Good things often evolve to meet a very specific need. That is certainly the case with the new Osborn Chapman OC50 cruising yacht. Company founder and life time yachtsman, Paul Charlton, was discussing with a sailing mate the inappropriateness of contemporary production yachts, so he set about designing and building, what has become, the OC50 Deck Saloon cruising yacht.
With a Yanmar 4JH4-HTE marine diesel engine installed under the saloon floor, Mase IS.7 gen set aft and Gori 3 blade folding propeller, the OC50 is superbly equipped.
Designed by Australian Naval Architect Andy Dovell, the OC50 was built at Jarkan in Nowra. What transpired is a superbly engineered yacht with a length overall of 15.24m (50’ 0”) and a displacement of 14 tonnes.
The fundamental concept upon which the OC50 is based centres on a couple who wish to start their big boat life with inshore sailing, and once confident, move to coastal cruising then passage making. While production boats in this category tend to focus upon more cabins and toilets, the OC50 has generous space for the owners with enough room for guests or any crew needed for an extended passage.
On every benchmark the OC50 scores high marks. This is a top line vessel in terms of quality, appointments, design features and construction.
The involvement of Yanmar occurred very early in the design process when the naval architect confirmed Yanmar as the preferred auxiliary engine option.
“The Yanmar 4JH4-HTE was right at the top of the recommended power range,” said Paul Charlton.
“Based on the hull characteristics of the OC50, the 110mhp Yanmar delivers the effortless cruising performance that we wanted to provide for our owners.”
Through his previous sailing and general boating experiences, Paul Charlton was familiar with the Yanmar brand. He has previously owned a yacht with a Yanmar 30hp SailDrive. He also had a workboat with a single cylinder, crank start Yanmar that proved to be a “pretty tough” unit.
The Yanmar 4JH4-HTE sits amidships in the hull, directly under the saloon floor. Despite the potential for the location to have issues with noise and vibration, the Yanmar is the ideal engine for the task with neither issue being a problem.
This model Yanmar is a 4 cylinder, 4 stroke marine diesel engine with a displacement of 1.995 litres. An intercooler is integrated into the turbo charged induction system. Peak power of 110mhp is achieved at only 3200 rpm. Highly rated amongst boaters as a powerful yet light weight engine, the Yanmar 4JH4-HTE is the ideal auxiliary yacht engine for vessels such as the OC50. It is whisper quiet and has a compact installation envelope. Low noise combined with low emissions and low vibration…. What more could a customer ask for?
In addition to the Yanmar 4JH4-HTE installed in the OC 50, Paul Charlton has also selected the Danish manufactured 3 blade Gori folding propeller to drive the 14.0 tonne boat.
The 3 blade Gori propeller is the only folding propeller operating the same pitch in forward and in reverse (The blades turn 180 degree), therefore it has the same thrust in forward and reverse. The propeller is actually more efficient than a 3 blade fixed propeller in reverse.
The 3 blade Gori propeller has an Overdrive, a second pitch which can be compared to the 5th gear in a car. You use the overdrive function when motoring in calm waters or when motor sailing. It can save you 20% in fuel and when you are pushing a 14 tonne yacht through the water, this can be quite considerable.
When sailing, and your 3 blade Gori propeller is folded, it has the lowest drag of all 2 and 3 blade propellers, fixed, feathering and folding with only 1.4 Newtons of drag at 6 knots. In addition, the 3 blade Gori propeller once folded, does not auto rotate, so no shaft brake or transmission lock is required.
Complementing the Yanmar 4JH4-HTE is a Mase IS.7 marine generator set. This is fitted under the rear cockpit floor, with access gained via the saloon bulkhead. The Mase IS.7 delivers a heap of power to drive the air conditioning, TV, microwave, refrigeration and anything which is plugged in to the 240 volts outlets in all of the cabins. The OC50, like most modern high spec’d vessels of this size, has a plethora of electronic equipment to operate the yacht. This equipment can be found out in the cockpit, at the navigation station and more generally with the Scada management system.
“We are immensely proud to have designed and built the OC50 as an all Australian effort,” said Paul Charlton.
“Yanmar, Mase and Gori are all important components that we have considered and purposefully selected.”