Abstract:
In one aspect of the invention there is provided a method of manufacture of an assembly comprising: forming an assembly by coupling a first component ( 150 ) to a second component ( 110 ) in spaced apart relationship therewith by means of coupling means ( 131 ); providing thermally activated seal means between the components, the first component, second component and seal means being arranged such that a gap exists between the first and second components allowing fluid flow therethrough; and subjecting the assembly to heat thereby to cause the seal means to expand and bridge the gap between the first and second components thereby to form a fluid tight seal between them. The second component may be at least partially enclosed between the first and a third component ( 161 ), and the second component may provide an aperture at a location opposite a portion of the third component whereby expansion of a seal means ( 112 S, 114 S) around the aperture causes the aperture to be sealed by the seal means and said portion of the third component

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an assembly and to a method of manufacturing an assembly. In particular but not exclusively the invention relates to a method of manufacturing an assembly in which is required to form a fluid tight seal between components. Aspects of the invention relate to an assembly and to a method of manufacturing an assembly for a motor vehicle. 
       BACKGROUND 
       [0002]    It is known to provide a vehicle audio system in which a sub-woofer is provided under a seat of a driver or passenger or in a luggage compartment of the vehicle. Sub-woofers are typically required to occupy a not inconsiderable amount of space in order to provide acceptable audio performance. It is desirable to provide a sub-woofer of reduced size in order to reduce an amount of cabin or payload space (such as boot space) occupied by the sub-woofer. 
         [0003]    It is an aim of some embodiments of the present invention to at least partially mitigate the disadvantages of known sub-woofers. 
         [0004]    Some embodiments of the invention provide an improved method of assembly of a vehicle, watercraft of aircraft. 
         [0005]    Some embodiments of the invention provide an improved method of assembly of a vehicle, watercraft or aircraft having a ballast tank. 
       STATEMENT OF THE INVENTION 
       [0006]    Embodiments of the invention provide a method, an assembly, a vehicle, a watercraft and an aircraft. Embodiments of the invention may be understood by reference to the appended claims. 
         [0007]    In one aspect of the invention for which protection is sought there is provided a method of manufacture of an assembly comprising: forming an assembly by coupling a first component to a second component in spaced apart relationship therewith by means of coupling means; providing thermally activated seal means between the first and second components, the first component, second component and seal means being arranged such that a gap exists between the first and second components allowing fluid flow therebetween; and subjecting the assembly to heat thereby to cause the seal means to expand and bridge the gap between the first and second components thereby to form a fluid tight seal between the components. 
         [0008]    Some embodiments of the invention have the advantage that the first and second components may be coupled to one another, immersed in a liquid, removed from the liquid to allow fluid to drain from the assembly through the gap and subsequently heat treated to seal the gap without a requirement for operator or tool access to the assembly to seal the gap. 
         [0009]    Some embodiments of the invention offer a particular advantage in the fabrication of components where a waterproof and/or airtight seal is required to be made between two components that become inaccessible during a process of manufacture before the assembly is subjected to a coating or other treatment requiring immersion of the assembly in a liquid such as an anti-corrosion liquid or other treatment. 
         [0010]    The presence of the gap between the first and second components allows the liquid to flow between and around the components. Once the treatment is completed any excess liquid may drain from the components through the gap before the components are subject to a thermal treatment to cause expansion of the seal means to seal the gap. 
         [0011]    It is to be understood that because operator or tool access to the components is not required, the first and second components may for example be contained within a third component and be substantially inaccessible to an operator or tool without compromising an ability to form a fluid tight seal between the first and second components. 
         [0012]    The seal means may comprise a thermally activated mastic arranged to expand upon heating. The seal means may be provided in the form of a layer of mastic, for example in the form of a gasket or like continuous loop of mastic. The seal means may alternatively be in the form of a discontinuous strip of mastic. 
         [0013]    It is to be understood that the first component may at least partially enclose the second component. 
         [0014]    Advantageously the method may comprise the step of providing a third component such that the second component is at least partially enclosed by the first and third components before the step of subjecting the first assembly to heat. 
