SECTION 1 - Boat Design Net

Pt B, Ch 6, Sec 33 Loading induced by deck diving intowaves (broaching)3.1 General3.1.1 This type of loading corresponds the situation wherethe catamaran sails in quartering head seas and has the foreend of the floats burying themselves into the encounteredwaves.3.1.2 The assumptions considered to determine the correspondingglobal loads are the following one:• 10° longitudinal trim• 10° tranverse list• 1g broaching horizontal deceleration• the float getting the bigger broaching effect is submergedfrom the extreme fore end to the forward part ofthe forward cross deck structure.3.2 Loads and stresses3.2.1 Vertical and horizontal forces to be applied on thefore part of the floats, in kN, are defined as follows.The vertical force F’, in kN, induced by Archimedian overpressureresulting from the deck diving, is to be calculatedaccording to the following formula:1, 8 ⋅ 9, 807 ⋅ Δ⋅ d ⋅ sin10 oF' = -------------------------------------------------------------------δ 1 + δ 2The horizontal force F’’, in kN, induced by Archimedianoverpressure resulting from the deck diving, is to be calculatedaccording to the following formula:F’’ = F’ cos 80°where:Δ : Full load diplacement, in T, of the catamarand : Horizontal distance between the extreme foreend of each float and the forward part of the forwardcross beamδ 1 , δ 2 : Sinkages, in m, of a point located at mid-distancebetween the extreme fore end of eachfloat and the fore stem of the forward crossdeck structure (at d/2)3δ 1 = -- ⋅ L8WL ⋅ tan10 o1δ 2 = -- ⋅ L8WL ⋅ tan16 oL WL : Length of each float, in m, at full load waterline.3.2.2 Load distributionThe distribution of the loads on the fore part of the floatsmay be considered as linear load applied according to Fig 4.3.2.3 For non conventional loaction of the fore part of thecross deck between hulls, the Society may decide to consideranother load distribution, on a case by case basis.3.2.4 Bending moment M E and shear force Q EThe bending moments and shear forces induced in the crossdeck by this type of loads are to be determined according toCh 8, Sec 2 for steel or aluminium yacht and Ch 9, Sec 2 forcomposite yacht.3.2.5 Admissibles stressesThe admissible stresses to be considered for the cross deckscantlings under this type of loading are defined in Ch 4,Sec 3.Figure 4 : Loading of catamarans due to digging in128 Bureau Veritas Rules for Yachts July 2006 with February 2008 Amendments