Bridgedeck
A style of yacht which gained popularity in the thirties, and was virtually perfected by the famous naval architect Ed Monk Sr. The style consists of a low after cabin, with a raised wheelhouse/saloon area amidships or forward of amidships, and a raised foredeck that intersects the bridge area.
Displacement Hull
Boats that remain fully immersed when underway, without getting any "lift" from planning surfaces. The advantage of displacement hulls are that they are the most efficient means of traveling through the water in terms of cost per mile. They also allow much greater weights to be carried for the same horsepower, so enabling more comfortable accommodations, greater fuel capacities, etc. Displacement hulls were the predominate hull form of pre-WWII yachts, but were largely replaced by planing and semi-planing hulls (for the smaller boats anyway), once higher output, lower weight engines became available. Even so, the famous naval architect William Garden once quipped, "A planing hull can't carry enough fuel to get out of sight.".
Fantail
The lounging area around the aft end of a classic yacht. Yachts with an overhanging stern, reminiscent of sailing ships, are said to have a fantail stern. If the fantail stern is a prominent defining feature of the classic yacht, then it is referred to as a "fantail" yacht.
Flying Bridge
"Flying" is from sailing ship terminology and refers to a part of a boat that is above the normal position. Some classic yachts were designed with some smart looking flying bridges, but they became much more common (ubiquitous, in fact) after the war. "Flying bridge" is the proper terminology, not "fly bridge.".
Hull Speed
The theoretical maximum speed of a displacement hull. It is related to the waterline length of a vessel by the formula, V = 1.34 x SquareRoot(LWL). Above this speed, a hull generally needs to get some "lift", i.e. it enters the semi-planning region.
Motor Yacht vs. Motor Vessel
The theoretical maximum speed of a displacement hull. It is related to the waterline length of a vessel by the formula, V = 1.34 x SquareRoot(LWL). Above this speed, a hull generally needs to get some "lift", i.e. it enters the semi-planning region.
Plumb Bow
A vertical or near-vertical stem, common on yachts built in the 20's and 30's. The classic yachts were designed for efficiency at displacement speeds, and the plumb bows knifed through the water easily, and were easy to construct out of wood. The bows were also fairly high off the water, and at displacement speeds flare was not needed to shed spray.
Saloon
This is the proper term for the living area of any yacht, but especially classic yachts. The word was originally used for the mess area on sailing ships. At some point, some enterprising innkeepers decided to start using it for their shoreside establishments in order to entice sailors into patronizing them. Eventually people began using "saloon" as synonymous with "tavern", but aboard ship saloon is still the proper term, and salon is considered lubberly.