ELEC­TRON­ICS

Soni­hull uses pulse fre­quen­cies to pre­vent per­for­mance-sap­ping, hull-bot­tom ma­rine growth.

Yachting - - CONTENTS - By David Sch­midt

Soni­hull was look­ing for an eco-friendly way to keep hull bot­toms growth-free. The so­lu­tion: ul­tra­sonic fre­quen­cies.

It starts silently and small. Given time and proper steep­ing con­di­tions, though, ma­rine growth can snow­ball into a per­for­mance-drain­ing mess. Here in Seat­tle, Puget Sound’s nu­tri­ent-rich wa­ters ric­o­chet be­tween 46 and 56 de­grees Fahren­heit year-round, and even those tem­per­a­tures don’t stymie growth. Stroll the docks at Shiles­hole Bay Ma­rina and plenty of oth­er­wise fine-look­ing yachts sport shaggy un­der­wa­ter beards that re­quire reg­u­lar diver vis­its or trips to fresh­wa­ter Lake Wash­ing­ton to rem­edy. Ex­trap­o­late out to Florida’s sun-baked, bath­tub-warm wa­ters and it’s easy to see how ma­rine growth can cre­ate sig­nif­i­cant prob­lems. ¶ Mariners have bat­tled be­fouled un­der­car­riages since the dawn of ex­plo­ration and trade. They at one point at­tached cop­per cladding to wooden hulls to solve the prob­lem, a les­son that re­ver­ber­ates with today’s ab­la­tive and hard-bot­tom anti-foul­ing paints that typ­i­cally em­ploy cuprous ox­ide as their ac­tive in­gre­di­ent. ¶ Now come ul­tra­sonic so­lu­tions such as Soni­hull sys­tems, which dis­rupt ma­rine growth’s food chain, ren­der­ing a ves­sel’s hull an in­hos­pitable habi­tat while help­ing to keep tanks, pip­ing and shaft/drive sys­tems growth-free. ¶ Ma­rine growth re­lies on a food chain that be­gins when free-swim­ming phy­to­plank­ton at­tach to a yacht’s hull and repli­cate. The re­sult­ing green al­gae is an ir­re­sistible habi­tat for higher-or­der zoo­plank­ton such as mus­sel and bar­na­cle lar­vae that at­tach to the hull, grow and repli­cate too, po­ten­tially dam­ag­ing the hull. While the tra­di­tional so­lu­tion to this prob­lem has been to use bio­cides that in­dis­crim­i­nately kill all at­tached growth, Soni­hull and other man­u­fac­tur­ers of ul­tra­sonic anti-foul­ing sys­tems, in­clud­ing Ul­tra­sonic An­tifoul­ing and Ul­tra­sonic Ma­rine, re­al­ized that if the food chain could be bro­ken, ma­rine growth would de­tach or die. ¶ “Al­gae is a sin­gle-cell an­i­mal,” says Phil Quar­tararo, prod­uct man­ager at PYI Inc., which is Soni­hull’s U.S. dis­trib­u­tor. Ul­tra­sonic anti-foul­ing sys­tems work on a cel­lu­lar level. By in­tro­duc­ing tar­geted pulse fre­quen­cies into a hull, the sys­tems cre­ate a res­o­nance that forces mi­cro­scopic move­ments of water. This water move­ment cre­ates sud­den, mi­cro­scopic cav­i­ta­tions each time

