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Optima propeller nozzles

Smallest ever Optima nozzles for yacht

10 June 2014

At DMC we pride ourselves on a new record with the ‘Optima’ propeller nozzle series. Defying the boastful biggest, fastest or strongest routine (after all, who needs that?), the two stars of this story measure a dapper 665 mm inside diameter. They have chipped a colossal 33.4 per cent off the previous 1,000 mm Optima entry level model.

Given the 8,000 mm inner diameter of the biggest Optima propeller nozzles, or the average size of any DMC nozzle for that matter, our new 665 mm milestone twins could almost be considered precision mechanics.

“They definitely brought dear, fine engineering and precision manufacturing to our teams indeed”, Aart Vogelaar, Sales Manager Damen Marine Components enthuses. The two record-breaking 665 mm nozzles are spectacular also, as they were built for a 50-foot (15 meter) yacht. They were commissioned from Damen Marine Components by a third-party (non-Damen) manufacturer of propulsion systems.

“Our clients had to install DMC Optima propeller nozzles by customer specific requirement from the owner, who, in addition, wanted his 50 foot 11 knot boat to have two propellers. He must be an expert, considering this explicit and uncompromising selection and configuration, including a stainless steel inside ring. Possibly a tugboat or inland waterway vessel captain. But definitely an expert”, Aart Vogelaar adds.

Lowest noise and vibration

The owner must be aware of both the Optima’s unparalleled characteristics for reducing both noise and vibration, and for its propelling performance. With its own special inside profile, the nozzle type was patented by DMC back in 1998 already. Thousands of units have since established the Optima’s reputation as a nozzle renowned for combining high comfort with performance within its specific operational range. “Its profile was designed for an optimum ratio between engine output, fewer revolutions and thrust, both forward and reverse”, Vogelaar specifies.

“As this includes modest sailing speeds, this model - with the matching propeller pitch - is widely deployed in inland waterway vessels, Stan tugs, push boats and hopper dredgers. Its noise-vibration-thrust performance is the Optima’s acknowledged trademark throughout the shipping industry. This is no illusive claim of ours, it’s a fact, full stop.”

Small hands

DMC’s Optima nozzles usually have an L/D 0.5 ratio (length = 0.5 x diameter) for dredgers, Stantugs or inland waterway vessels, and L/D 0.6 for push boats. The river yacht soon to boast the world’s smallest nozzles, will feature L/D 0.4 to still safeguard ‘crew comfort’ at its somewhat higher 11 knot speed. Like each and every DMC nozzle, these two have been engineered separately at the DMC center in Hardinxveld-Giessendam, Netherlands. Vogelaar explains: “No two vessels are the same, not even with identical dimensions, unless they are carbon copy sister ships. Consequently, every nozzle we produce, will have had dedicated engineering first, for optimum output. So this wasn’t just because these two measure only one twelfth of our biggest Optima’s. I love saying this. The two mini’s weigh only 188 kilos each. No, at DMC Gdańsk (Poland) we haven’t specially selected engineers with small hands for their production.”