Propeller Overload Factors for the Direct Power Method in ISO15016:2015 and ITTC 2014 Guidelines for Speed-Power Sea Trials Data Analysis

摘要

Propeller overload factors are required by the direct power method applied by the new guidelines of speed-power sea trials analysis, issued by ITTC and ISO in 2014 and 2015 respectively. The recommended approach in these procedures is to determine the overload factors by the propeller load varying (constant speed) method but this method is not always applied by model basins despite the new guidelines having been in place for several years. The procedure outlined in this paper shows how the propeller overload factors can be derived on the basis of the propeller open water characteristics. Whilst the derivation of these factors from the propeller load varying method is preferable, this proposal is intended to allow accurate corrections of ship trial data when the propeller constant loading method is used in carrying out the self-propulsion basin tests. This method is frequently preferred because it is less laborious.