US 3439366 A
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W. R. MATTHEWS BOAT CONSTRUCTION April 22, 1969 Sheet Filed Nov. 20, 1967 l A x INVENTOR. W/LL/ZLL/ E UJTTHEWS BY bMMA W April 2, 1969 w. R. MATTHEWS I 3,439,366
BOAT CONSTRUCTION Filed Nov. 20, 1967 Sheet 2 of 4 Z/ 22 f, (I /0 INVENTORL W/LU/M/ E MATH/[W5 BY zmva/ K/J/M April 22, 1969 w. R. MATTHEWS BOATCONSTRUCTION Filed No v. 20, 1967 Sheet Q A "gyqawefadmi g u IN V EN TOR.
W/LL/AL/ F MATT/1149 BY MMKW United States Patent 3,439,366 BOAT CONSTRUCTION William R. Matthews, Spokane, Wash., assignor to The Microlite Corporation, Spokane, Wash., a corporation of Washington Filed Nov. 20, 1967, Ser. No. 684,143 Int. Cl. B63b 3/00, 5/24; B44c 1/00 US. Cl. 9-6 6 Claims ABSTRACT OF THE DISCLOSURE A boat is built of an inner structural shell to which the deck and keel and all inner structural parts such as bulkheads, partition and floors are fixed. Outer reinforcing ribs are formed over the inner shell. These outer ribs are made up of laminations of monofilament tape where the filaments are glass fiber, the laminations being secured together by an epoxy resin of suitable formulation. These outer ribs are mechanically secured to the shell by fasteners such as rivets, screws or bolts.
The inner structural shell from deck to keel is completely encased in and bonded to a buoyancy provided shell made up of micro-sized hollow balls of glass mixed in a suitable epoxy resin and its catalyst which is compatible with the resin used in the outer ribs. The thickness of the outer shell is more than sufiicient to provide buoyancy to float the completed boat in water with the parts fixed therein. In constructing the boat, the inner shell may be built upside down and the outer shell composition then be laid on as a trowelable mix or the inner shell may be located in an outer mold and the buoyancy composition may be poured in between the mold and inner shell and then cured in place.
An outer skin may then be formed over the outer shell composition using known materials such as one or more finishing coats of known surfacing materials such as epoxy resin paint.
Background of the invention This invention relates to boats wherein the hull is formed with an inner frame embodying necessary ribs, clamps, chines, bulkheads and inner shell with outer reinforcing ribs and main hull of a plastic composition. Heretofore in making boats wherein the main hull is of plastic composition the practice has been, so far as I am aware, to build a mold on which or in which the structural parts of the hull are formed by reinforced plastic, the reinforcement being of fiberglass cloth or the like. The interior structure such as ribs, bulkheads, etc. are set in after rem-oval from the mold. Alternatively plywood hulls have been first prepared and the fiberglass and plastic laid directly thereon. These structures are outlined in the book Fiberglass Boats You Can Build published in 1963 by Motor Boating of 959 8th Ave., New York, NY. The composition for obtaining the desired buoyancy utilizes the micro balloons developed under the U3. Patents 2,978,339, 2,978,340 and 2,797,201.
Purpose of this invention 'It is the main purpose of this invention to provide a method of boat construction wherein a hull is constructed of a metal or equivalent inner structural shell to which the deck, bulkheads, floor, ribbing, clamps, keel and other interior parts are pro-secured, the deck being used as an assembly base and subsequently encasing the shell in and bonding it to an outer flotation shell which is essentially composed of micro-sized balls of glass and an epoxy resin matrix in sufiicient quantity and of such thickness as to provide more than adequate buoyancy to float the ice completed boat and its contents in water under normal load conditions even though the boat wall is ruptured to allow filling thereof with water.
