limiting effect on the hull shapes which could be made, since the overlapping rabbet area of the strake, where an adhesive or a bonding agent is to be applied, was suited to making only convex hull shapes.

There is a need, therefore, for an improved strake structure and an improved method for building lapstrake boats.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to overcome the above mentioned difficulties by providing an inexpensive, practical and easy to assemble strake structure and an improved method for building lapstrake boats.

Briefly, and in accordance with the preferred forms of the present invention, an improved method for building a lapstrake boat includes a lapstrake structure having a wide rabbet running the length of the lower edge and inside face of the strake and having a selected rabbet width which defines a joint overlap region. The width of the rabbet is preferably three times the plank's thickness. Also preferably, a plurality of pairs of spaced temporary tie-receiving holes is bored through the thickness of the strake, with the bores extending entirely within the rabbet segment of the strake. Adjacent strakes are tied together so that the wide rabbet segment in the bottom edge of one adjoining strake overlaps and is tied to a corresponding aligned surface area on the outside face of the adjoining strake.

More specifically, the present invention is directed to an improved method for building lapstrake boats which includes determining the two-dimensional shape of strakes, or planks, of a desired boat design. Each of the planks has a top edge, a bottom edge, an inside face and an outside face separated by a plank of the thickness required to build the boat. The strakes are then cut, or fabricated, to the desired shape, and a rabbet is cut along the length of the lower edge and inside face of each strake, with the exception of the bottommost strake on each side. The rabbet width is selected to be at least twice as wide as the plank's thickness. First and second spaced, temporary tie receiving holes are drilled or bored through the thickness each strake, with at least one of the holes being located in the rabbet of the strake.

The strakes are then positioned together so that a portion of the upper edge of one strake, which does not contain the rabbet, and a portion of its outside face fits into and is in contact with the rabbet in the bottom edge of an adjoining strake in such a manner that a portion of the strake adjacent to the rabbet overlaps the outside face of its adjoining strake and the angle between the adjacent strakes is between 30 and 180 degrees. The adjoining strakes are tied to one another with plastic or wire temporary ties, and are bonded together using a cementitious matter, whereby strakes are attached to adjacent strakes to form a boat hull.

In accordance with the invention, the strakes may be cut from wood such as plywood panels or fabricated from plastic panels and bonded by a material such as epoxy. The hull so formed may be completed by adding transoms, frames, stringers, and bulkheads as needed. The assembled hull formed in accordance with the foregoing method may be configured to include both convex and concave cross sectional shapes, and may include a reverse curve in the section.

In accordance with the invention, an improved strake structure for use when building a boat hull may consist of an elongated strake or plank having a top elongated edge opposite a bottom elongated edge, and an inside face and outside face separated by a plank thickness, At the intersection of the strake's lower edge and inside face, a rabbet segment running the length of the strake's lower edge and inside face is defined, the rabbet segment having a selected rabbet width and a selected rabbet segment thickness, the rabbet width being at least twice (and preferably 3 times) as wide as the plank's thickness. The rabbet segment preferably includes a plurality of pairs of temporary tie receiving holes through the thickness of the rabbet segment.

Compared to the structure and method of U.S. Pat. No. 6,142,093, the improved strake structure and method of the present invention provides three significant advantages, namely:

A. INCREASED STRENGTH. The essence of the improved system and method is a machined rabbet on the lower, inside edge of adjoining planks. This rabbet allows the boatbuilder to assemble and align precisely-precut hull planking and faithfully to recreate the desired hull shape without resorting to a traditional rigid mold. In the assembled hull, the rabbet creates a deliberately wide seam, which is filled with marine-grade epoxy to bond one plank to the next. The rabbet width controls how much epoxy may be applied, and thus ultimately the strength of the joint. At the time of the U.S. Pat. No. 6,142,093 patent filing, and for some years thereafter, the rabbet width was set at 1.5 times the thickness of the planking. (For example, the rabbet width for a boat with ¼-inch planking would be ⅜-inch.) As applicant's company, CLC, developed larger and more sophisticated LapStitch™ designs, stronger LapStitch™ joints were required. After much experimentation, applicant discovered that a rabbet width of 3 times the hull thickness provides larger margins of strength and is more forgiving to amateur boatbuilders.

B. STITCHING WIRE PLACEMENT. Wire stitches are used to hold LapStitch™ hulls together temporarily while the epoxy is applied. In U.S. Pat. No. 6,142,093 and most subsequent hulls, the wire stitch encircles the rabbet, forcing adjoining planks together and holding them in position while the epoxy is applied and until the epoxy cures. As applicant increased the width of the rabbet as described above, a wire stitch that encircles the entire rabbet was seen to distort the thin edge of the plank. By shifting the location of the computer-cut wire holes to be contained entirely within the rabbeted area, the possibility of distortion is removed and the wire stitches actually do a better job of aligning and holding adjacent planks.

C. ACCOMMODATION OF REVERSE CURVE IN HULL SECTIONS. The LapStitch™ method as defined in U.S. Pat. No. 6,142,093 is effectively limited to hulls with convex sections. To allow hulls with reverse curve (e.g., concave) segments in the sections, the LapStitch™ joint method in accordance with the present invention transitions from a rabbeted cross-section to a conventional stitch-and-glue cross-section. The length of the transition is related to how quickly the hull sections shift from convex to concave.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, particularly when taken in conjunction with the accompanying drawings, wherein like reference numerals in the various figures are utilized to designate like components, and wherein:

FIGS. 1A, 1B, 2, 3, and 4 illustrate prior art (traditional) methods and structures for constructing the hulls of lapstrake boats;

FIG. 5 illustrates prior art lapstrake joints having enlarged rabbet joints for use in constructing the hulls of boats;

FIG. 6 illustrates a hull assembly constructed using ties, in accordance with applicant's own prior art method;

FIG. 7 illustrates deformation caused by the use of the ties of FIG. 6, in accordance with applicant's own prior art method;

FIG. 8A illustrates an improved strake structure and paired hole rabbet embodiment of the tie joint construction of the present invention prior to the application of a bonding material;

FIG. 8B illustrates another improved strake structure and a single-hole rabbet embodiment of the tie joint construction of the present invention prior to the application of a bonding material;

FIG. 9 is a plan view of multiple planks for use in the assembly of a lapstrake hull, in accordance with the present invention;

FIG. 10 is an enlarged view of a plank for the hull of FIG. 9, in accordance with the present invention;

FIG. 11 illustrates a hull incorporating the an improved strake structures of FIGS. 8A and 8B configured to provide convex and concave curvatures, in accordance with the present invention;

FIG. 12 is an enlarged view of an improved plank for use in making the hull of FIG. 11; and

FIG. 13 is a pictorial illustration of a completed improved hull structure having convex and concave curvatures and configured to support a wine glass shaped transom, in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to a more detailed consideration of the drawings, for purposes of fixing nomenclature, another review of the prior art is provided where FIG. 1A illustrates a conventional lapstrake-type boat hull 20 fabricated on a strongback frame 22 and molds 30 utilizing planks, or strakes 40. As described above, such lapstrake hulls are constructed with each plank overlapping and being fastened to the strake below it. In other planking methods the hull may be formed by joining the planks edge-to-edge. As illustrated in FIG. 1A, one prior art method of fabricating a lapstrake hull is by shaping the strakes to fit the mold, with the bottommost plank 42 being connected at its bottom edge 44 to the mold or to a keel and with its upper edge 46 being beveled at an angle to fit the slope of the next adjacent plank 48. This next adjacent plank is angled with respect to plank 42 with its lower edge overlapping plank 42 and its upper edge 50 being beveled to fit the slope of the next adjacent plank 52. This process continues to complete one side of the hull, and a similar process is used to fabricate the opposite side of the hull, with the number of planks and their relative angles being dependent on the size of the hull and the number of planks desired for the construction. Upon completion of planking, the hull is removed from the strongback frame 22. Permanent frame members, bulkheads, and other components may be incorporated into the molds for removal from the strongback frame as parts of the hull. Alternatively, the frames, bulkheads or other components may be added to strengthen the hull after it is removed from the mold.

A more recent method of construction, illustrated in FIG. 2, is termed “stitch-and-glue construction,” and allows building boats without strongbacks and molds. The development of computer boat design programs has made it possible to easily determine the exact shape, or expansion, of each of the strakes, such as strakes 60, 62 and 64, and to cut them prior to building the hull. Both the two-dimensional shape (that is, the shape when the strakes are cut from wood or other flat stock) and the three-dimensional shape (the shape after the strake is bent to form part of the hull) of the strakes can be calculated. These boats are built without strongbacks and molds by butting the edges of the strakes as at 66 and 68 and joining them with epoxy fillets 70 and 72, and covering the joints with fiberglass reinforced plastic, as at 74 and 76.

A further refinement of the stitch-and-glue technique, as illustrated in FIG. 3, involves overlapping the strakes used in a hull design to make a lapstrake boat, without beveling the edges. Instead the strakes, such as strakes 80, 82 and 84 are assembled and held in position by flexible plastic rivets 86 and 88 and the joints are then bonded, as by epoxy fillets 90 and 92.

Another prior art method of constructing a lapstrake hull is illustrated in FIGS. 4, 5 and 6 and is described in detail in the above-mentioned U.S. Pat. No. 6,142,093. This method is an improved “stitch and glue” method for use in building a wide range of lapstrake-type boat hulls without requiring a strongback and molds, and without the need to cut bevels on the strakes.

This method, known as the LapStitch™ system and method, allows amateur boatbuilders, working from plans or a kit, to create lapstrake boat hull, such as that illustrated at 98 in FIG. 6, with a minimum of skill, time, and effort, as compared to traditional methods. In accordance with that described method, a two-dimensional shape is determined for each strake, such as the illustrated strakes 100, 102 and 104, using a computer program. Thereafter, the strakes are cut and narrow rabbets 106, 108 and 110 cut in the lower inside edges of each of the strakes. Holes are drilled in the strakes, away from the rabbets, for receiving temporary ties 112. Then the hull is assembled as illustrated in FIG. 6 without a strongback or molds by placing the top edges 116 and 118 of strakes 100 and 102 in the corresponding rabbets 108 and 110 in the bottom edges 120 and 122 of their next adjacent strakes 102 and 104, respectively, to hold the strakes in alignment. The adjacent strakes are bound together using the temporary ties 112 to secure them for the bonding step, wherein a suitable glue such as epoxy 124 is applied at each joint. The self-aligning nature of the narrow rabbet at the strake edges 116, 118 (FIG. 4) simplifies assembly of the hull with this method, but it was discovered that the narrow bottom edges of the strakes at the locations of the rabbets were deformed when the ties were tightened. This deformation was particularly evident in the version of the foregoing rabbet design illustrated in FIG. 5, wherein similar numbers are applied to elements common to prior Figures. In this embodiment, the rabbets illustrated at 130, 132 and 134 are elongated, with their length being two or preferably three times the thickness of the plank. As illustrated in FIG. 7 by the dotted lines 140 and 142, the wire ties 112, which are also referred to as stitches, tend to cause the ends of the bottom edges of the planks where the rabbets are formed when the ties are tightened to secure the planks before the epoxy is applied to the joints. Furthermore, it was eventually discovered that the lapstrake of the '093 patent was also not as strong as might be needed for some applications, so that the applicant's prior art method as illustrated in FIGS. 4-6 had a limiting effect on the hull shapes which could be made, since the overlapping rabbet area of the strake, where an adhesive or a bonding agent 120 is to be applied, was suited to making only convex hull shapes.

In accordance with the present invention, as illustrated in FIGS. 8A-13 to which reference is now made, an improved strake structure for use when building an improved boat hull of a type resembling those in FIGS. 1, 6 and may consist of a plurality of improved elongated strakes or planks such as the planks 150, 152 and 154 illustrated in FIG. 8A, each plank having a top elongated edge 156, 158 and 160, respectively, opposite a corresponding bottom elongated edge 162, 164 and 166, and each having an inside face 170 and an outside face 172 separated by a plank thickness (e.g., six millimeters) indicated by arrows at 180, at the intersection of each strake's lower edge and inside face, with the exception of the bottommost strake 150, a rabbet segment such as that illustrated at 182 and 184 for planks 152 and 154 runs substantially the entire length of the strake's lower edge, depending on the hull design. Each rabbet segment has a selected rabbet width and a selected rabbet segment thickness, the rabbet width (or vertical distance as viewed in FIG. 8A) being at least twice, and preferably the times, the plank's thickness 180 (or twelve to eighteen millimeters for a plank or strake thickness of six millimeters).

In accordance with the present invention, the boat hull is designed and drawn in the conventional manner, with a plurality of strakes forming the port and starboard sides as illustrated at 200 in FIG. 9. The three-dimensional shape of each strake is redrawn to show the two-dimensional shape, or expanded shape of the strake. This may be done using a known computer aided design program or panel expansion drafting technique. Many commercial boat-design computer programs include panel expansion features that allow the designer or builder to quickly determine the two-dimensional shape of the strakes, and most builders would choose to use one of these programs.

Each improved strake of the present invention (e.g., strakes or planks, 150, 152 and 154 of FIG. 8A) is cut out from wood, plywood (e.g., 6 mm thick Okoume marine grade plywood), plastic or another sheet material according to two-dimensional templates or dimensions gained from the computer design program or panel expansion drafting. The strake may be cut using conventional methods such as a handheld saw, band saw, or router. A computer numerical control router, computer numerical control laser cutter, or other method may also be used to cut the strake. Unlike traditional lapstrake construction, all strakes may be cut prior to beginning assembly.

A rabbet, such as rabbets 182 and 184 for strakes 152 and 154, is cut at the intersection of the corresponding bottom edges and the inside faces of each (but the bottom) strake, as illustrated for strake 152 in FIG. 10. The rabbets may each be cut at an angle of 90 degrees to the face and edge of the strake as illustrated in the Figures. Alternatively, the rabbet may be cut at an angle of other than 90 degrees to the face and edge of the strake to reduce the gaps in the joints 210, 212 between the adjoining strakes illustrated in FIG. 8A. The rabbet may be cut with a handheld router, table saw, hand rabbet plane, power jointer, computer numerical control router, or other cutting tool. This rabbet replaces the bevel used in traditional lapstrake construction and a bevel is not cut.

To assemble the hull, each strake, such as strake 150, is fastened or clamped to a second adjacent strake, such as strake 152, as illustrated in FIG. 8A, so that a portion of a top edge and a portion of an outside face of a first strake fits into the corresponding rabbet in the bottom of the next adjoining strake to hold the strakes in alignment. Temporary ties 112 of wire or plastic as described above, or another mechanical fastener, is used to hold the strakes together. As illustrated in FIGS. 8A and 9, if a temporary tie 112 is to be used, an aligned pair or series of holes 220, 222 (see FIG. 10) is drilled along the rabbet 182 in each strake, and a corresponding aligned pair or series of holes 224, 226 is drilled along the top of each strake, below its top edge 158 where the lower strake is overlapped by the next above strake, with the holes 220 and 224 and the holes 222 and 226 being aligned to receive the temporary ties. These ties are inserted through the corresponding holes in adjacent strakes in such a way as to join them. The ties are twisted or locked so as to hold a portion of top edge and outside face of one strake firmly in the overlapping rabbet of the adjoining strake. The fasteners must allow the strakes to flex at the joint, as the shape of the hull may change as it is being assembled and additional strakes are added.

An alternative embodiment is illustrated in FIG. 8B which illustrates a single-hole rabbet embodiment of the tie joint construction of the present invention prior to the application of a bonding material. Applicant has discovered, through experimentation that relocating even one wire holes internal to the rabbet comprises a substantial improvement over applicant's prior structure and method (as shown in FIG. 4). The embodiment of FIG. 8B has been determined, through development work, to be more suitable for certain hull shapes, because the embodiment of FIG. 8A has some technical limitations. The single hole embodiment of FIG. 8B has only one stitch hole internal to the rabbet, but applicant's development work has shown that the resulting hull structure is improved dramatically over the prior art.

The single hole embodiment of FIG. 8B also provides an improved strake structure for use when building a lapstraked boat hull of the type described above and illustrated, for example in FIGS. 1, 6 and may consist of a plurality of elongated strakes or planks such as the planks 350, 352 and 354 illustrated in FIG. 8B, each plank having a top elongated edge 356, 358 and 360, respectively, opposite a corresponding bottom elongated edge (e.g., 364 and 366), and each having an inside face 370 and an outside face 372 separated by a plank thickness (e.g., six millimeters) indicated by arrows at 180, At the intersection of each strake's lower edge and inside face, with the exception of the bottommost strake 350, a rabbet segment such as that illustrated at 382 and 384 for planks 352 and 354 runs substantially the entire length of the strake's lower edge, depending on the hull design. As above, each rabbet segment has a selected rabbet width and a selected rabbet segment thickness, the rabbet width (or vertical distance as viewed in FIG. 8B) being at least twice, and preferably the times, the plank's thickness 180 (or twelve to eighteen millimeters for a plank or strake thickness of six millimeters).

As above, the boat hull is designed and drawn in the conventional manner, with a plurality of strakes forming the port and starboard sides as illustrated at 200 in FIG. 9. The three-dimensional shape of each strake is redrawn to show the two-dimensional shape, or expanded shape of the strake. Each strake (such as the strakes, or planks, 350, 352 and 354 of FIG. 8B) is cut out from wood, plywood, plastic or another sheet material according to two-dimensional templates or dimensions gained from the computer design program or panel expansion drafting. The strake may be cut using conventional methods such as a handheld saw, band saw, or router. A computer numerical control router, computer numerical control laser cutter, or other method may also be used to cut the strake. Unlike traditional lapstrake construction, all strakes may be cut prior to beginning assembly.

A rabbet, such as rabbets 382 and 384 for strakes 352 and 354, is cut at the intersection of the corresponding bottom edges and the inside faces of each (but the bottom) strake, in the same manner as illustrated for the two-hole embodiment strake 152 illustrated in FIG. 10. The rabbets may each be cut at an angle of 90 degrees to the face and edge of the strake as illustrated in the Figures. Alternatively, the rabbet may be cut at an angle of other than 90 degrees to the face and edge of the strake to reduce the gaps in the joints (e.g., in the same manner as for gaps 210, 212 between the adjoining strakes illustrated in FIG. 8A).

To assemble the hull from single hole strakes as in FIG. 8B, each strake (e.g., strake 350), is fastened or clamped to a second adjacent strake, (e.g., strake 352, as illustrated in FIG. 8B), so that a portion of a top edge and a portion of an outside face of a first strake fits into the corresponding rabbet in the bottom of the next adjoining strake to hold the strakes in alignment. Temporary ties 112 of wire or plastic as described above, or another mechanical fastener, are threaded through the aligned holes in the juxtaposed planks and are then tensioned and tied to hold the strakes together. As illustrated in FIGS. 8B and 9, if a temporary tie 112 is to be used, the juxtaposed planks, when properly positioned coaxially align the tie-receiving through bores or holes so rabbet hole 220 (see FIG. 8B) is drilled at a selected locations along each rabbet (e.g., 382) in each strake, and a corresponding aligned hole 224 is drilled along the top of each strake, below its top edge (e.g., 356, 358) where the lower strake is overlapped by the next above strake, with the holes 220 and 224 being aligned to receive the temporary ties 112. These ties are inserted through the corresponding through-bores or holes in adjacent strakes in such a way as to join them. The ties are tensioned and then twisted or locked so as to hold a portion of top edge and outside face of one strake firmly in the overlapping rabbet of the adjoining strake. The ties (or other fasteners) must maintain alignment and structural integrity of the hull structure during assembly and during the duration of the epoxy curing, but must initially allow the strakes to flex at the joint, as the shape of the hull may change as it is being assembled and additional strakes are added.

One or more frames or bulkheads, or a transom such as that illustrated at 230 in FIG. 6, or other interior components may be inserted in the assembled hull, as needed, to bring the strakes to, and maintain the strakes in, the desired shape. The shape of the boat hull 200, or a similar object being built, and the stiffness of the strakes, will determine the number and location of frames, bulkheads, or other internal members.

The strakes are permanently joined with epoxy or another bonding agent or cementitious material, as described above and illustrated with respect to FIG. 5. This epoxy or other cementitious material fills any gap between the rabbet and the adjoining strake, making a strong, stiff bond. The epoxy or other cementitious material may be injected into the rabbet using an epoxy syringe or other device, or it may be poured into the rabbet of an upside down hull. When the epoxy or cementitious material has solidified, the ties or other fasteners may be removed and the boat may be painted or varnished.

Tests of the breaking strength of the strake joint made as described above show that it is as strong as a joint made with traditional lapstrake construction methods.

In accordance with the present invention, the improved strake has a significantly wider rabbet segment (e.g., eighteen millimeters) proximate one of the strake's edges, and the width of the rabbet segment is preferably at least three (3) times the thickness of the strake or plank (e.g., six millimeters, or three times the hull thickness) and first and second through bores are preferably arrayed within the rabbet segment at a selected spacing from the bottom edge and, when assembled with another strake, are in alignment with corresponding through bores in the adjacent strake to receive wire or plastic temporary ties. This improved method for building lapstrake boats requires no strongback or and mold, and requires no cut bevels on the strakes. The two-dimensional shape of each elongated plank or strake is determined and the strakes are cut to these shapes. A wide groove, or rabbet, is cut in the bottom inside edge of each strake, excepting only the bottom strake, and the rabbet may be shaped or tapered as needed to conform to the desired shape of the hull. The strakes are fastened or clamped so the top edge of each plank fits into the wide rabbet in the bottom of the adjacent strake to hold the strakes in alignment. The joints are filled with epoxy or other cementitious material making a strong stiff bond. One or more frames, bulkheads, or other interior components may be inserted as needed to maintain the strakes in the desired shape.

Compared to the structure and method of commonly owned U.S. Pat. No. 6,142,093, the improved strake structure and method of the present invention provides increased strength. The machined rabbets on the lower, inside edges of adjoining planks are made wider than prior art structures to allow the consumer or boatbuilder to assemble and align precisely-precut hull planking and faithfully recreate the desired hull shape as illustrated at 200 in FIG. 9 without resorting to a traditional rigid mold. In the assembled hull, the wider rabbet overlap defining joints such as those illustrated at 210 and 212 create deliberately wide seams, which are filled with marine-grade epoxy to bond one plank to the next, once the ties are tightened. The rabbet width controls how much epoxy may be applied, and thus ultimately the strength of the joint. A rabbet width of 3 times the hull thickness provides larger margins of strength and is more forgiving for amateur boatbuilders.

Elongated flexible plastic or wire ties or stitches 112 are used to hold the hull together temporarily while the epoxy is applied. In commonly owned U.S. Pat. No. 6,142,093 and most subsequent hulls, the wire stitch encircles the rabbet (as shown in FIGS. 4, 5 and 7), forcing adjoining planks together and holding them in position while the epoxy is applied and until the epoxy cures. By shifting the location of the spaced computer-cut wire holes to be contained entirely within the rabbeted area of the plank, the possibility of distortion is removed and the wire stitches actually do a better job of aligning and holding adjacent planks.

As noted above, the plank structure and assembly method of commonly owned U.S. Pat. No. 6,142,093 effectively limits available hull shapes to those with only outwardly bulging or convex sections. To allow hulls such as that illustrated at 240 in FIG. 11 to be constructed with reverse curve (e.g., concave) segments 242 in the sections, in accordance with the method of the present invention, and as illustrated by strake 250 in FIG. 12, the width of the LapStitch™ or rabbet overlap joint area 252 varies and tapers along the length of selected planks and transitions from a rabbeted cross-section at 256 to a conventional stitch-and-glue cross-section at 258. The length of the transition is related to how quickly the hull sections shift from convex to concave, as shown at 242 in the wine-glass shaped transom of boat 240 illustrated in FIG. 11, and in the pictorial photograph of FIG. 13.

In accordance with the method and improved strake structure (e.g., 150, 152 or 350, 352) of the present invention, when making the concave and convex hull shapes illustrated in FIG. 13, the improved strake rabbet extends along a portion of the length of a strake (as seen in FIG. 12) and the rabbet is configured in the strake to provide a reverse curve for use in concave segments in the hull, and the width of a rabbet overlap joint area defined between adjacent strakes varies and tapers along the length of selected strakes or planks and transitions from a rabbeted cross-section to a conventional stitch-and-glue cross-section. When making a hull with concave and convex external surfaces, the length of the rabbet transition is related to how quickly the hull sections shift from convex to concave and can be used to provide hull shape which snugly receives and supports a wine-glass shaped boat hull transom 315 (as best seen in FIG. 13).

Persons of skill in the art will appreciate that the method of construction of the invention allows an improved and economical method of constructing lapstrake wooden boats. Boats constructed using this method may be completed in substantially less time and require less skill to construct than those built using prior methods; and proper alignment and overlap of the strakes comprising the hull is assured.

While this description contains many exemplary specifics, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of preferred embodiments. Many other variations are possible. For example, the method and system of the present invention can be adapted for use in building (a) Bow roofs or panels on barns and other buildings and structures, (b) Barrels and water tanks, and (c) Decorative furniture such as boat-shaped baby cradles. In broad terms, the method of the present invention can be used to build such structural members by joining adjacent planks in a structure. The method would include the following method steps:

(a) providing first (e.g., 150 or 350) and second (e.g., 152 or 352) planks shaped to the design of a desired structure;

(b) cutting a rabbet (e.g., 182 or 382) along a bottom edge of each of said first and second planks;

(c) drilling a first array of aligned tie-receiving through bores 224 along a top edge of each of said first and second planks and corresponding second array of aligned tie-receiving through bores 220 through along the rabbet portion of each of said first and second planks;

(d) positioning first and second planks side by side with the top edge of said first plank abutting the rabbet in the bottom edge of said second plank, with said first array of aligned tie-receiving through bores 224 in said top edge of said first plank in coaxial alignment with said corresponding second array of aligned tie-receiving through bores 220 is said rabbet of said plank; and

(e) inserting ties 112 through said coaxially aligned tie-receiving through bores and through said first and second planks to secure said first and second planks in abutting relationship to define a bond receiving gap (e.g., 210 or 212) between said first plank and said second plank's rabbet.

Having described preferred embodiments of a new and improved method and structure, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention.

Claims

1. A method for building lapstrake boats from wood or plastic strakes without use of a strongback or mold comprising the steps of:

(a) providing a design for a lapstrake boat hull with a plurality of strakes forming port and starboard sides;

(b) determining two-dimensional shapes for said plurality of strakes, each said strake having a top edge, a bottom edge, and inside and outside faces separated by a plank thickness;

(c) fabricating said strakes in accordance with said two-dimensional shapes;

(d) cutting a rabbet along the bottom edge and inside face of each said strake in said hull design, with the exception of a bottom strake on each side of said hull, at the intersection of said strake's bottom edge and inside face; said rabbet having a selected rabbet width at least twice as wide as the strake's thickness;

(e) drilling first pairs of spaced temporary tie receiving holes through the thickness of at least a first strake, said first pairs of holes being located in and defined through the rabbet of said first strake;

(f) drilling second pairs of spaced temporary tie receiving holes through the thickness of a second strake, said second pairs of holes being located below the top edge of said second strake in alignment with said first pairs of holes when said first and second strakes are assembled;

(e) positioning said first and second strakes together so that a portion of the top edge and a portion of the outside face of said second strake fits into and is in contact with the rabbet in the bottom edge of said first strake in such a manner that a portion of said first strake adjacent to said rabbet overlaps the outside face of said second strake, adjoining;

(f) binding said first and second strakes to one another with temporary ties passing through corresponding pairs of holes in said first strake rabbet and said second strake top edge; and

(g) bonding said first and second strakes using a cementitious matter, whereby said first and second strakes are attached to each other.

2. The method for building a lapstrake boat hull as in claim 1, wherein bonding adjacent strakes includes applying epoxy.

3. The method for building a lapstrake boat hull as in claim 1, further including adding a transom, frames, stringers, and bulkheads to complete the hull.

4. The method for building a lapstrake boat hull as in claim 1, wherein cutting a rabbet includes cutting it to a width at least three times as wide as the strake's thickness.

5. The method for building a lapstrake boat hull as in claim 1, wherein multiple strakes are positioned together and adjacent strakes are bound together using temporary ties to form sides of said boat hull.

6. The method for building a lapstrake boat hull as in claim 5, wherein fabricating said strakes includes fabricating them from plywood panels.

7. The method for building a lapstrake boat hull as in claim 5, wherein fabricating said strakes includes fabricating them from plastic panels.

8. A method for building a lapstrake boat hull as in claim 5, wherein the step of drawing a lapstrake boat hull with a plurality of strakes forming port and starboard sides includes configuring a desired hull to include both convex and concave cross sectional shapes with a reverse curve in a cross-section, wherein a joint between adjoining strakes transitions from a rabbeted cross-section to a conventional stitch-and-glue cross-section, and wherein the length of the transition is related to how quickly the hull sections shift from convex to concave to provide a hull shape which snugly receives and supports a wine-glass shaped boat hull transom.

9. An improved strake structure configured for building a boat having a lapstrake hull, comprising:

(a) an elongated strake having a top elongated edge opposite a bottom elongated edge;

(b) an inside face and outside face separated by a strake thickness;

(c) a rabbet segment along said strake's lower edge and inside face, said rabbet segment having a selected width from said lower edge and a selected rabbet segment thickness, the rabbet width being at least twice as wide as said strake thickness; and

(d) wherein the rabbet segment includes at least a first array of single tie receiving rabbet holes through the rabbet segment thickness and corresponding pairs of temporary tie receiving holes through the top edge of an adjacent strake.

10. The improved strake structure of claim 9, wherein the rabbet width is at least three times as wide as said strake thickness, and said rabbet segment has a second array of tie receiving rabbet holes spaced from said first tie receiving rabbet holes to provide a plurality of pairs of temporary tie receiving holes through the rabbet segment thickness.

11. The improved strake structure of claim 10, wherein said rabbet extends along the full length of a strake for a convex hull.

12. The improved strake structure of claim 10, wherein said rabbet extends along a portion of the length of a strake for a convex/concave hull.

13. The improved strake structure of claim 9, wherein said rabbet extends along a portion of the length of a strake for a convex/concave hull constructed from a plurality of strakes with reverse curve (i.e., concave) segments in hull sections and the width of a rabbet overlap joint area defined between adjacent strakes varies and tapers along the length of selected planks and defines a transition from a rabbeted cross-section to a conventional stitch-and-glue cross-section having a transition length; and

wherein the transition length is related to how quickly the hull sections shift from convex to concave to provide a wine-glass shaped boat hull transom.

14. The improved strake structure of claim 9, wherein the strake is made from six millimeter thick marine grade plywood and the rabbet width is at least eighteen millimeters, and said rabbet segment's array of tie receiving rabbet holes are spaced from said strake's bottom edge.

15. A method of joining adjacent wood or plastic planks in a structure, comprising:

(a) providing first and second planks each having a plank thickness and each being shaped to the design of a desired structure;

(b) cutting a rabbet along a bottom edge of each of said first and second planks, wherein said rabbet defines a rabbet segment having a selected width from said bottom edge and a selected rabbet segment thickness, the rabbet segment width being at least twice as wide as the plank thickness;

(c) drilling a first array of aligned tie-receiving through bores along a top edge of each of said first and second planks and corresponding second array of aligned tie-receiving through bores along the rabbet segment of each of said first and second planks;

(d) positioning first and second planks side by side with the top edge of said first plank abutting the rabbet segment of said second plank, with said first array of aligned tie-receiving through bores in said top edge of said first plank in coaxial alignment with said corresponding second array of aligned tie-receiving through bores in the rabbet segment of said second plank; and

(e) inserting temporary ties through said coaxially aligned tie-receiving through bores and through said first and second planks to secure said first and second planks in abutting relationship to define a bond receiving gap between said first plank and said second plank's rabbet segment.

16. The method of claim 15, further including filling said bond receiving gap with a bonding agent and bonding said first and second planks.

17. The method of claim 16, further including repeating the steps of positioning, tying, and bonding additional planks to form said structure.