         [0015]    The second component may be substantially fully enclosed by the first and third components. 
         [0016]    It is to be understood that the first and/or third components may have apertures therein such that the second component is visible through the apertures and still be partially or fully enclosed by the first and third components. 
         [0017]    Further advantageously the method may comprise the step of coupling the third component to one or both of the first and second components. 
         [0018]    Optionally the third component is in the form of a single unitary component. Alternatively the third component may comprise a plurality of sub-components, the method comprising the step of assembling the third component from the plurality of sub-components. 
         [0019]    Optionally one or both of the first and second components may comprise a single unitary component. Alternatively one or both of the first and second components may comprise a plurality of sub-components. 
         [0020]    Advantageously the method may comprise providing seal means between the third component and one or both of the first and second components such that a gap exists between the third component and said one or both of the first and second components such that fluid may pass through the gap and drain from the assembly before subjecting the assembly to heat. 
         [0021]    This feature has the advantage that in some arrangements the seal means enables the third component to provide support to the first and/or second component by bridging the gap after expansion of the seal means. 
         [0022]    It is to be understood that in some embodiments the seal means may bridge the gap before and after the seal means expands. 
         [0023]    Optionally the step of providing seal means between the third component and one or both of the first and second components comprises providing the seal means such that expansion of the seal means causes a fluid tight seal to be formed between the third component and said one or both of the first and second components. 
         [0024]    Advantageously the method may comprise the step of exposing the assembly to a fluid before subjecting the assembly to heat to form the fluid tight seal. 
         [0025]    Further advantageously the method may comprise the step of providing the second component in a shape defining a tray having a free peripheral edge facing the first component whereby expansion of the seal means causes a fluid tight seal to be provided between the first and second components around the peripheral edge of the second component. 
         [0026]    The method may comprise the step of forming an aperture in the first component thereby to allow access to an interior of the tray defined by the second component. 
         [0027]    This feature has the advantage that the interior of the second component may be employed for a purpose such as storage of equipment, vehicle components or passenger personal items or luggage. Thus in the event the second component is in the form of a tray the tray may provide a useful volume for storage or other purposes. For example the tray may provide a useful volume as a cavity of an audio system as described below, a fluid reservoir and other useful purposes. 
         [0028]    Optionally the method may comprise the step of providing at least one aperture in the second component to allow flow of fluid through the second component via said aperture. 
         [0029]    This feature has the advantage that fluid such as a liquid or a gas may pass from one side of the second component to the other. 
         [0030]    This may be useful during manufacture, for example when the assembly is subject to an electro-coating process such as an electrophoretic deposition process commonly known as an e-coat dipping process. In such a process the assembly may be dipped in a bath of e-coat fluid such as a primer, paint or any other suitable fluid in order to form a coating of e-coat fluid over the assembly. Such processes are typically employed in the automotive industry, where a vehicle body may be subject to the dipping process. In some applications it is required to ensure that substantially all surfaces of the assembly are coated with fluid when the assembly is dipped in the fluid. Accordingly, the presence of the aperture in the second component may be useful in ensuring the second component is flooded with fluid during the dipping process. 
         [0031]    Advantageously the method may comprise providing thermally activated seal means around one said at least one aperture in the second component. 
         [0032]    It is to be understood that reference to one said at least one aperture is not to be understood to exclude the possibility that more than one aperture has the feature described, in the present case the feature of thermally activated seal means therearound. 
         [0033]    In some embodiments valve means may be provided to selectively allow or prevent flow of fluid through the second aperture when required. 
         [0034]    It is to be understood that some embodiments of the invention may be suitable for providing a ballast tank in or on or under a structure. For example a ballast tank of a motor vehicle or water craft. The tank may be arranged to be flooded and/or drained by opening or closing the valve means. 
         [0035]    The valve means may be coupled to or formed integrally with the aperture. Alternatively the valve means may be associated with a fluid conduit such as a hose or other conduit that may be arranged to deliver a supply of fluid to the ballast tank. The aperture may be provided in a lower region of the ballast tank with respect to an in-use orientation of the assembly. 
