Sta­bi­li­zers are cal­led to the bar - Na­iad Dy­na­mics for Be­net­ti

The re­sul­ts of the ana­ly­sis car­ried out by re­no­w­ned USA com­pa­ny Na­iad on the fins and in­ter­cep­tors fo­re­seen for Be­net­ti’s ya­cht “Spec­tre” whi­ch is sche­du­led for de­li­ve­ry by this co­ming sum­mer.

Superyacht - - What’s On The Market - by Lam­ber­to Bal­le­ri­ni

Na­iad Dy­na­mics’s ex­pe­rien­ce in sta­bi­li­ser sy­stems wi­th ac­ti­ve fins has few equals. The com­pa­ny is the re­sult of a joint ven­tu­re bet­ween Na­iad Ma­ri­ne Sy­stems and Ma­ri­ti­me Dy­na­mics, Vo­sper Mo­tion Con­trol, Vo­sper Sta­bi­li­ser, VT Ma­ri­ne Pro­duc­ts and Koop Nau­tic Hol­land. Na­iad Dy­na­mics has in­stal­led its sy­stems in­to about 10,000 uni­ts of eve­ry kind: lei­su­re craft , com­mer­cial and mi­li­ta­ry ones as well.the com­pa­nies re­sear­ch cen­tre has car­ried out si­mu­la­tion trials for Be­net­ti’s FB269, whi­ch is al­mo­st due for de­li­ve­ry Ju­ly next. A se­ries of com­plex trials ha­ve been car­ried out in com­plian­ce wi­th Na­iad Dy­na­mics Mo­no­hull Sea­kee­ping Pro­gram to te­st and fo­re­see the ya­cht’s be­ha­viour in dif­fe­rent wea­ther con­di­tions at di­ver­se speeds. In fact pro­to­col esta­bli­shed ship’s be­ha­viour in wa­ve trains mo­ving stea­di­ly in one di­rec­tion but at four dif­fe­rent heights at th­ree dif­fe­rent speeds and at thir­teen dif­fe­rent an­gles wi­thin an arc of 180 de­grees. As for the sta­bi­li­ser sy­stem itself the­re are two pos­si­ble op­tions: the fir­st

one con­sists in ac­ti­va­ting a pair of fins, the prin­ci­pal ones; the se­cond en­tails ex­ploi­ting “RCS” (Ri­de Con­trol Sy­stem) to its full po­ten­tial by ac­ti­va­ting a fur­ther pair of fins in­stal­led in the bow area that are in fact smal­ler than the prin­ci­pal ones plus a pair of in­ter­cep­tors. In this mo­de fur­ther si­mu­la­tion pro­vi­des da­ta enou­gh to gau­ge how mu­ch pit­ch and slam­ming ef­fec­ti­ve­ly di­mi­ni­shes.

The con­trol­ling fea­tu­res The main fins are in­stal­led amid­ships to dam­pen roll at ze­ro speed and un­der­way. Their sha­pe coef­fi­cient is equal to 0.47 for a sur­fa­ce area of 6,26 squa­re me­tres.

The fins in­stal­led in the bow area in li­ne wi­th fra­me num­ber 54 are de­ployed to dam­pen pit­ch wi­th a sha­pe coef­fi­cient equal to 1 for a sur­fa­ce area of 3.0 squa­re me­tres. The in­ter­cep­tors are in­stal­led in the stern tran­som and when ac­ti­va­ted they con­trol to what de­gree the stern si­ts back and/or heels to one si­de or the other, to what de­gree the ya­cht pit­ches and rolls.the in­ter­cep­tors are four me­tres long.

Si­mu­la­tion pro­ce­du­re This en­tails per­for­ming 5 se­pa­ra­te trials for ea­ch of the fol­lo­wing con­di­tions: Hull wi­th no sta­bi­li­sers; Hull wi­th prin­ci­pal fins on­ly; Hull wi­th prin­ci­pal fins, bow fins, and in­ter­cep­tor RCS (Ri­de Con­trol Sy­stem).

Pit­ch and roll The ob­tai­ned re­sul­ts are pre­sen­ted as oscil­la­to­ry de­via­tions in re­la­tion­ship to re­fe­ren­ce point pla­ced as “Ze­ro”. Four gra­phs ha­ve been ob­tai­ned for ea­ch speed and wa­ve height se­lec­ted:

1) Stan­dard de­via­tion of roll Wi­thout sta­bi­li­sers; On­ly wi­th prin­ci­pal fins; To­tal RCS.

