Ae­ro­dy­na­mic lift

Superyacht - - Design -

off ” due to their ve­ry hi­gh speed com­bi­ned wi­th the light­ness of the hulls them­sel­ves. That’s how and why the ground ef­fect idea and the lift fac­tor ca­me to be ex­ploi­ted so­le­ly in com­pe­ti­tion mo­dels for ma­ny years, at lea­st up un­til su­ch a ti­me when so­meo­ne do­wn si­zed this tech­no­lo­gy so that it could be de­ployed mo­re sa­fe­ly for mo­re con­ven­tio­nal usa­ges. So the ine­vi­ta­ble ad­vent of A2V com­pa­ny. A2V is short for Ad­van­ced Ae­ro­dy­na­mic Ves­sels. This re­cent re­sear­ch com­pa­ny foun­ded in 2013 has been fo­cu­sing on fluid dy­na­mics ever sin­ce in­cep­tion and has dra­wn up ex­tre­me­ly fa­st boa­ts whi­ch are tru­ly ef­fi­cient in terms of ener­gy. A2v’s foun­ding mem­bers ha­ve sin­ce de­ve­lo­ped and pa­ten­ted so­me of their pro­ject work in li­ne wi­th pas­si­ve ground ef­fect fin­dings so as to build a new kind of boa­ts wi­th the sa­me na­me A2V. This is not a me­re slo­gan be­cau­se the com­pa­ny’s team of young en­gi­neers ha­ve al­rea­dy built two boa­ts of the kind wi­th a third cur­ren­tly being built and we’re not tal­king about small wa­ter craft! The fir­st one off the chocks is an A2V- 25- CB. It was de­li­ve­red in Ja­nua­ry 2018. This mo­del car­ries up to 25 pas­sen­gers wi­th a top speed of 40 kno­ts. It has been de­si­gned to car­ry crew to and from off­sho­re plat­forms in we­st Afri­can wa­ters. Pe­schaud In­ter­na­tio­nal is the ow­ner of this Fren­ch build na­med “Cle­men­ti­ne” wi­th an LOA of 15 me­tres and a beam of 12 she’s po­we­red up by a pair of hy­dro- je­ts thanks to two 600 HP en­gi­nes but uses half as mu­ch fuel by com­pa­ri­son to others in alu­mi­nium ow­ned by the com­pa­ny whi­ch trans­la­tes in­to a year­ly sa­ving of 500,000 li­tres of die­sel fuel per unit. Half a mil­lion li­tres sa­ved per unit per year is by any stan­dard a con­si­de­ra­ble sa­ving. The se­cond unit an A2V- SHUT­TLE whi­ch was de­li­ve­red Sep­tem­ber la­st car­ries 10 pas­sen­gers at up to 50 kno­ts fer­ry­ing clien­ts stay­ing at lu­xu­ry ho­tels on la­ke Le­man in Swi­tzer­land. Wi­th an LOA of 12 me­tres and a beam of a lit­tle over 7 this craft shut­tles a grea­ter num­ber of pas­sen­gers in less ti­me and wi­th less fuel when com­pa­red to other mo­dels cur­ren­tly used. And abo­ve all the de­gree of com­fort the A2V of­fers is com­pa­ra­ble to bu­si­ness class! The­se re­sul­ts ha­ve been achie­ved thanks to pas­si­ve ae­ro­dy­na­mic lift and thanks to A2V en­gi­neers’ fi­ne tu­ning, the de­tails of whi­ch are sho­wn in the ap­pro­pria­te box. The tech­no­lo­gy de­ployed has en­tai­led a clear­ly vi­si­ble con­di­tio­ning of the ves­sels’ sha­pe whi­ch re­sem­ble lar­ge clo­sed sea shells whi­ch means that in­te­rior spa­ces are ine­vi­ta­bly pe­na­li­sed whi­le the ex­te­riors are prac­ti­cal­ly no­ne­xi­stent. The sum of the­se fac­tors do not en­cou­ra­ge any re­crea­tio­nal use at lea­st for the ti­me being as it is the ve­ry “wing li­ke” sha­pe they pos­sess whi­ch de­li­vers the per­for­man­ce ob­tai­ned. Ho­we­ver the pos­si­bi­li­ty of ope­ning up por­tions of the exi­sting ex­ter­nal “bo­dy” is being exa­mi­ned so as to en­joy se­ve­ral ex­ter­nal areas along the rear win­glet whi­ch ac­cor­ding to A2V’S en­gi­nee­ring team can con­vert in­to a ter­ra­ce over­loo­king the sea. The­re’s

