Abstract:
A closed molded system uses reaction injection molding for producing large vessels with hulls, such as a boat hull or large containers. Inserts are used to create a cavity to produce a core. Thereafter the inserts are removed and the same mold is then used to make the other layers of the hull. Closed molding provides controlling the shape of both the outside and the inside of the part. Filler inserts can be used to section off the molds in order to allow for separate core densities.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/657,645, filed Mar. 1, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a process of manufacturing a boat hull, deck, or other large laminate parts. The process utilizes a closed molded system for producing a unitary laminate part, whereby a pre-core and stringers are integrally molded during a reaction injection molding process.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0003]     Large fiberglass parts, such as boat hulls and large containers use stringers and bulkheads inside the part to increase their strength. The ribs or stringers create sections or flat parts between them. These flat parts are where one of the improvements arises. In an attempt to increase the strength of the laminate a closed mold system has been utilized to optimize strength through thickness and shape.  
         [0004]     Traditionally, a fiberglass boat hull is fabricated using a one-sided open mold where layers of laminate are applied on top of one another. The first layer is generally the outside layer made of a gel coat and subsequent fiberglass mat and resin layers are put down thereafter. In the middle of the laminate a core of wood, honeycomb, foam, etc. is applied. A final layer of fiberglass and resin is then applied to the core. Stringers, bulkheads and other structures are fabricated later.  
         [0005]     There are many disadvantages of the traditional open mold hand lay up process. For example, it takes many labor hours to fabricate a hull using the traditional process because each layer is applied by hand. Further, because the mold is open, workers are often exposed to toxic fumes from the resin. Also, the old method creates voids in the laminate which can require post lamination repair. Moreover, the traditional method only molds one side of the part at a time, which decreases the quality of the part. Moreover, the old method is not very reproducible, which decreases consistency of the final hull thus making no two parts the same. Further, the old method results in an unfinished interior surface, such as the headliner or engine compartment, which is labor intensive to later finish. Accordingly, it is therefore desirable to overcome the aforementioned problems with a new, less expensive, faster producing, higher quality, more repeatable process for molding a hull for a vessel.  
         [0006]     One aspect of the present invention uses a two-sided closed mold method of manufacturing a large hull for a boat, container, etc. With closed molding, the shape of both the outside and inside of the part can be controlled. Another aspect of the invention has the shape of the flats of the laminate in a concave manner by which the square or rectangle flat sections of the inside of the part have a slight dish shape to them. An additional aspect of the invention has the stringer, bulkhead, and gusset system built collectively as a unitary structure into the hull.  
         [0007]     One form of the present invention creates a hull having one or both sides of the laminate that are dish shaped. The dish shape will enhance the strength of the laminate without increasing the core thickness or matt and resin thickness. If only one side of the laminate is dished then it would actually decrease the amount of the core material in the laminate. If both sides of the core are dish shaped, meaning one side is concave and one side is convex, then the core would be the same thickness assuming both convex and concave shapes are consistent in size and shape. This dish shaped portion of the hull reacts against the pressure that is being applied to the bottom of the boat by the waves, thus making the laminate stronger by shape.  
         [0008]     A second form of the present invention provides an improved boat hull design with an integrally molded stringer, bulkhead, and gusset system for creating a one piece unitary structure. The resulting boat hull is stronger, takes less time to manufacture, has improved fit and finish from the inside of the boat hull, and eliminates the need for finishing the engine compartment, a typical additional step in the traditional method of manufacturing a hull.  
         [0009]     A third form of the present invention includes a method of manufacturing a boat hull using a two part closed molding process comprising the steps of building hull A and B molds, said molds having a top, bottom and a side, installing inserts into their respective molds, introducing the hull bottom and hull sides with material, and venting excess coring agent out of the top of the mold to allow for expansion. Next hull B mold and hull A mold are separated, sheeting hull bottom core with material, pulling stringer, bulkhead and engine compartment inserts, introducing core agent, pulling core and draping core with fiberglass mat. Pulling remaining inserts from molds, spraying molds with protective agent, inserting core into mold, closing molds, injecting material and releasing part.  
         [0010]     A forth form of the invention includes a boat hull constructed using a closed mold processes, comprising a first layer of composite material, a core layer adjacent to the first layer, and a second layer of composite material.  