         [0036]    The method may comprise the step of providing at least one aperture in the third component. 
         [0037]    This feature has the advantage that in some arrangements fluid may flow through the third component to flood a volume between the second and third components. 
         [0038]    Optionally the method comprises providing the aperture in the second component at a location of the second component opposite a portion of the third component whereby expansion of the seal means around the aperture causes the aperture to be sealed by the seal means and said portion of the third component thereby to prevent flow of fluid through the second component via said aperture. 
         [0039]    Advantageously the method may comprise the step of providing one said at least one aperture in the third component at a location displaced with respect to the aperture in the second component such that when the seal means around said one at least one aperture in the second component expands substantially no portion of the at least one aperture in the third component overlaps said one at least one aperture in the second component whereby said one at least one aperture in the second component may be sealed closed. 
         [0040]    This feature has the advantage that the assembly may be formed such that no direct path exists for the flow of fluid through the aperture in the third component and subsequently through the aperture in the second component. 
         [0041]    Advantageously the method may comprise the step of providing valve means for controlling flow of fluid into or out from one said at least one aperture in the second component in use. 
         [0042]    The step of providing valve means may comprise one selected from amongst the steps of coupling the valve means to the second component, forming the valve means integrally with the second component and providing the valve means in a fluid conduit through which fluid may pass to fill or drain the second component. 
         [0043]    Optionally the step of providing valve means comprises providing valve means for controlling flow of fluid through the second and third components to fill or drain the second component. 
         [0044]    The method may comprise providing the first component in the form of a floorpan assembly. 
         [0045]    Optionally the third component may comprise an underframe or understructure, a chassis, a ladder frame assembly, a monocoque structure or any other structure. The third component may be a portion of a motor vehicle, a watercraft, an aircraft or any other suitable structure. 
         [0046]    Advantageously the step of providing the third component such that the second component is at least partially enclosed by the first and third components may comprise the step of providing the second component within a longitudinal portion or cross-member portion of the third component. 
         [0047]    Optionally the step of providing the third component such that the second component is at least partially enclosed by the first and third components comprises the step of providing the second component within a longitudinal member or a cross member of the third component, such as a longitudinal member or cross member of an underframe or understructure, chassis, ladder frame assembly, monocoque or any other suitable structure. 
         [0048]    This has the advantage that in some embodiments space that is otherwise not utilised may be utilised to the benefit of the driver or vehicle, in this case a hollow of a longitudinal member or cross member, optionally a beam member. 
         [0049]    Other structural members also provide useful space for the location of the second component. 
         [0050]    Optionally the method is a method of manufacture of an assembly to form part of one selected from amongst a motor vehicle, a watercraft and an aircraft. 
         [0051]    Advantageously the method may comprise providing the aperture in the first component such that it is accessible from an interior of the motor vehicle, watercraft or aircraft. 
         [0052]    Advantageously the second component may define an air cavity of an audio speaker system. 
         [0053]    Further advantageously the second component may define a portion of a sub-woofer of an audio system. 
         [0054]    Alternatively the second component may define a tank of a ballast system. The ballast system may be employed to increase a weight and/or reduce a buoyancy of the assembly when required. For example where the assembly forms part of a vehicle it may be useful to reduce buoyancy of the vehicle when the vehicle is wading. This may be helpful in increasing a weight on wheels of the vehicle to enable or improve traction between the wheels and a driving surface, for example a river bed or flooded road. 
         [0055]    In a further aspect of the invention there is provided an assembly formed by the method of the preceding aspect. 
         [0056]    In an aspect of the invention for which protection is sought there is provided an assembly comprising: a first component and a second component coupled to one another in spaced apart relationship by means of coupling means; and thermally activated seal means between the first and second components, the first component, second component and seal means being arranged such that a gap exists between the first and second components allowing fluid flow therebetween; wherein the seal means comprises thermally activated seal means arranged to expand upon heating to bridge the gap between the first and second components thereby to form a fluid tight seal between the components. 
