SECTION 1 - Boat Design Net

Pt B, Ch 3, Sec 2Figure 1 : Severe wind and rollingg = 9,81m/s 2Table 1 : Beaufort scaleaLeverGZbl w1l w290θ 0Angle of heelθ 1θ 2 θ cBeaufort Wind pressure, in N/m 24 19 - 415 42 - 716 72 - 1187 119 - 1778 178 - 2559 256 - 36310 364 - 49111 492 - 648• from the resultant angle of equilibrium (θ 0 ), the yacht isassumed to roll owing to wave action to an angle of roll(θ 1 ) to windward• the yacht is then subjected to a gust wind pressurewhich results in a gust wind heeling lever (l w2 )• free surface effects, as described in [4], are to beaccounted for in the standard conditions of loading asset out in Ch 3, App 2, [1.2].UnrestrictednavigationRestrictednavigationTable 2 : Wind pressureL LL ≤ 70 mreduced pressureaccording to[3.2.4]reduced pressureaccording to[3.2.4]504 N/m 2L LL > 70 mreduced pressure subjectto the agreement ofthe Administration3.2.2 CriteriaUnder the assumptions of [3.2.1], the following criteria areto be complied with:• the area "b" is to be equal to or greater than area "a",where:a : area above the GZ curve and below l w2 ,between θ R and the intersection of l w2 withthe GZ curveb : area above the heeling lever l w2 and belowthe GZ curve, between the intersection ofl w2 with the GZ curve and θ 2• the angle of heel under action of steady wind (θ 0 ) is tobe limited to 16° or 80% of the angle of deck edgeimmersion, whichever is less.3.2.3 Heeling leversThe wind heeling levers l w1 and l w2 , in m, referred to in[3.2.2], should vary as the square cosine function of theyacht heel and should be calculated as follows:l W1 =PAZ--------------------1000gΔandl W2 = 1,5l W1where:P : Is according to Tab 2A : Projected lateral area in m 2 , of the portion of theyacht above the waterlineZ : Vertical distance in m, from the centre of A tothe centre of the underwater lateral area orapproximately to a point at one half the draughtΔ : Displacement in t.3.2.4 Calculation of the wind pressureFor yachts with a length equal or lesser than 70 m, the windpressure P, in t/m 2 , is to be calculated according to the followingformulae:Z – TP 0,0514⎛------------⎞ 1/3=⎝ 10 ⎠where :Z : Vertical distance in m, from the centre of A tothe centre of the underwater lateral area orapproximately to a point at one half the draughtT : Mean moulded draught in m, of the yacht.3.2.5 Angles of heelFor the purpose of calculating the criteria of [3.2.2], theangles in Fig 1 are defined as follows:θ 0 : Angle of heel, in degrees, under action of steadywindθ 1 : Angle of roll, in degress, to windward due towave action, calculated as follows:θ 1 = 109kX 1 X 2 rsθ 2 : Angle of downflooding θ f in degrees, or 50° orθ c , whichever is lessθ f : Angle of heel in degrees, at which openings inthe hull, superstructures or deckhouses whichcannot be closed weathertight immerse. Smallopenings though which progressive floodingcannot take place need not be considered asopen (see Ch 3, App 2, [1.3.3])θ c : Angle in degrees, of second intercept betweenwind heeling lever l w2 and GZ curves90 Bureau Veritas Rules for Yachts July 2006 with February 2008 Amendments