Abstract:
This invention relates to packaging of a modular aerodynamic trailer skirts that is adapted to minimize the size of a shipment thereof. The packaging further protects the skirt portions by stacking skirt portions and using interconnecting edges thereof to secure a skirt portion therebetween.

Description:
CROSS-REFERENCE 
       [0001]    The present application relates to and is a non-provisional application of U.S. Patent application No. 62/058,341 filed Oct. 1, 2014 entitled MODULAR AERODYNAMIC SKIRT ASSEMBLY, this document is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to aerodynamic trailer skirts adapted to be mounted on trailers to improve the aerodynamic efficiency of the trailer. The present invention more precisely relates to a modular aerodynamic skirt packaging assembly and method thereof. 
       BACKGROUND OF THE INVENTION 
       [0003]    Road tractors are generally used to pull trailers on roads to transport cargo. Aerodynamic apparatuses can be installed on the road tractor and/or on the trailer in order to reduce the aerodynamic air drag and improve fuel efficiency. 
         [0004]    Trailer aerodynamic skirts are generally parallelly installed on both longitudinal sides of a trailer to help manage the flow of air around and underneath the trailer. Brackets are affixed to the trailer to secure the aerodynamic skirts positioned thereto. These aerodynamic skirts are secured to the bottom portion of the trailer, or on the sides of the trailer&#39;s floor, to ensure proper positioning when the vehicle is moving. 
         [0005]    People who are familiar with the trucking industry know that trailers are subject to hazardous road conditions. The aerodynamic skirts, because of their position under the trailer&#39;s floor and their proximity with the road, are significantly vulnerable and might easily enter in contact with surrounding obstacles. The brackets holding the aerodynamic skirts, when put under significant stress, plastically bend and/or break to effect the aerodynamic skirts&#39; position in respect to the trailer thus reducing the efficiency of the aerodynamic skirts. Moreover, the aerodynamic skirt itself might bend and/or break if they contact a foreign object. This also increases the operation cost and the maintenance time that is required. 
         [0006]    The size of the aerodynamic skirts is substantial and shipping uninstalled aerodynamic skirts for remote installation is cumbersome. Aerodynamic skirts are generally considered by shipping companies to be of non-standard sizes and are too large to fit on a standard shipping pallet. They can be damaged during transport from the factory to the installation garage where the aerodynamic skirts are going to be installed on the vehicle because of their length and their width. 
         [0007]    Aerodynamic skirts assembly are sustaining a significant amount of stress when deflecting air in their operating positions on a vehicle. Mechanical stresses and sustained vibrations are challenging the skirt assembly. 
         [0008]    Therefore, there exists a need in the art for an improved aerodynamic skirt over the existing art. There is a need in the art for such an aerodynamic skirt assembly that can be easily and economically packaged and shipped. There is also a need in the art for an improved modular aerodynamic skirt assembly that is not jeopardizing the mechanical integrity of the aerodynamic skirt assembly. Moreover, there is also a need for a modular aerodynamic skirt assembly that is appropriately sustaining vibrations caused by the vehicle circulating on the road. 
       SUMMARY OF THE INVENTION 
       [0009]    It is one aspect of the present invention to alleviate one or more of the drawbacks of the background art by addressing one or more of the existing needs in the art. 
         [0010]    Accordingly, an aspect of our work, in accordance with at least one embodiment thereof, provides an improved aerodynamic trailer skirt over the prior art. 
         [0011]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic skirt assembly adapted to be installed on a trailer to reduce the aerodynamic drag produced by the movement of the trailer when pulled by a road tractor. 
         [0012]    An aspect of our work, in accordance with at least one embodiment thereof, provides a resilient aerodynamic skirt assembly that is adapted to bend when it contacts a foreign object and to self-recover its original position and shape thereafter. 
         [0013]    An aspect of our work, in accordance with at least one embodiment thereof, provides a resilient aerodynamic skirt assembly that can be easily installed and economically manufactured. 
         [0014]    An aspect of our work, in accordance with at least one embodiment thereof, provides a modular aerodynamic skirt including a plurality of skirt portions configured to be assembled together. 
         [0015]    An aspect of our work, in accordance with at least one embodiment thereof, provides a modular aerodynamic skirt including a plurality of skirt portions sized and designed to be packaged on a cargo pallet with other struts and connectors for reduced shipping size. 
         [0016]    An aspect of our work, in accordance with at least one embodiment thereof, provides a plurality of skirt portions sized and designed to be secured together to form a complete aerodynamic skirt assembly adapted to be installed on a trailer in an operating aerodynamic configuration. 
         [0017]    An aspect of our work, in accordance with at least one embodiment thereof, provides a plurality of skirt portions sized and designed to be secured together, the skirt portions being secured together with cooperating edges locates at an angle from vertical, when installed on a trailer, to distribute mechanical stresses thereof when the aerodynamic skirt assembly is bending when contacting a foreign object. 
         [0018]    An aspect of our work, in accordance with at least one embodiment thereof, provides a plurality of skirt portions sized and designed to be secured together with cooperating edges disposed at an angle from vertical to form a complete aerodynamic skirt assembly and reduces stresses, forces, moments and displacements the aerodynamic skirt assembly experiences by sharing the loads on several fasteners securing the skirt portions together. 
         [0019]    An aspect of our work, in accordance with at least one embodiment thereof, provides a plurality of skirt portions sized and designed to be secured together in a fashion allowing a progressive transfer of a wave traveling therein caused by a shock applied on the skirt from one skirt portion to an adjacent skirt portion. 
         [0020]    An aspect of our work, in accordance with at least one embodiment thereof, provides a plurality of skirt portions sized and designed to be secured together with cooperating edges disposed at an angle of about 10° from vertical to form a complete aerodynamic skirt assembly and to reduce stresses, forces, moments and displacements the aerodynamic skirt assembly by simultaneously sharing the loads on several fasteners securing the skirt portions together. 
         [0021]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic skirt assembly designed to have a natural frequency that is different from the excitation frequency of the trailer in motion. 
         [0022]    An aspect of our work, in accordance with at least one embodiment thereof, provides supports securing the skirt to the trailer disposed at the junction between adjacent skirt portions to reduce the mechanical stress at cooperating interconnecting edges thereof. 
         [0023]    An aspect of our work, in accordance with at least one embodiment thereof, provides a method of locating skirt supports in locations reducing or modifying the natural frequency of the aerodynamic skirt assembly. 
