Tin foil hat radio with a metal bucket. The AM radio is completely inside a metal enclosure. This leads to a noticeable reduction in signal strength received by the AM radio. The efficiency of a metal enclosure in blocking electromagnetic radiation depends on the thickness of the foil, as dictated by the "skin depth" of the conductor for a particular wave frequency range of the radiation. For half-millimetre-thick aluminum foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although aluminum foil is not sold in this thickness, so numerous layers of foil would be required
Bruce foil available to drive movement without the crew needing to move their weight. The main disadvantage is that the sails remain upright and keep the full force of the wind available, rather than depowering with increasing angle of heel as happens with traditional foils. The Bruce foil also produces increased drag as a result of the vertical component of force, as well as a yawing force due to the off-center placement of the foil, which may require alteration of the steering system to compensate. Bruce foil A Bruce foil is a variant of the leeboard, consisting of a foil typically mounted