La tec­no­lo­gia mes­sa a pun­to con gli A2V che ren­de pos­si­bi­le, A2V’S fi­ne tu­ning of all the tech­no­lo­gy in­vol­ved trans­la­tes in­to sa­fe pas­si­ve ae­ro­dy­na­mic lift and ef­fi­cien­cy whi­ch is ba­sed upon a pro­por­tio­nal ba­lan­cing of two fac­tors: the craft’s hy­dro­dy­na­mic and ae­ro­dy­na­mic com­po­nen­ts. The ae­ro­dy­na­mic part is re­pre­sen­ted by the abo­ve wa­ter struc­tu­ral sec­tion re­sem­bling wings whi­ch de­ve­lop lift or ver­ti­cal for­ce whi­ch ma­kes air­craft fly. The hy­dro­dy­na­mic part is ma­de up of two iden­ti­cal ca­ta­ma­ran hulls con­nec­ted to the wing su­per­struc­tu­re. As for A2VS in ad­di­tion to the lift ge­ne­ra­ted on the back ( top of the wing) ano­ther ver­ti­cal for­ce co­mes in­to play due to the quan­ti­ty of air chan­nel­led bet­ween the two hulls whi­ch is com­pres­sed bet­ween the lo­wer sec­tion of the wing or fa­ce wi­th the sea sur­fa­ce. The sum of the­se ver­ti­cal for­ces will par­tial­ly lift the hulls off the wa­ter sur­fa­ce the­re­by no­ta­bly re­du­cing drag. In fact ha­ving the hulls ad­van­ce not in wa­ter but th­rou­gh air ( whi­ch is 1000 ti­mes less den­se than wa­ter) means that the re­qui­red th­ru­st for­ward is con­si­de­ra­bly ve­ry mu­ch less. As you pro­ba­bly know lift ef­fect will grow ex­po­nen­tial­ly as speed ri­ses. Air com­pres­sion ef­fect will in­crea­se bet­ween the sea sur­fa­ce and the wings gi­ving ri­se to what we know as WIG or wing in ground ef­fect. As op­po­sed to con­ven­tio­nal ships whe­re all of this re­pre­sen­ts ad­ded drag, in­stead whe­re A2VS are con­cer­ned this means ex­ploi­ting ground ef­fect to par­tial­ly lift the hulls off the wa­ter the­re­by de­crea­sing sub­mer­ged vo­lu­me up to 50% whi­ch trans­la­tes in­to mu­ch less drag. In con­ven­tio­nal hulls drag ef­fect in­crea­ses ex­po­nen­tial­ly as speed in­crea­ses the op­po­si­te of whi­ch hap­pens in A2VS. Abo­ve 25 kno­ts all of this brings about a se­ries of si­gni­fi­cant ad­van­ta­ges. To be­gin wi­th, less po­wer is re­qui­red by the en­gi­nes whi­ch the­re­fo­re sa­ves fuel. For exam­ple, when a con­ven­tio­nal fa­st boat usual­ly re­qui­res 30 li­tres of die­sel per pas­sen­ger per 100 km at 40 kno­ts, an A2V re­qui­res on­ly ni­ne li­tres and what’s mo­re not at 40 but at a ground speed of 50 kno­ts in the sa­me sea con­di­tions. Fur­ther­mo­re, this re­mains true ir­re­spec­ti­ve of the ship’s si­ze, no mat­ter whe­ther it is 12 or 30 me­tres long and whe­ther it is car­ry­ing 10 or 100 pas­sen­gers. Up un­til to­day hi­gh speed over wa­ter has been the pre­ro­ga­ti­ve of lar­ge ships car­ry­ing con­si­de­ra­ble num­bers of pas­sen­gers over long hauls whi­ch al­low ship­ping com­pa­nies to bet­ter amor­ti­ze ve­ry hi­gh fuel con­sump­tion costs re­qui­red to crui­se at 40 kno­ts wi­th con­ven­tio­nal fa­st hulls. We’re tal­king about ca­ta­ma­rans or se­mi- pla­ning sin­gle hulls whi­ch de­spi­te their ca­pa­ci­ty to rea­ch 50 kno­ts and mo­re, ra­re­ly go beyond 40. In fact this is due to the fact that on­ly a han­d­ful of ex­tra kno­ts are enou­gh to dou­ble con­sump­tion. To sum up in plain words, the tech­no­lo­gy whi­ch A2V has de­ve­lo­ped and pa­ten­ted is be­st ex­pres­sed wi­th the fol­lo­wing slo­gan on the com­pa­ny’s web­si­te ( www. aa­ves­sels. com): “sa­fe­ly trans­fer­ring, the en­ti­re weight of the ship from wa­ter to air”. In ad­di­tion to the ad­van­ta­ges in terms of speed and of re­du­ced con­sump­tion, the tech­no­lo­gies de­ployed on A2VS trans­la­te in fur­ther be­ne­fi­ts when com­pa­red to con­ven­tio­nal fa­st hulls be­gin­ning wi­th sa­fe­ty. The at­ten­ti­ve and in dep­th de­tai­led stu­dy of the abo­ve sur­fa­ce ae­ro­dy­na­mics, of the hy­dro­dy­na­mics of the hulls, of the fi­ne tu­ned di­stri­bu­tion of weights ha­ve go­ne in­to har­mo­ni­zing and ba­lan­cing all the for­ces whi­ch co­me in­to play when crui­sing at se­ve­ral di­ver­se speeds in su­ch a way as not to ha­ve to re­sort to ac­ti­ve sta­bi­li­ser sy­stems ne­ces­sa­ry in con­ven­tio­nal hulls to con­trol pit­ch and roll wi­th flaps for in­stan­ce, in­ter­cep­tors and so on. In an A2V all of that is not ne­ces­sa­ry sin­ce sea kee­ping qua­li­ties are en­han­ced na­tu­ral­ly by an air cu­shion whi­ch is en­trap­ped bet­ween the two hulls gua­ran­teeing an all round smoo­ther ri­de.

The A2V-SHUT­TLE is well equip­ped wi­th sur­fa­ce props. the spe­cial step­ped geo­me­try of the hulls re­cal­ling tho­se of hy­dro­pla­nes can be clear­ly seen.

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