         [0024]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic skirt assembly positioning supports thereof at locations causing a reduction or a modification of the natural frequency of the aerodynamic skirt assembly. 
         [0025]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic skirt assembly made of composite materials offering a significant range of elastic deformation. 
         [0026]    An aspect of our work, in accordance with at least one embodiment thereof, provides a resilient strut adapted to secure a skirt panel to a trailer, the strut being made of a resilient material adapted to sustain significant deformation and adapted to resiliently self-recover its original shape. 
         [0027]    An aspect of our work, in accordance with at least one embodiment thereof, provides strut supports made of non-metallic material. 
         [0028]    An aspect of our work, in accordance with at least one embodiment thereof, provides a shock-resistant trailer aerodynamic skirt that is sized and designed to allow a temporary deflection of a bottom portion of the skirt panel upon contact of a foreign object. 
         [0029]    An aspect of our work, in accordance with at least one embodiment thereof, provides a fastening system for easily securing the skirt panel to the trailer; the fastening system uses a limited number of parts to reduce the assembly time and the weight added to the trailer. 
         [0030]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic skirt assembly comprising a plurality of support members adapted to secure the skirt panel to the trailer. 
         [0031]    Embodiments of the present invention provides a skirt assembly kit comprising a plurality of cooperating skirt panels adapted to longitudinally be disposed on a trailer to route air about the trailer, a plurality of upper supports adapted to secure the skirt panel to the trailer and a plurality of struts adapted to secure the skirt panel to the trailer. 
         [0032]    An aspect of our work, in accordance with at least one embodiment thereof, provides an aerodynamic modular skirt assembly having a reduced size for shipping. The larger parts of the modular skirt assembly, the pair of skirt panels, are separated in a plurality of smaller skirt portions adapted to be superposed for reducing the cargo size. 
         [0033]    An aspect of our work, in accordance with at least one embodiment thereof, provides a shipping configuration using at least one of the skirt portions on two opposed sides of a cargo arrangement and locate the additional parts of the modular aerodynamic skirt assembly between skirt portions for reduced cargo size and strength of the cargo arrangement. 
         [0034]    An aspect of our work, in accordance with at least one embodiment thereof, provides a method of packaging a modular aerodynamic skirt panel, the method comprising providing a plurality of skirt portions; and stacking the plurality of skirt portions, wherein the area covered by the stacked skirt portions is within the area of a larger of the skirt portions. 
         [0035]    An aspect of our work, in accordance with at least one embodiment thereof, provides a modular aerodynamic skirt packaging, the packaging comprising a plurality of skirt portions staked one on top of the other, wherein the area covered by the stacked skirt portions is within the area of a larger of the skirt portions. 
         [0036]    An aspect of our work, in accordance with at least one embodiment thereof, provides a modular aerodynamic skirt assembly kit comprising a plurality of skirt portions staked one on top of the other, wherein the area covered by the stacked skirt portions is within the area of a larger of the skirt portions. 
         [0037]    Other embodiments and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
         [0038]    Additional and/or alternative advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, disclose preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    Referring now to the drawings which form a part of this original disclosure: 
           [0040]      FIG. 1  is a perspective view of a road tractor operatively connected to a trailer including a skirt assembly secured thereto; 
           [0041]      FIG. 2  is a left elevational view of the road tractor of  FIG. 1 ; 
           [0042]      FIG. 3  is a bottom plan view of the road tractor of  FIG. 1 ; 
           [0043]      FIG. 4  is a left elevational view of a trailer of  FIG. 1 ; 
           [0044]      FIG. 5  is an elevational side view of a skirt; 
           [0045]      FIG. 6  is an elevational view of a skirt portion; 
           [0046]      FIG. 7  is an elevational view of a skirt portion; 
           [0047]      FIG. 8  is an elevational view of a skirt portion; 
           [0048]      FIG. 9  is a section view of an interconnecting edge of a skirt portion; 
           [0049]      FIG. 10  is a section view of an interconnecting edge of a skirt portion; 
           [0050]      FIG. 11  is a bottom-right isometric view of a trailer&#39;s floor beams and a skirt assembly; 
           [0051]      FIG. 12  is a right side elevational view of a skirt assembly; 
           [0052]      FIG. 13  is a top plan view of a skirt assembly; 
           [0053]      FIG. 14  is a front-right isometric view of a skirt assembly; 
           [0054]      FIG. 15  is a rear elevational view of a skirt assembly secured to a trailer floor; 
           [0055]      FIG. 16  is a right elevational view of a skirt assembly; 
           [0056]      FIG. 17  is a top plan view of a skirt assembly secured on beams of a trailer floor; 
           [0057]      FIG. 18  is a magnified portion of an isometric view of a support member secured to a beam of a trailer floor; 
           [0058]      FIG. 19  is a side elevational view of a support member secured to a beam of a trailer floor; 
           [0059]      FIG. 20  is a section view of a connection mechanism securing a resilient strut to a trailer floor beam; 
           [0060]      FIG. 21  is a section view of a connection mechanism securing a resilient strut to a trailer floor beam; 
           [0061]      FIG. 22  is a section view of a connection mechanism securing a resilient strut to a skirt portion; 
           [0062]      FIG. 23  is a section view of a connection mechanism securing a resilient strut to a skirt portion and a trailer floor beam; 
           [0063]      FIG. 24  is a schematic illustration of a resilient strut in the aerodynamic configuration; 
           [0064]      FIG. 25  is a schematic illustration of a resilient strut proximally bent away from the aerodynamic configuration; 
           [0065]      FIG. 26  is a schematic illustration of a resilient strut in the aerodynamic configuration; 
           [0066]      FIG. 27  is a schematic illustration of a resilient strut proximally bent away from the aerodynamic configuration; 
           [0067]      FIG. 28  is a schematic illustration of a resilient strut in the aerodynamic configuration; 
           [0068]      FIG. 29  is a schematic illustration of a resilient strut distally bent away from the aerodynamic configuration; 
           [0069]      FIG. 30  is a side elevational view of a skirt panels assembly joined with an angled interconnecting edge; 
           [0070]      FIG. 31  is a side elevational view of a skirt panels assembly joined with a straight vertical interconnecting edge; 
           [0071]      FIG. 32  is a top plan view of a skirt panels assembly; 
           [0072]      FIG. 33  is a top schematic plan view of a skirt panel with moment and shear forces thereon; 
           [0073]      FIG. 34  is a schematic side elevational view of a skirt panels assembly joined with vertical interconnecting edges schematically illustrating an exemplary shock wave transmission along the skirt panel; 