the pres­sure drops, caus­ing the sin­gle­celled al­gae to im­plode and die while pre­vent­ing zoo­plank­ton from at­tach­ing. ¶ Soni­hull sys­tems use a con­trol box hard­wired to at least one hull-mounted, IP68-rated trans­ducer en­cased in ther­mo­form plas­tic, thus avert­ing elec­trol­y­sis and pre­vent­ing cur­rent from en­ter­ing the hull. The trans­ducer is screwed onto a ring that’s epox­ied in place on the in­side of the hull (read: no through-hull holes re­quired). ¶ “Soni­hull com­mis­sioned a univer­sity to study al­gae un­der an elec­tron mi­cro­scope to nar­row down 21 [fa­tal] fre­quen­cies,” Quar­tararo says. These 21 fre­quen­cies range from 19.5 kHz to 55 kHz, and Soni­hull sys­tems cy­cle through an end­less play­back loop that the trans­ducer’s phys­i­cal de­sign en­hances. “The airspace in our trans­duc­ers is filled with metal fil­ings that make the trans­ducer act like a dead-blow ham­mer,” says Quar­tararo, adding that Soni­hull uses elec­tronic com­po­nen­try that matches im­ped­ance and re­sis­tance across the en­tire sys­tem to thwart heat buildup. ¶ PYI says Soni­hull turns a hull into a gi­ant ul­tra­sonic speaker, with the trans­duc­ers act­ing like speaker cores and the hull’s outer skin serv­ing as the speaker cone. But, Quar­tararo says, Soni­hull doesn’t dis­turb other in­stru­men­ta­tion, shy of pos­si­ble mo­men­tary in­ter­fer­ence from over­lap­ping fre­quen­cies. ¶ “It’s like hav­ing a fish finder and depth sounder run­ning at the same time,” he says. ¶ Each Soni­hull trans­ducer pro­vides anti-foul­ing pro­tec­tion for up to a 33-foot ra­dius, and Soni­hull sys­tems are avail­able with one, two or eight trans­duc­ers ($1,650 to $9,950 per sys­tem). In­stal­la­tions are scal­able to pro­vide the cor­rect hull pro­tec­tion, and the sys­tems are built to work on all hull types, ex­clud­ing wood and con­crete. Own­ers of boats with cored fiber­glass hulls will need to have the cor­ing ma­te­rial re­moved un­der each trans­ducer. ¶ Soni­hull sys­tems can be matched with adapters to pro­tect pip­ing and drives (see side­bar), while trans­duc­ers can be fit­ted onto sea chests, heat ex­chang­ers and water tanks, keep­ing potable water fresh longer and killing diesel bugs. ¶ Soni­hull is de­signed to run 24/7, but the low-draw sys­tems are con­fig­ured to use shore power be­fore tap­ping into the yacht’s di­rect-cur­rent re­serves, and they au­to­mat­i­cally turn off in low-volt­age (12 volts or less) sit­u­a­tions. ¶ “We know you’d rather have your bilge pumps run­ning than a clean bot­tom,” Quar­tararo says. ¶ Soni­hull is es­sen­tially a set-itand-for­get-it sys­tem, ex­cept for the rec­om­mended monthly task of in­spect­ing the LED in­di­ca­tor lights on each con­trol

box. While ex­act met­rics de­pend on a yacht’s per­for­mance char­ac­ter­is­tics and how hard it’s run, PYI says users could see fuel con­sump­tion drop by 20 to 30 per­cent. A Soni­hull sys­tem should dou­ble the life span of anti-foul­ing paint, the com­pany says, while halv­ing planned haul-outs. And clean hulls of­fer far bet­ter per­for­mance and in­cur less wear and tear on en­gines and steer­ing and trim­ming sys­tems. ¶ Soni­hull and other ul­tra­sonic anti-foul­ing sys­tems also of­fer en­vi­ron­men­tal ben­e­fits. Less fuel pumped equals less emit­ted car­bon diox­ide, while less bot­tom paint ap­plied means less cuprous ox­ide en­ter­ing the ocean. ¶ “Fish swim up to Soni­hull-pro­tected boats, but they don’t dart away,” Quar­tararo says. “These are fish-finder fre­quen­cies — they won’t kill whales.” ¶ While PYI says com­pe­tent DIYers can in­stall Soni­hull sys­tems, pro­fes­sional in­stall­ers are some­times re­quired for

big­ger in­stal­la­tions or jobs in­volv­ing cored GRP hulls. ¶ Quar­tararo says that, once in­stalled, the sys­tems are quiet. “They op­er­ate at fre­quen­cies above 19.5 kHz, which is be­yond the au­di­ble range of most hu­mans,” he says. ¶ PYI does say the sys­tems al­low some ma­rine growth to con­tinue. That in­cludes as­cid­ian (“sea squirts”) that ex­ist out­side the al­gae-fed food chain. For

those is­sues, anti-foul­ing bio­cides may still be re­quired. ¶ Even still, Soni­hull sys­tems seem to of­fer hand­some div­i­dends, both for yachts­men and for the en­vi­ron­ment. Given tight­en­ing reg­u­la­tions in some states re­gard­ing cuprous ox­ide in anti-foul­ing paint, Soni­hull could be a way of fu­ture-proof­ing a yacht while en­sur­ing that its hull bot­tom never looks like a “water wookie.”

SOUND DE­FENSE Son­ishaft trans­duc­ers are de­signed to dra­mat­i­cally re­duce ma­rine growth on pro­pel­ler shafts.

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