Abstract: A pressure-operated linear actuator in which the working liquid is Electro-Rheological (ER) fluid in which there is a single flow path between an inlet and an outlet of an associated pump in which there are two or more pistons and fluid chambers delineated by these pistons, which fluid chambers are connected in series by stationary ER valves distinct from the pistons such that the pressure as determined by each of the ER valves is applied to one or more of the chamber(s), wherein one or both of the ER valves are divided into two or more sections in order to minimize the length, and maximize the cross-sectional area, of the inactive connecting passages.

Abstract: A twin-hulled boat (1) is constructed from three individual parts being two parallel, relatively narrow and relatively long hulls (2) each individually connected, at releasable joints (13,9), to a central, rigid bridge section (3), and separable, upon release of the joints (13,9) into three individual parts. Each hull (2) has a bow section (4) and a stern section (5). The hulls (2) have virtually flat bottoms (6) apart from the bow sections (4). The releasable joints are two-part metal-to-metal friction joints with one-part (13) of each of said joints located within, and at a lateral side of, said central bridge section (3), and the other part (9) of each of said joints located at inner gunwales (21) of each hull (2), with, for each of said joints, individual independent, screw-incorporating means (26),(24),(27),(29), (33) operable on both parts (13,9) of each joint to urge the parts (13,9) of each said joint together into tight frictional engagement with one another.

Abstract: A fluid composition which is capable of exhibiting a substantial increase in apparent viscosity under the influence of an electric field and which is of the type wherein solid particles of a chemical substance are dispersed in an electrically non-conducting oleaginous vehicle, the chemical substance being a polyhydric alcohol which contains acid groups and which has an open structure wherein a significant amount of water is adsorbed.