         [0057]    The assembly may comprise a third component wherein the first and third components at least partially enclose the second component. 
         [0058]    The second component may be substantially fully enclosed by the first and third components. 
         [0059]    Advantageously the third component may be coupled to one or both of the first and second components. 
         [0060]    Further advantageously the second component may be provided with at least one aperture therein to allow flow of fluid into or out from the second component. 
         [0061]    Still further advantageously thermally activated seal means may be provided around the one said at least one aperture in the second component, the seal means being arranged to form a seal between the second and third components upon heating. 
         [0062]    The seal means around the one said at least one aperture in the second component may be provided at a location of the second component opposite a portion of the third component wherein expansion of the seal means causes the one said at least one aperture in the second component to be closed by the seal means and said portion of the third component thereby to prevent flow of fluid into or out from the second component via the one said at least one aperture. 
         [0063]    Optionally at least one aperture is provided in the third component. 
         [0064]    This feature has the advantage that fluid may flow through the third component to flood a volume between the second and third components. 
         [0065]    Advantageously one said at least one aperture in the third component may be provided at a location displaced laterally with respect to the 
         [0000]    at least one aperture in the second component such that when the seal means around the at least one aperture in the second component expands to form a seal between the second and third components no portion of the at least one aperture in the third component overlaps the at least one aperture in the second component. 
         [0066]    This feature has the advantage that no direct path exists for the flow of fluid through the aperture in the third component and subsequently through the aperture in the second component. 
         [0067]    Further advantageously the second component may comprise a tray, the seal means between the first and second components being provided around a peripheral edge of the tray, the seal means being arranged on heating to expand away from the peripheral edge of the tray to bridge a gap between the peripheral edge and the first component thereby to form the fluid tight seal therebetween. 
         [0068]    The assembly may comprise valve means for controlling flow of fluid into or out from the second component via one said at least one aperture. 
         [0069]    The valve means may be one selected from amongst coupled to the second component, formed integrally with the second component and provided in a fluid conduit through which fluid may pass to fill or drain the second component. 
         [0070]    The valve means may be arranged to control flow of fluid through the second and third components to allow filling or draining of the second component. 
         [0071]    Optionally an aperture is provided in the first component allowing access to an interior of the tray. 
         [0072]    Advantageously the first component may comprise a floorpan assembly of a motor vehicle. 
         [0073]    Further advantageously the third component may comprise one selected from amongst an underframe or understructure, a chassis, a ladder frame assembly and a monocoque. 
         [0074]    Still further advantageously the second component may be provided within a longitudinal portion or cross-member portion of the third component. 
         [0075]    Optionally the second component may define an air cavity of an audio speaker system. The second component may define a portion of a sub-woofer of an audio system. 
         [0076]    In an aspect of the invention for which protection is sought there is provided a vehicle, watercraft or aircraft comprising an assembly according to the preceding aspect. 
         [0077]    In one aspect of the invention for which protection is sought there is provided an assembly comprising a floorpan assembly and a baffle tray, the baffle tray comprising a tray portion and a seal member provided around a peripheral edge of the tray portion, the baffle tray being supported in spaced apart relationship with the floorpan assembly, the seal member comprising thermally activated seal means, the seal means being arranged on heating to expand away from the peripheral edge to bridge a gap between the peripheral edge of the tray and the floorpan assembly thereby to form a fluid tight seal therebetween around the peripheral edge of the tray. 
         [0078]    Advantageous features of the invention are mentioned in the following description and in the claims appended hereto. 
