MECHANICAL ENGINEERING
BASICS
Mechanical engineering has followed a traditional route to maintain simplicity. Hydraulic systems were considered but additional cost, slightly lower efficiency and complexity overruled their use.
PROPULSION
The engine is a Daewoo L136 8ltr 6 cylinder marine diesel. It is naturally aspirated and rated for heavy duty operation producing 160Hp at 2200rpm. In industrial service it has proved to be an extremely efficient and reliable engine. Many fishing vessels have replaced ageing Gardners with this engine or a turbo derivative. The UK importer makes very little money from the sale of spares other than routine servicing items. L136 Engine leaflet and power/torque curves.
The gearbox is a TK250 and has a ratio of 2.5:1. This ratio was chosen as a compromise between having a large propeller to maximise efficiency, the prop aperture available within reasonable draft constraints and the effect of increased propwalk with a larger prop.
The shaftline consists of a short 2 inch diameter tail shaft which has an outer cutlass bearing and an inner Deep Sea Seal. The tail shaft terminates at a Centaflex thrust bearing and flexible coupling. There is a second flexible coupling an the gearbox and between the two is a Centaflex AGM hollow tube shaft which does not require an intermediate support bearing. The engine is mounted on R&D flexible mountings. The Centaflex system was considerably cheaper than an equivalent Aquadrive system.
STEERING
Steering is by a hydraulic system with bypass valve enabling use of an emergency manual tiller..
BOWTHRUSTER
A Silette Sonic leg has been fitted into a 300mm diameter tube. This has a 3 blade kaplan BT prop. Power system still under consideration, but a 48v DC motor developing 14kW is looking attractive.
SPUD LEG
The spud leg is a 2.8m 200mm diameter tube which is handraulically lowered and raised using a trailer winch. It is fitted with a mechanical interlock.
ANCHOR WINCHES
Strikwerda anchor winches are fitted are fitted at bow and stern. Bow anchor is an 85kg fabricated klip anchor and fitted with 50m 13mm chain, stern anchor is also an 85kg klip anchor but fitted with 50m 10mm chain. Both winches have drum ends and are handraulic, although sprocket wheels were fitted to allow conversion to a motorised system.
