Boat Performance and Propulsion Analysis

CJR can carry out a performance assessment to determine whether a boat's propulsion system is operating efficiently.

As a first step we would perform a resistance prediction for the hull.  This is based on regression line theory developed by Southampton University on the basis of hundreds of tested hulls and gives accurate preliminary estimation of hull resistance. Our more sophisticated resistance estimation tool uses Computational Fluid Dynamic software that can predict flow around the hull, the hull pressure field as well as running trim angle with great accuracy. It can be further used to find the most optimum LCG position and running trim angle for the boat.

Having calculated the resistance, the theoretical top speed is estimated based on engine power.

The next step is to confirm the gear ratio used in the vessel. Engine power and gear ratio rule all shaftline components scantlings including propellers, shafts, P-brackets and all associated parts. Gear ratio is a factor that has a huge influence on overall propeller performance and should be carefully selected at the design stage.

The optimum propeller design for the given gear ratio is also calculated.  CJR uses purpose developed software based on number of different propeller series for quick selection of diameter, pitch and number of blades. More sophisticated Lifting Line and Lifting Surface software is utilised for detailed blade parameters selection including checking blade area requirement due to cavitation.  

  • Bearings

    Suitable bearings are required in stern tube and rudder tube assemblies.

  • CJR Propellers

    Every boat is different and the first sign of this difference can be seen in propeller operation.

  • Couplings

    Couplings are the elements that transfer torque from gearbox to the shaft and because of their role they are under strict supervision of class societies.

  • Ducted Propellers / Nozzles

    CJR can offer ducted propellers systems including any type nozzles and impellers under full IACS approval.

  • Rudder Tubes Assemblies

    CJR manufactures rudder tube assemblies designed for hull trough installation to suit stock diameter from 30mm up to 180mm.

  • Rudders

    Rudder profile and sections are carefully selected to specific regime of the flow around sterngear.

  • Shaft Brackets

    Our shaft brackets are designed bespoke to achieve optimum performance in line with every vessel individual requirements.

  • Shaft Seals

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  • Shafts

    Shaft design starts from designing entire shaftline incorporating all the components from the propeller to the gearbox and including the bearings to make the system safe, vibration free and efficient in operation.

  • Stern Tubes / Shaft Logs Assemblies

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  • Tie Bars

    Tie bars connect both rudder tillers on twin rudder boats to simply synchronise them together.

  • Tillers

    Tiller is important part of steering gear which design is covered by strict rules of classification societies when the boat is built under class.

  • Shaft Alignment

    Using laser technology and precision engineering a bespoke shaft alignment tool has been developed to aid the boat builder’s task of accurately fitting and aligning the stern gear.

  • PropSmith

    For the fast, simple and precise installation and removal of propellers, PropSmith is the professionals’ choice.

  • TrialDAS

    TrialDAS is a new data acquisition system specifically tailored for monitoring sea trials. The system is based on rate gyros, GPS, accelerometers and magnetic field sensors to record every movement of the boat.

  • Keyless Hub Hydraulic Kit

    Quick and convenient method of pushing and releasing large propellers or couplings to and from the keyless shaft cone.

  • Hydraulic Propeller / Coupling Pusher / Puller

    Quick and convenient method of pushing and pulling propellers or couplings to and from keyed shaft end.

  • TrialsAPP

  • Quality Policy

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  • Design

    We don’t only make propellers, we analyse entire propulsion system of each boat starting from hull resistance prediction and hull propulsive factors.

  • Pattern Making

    Precise pattern assures high accuracy of final product and it is one of the most important stages in manufacturing process

  • Casting

    CJR's foundry team has the combined benefits of over 150 years experience in the industry.

  • Machining

    CAD/CAM controlled machining of the cast propellers, P brackets and rudders are undertaken to the fine tolerances of their original design

  • Finishing

    Our processes ensure that the geometry of our finished castings is always true and accurate to the original design.

GET IN TOUCH

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CJR Propulsion Ltd
70-72 Quayside Road
Bitterne Manor
Southampton
SO18 1AD
United Kingdom

Tel: +44 (0)23 8022 2032
Fax: +44 (0)23 8021 1832

info@cjrprop.com