Engineering

  

If it seems that the attention to detail on the engineering of the vessel borders on extreme then we make no apology. All equipment is selected on the basis of performance and quality. 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 better profitability 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 in close proximity to the 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.

Engine Model
HP
Full Throttle
RPM
No
Cyl
Cylinder
Capacity
Kg
Shaft
Length
Drive
Ratio
Battery Charging
NMEA
2000
60
5000-6000
3
998 cc
122
658 mm
2.33
22
Yes
Yamaha FT60DETX
60
5000-6000
4
996 cc
116
644 mm
2.31
17
Yes
Suzuki DF70
70
5000-6000
4
1502 cc
156
637 mm
2.59
27
Yes
Suzuki DF80
80
5000-6000
4
1502 cc
156
637 mm
2.59
27
Yes
Yamaha FT80BETX
80
5000-6000
4
1595 cc
181
664 mm
2.31
17
Yes
Suzuki DF90
90
5300-6300
4
1502 cc
158
637 mm
2.59
27
Yes
Honda BF90
90
5300-6300
4
1496 cc
163
664 mm
2.33
35
No
Evinrude 90 Etec (2-stroke)
90
4500-5500
3
1295 cc
152
635 mm
2.25
25
Yes

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 easily removed if any maintenance is required. The location is close to the centre of buoyancy so that the vessel trim is least effected by fuel load. The fuel filler incorporates a neck breather to allow fast filling without blowback and an additional tank breather is installed. Each tank is fitted with an ultrasonic fuel level sensor that connects to port and starboard fuel gauges at the helm. The fuel lines have a priming bulb and primary fuel filter before feeding to each engine.

 

Steering

  
The vessel steering uses a conventional wheel attached to a hydraulic helm pump. A steering ram is fitted to each engine and a hydraulic tie bar is connected between the engines. Provision is made for the autopilot pump to be fitted in the aft bulkhead. It has a separate oil reservoir located high above in the seat back with an access port for service. 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.  

Electrical System

  

The vessel electrical system is called upon to provide all vessel power while away from the dock witout the need for a generator. Power is mainly generated by 3 solar panels (totalling 525 watts) mounted on the saloon top. The vessel engines provide additional charging while under way. Energy is stored in a house battery bank comprising four 105 amp hour AGM batteries. An additional battery is used for engine starting and serves as an emergency battery. 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.

A 2500 watt inverter converts battery power to 240 volt AC power for use by vessel appliances such as a convection microwave oven and 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 house battery bank is located under the aft section of the settee seat.

  

Bilge Pumping System

  
There are no bilges in a loose sense, the lower parts of the hulls (with the exception of aft lazarretes) are double skinned meaning that any hull fracture would limit water ingress to that cavity. There is no engine room space so there is no requirement for "engine room" bilge pumping. However for peace of mind and convenience if a pipe leak occurs somewhere, a portable electric bilge pump with a length of hose is provided. This pump can be deployed anywhere in the vessel.  

Fresh Water System

  

Two fresh water tanks of 220 litre capacity each are located under the floor of the forward cabins. Each tank has a dedicated pressure pump with individual circuit breakers used for the tank selection. 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 gas fired storage hot water system is used for the supply of pressurised hot water throughout the vessel.

  

Refrigeration

  

The galley is fitted with a pull out refrigerated drawer that is used as a galley working refrigerator. A large 180 litre front opening refrigerator is located behind the companion way bulkhead on the port side. A top load freezer/drinks fridge 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.

  

Waste Management

  

The toilet system is fitted with a class xx 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 breather uses a charcoal filter to eliminate odor. Full service is available to the holding tank by a removable panel on the aft head bulkhead. A ultrasonic level sensor transmits tank level to a gauge mounted at the electrical house panel.

The shower pan has an integrated sump that is covered with a grill. The sump is fitted with an automatic electric bilge 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.