         [0011]     The novel process has the capability of not only producing a boat hull or deck, but other large parts as well. Other examples include fuselage and plane parts for the aerospace industry, rocket housings and shells for the military and defense industry, containers for the storage, transportation and aggregate business, trailer shells for the truck and trailer business and housing units for the housing industry. Any large item which can be produced in a closed molded system needing a core for it&#39;s laminate can use this invention.  
         [0012]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0014]      FIG. 1  illustrates a cross section of a boat hull of the present invention;  
         [0015]      FIGS. 2   a - 2   c  illustrate a flow diagram of the steps in the method for manufacturing the present invention; and  
         [0016]      FIG. 3  is a cross sectional view of the boat hull after it has been constructed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For discussion purposes only, a boat hull construction will be described.  
         [0018]     With reference to  FIG. 1 , an improved boat hull mold  10  is illustrated with the configuration of the remainder of the boat  12  shown in phantom. The boat hull mold  10  utilizes a unique closed molded system that employs an exterior hull mold  14 , an exterior insert  16 , a core  18 , an interior insert  20 , and an interior hull mold  22 . Stringer inserts  24 ,  26 , and  28 , may be integral or located adjacent to the core  18  and are located within the engine compartment  30  and throughout the hull  116 . The exterior mold  14  sits on a base  32  during the molding process. A bulkhead  34  and gusset system  36  can also be molded integrally in the hull mold  10  in order to create a single unitary design.  
         [0019]     The interior hull mold  22  forms the inside of the hull mold  10  and has a stringer, bulkhead and gusset system integrally built into the structure. This design allows the manufacturer to include the stringer, bulkhead and gusset system built into the structure as one composite piece. Traditionally, boats have their stringer, bulkhead and gusset systems added after the hull laminate is done. The benefits of including the stringer, bulkhead and gusset components into the hull include 1) a stronger design because the components are an integral part of the hull, not a later addition; 2) It takes less time to build the components into the boat during the closed molding process; 3) the inside of the hull will have a bright, beautiful finish, much like the outside of the part; 4) the engine compartment comes out of the mold already done thus eliminating the need for further finishing; and 5) the inside of the hull forward which makes up the interior space of the boat is finished reducing manufacturing cost.  
         [0020]     The interior insert  20  is designed to take up the space that will eventually be the resin, or glue, and mat layer that makes up the inside of the hull laminate. Because each manufacture may use a different laminate depending on demand of physical properties of the part, the insert thickness will vary from mold to mold. The insert  20  allows the manufacture to produce a three dimensional core  18  utilizing the same mold  14  and  22  as the actual part uses. The core  18  must be thinner than the actual part because the manufacture adds resin and mat to the core. Without the inserts  16  and  20 , the manufacture would have to produce a separate mold for the core, which would increase the cost of the molds and take up valuable floor space. This invention contemplates a manufacturer producing multiple molds for the part and the core separately if they decide to do so. However, the most economical way to produce the part is with the utilization of the inserts  16  and  20 .  
         [0021]     The stringer inserts  24 ,  26 , and  28  and bulkhead inserts and core can be made of any material including, but not limited to, foam, fiberglass, plastic, or laminate and are designed to fill the stringers to allow the hull bottom  38  and hull sides  40  to be molded alone or separate from the stringers  24 ,  26 ,  28  and bulkheads  34 . The stringers often use a different density of foam than the bottom of the boat. This allows the builder to make the stringers separate from the hull bottom and sides. The benefit is to have a balanced laminate. If the stringers, bulkheads and gussets were all part of the hull core, there would not be a complete laminate sandwich. The sandwich aids in laminate strength. It is preferred to have the same amount of mat and resin on both sides of the core  18 . If the stringers, bulkheads and gussets are attached to the hull core  18 , there wouldn&#39;t be an opportunity to get mat underneath the stringers, bulkheads and gussets. This would potentially cause a weak point in the laminate that could jeopardize the strength of the product.  
         [0022]     It is contemplated that the stringer inserts  24 ,  26 ,  28  could be eliminated and to mold the stringer, bulkhead and gusset systems into the hull core  18  directly. There may be products that don&#39;t demand such completely balanced laminates. In which case it would save time and money to include the stringer, bulkhead and gusset system into the core  18  and make them one piece.  
