Trans RINA, Vol 157, Part C1, Intl J Marine Design, Jan - Dec 2015
below the water line to give a 3 .5m clearance over the vessel’s 2m draft in a sea state of 2.5m Hs. The WFSV is driven onto the bollards under partial throttle to constrain vessel motion. The beam has a design factor of 5 against shearing under tors avoid excess deflection. Once the WFSV motion is constrained the lifting cradle will be raised into contact with underside of the catamaran hulls.
sion to
The FEA analysis of an initial proposal for a bollard beam is shown in Figure 24. Where the Design Factor of 4 has been achieved for UKB steel I-beam with Max stress = 63.6MPa. The horizontal b
beam in high sea states, combined wiith the
technical challenges of implementing a system in the demi-hulls to retract the bollard beam from th we water, brought the feasibility of the solution into question.
risk of hull impact on the
Figure 26: FEA of modified lifting frame design Weight =
Max stress
= 295kN s = 62MPa
Design factor = 4.2
4.1 LAUNCH/RECOVERY DESIGN SOLUTION This initial proposal highlighted two of the key design
challenges. The first being the need to hold the vessel sufficiently above the waterline in high sea state, the significant moment effect off suspending 120 tons at the ack of the SWATH require a significant amount of betwe en
ba ba
allast. This proposal was a compromise Figure 24: FEA of initial bollard beam proposal
The lifting cradle has a design factor of 2.5 and is constructed from universal beams. The initial design shown in Figure 25 with four lifting points had a weight of 45 tonnes, which is over 50% of the load initially required to be lifted. The modified design shown in Figure 26 increased the number of lifting points to six. This redistributed the loading enabling the weight of these beams to be significantly reduced, reducing the overall weight of the frame to 31 tonnes.
Figure 27: WFSV on approac ch to SOV
available height of the wet deck above waterline while maintaining ve ssel stability and the motion of the WFSV in 2.5mHs+ during lifting using the rear area. The revis ed design proposal shown in Figure 27 has a watertight loading bay from which vertically.
h the WFSV is launched
Figure 25:FEA of initial lifting frame design Weight = 437kN
Max stress = 106MPa Design factor = 2.4 7
Figure 28: View of lifting frame in loading bay © 2015: The Royal Institution of Naval Architects C-117
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210