Since the introduction of the resistance calculation for yachts based on the results of the original Delft Systematic Yacht Hull Series (DSYHS), as presented by Gerritsma in 1979, 1985 and 1992, considerable changes have taken place in the design of both the shape and size of the appendages, i.e. keel and rudder. For the sake of consistency the original DSYHS was tested with one and the same set of appendages for all models, necessary for the heeled and yawed tests, which in design reflected the standards of the mid seventies for a hull like the Parent Model #1.

The wide variety of shapes of appendages used now-a-days made it necessary to be able to differentiate in the calculation routine between all these different configurations. Therefore the Shiphydromechanics Laboratory of the Technical University Delft decided to test a large number of the models of the DSYHS again, but now without appendages.

The implicit difficulty by doing this was that the resistance of the keel and rudder had to be added on. Although a large part of the appendage resistance originates from the viscous resistance, the residuary resistance of the appendages was not well known, neither the absolute magnitude nor the dependency on hull and keel geometry.

This study tries to shed some light on the subject by reporting on a number of model experiments and calculations carried out to define the resistance of four different appendages under two different hulls.

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