CP-propeller is known to have the following disadvantages compared with FF-propeller.

1) Increased risk of root cavitation due to the restricted blade width at the root.

2) Parts with an increased number of notches are required to function under fluctuating loads in the un-uniform stern stream.

In order to solve these problems, we conducted 1) blade stress measurements with real ships, 2) static loading tests with model propellers, 3) blade bolt fatigue tests, and 4) propeller cavitation tests, and on the basis of the data obtained through these tests we worked out a new blade suspension system suited for large CPPs, which we named "semi-integrated trunnion" and, have put to practical use successfully. We have also demonstrated that with adoption of this semi-integrated trunnion the upper limit for the severity index for CPP design set by KHI on the basis of the past records can be raised substantially.

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