Page 28: of Marine News Magazine (February 2015)

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CAD/CAM DESIGN

Propellers:

One Size and Shape Does Not Fit All

Hydrocomp’s newest release of PropCad incorporates 3 years of enhancements.Hydrocomp’s newest release of PropCad incorporates 3 years of enhancements.

By Adam KaplanBy Adam Kaplan ropellers are surprisingly complex devices, especial- the industry to move away from the traditional designs of ly considering most are a solid piece of metal with the 1960’s, when known performance was prerequisite for

Pno moving parts. The variation in vessels and op- investing in a pattern. Of course, one of the major changes erational requirements leads to wildly different designs, to the propeller industry has been the growth of CNC ma- from noise-sensitive propellers for luxury cruiseliners to chining which allows greater precision for producing pat- wide-blade sets for tugs. With different combinations of terns and ? nished propellers.

diameters, pitches, blade styles, and blade counts, there is The propeller industry accommodates demands for no limit to the design alternatives available. Creating these both traditional and contemporary designs. Existing in- different designs can be an extremely time-consuming and stallations of legacy propellers must be supported because specialized process. often the lifespan of the vessel is greater than that of the

Traditionally, propellers have been designed largely by propeller. As a result, the original manufacturer is usually hand, with manufacturers creating wooden foundry pat- expected to have the same propeller available in the future. terns of blades. These patterns are used to create sand-cast Clients also desire an expansion of product lines and avail- molds for manufacturing the propellers. While the pattern able variants, especially for popular models. This has led to can be used to produce propellers with different numbers a common problem for propeller manufacturers and de- of blades, new patterns must be created for geometrically signers: creating a design variant from an existing pattern similar variations. A given design is usually available in a with no formal design documentation. Quickly creating number of diameters and pitches, which means that the design and size variants, whether from scratch or from an manufacturer has several patterns. It is not unusual for existing design, is one of the tasks HydroComp PropCad these patterns to be a mixture of body ? ller and wood as has solved for the industry. they are modi? ed or improved over the years. Some of these patterns were created decades ago and are still in use today. Introduction to PropCad

HydroComp PropCad software geometrically mod-

New Considerations els marine propellers for design and manufacture with

A number of developments in the marine industry are automatic preparation of CAD/CAM data, 2D design changing propeller design. One development is the increase drawings, 3D offsets, and thickness classi? cation reports. in power densities of marine engines. Modern engines have Manufacturers, researchers and designers in over 40 coun- more horsepower packed into a lighter engine of the same tries use the software to quickly generate propeller designs. size. As a result, these vessels require stronger propellers with And, the newest version of this design tool includes three more blade area to accommodate the increased power and years of enhancements which both update and expand speed. Another contribution is cost of fuel and the desire PropCad’s propeller design capabilities. for ef? cient propeller designs. As fuel costs increase, there is At the heart of PropCad is a library of traditional propel- more incentive to optimize the performance of the propel- ler designs – allowing users to rapidly develop geometries. ler. The availability of analytical tools including model test- The library has over 10 different propeller series, includ- ing, ? ow measurements, and CFD simulation are allowing ing B-series, Gawn, Kaplan, and cleaver style propellers.

February 2015

MN 28