Static Stress Measurements on a Series of Skewed Propeller Blades with an without Forward Rake.
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD SHIP PERFORMANCE DEPT
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Static strains were measured in a systematic series of five marine propeller blades. The propeller blades have projected skew angle at the blade tip equal to zero, 36 degrees and 72 degrees without rake, and 36 and 72 degrees with sufficient forward rake to place the locus of the section midchord in the propeller plane. This combination of skew and rake is called warp. The primary experiments were conducted with the blades under uniform loading applied with air pressure using specially constructed chambers. Limited supplemental experiments were conducted using concentrated loads. The experimental results under uniform loading were correlated with modified beam theory. Both the experimental results and the modified beam theory indicate that for all the skewed and warped propeller blades evaluated, the largest value of the maximum principal stress is no greater than 1.20 times the maximum prinicipal stress on the unskewed propeller.
- Marine Engineering