those in the stern the opposite or practically vertical or by forming two air chambers not illustrated one at the bow and the other astern whose pressure varies differentially as the vehicle pitches longitudinally or by a combination of both methods to understand the working of the vehicle 39 s supporting system better reference is made to fig2 8 9 10 14a c and 15 in fig2 and 9 it can be seen that the air distribution takes place through a longitudinal channel 3 located above the entire length of the flexible keel 11 in the cross sections of fig2 and 8 it can be seen how the flexible keel 11 divides the air cushion longitudinally into two semichambers 10 39 and 10 34 when the vehicle is parallel to the surface 9 the air outlet areas of both semichambers 10 39 and 10 34 which are created between the skirts or side walls 6 and the surface 9 are substantially equal in size and therefore the pressure in both semichambers 10 39 and 10 34 is substantially equal the segments 13 of the flexible keel 11 then adopt a similar arrangement to that shown in fig6 the air passage areas to semichambers 10 39 and 10 34 from the distribution channel 3 being virtually the same these air passage areas are defined by the triangles 14 39 and 14 34 which form the transversal walls of the keel 11 and the bottom edge 16 of the longitudinal wall 14 39 34 see fig3 and 4 of each segment 13 the air passages of the flexible keel are much larger than the air outlet sections under the side flaps 6 through which the same flow rate must pass consequently.