         [0079]    Within the scope of this application it is envisaged that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings may be taken independently or in any combination thereof. Features described in connection with one embodiment are applicable to all embodiments unless there is an incompatibility of features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0080]    Embodiments of the invention will now be described with reference to the accompanying figures in which: 
           [0081]      FIG. 1  is a perspective view of a sub-woofer baffle tray according to an embodiment of the present invention; 
           [0082]      FIG. 2  is a schematic illustration of a process in which the sub-woofer baffle tray is coupled to an underside of a floorpan assembly of a motor vehicle; 
           [0083]      FIG. 3  is a schematic illustration of (a) the sub-woofer baffle tray coupled to the floor panel and (b) a close-up view of a coupling member holding the baffle tray and floor panel in a spaced apart relationship; 
           [0084]      FIG. 4  is a schematic illustration of a process in which the floorpan assembly is coupled to a ladder frame assembly of the vehicle to form a vehicle body assembly; 
           [0085]      FIG. 5  is a cut-away view of a portion of a vehicle body assembly showing the tray assembly enclosed within a longitudinal member of the ladder frame assembly; 
           [0086]      FIG. 6  is a cross-sectional view of the portion of the vehicle body shown in  FIG. 5  showing the tray assembly enclosed within the longitudinal member of the ladder frame assembly; 
           [0087]      FIG. 7  is a perspective view of the floorpan assembly from above; 
           [0088]      FIG. 8  is a schematic cut-away view of the floorpan assembly following installation of an upper portion of a sub-woofer system; and 
           [0089]      FIG. 9  is a cross-sectional view of a body assembly with a ballast tank installed therein according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0090]      FIG. 1  is a perspective view of a sub-woofer baffle tray  110  according to an embodiment of the present invention. The tray  110  is arranged to be coupled to an underside  150 U of a floor panel  150  of a motor vehicle floorpan assembly  155  ( FIG. 2 ) thereby to define a box portion of a sub-woofer system. 
         [0091]    The tray  110  is of substantially U-shaped, square cross-section defined by two elongate, parallel side walls  110 A,  110 C and a basal wall  110 E. A pair of end walls  110 B,  110 D are provided at opposed ends of the side walls  110 A  110 C and basal wall  110 E. Lateral web members  110 W are provided within the tray  110 , oriented transverse to a longitudinal axis thereof in order to increase a stiffness of the tray  110 . This allows a reduction in thickness of walls  110 A,  110 C,  110 B,  110 D of the tray  110  thereby reducing a weight of the tray  110 . In some embodiments the tray  110  is formed from a glass reinforced plastics (GRP) material. 
         [0092]    A free peripheral edge  110 P of the tray  110  defined by free edges of the side walls  110 A,  110 C and end walls  110 A,  110 B is provided with a seal member  110 S in the form of a layer of heat-activated mastic. The seal member  110 S is set in a channel  116  formed along the peripheral edge  110 P of the aperture ( FIG. 3 ). The mastic from which the seal member  110 S is formed is arranged to expand by up to around 2-3 times its volume at least when heated to a seal member activation temperature of around 180° C. 
         [0093]    The basal wall  110 B of the tray  110  has three drain apertures  112 ,  113 ,  114  provided therein. A seal member  112 S,  113 S,  114 S is provided around a peripheral edge of each of the apertures  112 ,  113 ,  114 . The seal members  112 S,  113 S,  114 S are provided on an outer face of the basal wall  110  facing in an opposite direction from the seal member  110 S. Like the seal member  110 S, the seal members  112 S,  113 S,  114 S shown in detail in  FIG. 5  and  FIG. 6  are similarly provided in channels around their respective apertures  112 ,  113 ,  114 . 
         [0094]    Six coupling elements  131  in the form of clips of the fir-tree type are provided around the peripheral edge  110 P of the tray  110 . The clips are arranged to allow the tray  110  to be coupled to the underside of the floor panel  150  such that a gap exists between the seal member  110 S and the panel  150  once the two are coupled.  FIG. 3  shows a coupling element  131  in-situ supporting the tray  110  in juxtaposition with the floor panel  150 . Any suitable clip or other mechanical fixing allowing the tray  110  to be supported in spaced apart relationship with the panel  150  may be used. 
