DMS’S new sta­bil­i­sa­tion fins could be­come a staple for mo­tor boats

Motorboat & Yachting - - Contents -

DMS Hol­land’s new fold­ing sta­bilis­ers plus Williams Mini­jet, Ocean­led’s Dock Lights, Fu­sion speak­ers and Kru life­jacket

Dutch com­pany DMS Hol­land is hop­ing to rev­o­lu­tionise the mar­ket for sta­bilis­ers with a new de­sign of flap­ping fins specif­i­cally de­signed for fast-plan­ing mo­tor boats. The com­pany orig­i­nally made a name for it­self with its cylin­dri­cal Mag­nus­mas­ter ro­tat­ing sta­bilis­ers for dis­place­ment boats, and last year it launched the An­tiroll ‘flap­ping’ fins for su­pery­achts. Now it plans to de­velop this An­tiroll tech­nol­ogy into a smaller, cheaper, more ef­fec­tive pack­age for fast pro­duc­tion boats.

The key to this new de­sign of high­aspect ra­tio fin is that they at­tach to the tran­som of the boat rather than be­ing fit­ted through the main sec­tion of the hull. This makes them eas­ier to in­stall (the hy­draulic ac­tu­a­tors of tra­di­tional fins of­ten have to be tucked un­der the floor of the mas­ter cabin) and en­sures that all the in­ter­nal work­ings can be kept in the en­gine bay, re­duc­ing noise dis­tur­bance at night. It also has a num­ber of in­ter­est­ing dy­namic ben­e­fits. Be­cause the fins ro­tate on two dif­fer­ent axes, they can be swiv­elled all the way round so that they tuck in be­hind the tran­som. This not only re­duces drag to neg­li­gi­ble lev­els at high speed, but also en­ables them to double up as ac­tive trim tabs, tilt­ing up and down to cor­rect both roll and lean in much the same way as Humphree’s Ac­tive In­ter­cep­tors. This means that in­stead of in­stalling sep­a­rate trim tabs and sta­bilis­ers, cus­tomers will soon be able to spec­ify one set of An­tiroll sta­bilis­ers that should cover ev­ery even­tu­al­ity from trim and lean to sta­bil­i­sa­tion at high speed, low speed and at an­chor.

Al­though DMS Hol­land won’t yet re­veal the full details of how the new sys­tem works across such a wide range of speeds, the il­lus­tra­tions ap­pear to show three dif­fer­ent op­er­at­ing modes: high speed, low speed and zero speed. At high speed, the fins tuck in along the trail­ing edge of the tran­som us­ing small ro­ta­tions of the fins to de­flect the water down and cre­ate the lift on one side or the other, much like an over­sized trim tab. The large sur­face area of the fins and high pres­sure of the water run­ning over them at speed means tiny move­ments will gen­er­ate sub­stan­tial lift. When com­bined with fast-act­ing elec­tric ac­tu­a­tors linked to

the sys­tem’s roll sen­sor, this should en­able them to re­act to any lean or roll and cor­rect it al­most in­stan­ta­neously. Their abil­ity to tuck away be­hind the tran­som will also be handy when it comes to berthing in a ma­rina or ma­noeu­vring in tight spa­ces.


At slower dis­place­ment cruis­ing speeds, the fins swivel round into their ex­tended po­si­tion where they will ro­tate up and down in the same way as the high-speed mode. Al­though the slower speed of the water pass­ing over them won’t gen­er­ate as much pres­sure, their greater dis­tance from the cen­tre of roll en­sures they will still cre­ate more than enough lift to coun­ter­act any side-to-side rolling. In fact, the long, thin, high-as­pect ra­tio de­sign of the fins, sim­i­lar in shape to a glider’s wings or the pec­toral fins of a hump­back whale, not only cre­ate 50-75% less drag than the equiv­a­lent sur­face area of con­ven­tional fins but are also more ef­fi­cient at gen­er­at­ing lift where it’s needed the most.


Fi­nally, when the boat is at an­chor and un­able to rely on water pass­ing over the fins to cre­ate lift, it re­verts to the same ac­tu­a­tor used to ex­tend and re­tract them to flap them up and down like a pair of wings. Once again, the high-as­pect ra­tio de­sign of the fins, the ex­tra lever­age gained from be­ing fur­ther away from the boat’s roll cen­tre and the fact that the whole fin is mov­ing up and down rather than piv­ot­ing around an axis is claimed to make them more ef­fec­tive than con­ven­tional fins. Al­though DMS Hol­land makes no ref­er­ence to it, we sus­pect that it may also re­duce the pad­dle ef­fect that causes some boats to ‘swim’ over their own an­chor. Pa­trick Noor, co-owner of DMS Hol­land, says, “Since there is cur­rently no sin­gle sys­tem that per­forms op­ti­mally at both high speeds and at low speeds as well as at an­chor, of­ten mul­ti­ple roll-damp­ing sys­tems have to be in­stalled on one yacht. Soon, with our new sys­tem, one roll- damp­ing sys­tem on board will be enough with­out hav­ing to com­pro­mise on sta­bil­ity at dif­fer­ent speeds.”

De­spite these claims, there is one ob­vi­ous draw­back of the new sys­tem – the po­si­tion and size of the fins when re­tracted makes them un­likely to be suit­able for twin stern­drive or mul­ti­ple out­board en­gine in­stal­la­tions. This rules out the ma­jor­ity of sportscruis­ers be­low 45ft, most of which are pow­ered by twin stern­drive set­ups. How­ever, for shaft­drive or Ips-pow­ered boats, this does look like a very in­trigu­ing new prospect. The An­tiroll tech­nol­ogy has al­ready been proven to work on much larger boats – a 37m Van der Valk was fit­ted with it last year, win­ning the ap­proval of the ship’s cap­tain and crew, so there is no rea­son it won’t work equally well on smaller pro­duc­tion craft. Ac­cord­ing to DMS, a num­ber of ma­jor ship­yards and deal­ers have al­ready shown in­ter­est in the sys­tem and have in­di­cated a will­ing­ness to test it on one of their mod­els. Alexan­der Jonkers, owner of the Dutch Fair­line and Jeanneau dealer, Jonkers Yachts, has agreed to help test the sys­tem on one of his craft, adding, “I can’t wait to be able to of­fer the sys­tem to my Fair­line and Jeanneau as­so­ci­ates. In the mean­time, I will sup­port DMS Hol­land in the de­vel­op­ment and the first pro­to­type will be tested with us.”

Full details of the new sys­tem will be re­vealed at the METS equip­ment show in Am­s­ter­dam later this year with the first de­liv­er­ies of pro­duc­tion sys­tems sched­uled for early 2019. DMS Hol­land hasn’t yet given any in­di­ca­tion of pric­ing but with so many play­ers now of­fer­ing sta­bil­i­sa­tion sys­tems, it will have to be com­pet­i­tive to make in­roads into an al­ready crowded mar­ket. Con­tact www.dmshol­

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