           [0074]      FIG. 35  is a schematic side elevational view of a skirt panels assembly joined with an angled interconnecting edge schematically illustrating a vectorial force separation of an exemplary shock wave transmission along the skirt panel; 
           [0075]      FIG. 36  is a schematic illustration of a graph with showing a forced frequency curve and a natural frequency curve of an aerodynamic skirt assembly; 
           [0076]      FIG. 37  is a schematic flow chart in accordance with an embodiment of the present application; 
           [0077]      FIG. 38  depicts an isometric view of a cargo configuration in accordance with an embodiment of the present application; 
           [0078]      FIG. 39  depicts an isometric view of a cargo configuration in accordance with an embodiment of the present application; 
           [0079]      FIG. 40  depicts a top plan view of a cargo configuration in accordance with an embodiment of the present application; 
           [0080]      FIG. 41  depicts a top plan view of a cargo configuration in accordance with an embodiment of the present application; 
           [0081]      FIG. 42  depicts a top plan view of a cargo configuration in accordance with an embodiment of the present application; 
           [0082]      FIG. 43  depicts an isometric view of a cargo configuration in accordance with an embodiment of the present application; 
           [0083]      FIG. 44  depicts an isometric view of a cargo configuration in accordance with an embodiment of the present application; 
           [0084]      FIG. 45  depicts a top plan view of a cargo configuration in accordance with an embodiment of the present application; and 
           [0085]      FIG. 46  depicts a skirt portions staking for compact and secure transportation thereof. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0086]    A preferred embodiment of the present invention is described bellow with reference to the drawings. 
         [0087]      FIGS. 1, 2 and 3  illustrate a road tractor  10  with a trailer  20  attached thereto equipped with a pair of skirt panels  31 , installed on each side of the trailer  20 , adapted to deflect and direct the airflow around the trailer  20  when assembled to the trailer  20 . Each skirt assembly  30  includes a skirt panel  31  including a plurality of skirt portions  32 . 1 ,  32 . 2 ,  32 . 3 , adapted to be disposed on the side of the trailer  20 , and a plurality of securing members adapted to secure the skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  to the trailer  20 . Once installed on the trailer  20 , the skirt assembly  30  helps channel the flow of air around the trailer  20  to reduce the air drag of the vehicle when the trailer  20  moves on the road, pulled by the road tractor  10 . 
         [0088]    Each skirt assembly includes three skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  as exemplified in the illustrated embodiment. A different number of skirt portions  32  remains within the scope of the present invention although three skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  is one preferred embodiment. Securing members securing the skirt panels  31  in an operating configuration on the trailer  20  are not illustrated on  FIGS. 1, 2 and 3  and will be discussed in more details later in this specification. 
         [0089]    The skirt assembly  30  of the present embodiment is mostly attached under the trailer  20 , between the wheels  12  of the road tractor  10  and the wheels  26  of the trailer  20 . The assembled skirt portions  32  can alternatively extend forward up to the trailer supports  14  of the trailer  20 , and be secured thereto, thus preventing complex skirt portions  32  arrangements around, or through, the trailer supports  14 . The skirt portions  32  are substantially vertically positioned on each side of the trailer  20 , preferably on the lower edge of the trailer  20  vertical sidewalls, with a clearance with the ground by illustratively about 20-30.5 centimeters (about 8 to 12 inches) while other clearances remain within the scope of the present application. The air management around the trailer  20  provided by the skirt assembly  30  reduces the air drag created by the trailer  20  by directing the flow of air around and under the trailer  20 . The flow of air would otherwise turbulently move around and under the trailer  20  to create substantial air drag having a negative effect on the aerodynamics of the trailer  20 . The airflow management around the trailer  20  provided by the skirt assembly  30  helps maintaining laminar airflow around the trailer  20  that helps diminish fuel consumption of the road tractor  10 . The skirt assembly  30  also improves the safety of the vehicle by providing a physical barrier that can significantly prevent foreign objects to get under the trailer  20 . 
         [0090]    As illustrated, the assembled skirt  30  is shaped with an optional progressive height of the front skirt portion&#39;s  32 . 1  forward section. The skirt panels  32  can alternatively also be installed at an angle, in respect to the vertical, on the trailer  20  to change the airflow pattern around the trailer  20  and more precisely adjust the aerodynamics to a particular vehicle shape and use. 
         [0091]    It can be appreciated from  FIG. 3  that each skirt panel portion  32  is installed directly on the side&#39;s edge of the trailer  20  and, when seen from above, has a front portion  34  that progressively proximally leans toward a longitudinal center  24  of the trailer  20 . The recessed front skirt portion  32 . 1  of the assembled skirt portions  32  improves the collection and routing of the turbulent airflow generated by the road tractor  10  thus improving the aerodynamic performance of the skirt assembly  30 . Additional details about the shape of the skirt panel  31  will be provided in further details below. A right side of the trailer  20  equipped with a skirt assembly  30  is illustrated in  FIG. 4 . Each skirt assembly includes three skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  in the illustrated embodiment. The skirt portions are embodied as three (3) different skirt portions  32  to split the length of the complete skirt panel  31  and facilitate its handling and shipping. Three skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  in the present situation seems to shorten the skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  in a sized compatible with standard shipping methods, however, a different number of skirt portions  32  could be used without departing from the scope of the present invention. The longitudinal length of each of the skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  can be adapted to different configurations. In the present situation, the middle skirt portion  32 . 2  is embodied as the larger skirt portion  32  because, for instance, of its rather rectangular shape. Other proportions of skirt portion  32  lengths could be used without departing from the scope of the present invention. 
         [0092]    Skirt portions  32  assembly is illustrated in  FIG. 4  and its components are depicted in  FIG. 5  throughout  FIG. 9 .  FIG. 6  depicts the forward skirt portion  32 . 1 . The forward skirt portion  32 . 1  is embodied with a straight vertical front edge  100 , an upper rectilinear edge  104  adapted to match the bottom edge of the trailer  20 , an angled bottom edge  108  configured to progressively manage the airstream around the trailer  20  and a rear edge  112  adapted to connect with the middle skirt portion  32 . 2 . The rear edge  112  is preferably at an angle α to increase the mechanical strength of the skirt portions  32  assembly; the effect of angle α is going to be discussed below in greater details. The angle α create an obtuse angle  80  allowing the lower edges  84  of the middle skirt portion  32 . 2  and the rear skirt portion  32 . 3  to slip over an external object  88  when the aerodynamic skirt assembly  30  is installed in an aerodynamic configuration and the trailer  20  is moving in a forward direction. 