         [0095]    It can be seen that the coupling element  131  passes through a portion of the seal member  110 S such that the seal member  110 S surrounds the coupling element  131  at the location at which the element  131  passes through the seal member  110 S. This feature has the advantage that a fluid tight seal may be formed around the coupling element  131  once the seal member  110 S has expanded after passing through a paint bake oven. The formation of the fluid tight seal has the advantage that it prevents fluid external to the tray  110  from passing from a side of the floor panel  150  on which the tray  110  is located through the floor panel  150  to the opposite side of the floor panel  150 , via the tray  110 . 
         [0096]    During assembly of the vehicle in which the tray  110  is to be incorporated, the tray  110  is coupled to the underside  150 U of the floor panel  150  by means of the coupling elements  131  as shown in  FIG. 2 . An aperture  151  in the floor panel  150  allows convenient access to the cavity defined by the tray  110  from within the vehicle as described below. 
         [0097]    Subsequently, the floorpan assembly  155  is joined to longitudinal members  161  (or ladder members  161 ) of a ladder frame assembly  160  to form a vehicle body assembly  101  as shown in  FIG. 4  and  FIG. 5 . The floorpan assembly  155  is joined permanently to the longitudinal members  161  (for example by welding, mechanical fixing elements or any other suitable method) such that the tray  110  is contained within one of the longitudinal members  161 . The longitudinal members  161  have a substantially U-shaped section. An external form of the tray  110  corresponds to the internal form of the longitudinal member  161  within which it is provided. 
         [0098]    The longitudinal member  161  has a drain aperture  161 A formed in a basal portion thereof as shown in  FIG. 5 . It can also be seen from  FIG. 5  that the coupling elements  131  pass through the floor panel  150  from the tray  110  and are enclosed by floor panel cross-members  153  running in a lateral (east-west) direction across the floor panel  150 . This feature has the advantage that a risk that clashes occur between the exposed portions of the seal members  131  and components of the body assembly  101  is reduced or substantially eliminated. 
         [0099]    Once the floorpan assembly  155  has been joined to the ladder frame assembly  160  the vehicle body assembly  101  is subject to an electro-coating process such as an electrophoretic deposition process commonly known as an e-coat dipping process. The vehicle body assembly  101  is dipped in a bath of e-coat fluid such as a primer, paint or any other suitable fluid in order to form a coating of e-coat fluid over the vehicle body assembly  101 . 
         [0100]    The aperture  151  in the floor panel  150  is arranged to allow e-coat fluid to flood the internal volume defined by the tray  110  when the assembly  101  is dipped in the fluid. The drain apertures  112 ,  113 ,  114  provided in the basal wall  110 B of the tray  110  and the aperture  161 A formed in the longitudinal member  161  allow e-coat fluid to flood the volume between the tray  110  and longitudinal member  161  during the e-coat dipping process. 
         [0101]    When the body assembly  101  is subsequently removed from the bath of e-coat fluid, excess e-coat fluid is allowed to drain from the assembly  101  through the apertures  151 ,  112 ,  113 ,  114 ,  161 A leaving substantially all surfaces of the floor panel  150  and longitudinal member  161  coated in a layer of e-coat. It is to be understood that in embodiments in which the tray  110  is formed from a plastics or other non-conducting material the tray  110  is unlikely to be coated with e-coat following removal from the bath. In embodiments in which the tray  110  is formed from a conductive material the tray  110  may be arranged to become coated with a layer of e-coat. 
         [0102]    Thus it is to be understood that portions of the underside  150 U of the floor panel  150  that are enclosed by the tray  110  or longitudinal member  161  may be coated with a layer of e-coat fluid in a coating process performed after the assembly  101  has been formed, whilst still allowing the tray  110  to be sealed against the floor panel  150  thereby forming a sealed internal volume or cavity of the tray  110 . This has the advantage that coating of individual components of the assembly  101  before the assembly  101  is formed is not required. 
         [0103]    It is to be understood that in some assembly processes it is not possible to perform an e-coating process before the body assembly  101  is formed. In some arrangements this is because the joining method employed is not compatible with coated surfaces. 
