Abstract: In a method of drying boards by radio-frequency heating a stack of boards is passed between live and earthed electrodes. The connections to the electrodes are periodically reversed so that each is alternately live and earthed; this increases the uniformity of heating in the stack. Preferably the boards are stacked in short spacer sticks to delay the escape of steam from intermediate boards in the stack and reduce surface checking. The escape of steam from the top and bottom boards of the stack to be dried can be delayed by using top and bottom covering boards treated with a liquid substantially unaffected by radio-frequency heating.

Abstract: A multi-hull vessel includes at least a pair of substantially parallel interconnected hulls and the outermost hulls each include a mast for supporting a sail. When sailing close hauled the wind on the leeward sail produces a force having a component tending to lift the adjacent windward hull out of the water which is counterbalanced by a corresponding downward component of the force produced by the wind on the windward sail.

Abstract: A multi-hull sailing vessel includes at least a pair of opposing hydrofoils that have their longitudinal axes inclined inwardly toward one another beneath the vessel at a fixed angle to the horizontal, each foil being independently rotatable whereby the angle of attack of each hydrofoil can be adjusted to assist in maintaining the vessel in an upright position. The rotation of the hydrofoils can be automatic to produce greater lift for the leeward hydrofoil to resist the tendency of the vessel to heel to leeward.