Added: May 27, 2008 2:01 pm
Most commercial and naval vessels employ metallic propellers. The most popular materials are a nickel-aluminum-bronze (NAB) alloy and stainless steel. In the small-boat industry, composite propellers are becoming increasingly popular over metallic propellers due to their light weight, relatively low cost, and maintenance advantages. Composite propellers for large vessels require significant developmental efforts in many areas, particularly in the manufacturing area. Although composite materials are used heavily in the aerospace and the wind turbine industries, the development in the marine industry has been slow primarily due to technical difficulties associated with the in-water operating environment and smaller market size.
The Office of Naval Research (ONR) is initiating the development of marine composite propeller technology for applications to large ships and submerged vehicles. The objective of the program is to develop and demonstrate composite marine propeller technology that can achieve benefits such as reduced weight, reduced life-cycle cost and reduced maintenance needs, as well as some perceived benefits for naval applications. Under this BAA, ONR is soliciting proposals for the development of composite marine propeller technology in a building-block approach, starting from small-scale and progressively increasing size to large- and full-scale prototypes.
Traditional propellers are rigid. Though the rigid propellers may deflect under load, the pitch of the propeller does not change when the blade is loaded. One advantage of composite materials is the ability to tailor the structure for improved performance. A composite propeller with blades structurally tailored in such a way that the blade tip is passively deformed through bend/twist coupling in response to the onset flow is expected to provide improved efficiency and other performance. This kind of propeller is called a pitch-adapting propeller.
The objective of this program is to develop, demonstrate and transition composite propeller technology for applications to naval ships and submerged vehicles. Two types of composite propellers will be developed under this program: rigid and pitch-adapting.
The program will consist of three phases. The first phase will have up to three vendors. The purpose of the first phase is to evaluate the vendor's structural design and manufacturing capabilities. The second phase will have up to two vendors and use a building block approach to develop the structural design and manufacturing capabilities for the unique geometries involved in propeller manufacture. The third phase will have up to two vendors and focus on structural design and manufacture of propellers at large scale.
All phases will have Classified and Unclassified structural design components. The manufacturing process in the first phase will be Unclassified. The manufacturing process in the subsequent phases will be Classified.