         [0093]    The forward skirt portion  32 . 1  is assembled to the middle skirt portion  32 . 2  with a plurality of fasteners  116 , like bolts, rivets or other means adapted to secure the skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  together. The middle skirt portion  32 . 2  illustrated in  FIG. 7  includes an upper edge  120 , a bottom edge  124  a forward edge  128  and a rearward edge  132 . The upper edge  120  and the bottom edge  124  are embodied parallel to one another. The forward edge  128  and the rearward edge  132  are interconnecting edges  136  configured to receive and secure thereto respectively the forward skirt portion  32 . 1  and the rear skirt portion  32 . 3 . The two interconnecting edges  136  are located on the middle skirt portion  32 . 2  to restrict the complexity provided by the interconnecting edges  136  the panels  32 . 1 ,  32 . 2 ,  32 . 3  to a single panel portion  32 . 2 . Each interconnecting edge  136  includes a recessed portion  140  adapted to secure thereon the cooperating edge of the adjacent skirt portion  32 . The recessed portion can extend about 37 mm (˜1.5″) of flat section that is shaped directly in the middle skirt portion  32 . 2 . The recessed portion  140  is proximally recessed of the equivalent of the thickness of the skirt  32  sheet material, which is illustratively of about 4.5 mm (˜0.180″), to overlap and joint the adjacent skirt portions  32 . 1 ,  32 . 2 ,  32 . 3 . This embodiment is illustrated in  FIG. 9 . Alternatively, an additional interconnecting part  148  can be used to secure together two adjacent skirt portions  32  (illustrated in  FIG. 10 ). The additional interconnecting part  148  would then be secured on the proximal side of the two adjacent skirt portions  32 . Both configurations are ensuring that the distal surface of the assembled skirt portions  32  is flush, at the same level  144 , and facilitate the airflow thereon. The interconnecting edge  136  includes a plurality of holes  152  sized and designed to receive therein fasteners  116  to secure the assembly; e.g. 8 mm (˜ 5/16″) bolts. 
         [0094]    The rear portion  32 . 3  exemplified in  FIG. 8  includes a forward edge  156 , a rearward edge  168 , an upper edge  160  and a bottom edge  164 . In the present configuration, the forward edge  156  is configured to be assembled with the rear interconnecting edge  132 ,  136  of the middle skirt portion  32 . 2 . 
         [0095]      FIG. 11  is a perspective image of the skirt assembly  30  installed on the right side of a trailer  20  from which is only illustrated a series of frame members  23  forming a portion of the trailer floor frame  22 . A series of support members  40  are secured to the trailer to secure the juxtaposed skirt panels  31  thereto. The support members  40  could be omitted altogether and the skirt panel could alternatively be attached directly to the trailer  20  without deviating from the scope of the present application. The rear portion of the skirt panel  31  is preferably positioned on the edge of the trailer&#39;s wall  28 . It is also covered by the present invention that the skirt panel  31  could be installed a little in recess about the side of the trailer  20  to avoid winches, lights, toolbox or ladders located on the side/edge of the trailer  20 . In contrast, it can be appreciated that the front skirt portion  32 . 1  of the skirt panel  31  is progressively positioned and secured toward the center  24  of the trailer  20 . The skirt panel  31  is secured adjacent to the frame  22  with a series of support members  40  secured to both the frame members  23  and the skirt panel  31 . Lower, the skirt panel  31  is secured to the trailer  20  with a series of intervening resilient struts  42  also secured to both the frame members  23  and the skirt panel  31 . Additional details about the support members  40  and the resilient struts  42  are provided later in reference with other Figures. 
         [0096]    Still referring to  FIG. 11 , it can be appreciated that the upper series of holes  35  disposed on a top portion of the skirt panel  31  is used to fasten the skirt panel  31  to respective support members  40  that, themselves, are secured to frame members  23  of the trailer  20 . A number of connection points between the skirt panel  31  and the trailer  20  are used to ensure the skirt panel  31  is well secured to the trailer  20  and will not vibrate or deflect (however some deflection can be acceptable under certain conditions) during operation. The series of holes  35  disposed on a lower portion of the skirt panel  31  are adapted to attach to an end of each resilient strut  42 . Similarly, with this configuration of struts  42 , the other end of the resilient strut  42  is connected to the frame members  23  of the trailer  20  via a fastener mechanism that will be discussed below in details. 
         [0097]      FIG. 12  throughout  FIG. 15  are additional views of the skirt assembly  30 . It can be further appreciated that a curved portion  38  is defined on the rear portion  36  of the skirt panel  31  and preferably corresponds to the exterior shape of the adjacent wheels  26  of the trailer  20 . In so doing, it is possible to install the skirt panel  31  close to the wheels  26  without risking any contact thereto. It is preferable to leave a distance between the wheels  26  of the trailer  20  and the skirt panel  31  to avoid any risk of interference therebetween. 
         [0098]    The wheels  26  of a trailer  20  are commonly adapted to be longitudinally adjustable to distribute the mass of the trailer  20  in a desired fashion. The adjustment of the position of the axels of a trailer  20  is desirable, for instance, when a heavy load is carried or during thaw and freeze periods. In this respect, and to avoid reinstalling the skirt panel  31  in various positions on the trailer  20 , it might be desirable to install the skirt panel  31  in respect with the forwardmost possible position of the axels of the trailer  20 . That would prevent to remove and reposition the skirt panel  31  when the trolley&#39;s  16  position is modified. 
         [0099]    The trailer wheels  26  are mounted on a trailer buggy  16  adapted to move the wheels  26  along a portion of the trailer&#39;s length to distribute the weight of the trailer  20  in a desired fashion. The skirt assembly  30  is preferably permanently secured to the trailer  20  taking in consideration the forwardmost position of the trailer buggy  16 . The gap between the skirt panel  31  and the trailer&#39;s wheels  26  is however increased when the trailer buggy  16  is move toward the rear of the trailer  20  thus likely reducing the aerodynamic efficiency of the skirt assembly  30 . The present invention provides a skirt panel extension module  33  adapted to reduce the gap between the skirt panel  31  and the trailer&#39;s wheels  26  to prevent any aerodynamic efficiency reduction. The skirt panel extension modules  33  are secured to the trailer in a similar fashion. The skirt panel extension module  33  can be provided in various lengths to fill gaps of various sizes. They can also be provided as skirt panel extension modules  33  kit. An alternate embodiment provides a sliding skirt panel extension  33  that is permanently secured to the trailer  20  and extendable to the desired length when the trailer buggy  16  is moved. 