         [0023]     The hull core  18  is what the laminate is built around. It is the first part in the lamination process to be built. The hull core  18  will start as an empty cavity in the shape of a boat hull. That cavity will be filled with core material to produce a three dimensional part which will ultimately be draped with mat and reinserted into the molds, less the inserts, and injected, poured, sprayed or rolled by hand. This will then produce the hull part. The foaming core agent will be vented out of the molds to allow for expansion and density control. The vents will be able to be open and closed utilizing a ball valve type vent. Once the core  18  is cured or hardened the vents can be opened and the hardened core can be cleared by use of a stop drill. This drill is slightly smaller diameter of the vent itself and will have a built-in stop to allow for depth control. This will also allow the builder to blow air into the mold to help release it from the mold.  
         [0024]     The exterior insert  16  is designed to take up the space that will eventually be the resin and mat layer that makes up the outside  42  of the hull laminate. Because each manufacture may use a different laminate depending on demand of physical properties of the laminate, the insert thickness will vary from mold to mold. The exterior hull mold insert  16  will ultimately be the mat and resin layer for the bottom of the boat part.  
         [0025]     There are two molds for each part. The interior hull mold  22  that makes the inside of the hull part. The exterior hull mold  14  makes up the outside of the hull part. The following is a brief description of how a mold is made. A CAD or computer-generated drawing is made, that drawing is downloaded then into a CNC machine. The CNC machine mechanically shapes a block (foam, wood, plastic, etc.) into the plug part. This plug is used to make a duplicate, in female form, of the part to be produced. The female form is the master mold. It will be appreciated that the mold  14  could be produced from a CNC type machine, eliminating the forming of the plug and going straight to the mold. Molds made of metals including aluminum, currently utilized by the automotive industry, are made without the use of plugs or models. This invention contemplates the hand-making or lofting the hull plug although most manufacturers now utilize computers and robots.  
         [0026]     With reference to  FIGS. 2   a - 2   c , the steps for manufacturing a boat hull of the present invention will be described.  
         [0027]     The first step requires building all necessary molds  44  which in this instance includes exterior mold  14  and interior mold  22 . The next step requires building inserts  46  that are to be later used inside the mold. These include exterior insert  16 , interior insert  20 , stringer inserts  24 ,  26 , and  28 , bulk head inserts, and transom inserts. Now that the molds and inserts have been created, the manufacturer can begin the specific process of making a hull.  
         [0028]     The next step requires locating the inserts into the molds  48 . The next step  50  requires blowing, inserting, injecting, or pouring core material into the hull bottom insides. Thereafter the venting step  52  allows excess coring material to come out of the mold to allow for expansion. The drilling step  54  takes place next where the vents are drilled with a stop drill in order to clear excess core material and to allow for a passageway for air to be blown into the core thereafter. The next step  56  requires blowing air into the vents in order to aid in the release of the core from the molds. Separating molds  58  is the next step which opens up the mold and exposes the core  18  to be later processed.  
         [0029]     Once the molds are open, the hull core is sheeted  60  with material in order to separate the hull core from stringer and bulk head. It will be appreciated that this step is optional and is done only if the builder desires a separation of the hull core from the stringer and bulk head core. The next step requires removing the stringer and bulkhead inserts  62  from the molds. The next step is optional which includes removing engine compartment and transom inserts  64 . This step  64  is only performed if the builder desires separation of the forward stringer and the bulk-head core from the engine compartment stringer and the transom core. The stringer and bulkhead inserts may be joined as one piece to the engine compartment stringers and transom inserts.  
         [0030]     The next step  66  is also optional which includes sheeting or separating the engine compartment stringers from the engine compartment bulkheads. This optional step  66  is done only if the builder desires a different density core agent to be used in the engine compartment versus the forward stringers and bulkheads. Thus, the present design provides for a flexible construction that provides for a hull having different performance characteristics. The next step  68  requires joining the interior and exterior molds after the sheeting and removal of insert steps have been completed.  