         [0104]    In some arrangements the body assembly  101  is rotated after removal from the bath of e-coat fluid in order to allow draining of e-coat fluid therefrom. In some arrangements the body assembly  101  is rotated through an angle of substantially 360° after removal from the bath. In some arrangements the body assembly  101  is also rotated whilst the body assembly  101  is submerged in the bath. 
         [0105]    It is to be understood that whilst a process has been described in which the body assembly  101  is exposed to an e-coat fluid, in some alternative embodiments the body assembly  101  may be exposed to a fluid other than an e-coat fluid such as an electrolyte of an anodisation process, a cleaning fluid or any other fluid to which it is required to expose the body assembly  101 . Processes other than e-coating processes are also useful. 
         [0106]    The body assembly  101  is then heated in an oven to allow curing of the e-coat layer. It is to be understood that the body assembly  101  is first heated to a curing temperature at which curing of the e-coat layer takes place, the curing temperature being below the seal member activation temperature. Once curing has taken place the temperature of the assembly  101  is then increased to the seal member activation temperature. 
         [0107]    It is to be understood that in some arrangements the body assembly  101  may be heated to a temperature at which curing of the e-coat layer takes place to an extent sufficient to allow activation of the seal members  110 S,  112 S,  113 S,  114 S to take place, further curing taking place after the seal members  110 S,  112 S,  113 S,  114 S have expanded to seal the respective gaps. 
         [0108]    In some arrangements the assembly  101  is heated to the seal member activation temperature over a period of time that is sufficiently long to allow curing of the e-coat layer before the seal member activation temperature is reached. 
         [0109]    Once the seal member activation temperature is reached, the heat-activated mastic forming the seal members  110 S,  112 S,  113 S,  114 S expands. The seal member  110 S around the peripheral edge  110 P of the tray  110  expands to seal the gap between the tray  110  and floor panel  150 . The seal members  112 S,  113 S,  114 S around the drain apertures  112 ,  113 ,  114  in the tray  110  expand to seal the gap between the drain apertures  112 ,  113 ,  114  and longitudinal member  161 . 
         [0110]    Thus it is to be understood that once the seal members  110 S,  112 S,  113 S,  114 S have been caused to expand fluid communication between an internal volume of the tray  110  and an environment external to the tray  110  is possible only through the aperture  151  formed in the floor panel  150 . 
         [0111]    It is to be understood that the seal members  112 S,  113 S,  114 S around the drain apertures  112 ,  113 ,  114  are not provided opposite the drain aperture  161 A in the longitudinal member  161 , and therefore the apertures  112 ,  113 ,  114  are closed once the seal members  112 S,  113 S,  114 S have expanded to bridge the gap between the tray  110  and longitudinal member  161 . 
         [0112]    In some embodiments the aperture  161 A in the longitudinal member  161  remains open during a service life of the vehicle in order to allow ventilation of the volume between the tray  110  and the longitudinal member  161 . This volume may be referred to as a ‘wet’ region because if the longitudinal member  161  is immersed in liquid when the vehicle is in use, for example in a wading operation, the volume may become exposed to the liquid. 
         [0113]    In a further step of assembly shown in detail in  FIG. 8  an upper portion  181  of a sub-woofer system  180  is installed above the tray  110  within a cabin of the vehicle. The upper portion  181  has an aperture  181 A that forms a substantially fluid-tight seal with the aperture  151  in the floor panel  150 . 
         [0114]    It is to be understood that in use the pressure in the sub-woofer baffle tray  110  may range between around 1 atmosphere above atmospheric pressure and 1 atmosphere below atmospheric pressure as air is forced into and out from the baffle tray  110  by a sub-woofer driver. The path of air flowing into (AI) and out from (AO) the sub-woofer baffle tray  110  is illustrated schematically in  FIG. 8 . 
         [0115]    In some embodiments the tray  110  is provided with a further one or more seal members at one or more other locations of an outer surface thereof in order to form a seal bridging the gap between the tray  110  and longitudinal member  161  following activation of the mastic of the seal member(s). This feature allows the tray  110  to be supported at further locations along a length thereof and can be useful in reducing vibration of the tray in use, such as vibration at one or more resonant frequencies of the tray  110 . 