Brief description of the drawings In the drawings:
FIG. 1 is a somewhat diagrammatic perspective view illustrating the construction of an inner shell;
FIG. 2 is a cross-sectional view through a finished boat showing the inner structural shell and the parts carried thereby encased in the flotation shell;
FIG. 3 is an enlarged cross-sectional view taken on the line 3-3 of FIG. 2;
FIG. 4 is an enlarged sectional view across the bottom of a boat showing a modified keel section wherein a metal keel is completely encased in the material of the outer shell;
FIG. 5 is an enlarged fragmentary plan view looking down upon a portion of the interior of the boat at the bottom thereof;
FIG. 6 is a sectional view through an assembly of an inner structural shell, with an outer mold with the flotation composition being filled in between the mold and inner shell; and
FIG. 7 is a greatly enlarged sectional view through the flotation composition showing the relation of the hollow balls and the epoxy resin matrix.
General description In the construction of a boat of predetermined size and shape according to my invention the initial step is preferably to cut a deck member 1 to the exact contour desired for the boat hull at the deck line. This deck member 1 may be of any suitable material such as metal, plywood or molded resin or a combination of any two or more of such materials and may be reinforced by members In such as T-bars of metal. The completed deck is secured topside down on blocks (not shown) upon a support platform P which in turn is mounted on pivots R so that the platform can be turned over whenever it is desired to bring the boat right side up. Following the securement of the deck 1 on the platform P the sequence in building is to fix to the deck the bulkheads 3 and any other partitions needed. Where longitudinal stifieners 4 are desired for the hull these members are secured on the bulkheads 3. A keel 5 with bow section 5b and stern section 5s is secured in notches in the bulkheads 3 and temporary supports 5t are used wherever needed to support the keel 5 on the deck 1. While the deck 1 is inverted on the platform P such needed interior framing as inner cross ribs 2 are secured to the keel and deck, and floor supports 7 and engine mounts 6 are secured to the bulkheads and cross ribs to complete the interior frame construction of the boat body. Any interior piping, etc. is also installed in the frame wherever possible before covering it. Gussets indicated at 8 can be used in the usual manner to strengthen intersection points of the frame members.
The next step following the frame construction is to cover the frame with an inner shell 9 to which the already located bulkheads 3 and keel 5 and other frame members such as the stiifeners 4 and cross ribs 2 are permanently aflixed. It is preferred that this inner shell be made up of overlapped corrugated strips where the corrugations are substantially regular. These strips must be of a material that has considerable strength and that can withstand continued vibrations Without cracking. An aluminum strip is satisfactory.
Plastic or metal strips of the configuration shown can be overlapped with their side portions nesting as shown in FIG. 3 of the drawings to produce the desired shell 9.
These strips are secured directly to the deck 1, the bulkheads 3 and keel 5. In lighter boats the corrugated strips may not need the ribs 2 for giving the shell 9 the necessary strength and stiffness. The strips 10 may run more or less diagonally from top to bottom of the boat as shown in FIGS. 2 and 5, or even lengthwise if desired. When made of metal such as aluminum of adequate thickness all of the needed strength can be obtained in the strips 10. All of the necessary fastenings 11 and 12 of the bulkheads 3, the stiffeners 4, the deck 1 and the keel 5 are made by known devices such as rivets, bolts etc. Whenever desired, the parts may be additionally secured by bonding with an epoxy resin adhesive which will bond to the materials used.
Following the completion of the shell 9, and the fasten ing of the frame members thereto, the buoyance producing hull is applied over the shell 9. The shell 9, as shown in the drawings, is preferably provided with ribs 14 running from top to bottom of the shell 9. These ribs are made up of laminations of monofilament fiberglass tape 15 and epoxy resin adhesive 16. The tape is place directly opposite the bulkhead edges preferably and, where the ribs 2 are used, opposite the ribs 2. Rivets 17 are used to tack these ribs 14 to the shell 9. The ribs 14 may taper in thickness from top to bottom as shown, to enable them to be covered by a buoyancy producing shell 18 which also increases in thickness from bottom to top of the boat. The ribs 14 are generally close enough together to act as guides for applying the buoyance producing material of the shell 18 over the shell 9. The material can also be filled in over the keel, as shown.
