Abstract:
A flexible skirt assembly for surface effect vehicles having an upper and lower skirt. The upper skirt cooperates with the vehicle body to form a pressurized chamber. The lower skirt has a plurality of segments with adjacent ones having common supports. The upper and lower skirts are supported by a plurality of horizontally spaced cables and with such cables supporting the segments at their upper edges.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to gas-cushion vehicles which are also referred to as surface-effect ships, wherein the ship rides on a cushion of air permitting the ship to cruise at a higher speed by reducing the resistance to its movement. 
     The preferred form of this invention is directed to surface-effect ships that have fixed side walls with flexible skirts or seals fore and aft although such invention is also applicable to where the skirt bounds the entire lower periphery of the vehicle. The side walls cooperate with the skirts to contain the air bubble and act as a keel to give the vehicle greater lateral stability in water. The invention is equally applicable to land vehicles. 
     In operating vehicles on gas-cushion principles, it is important to provide skirts that are flexible and able to withstand the tremendous impact forces encountered when traversing waves or projections and depressions in the case of land vehicles. The present invention provides a novel suspension system for maintaining the flexible skirt in position, while permitting it to be made of light-weight material and permitting it maximum resiliency. When building ships employing the surface-effect or gas-cushion principle, the carrying capacities have been limited because the skirts which provide the containment of the air cushion must be of adequate strength to withstand the forces developed both internally and externally. By the mere scaling up of existing designs as an example of from a 100 ton to a 2,000 ton vehicle, the strength of the coated fabric materials scales up to a 11,000 pounds tensile per inch of width and the weight of the coated fabric material is estimated to exceed 75 tons. Fabric material in this strength range are not readily available and the processing of such massive structures becomes a major problem. In addition, the seams employed for such fabric material would become cumbersome and extensive to further complicate the problem of weight, processing and fabrication. 
     The present invention overcomes these difficulties by providing a new and improved construction for the skirt assemblies, wherein the skirt of elastomeric coated fabric membrane or material is supported from the main frame of the vehicle by a plurality of cable-like or belt-like high strength members arranged in vertical planes, which members are the primary load-bearing members of the skirt structure enabling the use of lightweight material since the construction permits a reduction in fabric strength. 
     SUMMARY 
     The present invention contemplates a skirt construction assembly which has an upper skirt and a lower skirt with a plurality of segments, wherein a plurality of reinforcing cables, laterally spaced, are attached to adjoining portions of the upper and lower skirts and to the fabric material of the upper skirt in such a manner that the stresses are equalized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a gas-cushion vehicle of the fixed sidewall or surface-effect ships; 
     FIG. 2 is an inverted plan view of the gas-cushion vehicle; 
     FIG. 3 is an enlarged cross sectional view of the front portion of skirt assembly; 
     FIG. 4 is a view in perspective of a portion of the front skirt assembly; 
     FIG. 5 is an enlarged perspective view of a finger of the lower portion of the rear skirt assembly; 
     FIG. 6 is a plan view in section of a modified form of construction of the skirt assembly. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like reference characters designate like or corresponding parts through the several views, there is shown in FIG. 1 a gas-cushion vehicle also known as a surface-effect ship 1 of the sidewall type moving over the surface 2 of the water. Such ship 1 is supported above the surface 2 by a cushion of pressurized air formed and contained between the vehicle body 4, the sidewall structures and the fore-and-aft flexible skirt assemblies 6 and 7. 
     The wall structures are a pair of laterally spaced rigid sidewall members 5 that extend longitudinally along the side of the ship&#39;s body 4 in a direction parallel to the body&#39;s 4 fore-and-aft axis. The sidewall members 5 of the wall structures extend into the water 2 to contain the air bubble and act as keels to give the ship lateral stability. Side slipping is a major problem in surface-effect ships. Each sidewall member 5 carries a propeller 8 suitably driven and a rudder 9. 
     The forwardly disposed or front skirt assembly 6 of the surface-effect ship 1 has an upper skirt and a lower skirt. The upper skirt of skirt assembly 6 has a plurality of horizontally spaced cables or constraining means 15 which assume an arcuate shape in a vertical plane. A flexible fabric material 16 forms the upper skirt of skirt assembly 6 by being suitably attached to the respective cables 15 along the entire extent of ship&#39;s forward bow to form a closed plenum chamber 17 in cooperation with the forward portion of body 4. The flexible fabric material 16 between the respective cables 15 assumes an arcuate shape in horizontal cross-section as noted in FIG. 2 when the plenum chamber 17 is pressurized. 