2) Per­cen­ta­ge of roll re­duc­tion in the sa­me con­di­tions ex­pres­sed abo­ve

3) Ex­cur­sion of pit­ch Wi­thout sta­bi­li­sers; Wi­th RCS.

4) Per­cen­ta­ge of pit­ch re­duc­tion in the sa­me con­di­tions ex­pres­sed abo­ve; The gra­phs re­fer to roll/pit­ch at 16 kno­ts wi­th 1.1 me­tre hi­gh wa­ves and 1.526 me­tre hi­gh wa­ves wi­th a ca­den­ce of 7.0 se­conds. Emer­gen­ce/slam are ex­pres­sed in emer­gen­ce/hour and slam/hour at the sa­me speed of 16 kno­ts wi­th 2 me­tre hi­gh wa­ves and 3,25 me­tre hi­gh wa­ves wi­th a ca­den­ce of 7.5 se­conds. Fi­nal­ly, ac­cor­ding to the si­mu­la­tion trials per­for­med by Na­iad Dy­na­mics, the re­duc­tion of pit­ch in head seas was bet­ween 25 and 47 per cent ac­cor­din­gly; whe­reas roll in the wor­st con­di­tion exa­mi­ned wi­th a wa­ve train co­ming in at 75 de­grees (al­mo­st broad­si­de on edn.)was re­du­ced bet­ween 79 and 88 per cent.

BE­NET­TI FB 269 “SPEC­TRE” De­si­gned for John Sta­lu­pi one of the shi­pyard’s mo­st fai­th­ful clien­ts who should be ta­king de­li­ve­ry of the Be­net­ti FB 269 in Ju­ly next. This ya­cht is the re­sult of the mo­st ad­van­ced tech­no­lo­gy avai­la­ble to lar­ge di­spla­cing uni­ts. Her hull li­nes ha­ve been dra­wn up by Dut­ch stu­dio Mul­der De­si­gn to de­li­ver ma­xi­mum ef­fi­cien­cy un­der­way wi­thin a con­si­de­ra­ble speed ran­ge whi­le gua­ran­teeing a re­mar­ka­ble ran­ge equal to 6,500 nau­ti­cal mi­les at an econ speed of 12 kno­ts wi­th a top one of about 21. Among her main fea­tu­res: Na­iad Dy­na­mics sta­bi­li­ser sy­stem whi­ch has been the ob­ject of the re­sear­ch work re­por­ted in this text.

TECH­NI­CAL DA­TA Na­val ar­chi­tec­tu­re: Mul­der De­si­gn - Ex­te­rior de­si­gn: Gior­gio Ma­ria Cas­set­ta - In­te­rior de­si­gn: Be­net­ti Shi­pyard - LOA: 69.30 m - Beam:11.70 m - LWL: 63.07 m - Beam at wa­ter­li­ne:10.526 m - Draught at bow: 2.896 m - Draught at stern:3.034 m - Di­spla­ce­ment: 900 t - Ver­ti­cal cen­tre of gra­vi­ty: 5.00 m - Lon­gi­tu­di­nal cen­tre of gra­vi­ty: 30.125 m - GML: 147.2 m - GMT: 1.6 m - Fuel tank ca­pa­ci­ty: 120,000 li­tres - Wa­ter tank ca­pa­ci­ty: 18,000 li­tres - En­gi­nes: MTU 2 x 3.500 HP - Top speed de­cla­red: 21kno­ts - Class: ABS Com­plian­ce LY3

No­te: 13 di­ver­se wa­ve di­rec­tions ha­ve been si­mu­la­ted ran­ging from 0 to 180 de­grees at 15 de­gree in­ter­vals to re­pre­sent the ty­pi­cal sea whi­ch forms in coa­stal wa­ters or that is ge­ne­ra­ted by a wind wi­th lit­tle fet­ch by de­ploy­ing Jon­swap Spec­trum, whi­ch de­ri­ves from Pier­son-mo­sko­wi­tz Spec­trum mul­ti­plied by the ϒr. ex­tra-peak fac­tor.

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