The propeller of a moderately large pleasure boat has been cast from a nickel-aluminum-bronze alloy that contains 82% Cu, 9% Al, 4% Ni, 4% Fe, and 1% Mn. It is approximately 13 inches in diameter with three 10-pitch blades, and has been designed for both fresh- and saltwater usage.
1. One of the blades has struck a rock and is badly bent. A replacement propeller is quite expensive and cannot be obtained for several weeks. An attractive alternative, therefore, may be to repair the existing piece. Would you recommend such a repair and how would you proceed? Can it simply be hammered back into shape? Would you recommend any additional processing, either before or after the repair? What is the rationale for your recommendations?
2. A second propeller, identical to the one above, has also been damaged by an impact. This time, however, the damage is in the form of a crack at the base of one of the blades, as shown in Figure CS-17. Since the crack does not penetrate into the hub, it is proposed that a repair be made using some form of welding or brazing process. Would you recommend such a repair? If so, how would you suggest the repair be made? Explain the rationale for your recommendations and outline the procedure that should be followed. Would there be any sacrifice in quality or performance with the repaired propeller?

Transcribed Image Text:

Crack FIGURE CS-17