The buoyancy producing material of the shell 18 is composed of hollow balls 19 of glass or equivalent material in a matrix 20 of epoxy polyamide resin which can be readily cured by low heat. Preferably the hollow balls 19 of glass are of a diameter of the order of 75 to 250 microns. In the preparation of mixture the hollow glass spheres 19 are treated to remove any surface moisture so that an epoxy polyamide resin, of low surface tension, can by mixing, be made to fill all the voids between the surfaces of the spheres. A mixture of balls and resin is rather critical for best results. The best results are attained when barely sufficient resin is used to fill the voids between the spheres when the balls are in contact with each other. The glass balls are micro-balloons and the characteristics thereof are described in the U.S. Patent No. 2,978,340. The hollow spheres nest together so closely that I have found it is possible to fill the voids with a proportion of 75 to 85% spheres to to 15% resin by volume. The specific gravity of such a composition is of the order of 0.40 as compared to water having a specific gravity of 1.
Specific gravity of aluminum is approximately 2.7. So to balance or float each unit volume of the metal aluminum in the inner shell 9 we must employ about 4 unit volumes of the buoyance composition. By employing simple calculation one can determine how much of the buoyance composition is needed to float the boat and its contents. This then enables one to establish the thickness of the lighter than water shell 18 that must be employed. I prefer to utilize enough of the light weight composition of hollow glass spheres and resin to float the boat and its contents including the power supplying devices and a reasonable allowance for load. The boat then will float even if it is filled with water. The placement of the buoyancy producing material in the boat hull can be predetermined so as to attain the proper stability. For example, it is desirable in a boat to have its center of gravity at a level substantially below its center of volume in order that the boat will at all times tend to right itself in the water whether loaded or empty.
As shown by FIGS. 2 and 3 in the drawings, the composition of the flotation shell 18 is filled into the corrugations of the shell 9 and built up to cover the outer ribs 14. The resin 16 used in laminating the ribs 14 and the resin 20 preferably are the same so that in curing they bond firmly together. By reason of this the outer ribs 14 and flotation composition become practically an unbroken layer encasing the shell 9. For convenience in obtaining uniformity in thickness of this layer, bars of the proper thickness may be used as guides to predetermine the thickness of the hull over the inner shell 9. I find that bars made of the material sold under the trade name Teflon can be used and the composition will not stick to the bars. The bars after being used to determine the thickness of the composition 18 can be used over again. The composition can be made sufficiently stiff that when trowelled or forced in place it does not sag or run until it is cured.
The exterior shell 18 requires no further covering layer, as its outer surface serves as a water impervious outer surface of the boat hull. Where desired, a final finish coat of resin or paint may be applied as a surfacing material.
With this construction the parts of greatest specific gravity such as the keel 5 and the corrugated strips 10 are concentrated in the lower portion of the boat while the greatest volume of the flotation composition is naturally in the upper part of the hull where the circumference, horizontally of the hull, is greatest. This of itself tends to stabilize the boat in an upright position. A boat constructed in accordance with my invention tends to right itself regardless of the depth to which it sinks in the water because of the gradual increase in proportion of lighter hull material to heavier material in the hull from bottom to top of the hull.
The deck bulkheads and other interior parts may be cast from the same micro-balloon composition as the shell and have suitable reinforcements and connecting and fastening elements pre-cast therein if desired. Any known method of precasting these parts may be used. The essential feature is that the entire hull and the parts fixed thereto are lighter in weight than an equal volume of water so that the hull will not sink even though the interior is filled with Water and, due to the distribution of the flotation material and the heavier than water material, the boat endeavors to remain upright whether or not it is filled with water.
As shown best in FIG. 2, the inner shell strips 10 are extended to form a bulwark B around the boat above the deck 1. The strips 10 are bent to the desired hull shape where hulls of a particular contour are desired. The side edges of the corrugations of adjacent strips 10 overlap as shown, to produce a continuous shell 9. I prefer to have the strips 10 run upward from the keel to the rail B and to fasten the strips 10 to the keel 5 and to the deck 1. Also the bulkheads 3 preferably have their edges set into corrugations of the strips 10 as indicated in the enlarged section in FIG. 3 of a portion of the hull. In light boats where the loading is not excessive adequate strength is obtained by joining the bulkheads, deck, floor members, and keel to the strips 10 without use of the ribs 2. Alternatively, where no bulkheads are used or the bulkheads are not close enough together to give the desired support, ribs 2 may be used without obstructing the space within the hull to any appreciable degree.
