Custom propellers are designed for specific vessel and engine combinations, allowing the vessels to achieve their optimum performance. Both the lifting line theory and the lifting surface theory are used to design propellers with higher performance requirements.

For vessels with maximum speeds over 25 knots, the custom propeller design provides sigificant benefits in many areas such as efficiency, vibration/noise, and cavitation erosion. Custom propellers are designed first by using the propeller lifting line theory to optimize performance in accordance with customer's requirements; including the vessel speed, horsepower, effectinv horsepower curve, propeller diameter,

> This lifting ;ine theory is used to develop the optimum expanded area ratio and chord length distribution to meet the cavtation requirements, Fingally, a lifting surface theory is used to obtain camber and pitch distrbution. Skew and blade thickness are also optimized in the design for maximum performance.