Abstract: A method of monitoring ion mobility in an electro-conductive fluid, such as an electrolyte in a lead-acid battery to determine the state of charge of the battery, includes the steps of immersing a pair of test electrodes in the electro-conductive fluid, and generating a test signal having a pulsed waveform. The pulsed waveform of the test signal has a voltage which remains constant over a predetermined portion of the signal's period, that portion being selected to ensure that ion mobility in the electro-conductive fluid has reached a steady state velocity. The method further includes the steps of applying the test signal to the pair of test electrodes to cause a current to flow through the test electrodes and the electro-conductive fluid, and sensing the current flow through the test electrodes and fluid. The sensed current is indicative of ion mobility in the electro-conductive fluid.

Abstract: An automatic power control device comprising a passive, non-linear voltage detector controlling a series bipolar transistor regenerative latch circuit, acts to connect the load to a power source only when the voltage obtainable from the power source is sufficient to prevent improper ambiguous operation of the load, and further acts to disconnect the load from the power source when its voltage declines to that range which could result in ambiguous and/or erroneous operation. An electronic thermometric digital display instrument is shown, powered solely by a miniature solar panel. The instrument is amply powered, and the display is legible, even in dim light. Operation at lower levels of light is available with an economical auxiliary battery that is cut out of the circuit at when the light is as little as 5 lux.

Abstract: A rotary stepping device includes a rotatable shaft which is driven by means of a coiled spring clutch which is alternately tightened to grip and rotate the shaft and released to return it to a resting position. An actuator formed of a memory metal is used to pull the spring clutch to tighten it and rotate the shaft. The actuator is activated by heating it above its critical temperature and is returned to an elongated configuration by means of the force of the spring clutch.

Abstract: An improved single-boom sailing rig for sailboards, and methods of use, are disclosed. A curved, rotatable boom (100) is provided with a forward end set at a slight angle with respect to the chord, with a separately-rotatable camber control (110) located in the forward end within reach of the sailor's forward hand, for controlling sail curvature with sails (18 and 19) filled and drawing. A finger-operated mast clamp (120) connects boom (100) to mast (13) and provides pivot pin (126) as a bearing onto which the boom (100) may be pushed during assembly. A boom extension (130) is provided with an eccentric locking mechanism for matching boom length to various sail sizes. An alternative extension (230) is locked by insertion of a pin (233) through any of a series of holes (234). Boom extensions (130 and 230) are provided with a sand-proof aft boom bearing assembly (140) having an aft pivot pin (141) which is pushed into plug (145) during assembly, to connect the clews of sail components (18 and 19).

Abstract: A technique for negatively coupling the outputs of polyphase choppers is disclosed, wherein the output inductance of each phase is divided into two windings, and each winding is negatively coupled to a corresponding winding of a neighboring phase. In a preferred embodiment for a three-phase chopper circuit, the output inductance of phase A is divided into windings 100 and 102, the output inductance of phase B is divided into windings 110 and 112, and the output inductance of phase C is divided into windings 120 and 122. Pairs of windings 100 and 110, 112 and 120, and 102 and 122 are respectively disposed in transformers arranged for negatively coupling the windings of each pair.

Abstract: Planar optical circuits may be made to cross through each other, (thus eliminating extra steps required to fabricate elevated, nonintersecting crossovers) by control of the dimensions of the crossing light conductors (10, 12) to be significantly greater than d=0.89.lambda. and the angle of crossing as nearly 90.degree. as conveniently possible. A light trap may be provided just ahead of the intersection to trap any light being reflected in the source conductor at angles greater than about 45.degree.. The light trap may take the form of triangular shaped portions (16a, 16b) on each side of the source conductor with the far side of the triangular portion receiving incident light at an angle so that incident light will be reflected to the other side, or it may take the form of windows (18a, 18b) in place of the triangular portions.

Abstract: In accordance with one aspect of the disclosure, the sail portion of a sailboard has upper and lower sections, and the lower edge (foot) of the upper section is lapped relative to the upper edge (head) of the lower section. Apparatus is provided to cause the lower edge to be on the upwind side of the upper edge, regardless of the tack that the boat is on. Such apparatus comprises a rotating boom which rotates through the sail, in such manner as to shift from one side of the sail to the other and also cause the above-described lapped relationship to occur in either tack. The diclosure further relates to a combination of the sail system with the board, to the method of achieving the indicated lapped relationship and of rotating the boom, and to other important features.

Abstract: A plural-hull craft incorporates separate hulls pivotally attached at the extremities of an interconnecting structure, which hulls may be rotated either separately or in unison to longitudinally align two or more hulls with substantial hydrodynamic continuity, whereby leeward hull buoyancy is increased to improve longitudinal stability. The drag incurred between the longitudinally-aligned hulls is substantially reduced by shaping the adjacent bow and stern to be conjugates, or by use of a fairing which extends the contours of the forward hull into the aft hull.

Abstract: A high efficiency aerodynamic sail system for boats comprises a triangular fabric sail pivotally suspended at its head from the apex of a tripod mast structure such that air impinging upon the luff of the sail is free from the turbulent wake of any upwind structure. The foot of the sail is attached only at its tack and clew ends to opposite ends of a spar which is pivotally attached at its center to a short stub mast centrally positioned in respect to the tripod mast. The sail luff and leech side deflections are caused to be identical by cables to provide a constant angle of attack of the sail to the wind along the entire sail height. A sail-shaping batten having a longitudinally varying cross section is employed along the foot of the sail. Loading of the batten by pressure generated by the wind causes the batten, and thus the sail, to assume an optimum airfoil shape.

Abstract: A plural-hull craft incorporates separate hulls pivotally attached at the extremities of an interconnecting structure, which hulls may be rotated either separately or in unison to longitudinally align two or more hulls with substantial hydrodynamic continuity, whereby leeward hull buoyancy is increased to improve longitudinal stability. In such configuration, the aligned hulls may be horizontally counterrotated into an approximate arc for turning the craft, or may be counterrotated horizontally into the approximate shape of a cambered airfoil so as to provide sideways lift to counteract lateral drift. Additionally, at least one hull may be individually rotated about its pivotal attachment point to maneuver the craft.