         [0100]    A skirt panel extension  33 , illustrated on  FIG. 16 , can alternatively be added between the skirt panel  31  and the wheels  26  when the axles of the trailer  20  are located in a rearward position leaving an increased distance therebetween to improve the aerodynamic efficiency of the skirt assembly  30 . A reasonable distance between the skirt panel  31  and the wheels  26  could be between about 15 centimeters and about 30 centimeters although a shorter distance, or even a superposition of the skirt panel  31  (or skirt panel module(s)  33 ) over the wheel  26 , can be achieved. 
         [0101]      FIG. 17  is a top elevation view of the trailer frame  22 . As mentioned above, it can be appreciated from  FIG. 17  that the skirt panel  31  is disposed inwardly on the forward portion of the trailer  20  and is progressively located on the edge of the trailer&#39;s wall  28  toward the rear end of the trailer  20 . A departure support member  60  and a cooperating forward support member  64  are secured to the trailer to correctly locate the skirt panel  31  on the trailer  20 . The departure support member  60  and the forward resilient strut  64  are installed on the trailer  20  prior to install the skirt panel  31 . The rear portion  36  of the skirt panel  31  is secured to the trailer  20  up to the departure support member  60  and then the skirt panel  31  is bent to reach the forward support member  64  and secured thereto. That bent locates the skirt panel  31  to the trailer  20  and defines the shape of the skirt panel  31  with the desired progressive proximal bent. The remaining support members  62  and resilient struts  42  are installed thereafter to further secure the assembly. 
         [0102]    The rear portion  36  of the skirt panel  31  is intended to be secured to the trailer to leave only a minimum gap with the trailer wheels  26  to improve the aerodynamic efficiency of the skirt assembly  30 . The skirt panel  31  extends to the front of the trailer  20  and includes a curved portion on its front portion  34 . A long skirt panel  31  appears to be more efficient than a shorter skirt panel  31  and should therefore extend as far as possible to the front of the trailer  20 . However, for reasons of complexity, the front portion  34  of the skirt panel  31  is likely to stop at the trailer supports  14 . It is nonetheless encompassed by the present invention that the skirt panel  31  alternatively extends in front of the trailer supports  14 . The lowermost portion of the front portion  34  of the forward skirt panel  31 . 1  is provided with a radius thereof as it is best seen in  FIG. 16 . 
         [0103]    In an embodiment of the invention adapted to fit a standard 16.1 meters (˜53 feet) long trailer  20  the forward end of the departure support member  60  is located at a distance d 1  from the forward end of the skirt panel  31 . A forward support member  64  is secured to the frame at a distance d 2  from the side edge of the trailer  20  as it can be appreciated in  FIG. 16  and  FIG. 17 . Distance d 1  is about between 1.5 meter and 3 meters, preferably about between 2 meters and 2.5 meters and most preferably about between 2.1 meters and 2.4 meters. Distance d 2  is about between 0.20 meter and 0.40 meter, preferably about between 0.25 meter and 0.35 meter and most preferably about 0.27 meter and 0.32 meters. More precisely, distance d 1  is preferably about 2.29 meters and distance d 2  is preferably about 0.31 meter in a preferred embodiment. Corresponding support members  40  and resilient struts  42  are installed to further secure the skirt panel  31  at the desired position. 
         [0104]    A right side elevation view schematically illustrating, on  FIG. 16 , the overall size of the skirt panel  31 . Length d 3  of the skirt panel  31  is about between 5 meters and 9 meters, preferably about between 6 meters and 8 meters and most preferably about between 5.8 meters and 7.5 meters. The height d 4  of the skirt panel  31  is about between 0.5 meter and 1 meter, preferably about between 0.6 meter and 0.9 meter and most preferably about between 0.7 meter and 0.9 meter. And the forwardmost height d 5  of the skirt panel  31  is about between 0.3 meter and 0.7 meter, preferably about between 0.4 meter and 0.6 meter and most preferably about between 0.45 meter and 0.5 meter. More precisely, distance d 4  is preferably about 0.81 meter and distance d 5  is preferably about 0.48 meter in a preferred embodiment. 
         [0105]    Alternate embodiments providing a skirt assembly  30  sized and designed to fit trailers  20  of different lengths can be inferred from the dimensions discussed above. For instance, a skirt assembly  30  can be designed to fit a 14.6 meters (˜48 feet) trailer  20  or any other trailer  20  sizes and lengths. 
         [0106]    In one embodiment, the skirt panel  31  is made of composite material. Recommended multilayer composite material, fiber reinforced polypropylene, a combination of a polypropylene component and woven component or unidirectional thermoplastic manufactured by Transtex Composites Inc. is used in the present embodiment. The composite material forming the skirt panel  31  of the illustrative example is shaped in a planar material adapted to allow skirt panel  31  to bend when the skirt panel  31  is pushed toward the center of the trailer  20  (proximally) when, for instance, contacting an obstacle or having a force applied thereon. The skirt panel  31  bends, allowing a significant displacement of the bottom portion of the skirt panel  31  proximally and distally from a longitudinal centerline of the trailer  20 , and is adapted to retrieve by itself its original position when the force is removed from the skirt panel  31 . As further illustrated in  FIG. 16 , the skirt panel  31  is provided with a series of holes  35  therein used to connect the skirt panel  31  to the support members  40 ,  42  and  46 . The series of holes  35  disposed on the upper portion of the skirt panel  31  is used to connect the skirt panel  31  to the frame  22  of the trailer  20  whereas, in a similar fashion, the series of holes  35  disposed on the bottom portion of the skirt panel  31  is used to connect the skirt panel  31  to the skirt connecting portion  48  of the resilient strut  42 . The resilient strut  42  is connected to the frame member  23  of the trailer via the trailer-connecting portion  46  of the resilient strut  42 . The skirt connecting portion  48  and the trailer-connecting portion  46  include respective series of holes  35  to receive fasteners therein. The holes  35  can be factory pre-drilled or can be drilled during installation to ensure desired customization. Rivets or bolts are placed in the holes  35  to secure the skirt panel  31  to the trailer frame  22  or the support assembly. Other appropriate fastening mechanism variations well known in the art are encompassed by the present disclosure and can be used without departing from the scope of the invention. 
         [0107]    An opening  70  is defined in the skirt panel  31  to allow access to an optional fuel tank disposed on the trailer  20  to fuel an onboard generator or freezer. Such a fuel tank is commonly disposed under the floor  22  of the trailer  20  and is most likely hidden by the skirt assembly  30 . The opening is sized, designed and located on the skirt panel  31  to allow access to the fuel tank. A door (not illustrated) can optionally be added to close the opening  70 . 
         [0108]    Turning now again to  FIG. 15  where is illustrated a plurality of resilient struts  42  and angles support  40  secured between the frame  22  and the skirt panel  31 . The rear elevation view shows that the front portion  34  of the skirt panel  31  is proximally recessed from the left lateral side of the trailer  20  by, illustratively, about 30 centimeters. It can also be appreciated that the skirt panel  31  is held to the trailer frame  22  via the series of angled support  40  on its upper portion. The trailer connecting portion  46  of the resilient strut  42  is connected to the frame member  23  at an angle α 1 , which is an angle of about 45° in the present illustrative embodiment and could be different without departing from the present description. 
