Section 1 Definitions

101. Application

The definitions of symbols cordance with this section.

and terms used in this part, except otherwise specified, are to be in ac- And, the symbols and terms, not defined in this rules, are to be in ac-

cordance with Rules for the Classification of Steel Ships.

102. Length

The length ( ) of yacht means the overall length of the underwater watertight envelope of the rigid hull, excluding appendages, at or below the design waterline in the displacement mode with no lift or propulsion machinery active.

103. Volume of displacement

Volume of displacement (∇ ) means volume of displacement corresponding to the design water line (m )

104. Breadth

The breadth ( ) of yacht means the breath of the broadest part of the moulded watertight envelope of the rigid hull, excluding appendages, at or below the design waterline in the displacement mode with no lift or propulsion machinery active.

105. Depth

The depth ( ) of yacht means the vertical distance at the middle of L measured from the baseline to the top of the freeboard deck beam at side. Where watertight bulkheads extend to a deck above the freeboard deck and are to be registered as effective to that deck, is the vertical distance to that bulkhead deck.

106. Load draught

The load draught ( ) means the vertical distance (m ) from the top of keel to the load line meas-

107. Full load displacement

The full load displacement (∆) is the displacement (including shell plating and appendage, etc.) (ton s) at the load line.

108. Block coefficient

The block coefficient ( ) is in as the following

= the breadth of yacht at the load line, with the yacht at rest. For multihull yacht, net sum of the waterline breadths.

is the

109. Maximum speed

The maximum speed ( ) of yacht is the speed achieved at power for which the yacht is certified at maximum operational

the maximum continuous propulsion weight and in smooth water.

110. Freeboard deck

1. The freeboard deck is normally the uppermost continuous deck. However, in cases where openings without permanent means of closing exist on the exposed part of the uppermost continuous deck, or where openings without permanent means of watertight closing exist on the side of the yacht below that deck, the freeboard deck is the continuous deck below that deck.

2. In a yacht having a discontinuous freeboard deck, the lowest line of continuation of that line parallel to the upper part of the deck, is taken

3. Where the designed load draught is less than the draught determined

the exposed deck, and the as the freeboard deck.

assuming the existing deck

below the freeboard deck is the freeboard deck in accordance with the provision in Pt 3, Ch 1,

106. the existing lower deck is taken as the freeboard deck in the application of the rules. In this case, the lower deck is to be continuous at least between the machinery space and peak bulkheads and continuous athwartships. Where a lower deck is stepped, the lowest line of the deck and con- tinuation of that line parallel to the upper part of the deck is taken as the freeboard deck.

111. Superstructure

The superstructure means a decked structure on the freeboard deck, extending from side to side of the yacht or having its side walls at the position not farther than 0.04 from the side of yacht. Raised quarter deck is to be considered as a superstructure.

112. Deckhouse

The deckhouse means a decked structure above the freeboard deck with the side plating being in- board of the shell plating more than 0.04 from the side of yacht.

long deckhouse : deckhouse having more than 0.2 of its length within 0.4 amidship

short deckhouse : deckhouse, not defined as a long deckhouse

113. Strength deck

The strength deck means the uppermost continuous deck. A superstructure deck which, within 0.4

amidship, has a continuous length equal to or greater than is to be considered as the

strength deck instead of the covered part of the uppermost continuous deck.

For twinhull yachts m

For monohull yachts m

= height(m ) between the uppermost continuous deck and the superstructure deck.

114. Bulkhead deck

The bulkhead deck means the highest deck to which the watertight transverse bulkheads except both peak bulkheads extend and are made effective.

115. Girder

The girder is a collective term for primary supporting members, usually a supporting stiffener. Other terms used are bottom, side and deck transverse, floor (a bottom transverse), stringer (a hori- zontal girder), web frame, and vertical web.

116. Stiffener

The stiffener is a collective term for secondary supporting members. Other terms used are beam, frame, reverse frame (inner bottom transverse stiffeners) and longitudinal.

117. Displacement mode

The displacement mode is the regime, whether at rest or in motion, where the weight of the yacht is fully or predominantly supported by hydrostatic forces.

118. Non-displacement mode

The non-displacement mode is the normal operational regime of a yacht when non-hydrostatic forces substantially or predominantly support the weight of yacht.

119. Transitional mode

The transitional mode is the regime between displacement and non-displacement modes.

120. Critical design condition

The critical design condition is the limiting specified condition, chosen for design purposes, which the yacht should keep in displacement mode. Such condition should be more severe than the worst intended condition by a suitable margin to provide for adequate safety in the survival condition.

121. Service area restriction notations

All high speed and light yacht are to be given a service area restriction notations of SA followed by a number. Service area restrictions, ranging from SA0 to SA5, given in nautical miles and rep- resenting the maximum distance from nearest harbour of safe anchorage, are given in Table 3.1.1.

Table 3.1.1 Service Area Restriction Notation