Marine composite propellers are ship propellers, usually made from fiber composites like

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...

carbon fibers Carbon fibers or carbon fibres (alternatively CF, graphite fiber or graphite fibre) are fibers about in diameter and composed mostly of carbon atoms. Carbon fibers have several advantages: high stiffness, high tensile strength, high stren ...

infused with a high-strength resin like

epoxy Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...

polyimide Polyimide (sometimes abbreviated PI) is a polymer containing imide groups belonging to the class of high-performance plastics. With their high heat-resistance, polyimides enjoy diverse applications in roles demanding rugged organic materials, e.g ...

. These kinds of composites are made from strong, light, and

high-tech High technology (high tech), also known as advanced technology (advanced tech) or exotechnology, is technology that is at the cutting edge: the highest form of technology available. It can be defined as either the most complex or the newest te ...

materials. Such composite propellers can be produced in several ways, including vacuum infused molding and

injection molding Injection moulding (U.S. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals (for ...

processes, depending on size and resin viscosity.

Advantages

The composite propellers can be made with Lay-Up process which causes anisotropic properties. This can be designed to create a passive adaptation of the propeller blades passive self-twisting propeller. Self-twisting blades are much more energy-efficient compared to rigid propeller blades. Passive adaptation in form might also be affected by propeller geometry. Lower unit production cost and production without heat are the main advantages of composite material. While the initial cost of a composite propeller is usually comparable to

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

, it is significantly less than a

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

propeller. Additionally, replaceable blades offer significant savings compared to repairing metal propellers. Another advantage to using composite propellers is that it is a lightweight material. The composite material is about half the weight of aluminum and 1/6 the weight of stainless steel propeller. A lightweight propeller reduces the amount of wear and tear on the entire boat.

Effect on the environment

Composite materials are an environmentally friendly option as the corrosive resistance and resistance to impact damage of composites can lead to a long lifetime in composite propellers. When a composite propeller hits debris, the propeller absorbs the impact energy instead of transferring it to the lower unit; therefore, providing more protection for the drive train.

Corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

from

saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

and

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

are basically nonexistent with composite material in water. Still, the water saturation of the propellers and the propeller application cause some problems to the longevity of composite propellers. The corrosive resistant properties of composites cannot be said to be undeniably better than traditional metal alloys in the propeller application with today's technology.Study on Composite Material Marine Propellers (Toshio Yamatogi, Hideaki Murayama, Kiyoshi Uzawa, Takahiro Mishima, Yasuaki Ishihara)
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References

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External links

Living in a Material World
at ''piranhapropellers.com'' Propellers