         [0109]      FIG. 18  and  FIG. 19  are illustrating a close up view of the connection between the skirt portions  32  and the trailer frame members  23  via support members  40 . It can be appreciated that the recessed portion  140  of the skirt portion  32 . 2  is shorter at the top to allow the support member  40  to be in contact with the skirt portions  32  all along its length. 
         [0110]    In one embodiment, the resilient strut  42  has a rectangular section and is made of composite material. Recommended multilayer composite material, polypropylene component, glass component, fiber reinforced polypropylene, a combination of a polypropylene component and woven component, or reinforced thermoplastic manufactured by Transtex Composites Inc. is used in the present embodiment. The composite material forming the resilient struts  42  of the illustrative example is shaped in a rectangular section to allow the resilient strut  42  to bend when the skirt panel  31  is pushed toward the center of the trailer  20  (proximally) when, for instance, contacting an obstacle or having a force applied thereon. The resilient strut  42  bends, allowing a significant displacement of the bottom portion of the skirt panel  31 , is adapted to self-retrieve its original position when the force is removed from the skirt panel  31 . The resilient strut  42  is preferably made of a one-piece material where both ends are slightly angled  44  to evenly contact the skirt panel  31  and the trailer frame member  23 . In so doing, no additional intervening parts are required between the resilient strut  42  and both the skirt panel  31  and the trailer frame member  23 . 
         [0111]      FIG. 20  and  FIG. 21  depict with more details the connection mechanism between the resilient struts  42  and the trailer frame members  23 . One of the resilient strut  42  ends is juxtaposed on the lower surface of the trailer frame  22 . A set of holes, identified with holes axes  54 , are used to fasten two clamps  50 , one on each side of the frame member  23  with fasteners  52 , to secure the resilient strut  42  to the trailer frame  22 . The clamps  50  can be designed such that they are elastically deforming to secure the frame member  23  and are illustratively made of a shaped stainless steel plate material to prevent corrosion. 
         [0112]      FIG. 22  illustrates the connection between the resilient strut  42  and the skirt panel  31 . The end of the resilient strut  42  is positioned to the surface of the skirt panel  31  and secured thereto. Any types of fasteners  56  can be used to fasten both parts together. Rivets are preferably used to secure the assembly with the resilient strut  42  although a bolt could also fit into the holes performed in the skirt panel  31 , identified with hole axis  54 , to secure the assembly. Glue or resin could alternatively be applied between the resilient strut  42  and the skirt panel  31  to secure the resilient strut  42  and the skirt panel  31  together and is also encompassed by the present invention. 
         [0113]      FIG. 23  shows the assembly between the upper portion of the skirt panel  31  and one of the angled supports  40 . The support member  40  is disposed next to the edge of the trailer  20  to position the exterior surface of the skirt panel  31  significantly co-planar with the lateral wall of the trailer  20 . Again, any types of fasteners can be used to fasten both parts together. Rivets are preferably used but a bolt could also fit into the holes  54  in the skirt panel  31  and the angled support  40  to secure the assembly. Here again, glue or resin could alternatively be applied between the support member  40  and the skirt panel  31  to permanently secure the support member  40  and the skirt panel  31  together. 
         [0114]    The resilient struts  42  of the present embodiment is about 4 millimeters thick and can reach a flexing radius of about 20 centimeters without reaching plastic deformation, or breaking. In some designs, the thinner the resilient strut  42  is, the shorter will be its maximum radius of curvature. A lateral proximal displacement of about 60 centimeters of the bottom portion of the skirt panel  31  is possible. The lower portion of the skirt panel  31  can even reach, under certain circumstances, a position parallel with the trailer  20  floor. The skirt assembly  30  and the skirt panel  31  will self-recover their original positions when the force causing the bending is removed. Further, the bending of the resilient struts  42  provides energy absorption in case of impact from another vehicle for example. It can be noted that a distal displacement of the skirt panel  31  is possible. A distal and proximal displacement of the skirt panel  31  will occur when a properly directed force is applied to the skirt panel  31  to bend the skirt panel  31 . 
         [0115]      FIG. 24  throughout  FIG. 29  illustrate an embodiment where the resilient strut  42  is fixed to the trailer frame  22  and the skirt panel  31  in different possible configurations. A first configuration is illustrated in  FIG. 24  and  FIG. 25  illustrated with a force F proximally applied toward the vehicle. Instead of installing the resilient strut  42  with both ends slightly angled to mate with the skirt panel  31 ,  FIG. 26  and  FIG. 27  are illustrating a configuration where both ends of the resilient strut  42  are further angled to contact the skirt panel  31  from the opposite side. This alternate layout assembly reduces the stress on the resilient strut  42 , when the skirt panel  31  is deflected, for instance, under a force F, by expending the radius of curvature of the resilient strut  42  throughout the resilient strut  42  ergo significantly reducing local stress points in the resilient strut  42 .  FIG. 28  and  FIG. 29  are depicting the same resilient strut  42  configuration as in  FIG. 24  and  FIG. 25 , this time with a force applied away, distally from the vehicle. 
         [0116]    As would be appreciated by those skilled in the art, in view of the present specification, the nature of the material used to build the skirt panel  31  and the resilient strut  42  can vary. These materials are also contemplated to fall within the scope of the invention if they lead to the flexibility and resilience required to build a resilient skirt assembly  30 . 
         [0117]      FIG. 30  illustrate a skirt panel  31  including three (3) skirt panel portions  32 . 1 ,  32 . 2 ,  32 . 3 . The interconnecting edges  136  between adjacent skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  is not located at 90° from the upper and lower edges of the skirt panel  31 , in other words the interconnecting edges  136  are not vertical when the skirt panel  31  is mounted on a trailer  20 . The interconnecting edges  136  are rather disposed at an angle α from vertical to allow progressive mechanical stress transmission between adjacent skirt portions  32 . The mechanical stress can be pictured as a “wave” transmitted in the skirt panel  31  that is caused by a contact with an external object with the front portion of the skirt panel  31 . Generally, the more significant the angle α is, more progressive is going to be the mechanical stress transmission along the skirt panel  31  between adjacent skirt portions  32 . For practical and economical reasons, like manufacturing limitations and waste, and shipping size, the angle α is not too large and could be selected among the following values: 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Minimum angle α 
                 Maximum angle α 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Range A 
                 0° 
                 45° 
               