     The lower skirt of front skirt assembly 6 consists of a plurality of successive independent segments wherein each segment has a pair of spaced flexible walls or sidewall members 18 that extend inwardly toward said air cushion. Such sidewall members merge with an outer wall portion 19 to form a channel shaped segment. When inflated, the sidewall members 18 cooperate with the forward portion 19 to form a U-shaped member in cross-section which communicates with the contained cushion of gas. The adjacent sidewall members 18 of neighboring segments are held together by the air-cushion pressure which maintains a seal for the air-cushion. The upper edges of the sidewall members 18 are arcuately contoured to the arcuate depending shape of the lower part of the upper skirt and is suitably attached either to the fabric material or to the cables 15. The cables 15 provide the spacing of the segments and each cable 15 may suitably support upper adjacent contiguous edges of adjacent sidewall members 18 in addition to supporting the flexible fabric material for the upper skirt. The flexible fabric material separating the plenum chamber 17 from the respective segments has a plurality of bores 20 which communicate the pressurized plenum chamber 17 with the respective chamber as defined by the spaced sidewall members 18 and the forward portion 19 of each segment. 
     The rearwardly disposed flexible skirt assembly 7 is essentially similar to the above described forwardly disposed skirt assembly 6, having a plurality of laterally spaced cables 30 with one end suitably secured to the upper rear portion of the vehicle body 4 and the other end suitably secured to the underneath portion of the body 4. Flexible fabric material is secured to the cables 30 as in the forwardly described embodiment, presenting a plurality of horizontally spaced supporting means. The lower portion of the rear skirt assembly 7 has individual segments as in the front skirt assembly 6 with sidewall members 31-32 of each segment merging with the segments&#39; rearward portion 33. Unlike the forwardly disposed fingers which open directly to the air-cushion 4, the rear segments have the respective side members 31-32 merging with a forwardly disposed portion 34 to prevent scooping up of water as the surface-effect ship moves through the water. The forwardly disposed portion 34 has a plurality of bores 35 communicating the chamber defined by the side members 31-32, the forwardly and rearwardly disposed portions 33 and 34 with the contained air-cushion. The fabric material secured to cables 30 forming the rear upper skirt separates the chamber so formed by such skirt with the body 4 and communicates with the chamber formed by the rear segments via bores 36 (FIG. 2) such as to maintain all such rear segments pressurized as well as contributing to the overall air-cushion contained by the sidewall members 5 and the fore-and-aft skirt assemblies 6 and 7. 
     Such contained air-cushion is formed by drawing in atmospheric air through suitable in-takes, and by means of compressors 38 and 39 driven by suitable engines provide pressurized air via ducts 40 and 41 to the respective upper plenum chambers of the fore-and-aft skirt assemblies 6 and 7. The pressurized air in plenum chamber 17 of forwardly disposed skirt assembly 6 pressurizes the chamber of the segments therebelow via bores 20 to maintain the fingers in distended position and communicates directly with the supporting or contained air-cushion of the vehicle. The pressurized air in the plenum chamber of the upper skirt of the rearwardly disposed assembly 7 pressurizes the chamber of the rear segments therebelow via bores 35 to the contained air-cushion of the vehicle. With the aid of propellers 8, and with the use of the air-cushion so provided the vehicle or surface-effect ship is propelled across the surface 2 with the skirt assemblies deflecting sufficiently to conform to waveform surface minimizing drag and air leakage. The use of a single skirt is also contemplated where the skirt employs a plurality of cables or constraining means in vertical planes as described above to provide the primary load-bearing members for the elastomeric coated fabric flexible membrane of the skirt structure. 
     A modification of means for reinforcing the skirt assemblies is shown in FIG. 6 wherein the flexible fabric material 16 is bonded to a plurality of laterally spaced belt fabric bands or constraining means 38. Such bands can be made from nylon, steel, kevlar strand material or other suitable strand material having suitable strengths which are impregnated with rubber to facilitate their attachment to the skirt fabric material. 
     It will be apparent that, although a specific embodiment and certain modifications of the invention have been described in detail, the invention is not limited to the specifically illustrated and described constructions since variations may be made without departing from the principles of the invention.