Fixed Pitch Propeller Specifications
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Fixed Pitch Propeller Specifications All Clements' high performance propellers are manufactured from high integrity castings and a full range of designs are available with a three, four or five blade configuration suitable for all types of semi and deep V planing hulls. Sizes range up to i .2 metres in diameler. in accordance with ISO standard 484/2 and. if required, to meel the demands of classification society inspection. Our unique Hyperform blade propellers are acknowledged as having the ability to provide optimum speed and acceleration under vibration-free operation for all hull designs lifting the hull up on to the plane in the shortest possible time. The careful analysis and design of propellers for an individual hull is essential, requiring close liaison between Clements Marine and the customer. This Is particularly important, for example, for a new boat which is designed for series production with several engine options and alternative gearbox reduction raiios. Only by strict attention to detail can the customer expect maximum efficiency in terms of ultimate speed and smoothness from ihe propeller design. All propellers are cast from pure ingot using specialised mould design, and certification can be supplied on request detailing full mechanical characteristics and chemical composition. Castings are normally made from EN1982.CB333G 'AB2' nickel aluminium bronze, but EN1982CB765S 'HTB1' high tensile brass is often used for certain commercial and leisure applications. All propellers are precision balanced to ensure maximum smoothness and can be finished lo ISO Classification. Our range of three, four and five bladed high performance propellers are based upon blade area ratios designed to suit individual hull application The Company also manufactures ranges of standard propellers lor displacement leisure and commercial craft, and we design custom propellers for 'special service' commercial vessels. Propeller Repair Facilities. The Company maintains full propeller repair lac i litios, using TIG and MIG welding and highly accurate repitching methods and standard practices. Recognising that a quick turnaround is vital for our clients, we can normally respond within a 24 or 36 hour timescale. Pitch checking ensures that the vessels' speed requirements are maintained. If alterations have been made to engine output or gearbox reduction ratios, the required pitch alterations can be made following the repair process. Repaired propellers are then carefully balanced and finally inspected before despatch to ensure vibration free operation. Design and Quality Control Our design department will always help with difficult propeller applications, particularly with the choice of optimum gearbox reduction ratio(s) and the most efficient propeller design, so that the hull achieves its optimum performance potential. Design Criteria When designing a propeller, its performance is not totally dictated by its own geometry, but is also dependant upon hydrodynamic considerations which must be taken into account to produce the most elficient shape Propeller Blade Designs can therefore be divided into three categories: subcavitating, For fully planing and semi-displacement hull lorms with speeds up to around 35 knols, subcavilating propellers are normally used. This conventional blade form has an aerofoil section (Ogival) using a flat blade face and curved back face.(continued pto|

Fixed Pitch Propeller Specifications Trans-cavitati ng propellers produce thrust with the blade tace whilst the back remains in total cavitation This type of propeller also offers good propulsion efficiency at intermediate speeds. For ultra high performance boat installations, supercavitating propellers should be titled. The latest developments in supercavitating propeller technology have resulted in these designs being available for certain high performance applications where physical restriction and PRM are constricting factors. Propeller Installation Considerations Please use TD Sheet 12...