               
                   
                 Range B 
                 2° 
                 30° 
               
               
                   
                 Range C 
                 5° 
                 15° 
               
               
                   
                 Range D 
                   7.5° 
                   12.5° 
               
               
                   
                 Range E 
                 9° 
                 11° 
               
               
                   
                   
               
             
          
         
       
     
         [0118]    All the above ranges are considered to be within the scope of the preferred possible embodiments. Range A, range B and range C are contemplated although their respective range include pronounced angles and an angle of, for example 45°, would smoothly distribute the mechanical stress between the skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  but would produce skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  that are longer than a more reduced angle α. Manufacturing acute angles with materials contemplated for constructing the skirt panel  31  could be more challenging, more expansive, could increase the amount of defective parts and increase the risk of injury with sharp edges, as well as increasing waste. Shipping package is consequently going to be larger and thus, costlier. For at least some of these reasons, the angle α of about 10° is going to be considered as a typical angle offering a functional stress distribution while keeping the longitudinal length of the skirt portions  32  to a minimum. The angle α of about 10° is going to be used below for the purpose of the description although it is not intended to limit the range of the angle α for the described invention. 
         [0119]    Still referring to  FIG. 30 , a typical cut joint  172  having an angle α, from vertical, of about 10° is illustrated as opposed to a straight 90° vertical cut joint, as illustrated in  FIG. 31 . Still referring to  FIG. 30 , a foreign object getting in contact with the skirt portion  32 . 1  and causing a shock  176  is going to produce a wave  180  of energy traveling in the skirt  32 , for instance, in the longitudinal direction toward the rear of the skirt panel  31 . The wave  180  motion traveling in the skirt panel  31  toward the back and is progressively transferred to the second adjacent skirt portion  32 . 2 , and then the third adjacent skirt portion  32 . 3 . The progressive transfer of the energy carried by the wave  180  is permitted by the longitudinally progressive interconnecting edge  136  that is at angle α. The wave  180  is going to hit the upper portion of the interconnecting edge  136  before the lower portion of the interconnecting edge  136 . Conversely, the wave  180  motion would not be progressively transferred should the angle α be a straight 90° vertical cut joint because the wave  180  would hit the straight 90° vertical cut joint all at the same time over the height of the skirt panel  31 , as illustrated in  FIG. 31 . For more details, the skirt panel  31  is seen from a bottom view in  FIG. 32 . Each skirt portion  32 . 1 ,  32 . 2 ,  32 . 3  is joint with its adjacent skirt portion  32  with fasteners  116  through holes  152  therein at the interconnecting edge  136 . The fasteners  116  contemplated in the embodiments could be bolts and nuts, rivets, glue or other types of welding or material fusing. Further simplifying and representing only the center skirt portion  32 . 2  in  FIG. 33  with two interconnecting edges  136 , one on each end thereof with shear and bending moment distribution along the skirt portion  32 . 2 . Put differently, rotational stiffness is increased with an angle α that is not 90° because of the more significant bending moment that is required to bend it. The longer the interconnecting edges  136  are, the higher the bending moment is, hence increasing the rotational stiffness. 
         [0120]    In  FIG. 33  and Equation 1 below, V=shear Force and M is the bending moment about the interconnecting edge  136 . As it is indicated, the shear force per unit of length will cancel and balance each other. 
         [0121]    On 10° degree cut skirt, the bending moment per unit deflection required along the joint line is more due to longer joint than that of straight cut joint and results in a more significant rotational stiffness. The bending moment along the skirt panel  31  is applied with a phase difference at different points on the 10° joint due to its inclination along the length of the skirt panel  31 . Therefore, the bending waves cannot be set up easily as in straight case. On 10° degree cut skirt portion  32 , the bending wave propagates along the skirt panel  31  from one panel portion  32  to another through the bolted joints one by one, as the bolts are inclined unlike straight cut skirt. 
         [0122]    A vibration wave travelling along the length of the skirt with a velocity of V after impacting with 1st joint will tend to change its direction perpendicular to the joint as illustrated in  FIG. 35 . The magnitude of this velocity is the product of initial velocity and cosine of the angle. This phenomenon when observed all along the length of the joint from bottom towards top of the joint, the velocity waves emerging at top portion of the joint will bounce back and forth on the top portion of the panel and these returning waves interfere with primary waves emerging from the joint and hence these waves will be out of phase with respect to each other. While in a straight cut skirt, the wave will propagate and pass onto the next panel without change in direction. 
         [0123]    There is an established standing waves on the straight cut skirt with maximum displacement at anti nodal points as depicted in  FIG. 34 . While on the 10° degree cut skirt portion  32 , the displacement is lower as the vibration waves have a change in their course after passing through the inclined joint and have difference in phase. Consequently, there will be less displacement at anti nodal point. As a result, the 10° degree cut skirt portion  32  is superior to a vertically straight cut skirt portion  32 . 
         [0124]    A more progressive transmission of the bending wave  180  implies that the total energy carried by the bending wave  180  is transmitted over a longer period of time and the maximum peak mechanical stress transmitted to the skirt panel  31  interconnecting edge  136  is reduced hence requiring less fasteners  116  to sustain the transmitted mechanical stress from one skirt portion  32 . 1  to an adjacent skirt portion  32 . 2 . The holes  152  are also required to be less sturdy and have a reduced likelihood of breaking under load. 
         [0125]    The bending wave propagating progressively from one skirt portion  32 . 1  to the adjacent skirt portion  32 . 2  through an angled interconnecting edge  136 , the fasteners securing both skirt portions  32  are progressively sustaining the bending wave. The fasteners  116  are supporting peak stress one by one as fasteners are disposed along a 10° angle and not aligned like they are at 90° angle. This effect is represented by the following equation: 
         [0000]        V′=V ×cos(10°)
 
       Equation 1 
       [0126]    This means that, for example: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 V 
                 angle α 
                 V′ 
                 V − V′ 
                 Difference (%) 
               
               
                   
               
             
             
               
                 100 
                 10° 
                 98.48 
                 1.52 
                 −1.5% 
               
               
                   
               
             
          
         
       
     
