bushing greater outside diameter 49 exceeds the diameter of lower unit housing roof bore 65 and the diameter of lower unit housing floor bore 67 lower unit bushing bore 47 is sized to slidably admit lower unit 38 as may be observed in fig6 a lower unit bushing 46 is inserted into lower unit housing roof bore 65 as indicated by arrow 68 and a lower unit bushing 46 is inserted into lower unit housing floor bore 67 as indicated by arrow 69 then lower unit 38 is inserted through the lower unit bushing bores 47 as indicated by arrow 76 in this embodiment lower unit 38 turns within lower unit bushing bores 47 thus avoiding direct contact between lower unit 38 and lower unit housing roof bore 65 and lower unit housing floor bore 67 lower unit bushings 46 serve to cushion and reduce friction associated with the slidable attachment between lower unit housing 42 and lower unit 38 in the preferred embodiment lower unit bushings 46 were made of nylon synthetic plastic teflon stainless steel or other metal or coated material or other appropriate low friction corrosion resistant material fig8 is a front quarter isometric view of base foot 32 as may be observed in fig3 and 5 a base foot 32 may be disposed on either side of the aft end of base 30 in the preferred embodiment base 30 incorporated base side spars 33 at whose aft end base feet 32 were attached although it is intended to fall within this disclosure that base foot 32 may be attached to base 30.