Method of making fiber-reinforced plastic unitized boat hull frame

A unitized fiber-reinforced plastic boat hull frame is disclosed in which the structural members, most commonly a keel and ribs, comprising the frame are constructed of fiber-reinforced plastic formed within a mold corresponding to the shapes of the various members. The members are attached to one another by either contacting them together prior to the completion of curing to produce a plastic bond, or with appropriate adhesives after curing. Planking comprised of any suitable material, wood for example, is added to complete the hull.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to boat hulls and boat hull frames and more 
particularly to a unitized frame comprised of fiber-reinforced plastic and 
a method for manufacturing the same. 
2. Description of the Prior Art 
The prior art is replete with designs and techniques for constructing boat 
hulls and boat hull frames of moderate size. Included in the art is the 
ancient and well-known craft of building frames consisting of a keel and 
rib members of wood and the planking over the assembled frame to complete 
the hull. Also known in the art is the technique of casting an entire hull 
of fiber-reinforced plastic or fiberglass, as it is often referred to. 
Several patents are illustrative of techniques combining both wood and 
synthetics or plastics. For example, U.S. Pat. No. 2,758,321 discloses a 
hull structure which is fundamentally a plastic shell layed up over 
wood-reinforcing ribs. U.S. Pat. No. 2,569,224 reveals a technique 
utilizing a thin layer of sheet plastic between two layers of wood 
planking. U.S. Pat. No. 2,743.465 discloses a hull comprising an exterior 
and interior layer of plastic layed over wood planks. U.S. Pat. No. 
3,139,371 describes a material comprised of plastic-impregnated nylon mesh 
forming inner and outer layers over a balsa wood core which may be easily 
molded into boat hull configurations. As will be described below, the 
present invention involves an approach heretofore unknown to the inventor 
employing the reverse of the general technique of plastic over wood 
illustrated above. 
SUMMARY OF THE INVENTION 
The invention may be summarized as a unitized boat hull frame comprised of 
fiber-reinforced plastic and a method for constructing such frames. 
Conventional planking may be added to complete the hull. 
The advantages of the concept over wood frames are many and include: 
The ability to form a frame having built-in structural reinforcement that 
can be stronger or stiffer as stresses demand without adding or cutting 
away quantities of material as is necessary when using wood; 
The ability to reproduce any hull shape by making a mold of an existing 
boat or by traditional lofting methods; 
The lack of need to produce a finely finished mold as is usually required 
in fiberglass hull moldings; 
The ability to transport the frame in disassembled condition for 
construction of a complete hull at a separate location from the place of 
manufacture; and 
The ability to mold fairing tapers into all structural members. 
All of the above is accomplished by the technique of molding the frame 
members to shape by laying uncured fiber-reinforced plastic material of 
appropriate size and composition into mold portions corresponding to hull 
frame members, in particular into special channel molds for each member to 
be constructed. The members may be bonded either by allowing them to cure 
on contact to form a plastic bond or by adhesives after curing. 
The resulting frame is simple and inexpensive to manufacture, strong, 
lightweight, imprevious to rot and deterioration, easily bonded by 
adhesives rather than nails, screws, or bolts, and highly accurate and 
faithful to the original boat design. The technique is appropriate for all 
manner of moderate size boats which might be constructed by the plank and 
frame method. The invention will be more particularly detailed in the 
drawings and description of the preferred embodiment which follow.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown in perspective view a boat hull frame, 
partially planked, comprised of fiber-reinforced plastic. The frame is 
constructed of a longitudinal or keel member 10 and a plurality of 
transverse or rib members 12. They are attached either by allowing the 
members to cure in contact to form a plastic or self bond or by preventing 
such contact during the curing process and later bonding the cured members 
with an adhesive such as epoxy. In the embodiment illustrated, the rib 
members overlap the keel member, but the positions may be reversed. In 
either case, precise positioning for bonding after curing is assured by 
the interlocking nature of the design and optionally, alignment indicators 
such as marks, small holes, or impressions which may be added during the 
molding process. 
Other structural members may be added according to the stress demands which 
will be placed on the frame. The include additional stringers or 
longitudinal supports, seat supports, and in general all structural 
elements common to boat hull design. 
The frame, when assembled, can be planked with any suitable material, 
preferrably thin strips of wood 14 which bend easily to the configuration 
of the hull. The wood may be attached by adhesives, such as epoxy, 
eliminating the need for nails or screws which deteriorate through 
electrolysis. 
FIG. 3 is a cross-sectional representation of an alternative shape for rib 
members. The fiber-reinforced plastic 16 is molded in a step configuration 
to produce a finished hull of lap-strake construction when planks 18 are 
layed over and affixed to the ribs in the manner described above. Step 
molding provides the additional advantage of acting as a fix or locator 
for each plank simplifying the overall construction. 
Referring next to FIG. 2, mold apparatus used in the method of constructing 
the above described frame is illustrated. The hull to be reproduced may be 
a complete boat hull, for example a classic shape such as a cat boat or 
friendship sloop available as a complete boat in drydock, or a design 
which is built up for the purpose. The model or original hull, not shown, 
becomes the plug over which a support mold 20 is formed, typically of a 
fiberglass material. The interior 22 of the support mold thus exactly 
reproduces the shape of the exterior of the original hull to be 
reproduced. However, the interior of the support mold need not be finely 
finished as is the case when producing molds for conventional fiberglass 
shell boat hulls. 
Channels 24 for the specific structural members are attached to the 
interior of the support mold by adhesives or counter-sunk nuts and bolts 
or other means as would be appropriate. The channels are placed wherever a 
longitudinal or transverse structural member is desired and are 
constructed of any suitable material, preferrably a flexible plastic which 
will conform and bend to the shape of the support mold, one which is not 
degraded by polyester or plastic resins, nor one to which these resins 
will bind. Plastics appropriate for the purpose include polyethylene, 
polypropylene, and polyvinyl chloride. These ae commonly available in 
standard extuded profiles and can be used with little or no modification. 
The number, size and spacing of the channels may be varied at will to 
provide structural reinforcement wherever desired. 
Once the support mold and frame member channel molds are combined into an 
assembly, strips of uncured fiber-reinforced plastic are layed in the 
channels and allowed to cure. Where a self bond is desired, the uncured 
members are allowed to contact one another. Where no bond is desired and 
it is intended that the members be attached after removal from the mold, a 
thin membrane of plastic abhorent material such as polyethylene or 
polyvinyl alcohol is inserted between the strips. Such a practice allows 
the frame to be shipped in kit form to be assembled at the destination. As 
mentioned, the channels themselves are plastic abhorent or are covered 
with such a material. 
A number of plastics or more precisely resin-catalyst promoter systems may 
be used in combination with glass, nylon, carbon or polypropylene fibers 
to mold the frames. These include polyester and epoxy resins. For normal 
gel times of approximately an hour, cobalt promoted methyl ethyl ketone 
peroxide catalyzed resins may be used. Where a short gel time is desired 
for quick-setting structural fillers, benzoyl peroxide catalyst may be 
used. For long gel times, an unpromoted resin catalyst system can be 
employed, requiring in addition the application of heat to produce curing. 
Other combinations of material fitting into the fiber-reinfoced plastic 
category may be employed, as would be obvious to those skilled in the art. 
In constructing any particular hull frame configuration, care must be taken 
not to mold the frames such that the cured assembly locks up in the 
support mold. This is accomplished, when necessitated by the frame design, 
by making some or all of the frame members removable from the frame after 
molding; that is, by preventing self of plastic bonds by inserting contact 
preventing membranes as described above. Also a multipiece or sectional 
support mold duplicating separate portions of the hull can be used, 
assembling such sections to form a complete mold and disassembling them to 
free the frame. 
An additional technique which may be used to add structural members and 
prevent lock up is illustrated by the apparatus of FIGS. 4, 5, and 6. 
Shown in perspective view is a demountable support assembly which may be 
used to add additional structure to the frame, a seat or deck support for 
example. Support mold 20, employing like members from previous figures for 
clarity, serves to shape and contain mold channel 24. Removable support 
block 26 is held up against removable spacer blocks 28 by bolts 30 and 
wing nuts 32. Blocks 26 and 28 are comprised of or covered with a plastic 
abhorent material in the manner previously described. A strip of uncured 
fiber-reinforced plastic 34 may now be placed along block 26 in contact 
with an additional transverse strip in channel 24 to form the desired 
component. After curing, the blocks are removed to free the frame 
components from the mold. As before, depending upon the hull design, 
additional structural members may be cured together in contact or 
prevented from contact and later bonded by adhesives. 
As will be obvious, the concept of the invention encompasses an extensive 
range of frame configurations and fiber-reinforced plastic materials to 
produce a unitized frame of the type described above. Accordingly, the 
scope of the invention is defined by the following claims.