         [0127]    A bending wave  180  travelling along the length of the skirt panel  31  with a velocity of V′ after impacting the first joint, at the interconnecting edge  136 , will tend to change its direction perpendicular to the interconnecting edge  136 . The magnitude of the velocity V′ is the product of initial velocity V and cosine of the angle α. The velocity waves emerging at top portion of the interconnecting edge  136  will bounce back and forth on the top portion of the skirt panel  31  when observed all along the length of the interconnecting edge  136 , from bottom towards top. In contrast, in a straight interconnecting edge  136  at 90°, the wave will propagate and pass onto the next skirt panel  32  without change in direction. 
         [0128]    As a result, illustrated in  FIG. 35 , there is an established standing waves on the straight cut interconnecting edge  136  at 90° with maximum displacement at anti nodal points. While on the 10° degree interconnecting edge  136  skirt panel  32 , the displacement is lower as the vibration waves have a change in their course after passing through the inclined interconnecting edge  136  joint and have a difference in phase. Therefore, less displacement at anti nodal point is resulting from a 10° interconnecting edge  136  skirt superior to straight 90° interconnecting edge  136  skirt panel  32 . 
         [0129]    The trailer  10  has a forced frequency about which its mechanical structure becomes “excited” and vibrations of the trailer  10  are transmitted to the skirt assembly  30  at the forced frequency. When the mechanical structure of the trailer  10  is excited, it vibrates. Natural frequency is the frequency at which a system tends to oscillate in the absence of any driving or damping force. Free vibrations of any elastic body is called natural vibration and happens at a frequency called natural frequency. Natural vibrations are different from forced vibration that happen at frequency of applied force (forced frequency). If forced frequency is equal to the natural frequency, the amplitude of vibration increases manifold. This phenomenon is known as resonance. The natural frequency of the skirt assembly  30  and the forced vibration of the trailer  10 , due to trailer  10  vibrations, should be different. It is desirable to design and “tune” a skirt assembly  30  in a way that the natural frequency of the skirt assembly  30  is not in sync with the forced frequency of the trailer  20 . Experimental testing has found that the skirt assembly  30  presented in the embodiments has two natural frequencies. A first natural frequency at about 7.1 Hz and a second natural frequency at about 15.5 Hz. It is therefore desirable that the forced frequency of the trailer  20  be different. 
         [0130]    Frequency tuning of the skirt assembly  30  can be made in various ways. One way consists in moving the securing locations of the supports  40  and the struts  42  on the skirt panel  31 . Changing the securing locations of the supports  40  and the struts  42  is modifying the natural frequencies of the skirt panel  31 . Minor changes in the location of a support  40  or a strut  42  can be enough to cause a significant change in the natural frequencies of the skirt panel  31 . Disposing supports  40  between two adjacent skirt portions  32 . 1 ,  32 . 2 ,  32 . 3  could be efficient to change in the natural frequencies of the skirt panel  31 . This is an explanation of how the natural frequencies of the skirt panel  31  is a parameter to consider and one example how to tune the natural frequencies of the skirt panel  31 . The natural frequencies of the skirt panel  31  are dependent on various parameters like the size of the skirt, its material, and its shape, among others. It can be evaluated by vibration behavioral analysis. The present invention provides an illustrative example of a specific embodiment however, the consideration of the natural frequencies of the skirt panel  31  and tuning thereof is considered to be within the scope of the present invention. The forced frequency of the trailer  10  can vary depending of the trailer configuration, speed, the material used in its manufacturing, the cargo load, the speed, taken individually or collectively. The installation of the skirt assembly  30  to a trailer  10  can include a method including steps of determining the more significant forced frequencies of the trailer  10  and adjust the installation of brackets to the skirt assembly  30  accordingly.  FIG. 36  exemplifies the above with a chart illustrating the natural frequencies  184  of the skirt assembly  30  and a forced frequency  188  of the trailer  10 . The trailer  10  natural frequencies  184  and peak forced frequencies  188  are not superposed in the illustrated embodiment.  FIG. 37  illustrate a typical flow chart for determining the tuning of a skirt assembly  30  that could be desirable to avoid a forced frequency that is exciting the natural frequencies of a skirt assembly  30 . 
         [0131]      FIG. 38  throughout  FIG. 45  are illustrating a cargo configuration  192  for shipment of the modular skirt assembly  30 . Cargo configuration  192  size of a modular skirt assembly  30  is a fraction of a non-cargo configuration size of a non-modular skirt assembly  30 . The cargo configuration  192  embodied in  FIG. 38  throughout  FIG. 45  is one configuration of parts adapted for shipment and other configurations could become apparent for a skilled reader and remain within the scope of the present application.  FIG. 38  illustrates the three skirt portions  32 . 1 ,  32 . 2  and  32 . 3  superposed on a first side of a cargo box or the like. The three skirt portions  32 . 1 ,  32 . 2  and  32 . 3  forming a first layer are thus providing a compact arrangement that offers rigidity to the cargo configuration and also protects the additional parts  200  that are going to be stacked over. The cargo configuration  192  includes preferably two supports  196  above and below the three superposed skirt portions  32 . 1 ,  32 . 2  and  32 . 3  as it is illustrated in  FIG. 39 . The two supports  196  can be made or rigid and inexpensive materials like wood, plastic or cardboard. Then the additional parts  200  are disposed over the stacked skirt portions  32 . 1 ,  32 . 2  and  32 . 3 . The additional parts  200  are preferably secured in boxes  204  for easy manipulation and to prevent relative moments thereof in the cargo configuration  196 . The additional parts  200  are generally, for a standard modular skirt assembly  30 , struts  42 , supports  40  and fasteners  116  as depicted in  FIG. 41 ,  FIG. 42 ,  FIG. 43  and  FIG. 44 . 
         [0132]    The cargo configuration  192  depicted in  FIG. 43  includes additional side fillers  208  and bracket box fillers  212  on the upper and lower sides of the cargo configuration  196 . Fillers  208 ,  212  can be embodied as cardboard boxes, foam or any suitable filling material adapted to keep the parts of the modular skirt assembly  30  at their respective locations in the cargo configuration  192 . Additional elements to be shipped with the modular skirt assembly  30  can be inserted in the fillers  208 ,  212  if needed. One can appreciate the opposed symmetrical arrangement of the boxes  204  and the fillers  208 ,  212  to ensure a balanced weight that is going to ease transportation of the cargo load. In turn,  FIG. 45  depicts the final layout of the cargo configuration  192  with the second skirt panel portions  32 . 1 ,  32 . 2 ,  32 . 3  stacked on the top of the other parts. The three skirt portions  32 . 1 ,  32 . 2  and  32 . 3  forming a second layer, opposed to the first layer, are thus providing a compact arrangement that offers rigidity to the cargo configuration and also protects the additional parts that are located between the two layers of skirt portions  32 . 1 ,  32 . 2  and  32 . 3 . Once all the parts are disposed in the cargo configuration, the overall package can be covered with cardboard, plastic or the like to be shipped as cargo having a significantly reduced size. 
         [0133]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments and elements, but, to the contrary, is intended to cover various modifications, combinations of features, equivalent arrangements, and equivalent elements included within the spirit and scope of the appended claims. Furthermore, the dimensions of features of various components that may appear on the drawings are not meant to be limiting, and the size of the components therein can vary from the size that may be portrayed in the figures herein. Thus, it is intended that the present invention covers the modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalents.