Designing a Passion for Yanmar

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Naval architect Stuart Ballantyne is a highly talented man of the sea.  He frequently challenges conventional wisdom in ship design, but when it comes to power plants he is very much a Yanmar advocate.

His own vessel, Passion, is a design which he initially developed 15 years ago as the Crusader design.  Passion is an all alloy 17m cat with a beam of 7.4m, a draft of 1m and a single Yanmar 6LPA-STP2 shaft drive engine installed in each of the hull sponsons.

While most look at a vessel like Passion and refer to it generically as a catamaran, Stuart Ballantyne terms this as a Small Waterplane Area Twin Hull (SWATH) hull form, developed by his naval design company, Sea Transport Corporation and refined with advanced tank testing in Hobart.

The entry of each hull has a piercing bulb mounted below the waterline, very much the same as the large seagoing commercial ships.  This bulbous bow design delivers a series of benefits including better handling, less pitching and greater hull efficiencies.

Designed on the Gold Coast and built in Vietnam by Strategic Marine, Passion was shipped STP2 engines comfortably slotted into their respective engine rooms with ample space all the way around for easy access.

In many ways, having just 315 mph on each side of the hull would appear to be less power than needed in a hull of this water performance stats certainly tell a very different and impressive story.

At wide open throttle, Passion is good for 23.5 knots or 44 km/h.  At a more sedate cruise speed of 18 knots (33 km/h), the Yanmar 6LPA-STP2 engines are ticking Over at 2800 rpm and returning modest fuel consumption figures of 22.5 litres per engine per hour.   With 4000 litres of fuel on board, Passion has a massive 1000 nautical miles cruise range at 18 knots.

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“This is a highly efficient hull with equally as efficient Yanmar engines,” said Stuart Ballantyne.

My research proves that a monohull of the same length and weight would need a massive boost in horsepower and associated fuel consumption to achieve the same performance.  ”

-performance and well-proven package with a direct injected, mechanical governor equipped turbocharged and intercooled straight 6 cylinder engine pumping out 315mhp at 3800 rpm at the flywheel. The 4 valve per cylinder engine boasts a 4.2-litre displacement for sustained torque through the mid rev range while still offering an impressive power to weight advantage coming in with a dry weight of only 408kgs without the transmission.

The strength of a Stuart Ballantyne’s Crusader design lies in its versatility.  It has been built in both alloy and fibreglass, in both motor and motor sailing configurations.  There have been commercial variants operating as game boats, charter vessels and as commuter ferries.
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As a naval architect, Stuart Ballantyne pushes the boundaries of conventional wisdom.  His absolute commitment to SWATH catamaran hulls is gaining favour the world over.  Even his design for military and commercial landing vessels that unload on a beach via a stern ramp (as opposed to the conventional drop bow design) is proving to be a commercially viable and superior operational system.

One constant however, is his commitment to the Yanmar brand.  “I’ve got a wealth of experience with Yanmar marine diesel engines,” said Stuart.
“Yanmar engines across the range are clean and quiet.  The Yanmar 6LPA-STP2’s in Passion have a vee drive configured transmission so are really easy to access.  Servicing is a breeze, with all maintenance points on the engine easy to get at, with no need for any specialised diagnostic tools or laptop computers, which is another reason why I like Yanmar’s.”

Stuart Ballantyne’s preference for Yanmar extends to his professional life with his design office currently very busy with numerous projects around the world under construction.  One such project which features Yanmar commercial engine power is a new fleet of ten 50m ROPAX vessels being built for the Philippines.  Each vessel is being fitted out with four Yanmar 6AY- 20 litre displacement 659mhp continuously rated engines (2 engines in each hull) complete with Yanmar Marine transmissions driving through conventional shafts.

Each of these vessels is designed to carry 52 vehicles and 350 passengers for inter-island transfers.  They are being built to full ABS classification and will provide an unprecedented level of safety, high speed and cost effective transport in the Philippines. Further details on this exciting project and the many other renowned Sea Transport designs can be found of their web site

On a personal level, the University of Strathclyde in Scotland has recently awarded Stuart Ballantyne the honorary degree of Doctor of Science. This award recognises his achievements in the field of Naval architecture and his work in providing safer, more economical and environmentally compelling commercial vessel designs.