The manner of connecting the keel 5 to the shell 9 and to the ribs 2 is best illustrated in FIGS. 2 and 5. In FIG. 2 the heavy keel 5 is shown as a box made of two metal extrusions of hat shape in cross section. Transverse bars 21 are set into the extrusion at intervals throughout its length and secured by any suitable means such as the screws 22 shown, or equivalent. The ribs 2 overlap the ends of the bars 21 and are secured by welding or other means. The strips 10 abut the keel 5 and are also fastened to the bar members 21 by screws such as 22. The keel 5 projects outwardly beyond the strips 10 so that the composition shell 18 and the outer ribs 14 can abut the projecting keel surface. In FIG. 2 the strips 10 directly overlap the flanges of the extrusion and are secured thereto as shown.
In all of the connections of the shell 9 to the keel 5 it is preferred to have the mechanical connections inward of the outer ribs 14 and the composition shell 18. The entire keel 5 is preferably filled and covered wherever possible, with the composition 18. The exposed exterior surface of the keel 5 preferably is covered with a wear strip 23 of abrasion resistant resilient material such as neoprene or butyl rubber or other suitable plastic composition. The strip 23 is vulcanized or cemented to the keel 5.
When the demand is for a multiplicity of boats that can be alike in size and shape, it is a labor-saving expedient to employ a mold 25. This mold is made from a pattern boat of the exact size and shape desired. With the pattern inverted, I lay over the pattern one or more layers of plastic fibre cloth made of a suitable fiber and saturated with a suitable thermosetting resin such as an epoxy. The layers are smoothed out and cured to form a removable mold 25. This mold can be used as shown in FIG. 6. The inner structural shell 9 can be made in any suitable manner and then positioned in the mold 25. The space between the shell 9 and the mold 25 is then filled with the flotation composition which is packed in such fashion as to leave no air pockets. The mold 25 is lined with a suitable known parting material to prevent the flotation composition from sticking to the mold. When the flotation composition is cured, the mold is stripped from it and the surface finish or paint is applied. The mold should be of such material that Where the flotation composition is heated or heat is used to cure the resin of the flotation composition while it is still in the mold, the mold will stand up under the temperatures required. A metal mold can be used.
In FIG. 7 there is shown a sectional view of the flotation composition showing how the matrix material fills the voids between the hollow spheres but the spheres contact each other. Other materials can be used to make the hollow spheres but I prefer the glass material of Patent No. 2,978,340 because of its strength and resilience. In order to fill the voids fully it is desirable that the uncured matrix material flow readily. I have found it desirable to treat the glass spheres with a silane compound to overcome the bound water layer on the glass. This is done by tumbling the spheres with a small percentage of silane liquid diluted with ethanol so the liquid will be better distributed on the spheres. After mixing, I heat the spheres in an oven at about 120 degrees C. to drive off the ethanol water mixture that results from the silane liquid treatment.
After treating the spheres in the above manner they are mixed with the matrix or hinder material while still hot. I prefer to use the following ingredients for the binder material:
Parts by weight Epoxy resin (shell 815 or 828) 1 Polyamide resin (General Mills 125 2 Non-reactive oil (Mobiloil 66) 2 It is desirable to heat the non-reactive oil to at least about 90 degrees C. before mixing it with the other parts. The proportion of glass spheres to resin mixture by volume is about 75 parts glass spheres to 25 parts of resin mixture. This composition, when thoroughly mixed and hot, can be poured into a mold. It can also be trowelled in place at lower temperatures of the order of 50 degrees C. The mixture has a pot life of at least one-half hour so it may be applied without haste. The composition will set up at room temperatures above 50 degrees C. in four to twelve hours. However, it is desirable to subject the completed assembly of the shells 9 and 18 to a post-cure by further heating in an oven. Typical post-cure temperatures and times are as follows:
At 200 degrees F. hold temperature 4 hours.