         [0116]    In the present embodiment three substantially U-shaped seal members  118  are provided at spaced apart locations along a length of the tray  110 , the seal members  118  running around an outer surface of the walls  110 A,  110 E,  110 C from one side of the peripheral edge  110 P to the other. The presence of these seal members  118  helps to increase a stiffness of the tray  110  in use when installed in the longitudinal member. This feature is particularly useful due to the relatively large changes in pressure that may occur within the tray  110  when in use as described above. 
         [0117]    It is to be understood that the use of seal members  110 S,  112 S,  113 S,  114 S formed from a heat-activated mastic has the advantage that variations in the size of a gap between the tray  110  and longitudinal member  161  or floor panel  150  can be readily accommodated when the seal members  110 S,  112 S,  113 S,  114 S are activated. 
         [0118]    It is to be understood that whilst embodiments of the invention have been described in respect of the provision of a sub-woofer baffle, in some alternative embodiments the tray  110  may be used for a different purpose. For example the tray  110  may be arranged to be accessible by a driver or passenger for the purpose of storing items such as personal items or vehicle accessories. In some embodiments the panel may provide a fluid reservoir such as a reservoir for screenwash or any other suitable liquid. Alternatively or in addition the panel may be employed to store one or more vehicle systems or system components. Other uses or functions are also useful. 
         [0119]      FIG. 9  shows a portion of a body assembly  201  in which a tray  210  has been coupled to an underside  250 U of a floor panel  250  of a motor vehicle floorpan assembly  255  thereby to define a ballast tank  210 BT. 
         [0120]    The tank  210 BT is enclosed by a longitudinal member  261  of a ladder frame assembly in a similar manner to the tray  110  of the embodiment shown in  FIG. 5 . The tray  210  has a pair of fluid drain apertures  210 FD in a lower surface thereof located directly above a corresponding pair of fluid drain apertures  261 FD formed in the longitudinal members  261 . Respective fluid conduits  210 C are provided to direct fluid into and out from the tank  210 BT via respective apertures  210 FD,  261 FD. Valves  210 V are coupled to an underside of the longitudinal members  261  at each of the apertures  261 FD for selectively opening and closing the apertures  261 FD to allow or prevent flow of fluid into or out from the tank  210 BT. 
         [0121]    An air vent aperture  255 AV is provided in the floor panel  250  of the assembly  201  to which an air vent valve  255 V is attached. The vent valve  255 V may be opened when it is required to flood the tank  210 BT with water or drain water from the tank  210 BT. 
         [0122]    Each of the valves  210 V,  255 V may be controlled to open and close by means of a signal from a controller. 
         [0123]    In use, if a vehicle is wading in water and it is determined that a reduction in buoyancy of the vehicle is required, the fluid drain valves  210 FD and air vent valve  255 V may be opened to allow water to flood the ballast tank  210 BT. When a sufficient amount of water has been drawn into the tank  210 BT the air vent valve  255 V may be closed, and optionally the drain valves  210 FD. When it is required to empty the tank  210 BT the vent valve  255 V may be opened (and fluid drain valves  210 FD if not already open) to allow water to drain. 
         [0124]    It is to be understood that the air vent valve  255 V and fluid drain valves  210 V could be controlled so as to remain open whilst wading. However if a risk exists that a level of liquid may rise such that water flows through the air vent valve  255  it is advisable to close air vent valve  255 V or the fluid drain valves  210 FD or all three valves  255 V,  210 FV in order to prevent flow of water through the air vent valve  255 V. 
         [0125]    Other arrangements are also useful. 
         [0126]    Embodiments of the invention have been described with respect to a monocoque motor vehicle construction. It is to be understood that embodiments of the invention are suitable for use in motor vehicles having an alternative construction such as a body/chassis construction or any other form of construction. Embodiments of the invention are also useful in construction of other articles such as components of buildings, aircraft including fixed and rotary wing aircraft, watercraft including ships and other vessels and many other articles and objects. 
         [0127]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
         [0128]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0129]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.