Engineering

The systems engineering of the vessel has been a key part of accomplishing an end result suitable for the coastal cruising role. The installation arrangement is designed for serviceability down the road rather than targeting ease of manufacture. The systems are engineered as part of the original boat design instead of being thrown in towards the end of the build more like an afterthought. The end result is a reduced total cost of ownership for the owner and less warranty effort for the builder..

Propulsion Engines

The table below lists a range of engines that meet the base criteria of a 25" or 650 mm nominal shaft length. All engines are 4-stroke except for the Evinrude 90. At anchor or dock the engine bracketing and leg are completely clear of the water which means that engine antifouling is not required.

The recommended engines in the 60 - 90 HP class will maintain a vessel cruise speed in the 12 to 16 knot range. However the real and perceived stress level of a particular engine will probably decrease as engine cylinder capacity increases. Where a 60 HP engine might be a good choice for a boat that is used in a bay or river application, an 80 or 90 HP engine might be better where a higher top end or sustained cruising speed is required. As horsepower is increased, there is a diminishing return on boat speed so more horsepower does not necessarily mean better.

An electronic throttle and gear shift actuator is fitted as standard for each engine. The actuators are mounted in each hull within a couple of metres from each engine. The control head at the helm is compact and provides a very smooth engine operation without friction. In particular this makes it easier to balance engine RPM.

Another aspect of engine selection is the support of NMEA 2000 which is a digital communications link that allows the engine electronics to share data with third party instrument manufacturers. All engines are typically supplied with the manufacturers tachometer module however additional engine data such as fuel consumption, trim angle, engine temperature, oil pressure and so on may be available to third party instrument products that enhance the helm experience.

The boat takes good advantage of engine battery charging while under way however alternator amps is not a key selection factor for engine choice. See the electrical section below.

Fuel System

Each engine has an independent fuel system. A 300 litre capacity baffled fuel tank is located in each hull just aft of the companion way bulkhead. The tanks are fully serviceable in that they can be removed if the need ever arises - although it is not expected. The fuel lines have a priming bulb and primary fuel filter before feeding to each engine.

Helm

The vessel steering is electric using the autopilot controller and a proportional joystick that controls the rudder position. The rudder position tracks the deflection held on the joystick. A knob on the autopilot computer can also be used as a power steer device to alter heading. In practice, the joystick control is used for close quarter maneuvering while the autopilot control is used for longer runs. A steering ram is fitted to each engine and a hydraulic tie bar is connected between the engines. An autopilot pump is fitted in the aft bulkhead area. The aft pump location eliminates autopilot pump noise in the vessel interior. A small keel section is provided under each hull to maximize steering responsiveness.

The engine tachometers, morse control, Autopilot control head, steering joystick and dash switches are arranged in the centre to be accessible from either helm seat location. The electronic "morse" control head features fingertip control and automatic engine RPM synchronisation.

The vessel is fully equipped with an electronics package suitable to support coastal cruising navigation. A 12" multifunction colour display with integral GPS is equipped with Australia wide charts. The display also interfaces to a saloon roof mounted radome, the autopilot computer and a fish finder to provide an integrated navigation solution. A DSC equipped VHF radio and a class B AIS system round off the safety package. Ample space is provided either side of the helm to accommodate owner provided paper charts.

Electrical System

The vessel electrical system provides all vessel power while away from the dock without the need for a generator. Power is generated by 3 solar panels (totaling 525 watts) mounted on the roof. The vessel engines provide additional charging while under way and a 1000 watt petrol generator may be used as a backup on the odd occasion when the solar energy is not sufficient.

Energy is stored in a main battery bank comprising two 255 amp hour AGM batteries. An additional battery is provided as a reserve battery in case there is a main battery failure. The battery management system automatically maintains cross charging of the batteries and provide a means of cross coupling in case of a battery bank failure. Solar charging is regulated by a maximum power point tracking regulator that operates the solar panels at their most efficient power output according to sun exposure and battery state of charge. This means that the solar charging system efficiency is particularly enhanced in overcast conditions. A 2500 watt inverter converts battery power to 240 volt AC power for use by vessel appliances such as a convection microwave oven or toaster.

Power outlets are available at the galley bench and saloon table. The electrical switch panels are located at the starboard side of the helm panel. The electrical system is centrally located under the starboard side settee seat. The main DC distribution board has remote controlled battery isolation switches and fused connections for each heavy DC supply. An engine power board mounted aft has separate power switches to isolate engine power for maintenance.

Bilge Pumping System

Refrigeration

The galley is fitted with a pull out refrigerated drawer that is used as a galley working refrigerator. A 70 litre top opening freezer is located behind the companion way bulkhead on the port side. A top load 140 litre refrigerator is located opposite on the starboard side. All compressors are powered from the 12 volt house battery bank and the vessel solar panel capacity is sufficient to maintain all refrigeration on a continuous 24/7 basis.

The refrigeration system use a water cooling circuit for each condenser set. Water is recirculated through a pipe embedded into the lay up of the port hull which exchanges heat from the outside water. A parallel cooling circuit recirculates water through a heat exchanger on the vessel hot water system. A thermostat controller will switch between the two circuits to maintain the hot water system temperature.

Plumbing System

Two fresh water tanks of 220 litre capacity each are located under the floor of the forward cabins. The tanks are fitted with ultrasonic tank senders that connect to level gauges at the electrical house panel. For use in remote cruising applications, provision is made for installation of a 12 volt powered desalination system in the starboard hull aft of the fuel tank. Tank fill lines, intake and discharge thru hull fittings and electrical cable are pre installed.

A reverse cycle heat pump system utilises waste heat from the refrigeration system to heat the vessel hot water. A target hot water system temperature of around 45 degrees celcius is maintainable. An electrical heating circuit can be used from shore power or to supplement the heat pump system with an on board generator if required. The hot water system is located under the freezer cabinet on the aft deck.

The toilet system is fitted with a holding tank located behind the aft toilet bulkhead. The electric toilet pumps waste to the tank which is fitted in an above waterline configuration to allow gravity discharge through a below waterline hull fitting (if allowed by local law). A deck fitting is installed for suction pump out. The tank breaths through a pipe connected to a skin fitting under the wing deck. Full service is available to the holding tank by a removable panel on the aft head bulkhead. The tank is fitted with a "nearly full" indicator.

The shower pan has an integrated sump that is covered with a grill. The sump is fitted with a pipe that connects to a diaphragm pump that pumps the grey water waste overboard through a skin fitting located just above the waterline on the inboard side of the starboard hull. The galley sink is self draining to a skin fitting located just above waterline on the inboard side of the port hull.

All pumps are located at the aft bulkhead of the head area behind a removable panel. Any leak that may occur is limbered directly into the shower wet area.