At 250 degrees F. hold temperature 2 hours.
At 300 degrees F. hold temperature 1 hour.
The resin formulation given hereinbefore gives enough flexibility for most boat uses. However, in some instances a more flexible flotation composition may be desired. The following formulation gives a greater flexibility.
Parts by weight Epoxy resin powder 1 Polyvinyl chloride resin powder l Diethanolamine catalyst 5 Other formulations of resin and catalyst may be employed of course. It is desirable to use in all cases a resin composition that has a low surface tension before curing so that it will readily flow between the glass spheres and cover or wet the exposed surfaces thereof. The epoxy resin formulations given above appear to do this very Well. They have a low exothermic reaction in curing and therefore avoid the production of vapor or gas bubbles in the matrix. They also provide a strong adhesion of metal and wood par-ts. This is important in bonding the outer shell 18 to the inner shell 9 and the keel 5. The outer shell forms a monolithic shield encasing the inner shell which is much thicker than the shell 9 and yieldable under exterior impact to cushion the inner shell.
It will be noted that in FIG. 4 and FIG. 6 the design of the keel 5 is such that it can readily be completely covered by the flotation composition of the outer shell 18. The wearing strip 23 can be applied on the keel covering portion of the shell 18 as readily as it is applied to the keel 5 in the showing in FIG. 2.
While it is preferred to employ the corrugated metal strips 10 for the inner shell 9 because of its great resistance to forces in all directions, other suitable materials may be used for this shell 9, such for example, as preformed strips of wood, plywood, etc. One advantage of the metal corrugation is that it gives a thin, very high strength shell to which all of the other frame parts such as the deck, the keel, the partitions and the floor supports may be attached with known fastening elements. It can also be protected inside the boat by coatings of a nature to prevent corrosive attack upon the metal itself.
The combination of the inner shell 9 of the corrugated material and the outer shell 18 of the flotation composition is contrary to the generally used method of providing flotation by putting in linings or interior blocks of a flotation material. In my construction the flotation shell 18 is both a resilient butter against external forces that might rupture the hull and a means of keeping the boat afloat. If a hole is made in the shell 18 or a portion of it is gouged out, the damage can be remedied by filling the hole with a patching composition mixed from the same ingredients that are in the shell 18.
My invention is defined in the following claims:
1. A boat hull construction, comprising:
an inner shell having a bow portion, a stern portion and a midship portion therebetween, the inner shell being formed of high strength material and having structural frame members fixed thereto, said inner shell having an outer surface configuration substantially conforming to the desired hull shape;
a monolithic exterior shell having a resin matrix bonded to and completely encasing the outer surface of the inner shell, the outer surface of the exterior shell being the exterior surface of the boat hull;
said exterior shell being water impervious and yieldable under exterior impact;
the specific gravity of the material forming the exterior shell being less than one, and the thickness and resulting volume of the exterior shell being such as to float the boat hull and its contentsin water under normal load conditions following rupture of the boat hull and filling of the boat hull with water.
2. The boat construction defined in claim 1 wherein the exterior shell is composed of hollow halls of glass abutting each other and held in place by a matrix binder that also adheres to the inner shell.
3. The boat construction defined in claim 1 wherein the inner shell embodies spaced apart exterior ribs ruhning from top to bottom thereof.
4. The boat construction defined in claim 1 wherein the exterior shell is of substantial thickness as compared to the thickness of the inner shell.
5. The boat construction defined in claim 1 wherein the exterior shell comprises hollow, gas-filled balls of a hard resilient material packed together in a resilient matrix binder substantially softer than the balls.
6. The boat construction defined in claim 1 wherein the exterior shell of lighter than water material increases in thickness from the lower portion of the boat to the top thereof.
8 References Cited FOREIGN PATENTS 10/1964 Canada.
MILTON BUCHLER, Primary Examiner.
RICHARD A. DORNON, Assistant Examiner.
US. Cl. X.R.