         [0031]     With reference to  FIG. 2   b , the method of manufacturing a hull is continued. Once the molds have been closed, the next step  70  requires blowing, inserting, injecting, or pouring coring agent into all stringer, bulkhead and transom cavities. At this point, the builder may use a different density core material so as to meet the needs of the predetermined laminate construction. This step allows for flexibility of the hull design. The next step  72  allows for venting excess coring agent out of the mold to allow for expansion of the agent within the cavities. Once the coring agent has expanded and cured, the next step requires drilling vents  74  with a drill in order to clear excess core material so as to create an air passageway. Once the vents have been drilled out, the next step  76  requires blowing air into the vents in order to help release the core. The next step  78  requires separating the molds so as to provide access to the cavity. Once the molds are separated, the next step  80  requires removing all the cores from the molds, and then stripping the sheeting material from the hull core  82 . After that has been completed, there is an optional step  84  wherein the manufacturer can cut the engine compartment stringer core from the transom core in the jig. This allows the builder to have a balanced laminate on transom if so desired.  
         [0032]     The next step requires placing cores  86  into a proper position for mat draping. Thereafter, the step of draping the outside hull core  88  is performed where glue is used if so needed. Thereafter, hull mold insert  16  is removed  90  and then the interior insert  20  is removed at step  92 . Thereafter draping the hull core  94  is performed.  
         [0033]     With reference to  FIG. 2   c , the method of manufacturing a hull is further illustrated. The next step  96  requires shooting, spraying, rolling, or applying the exterior hull mold  14  with a protective material such as gel coat or polyurea. It will be appreciated that other protective material could be utilized. The next step  98  requires shooting, spraying, or rolling the interior hull mold  22  with a protective material as previously described. The next step  100  requires shooting, spraying, rolling, or injecting resin or glue in order to prepare the hull core  18 . It will be appreciated that this may be done with the part in the molds and with the molds closed or open. The next step  102  requires closing and joining the molds together one last time. The next step  104  requires venting the excess resin or glue out of the mold so as to allow for expansion of the material therein. The next step  106  requires screwing or clamping the molds together to squeeze out excess resin or glue, the benefit of which is to assist in eliminating voids in the final laminate structure. The part is then cured  108 , wherein thereafter, vents are drilled  110  in order to clear excess resin or glue so as to create a passageway. The next step requires the blowing of air  112  into vents in order to help release the part. The final step  114  is actually releasing the part from the molds. It will be appreciated that the above-referenced steps can be varied in order to create the invention.  
         [0034]     With reference to  FIG. 3 , the resulting boat hull  116  is depicted that has been made through using the steps outlined in  FIG. 2  above. The components of the boat hull include an outer gel coat layer  118 , an outer resin and mat layer  120 , a central core  122 , an inner resin mat layer  124 , and an inner gel coat layer  126 . A radius  128  is used with the gusset  36  and becomes integral with the structure. It will be appreciated that the gusset  36  can be located at predetermined locations throughout the boat hull  116  so as to provide structural integrity. A laminate layer  130  is positioned underneath the core  132  of the stringer  134 . Each stringer  134  has an exterior gel coat  136 , a mat with resin layer  138  and its own core  132 . By placing the laminate layer  130  between the core  132  and the core  122 , the core  132  can be made of different material as so desired by the manufacturer.  
         [0035]     Further illustrated in  FIG. 3  is the concave shape portion  140  disposed between stringers that can be located systematically throughout the hull. It will be appreciated that the concave shape could be continuous throughout the linear length of the hull. The concave shape is an integral part of the hull and is created during the close molding process. For illustrative purposes only, the concave shape  140  is only shown on the right side of the hull  116 . The inner gel coat  126   a , inner resin and mat layer  124   a , and the core  122   a , take on this concave shape which aids in the structural integrity of the hull. The outer gel coat layer  118  and the outer resin and mat layer  120  preferably employ a flat configuration as illustrated. However, it will be appreciated that they too could be configured to take on a concave shape by changing the shape of the mold.  
         [0036]     An alternate embodiment to the present closed molded system includes modifying the stringers and bulkheads that form part of unitary hull. Typically, the ribs or stringers and bulkheads are glassed or glued into the hull bottom where the transition from the stringer or bulkhead to the hull bottom has no radius or very slight. The closed molding would allow for a predetermined radius to be added or built into the mold, which would increase the strength of the joint. It will also make cleaning easier and look more attractive.