Page 524 - Practical Design Ships and Floating Structures

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Figure 9: CW vs. F, for different stem wedge angles (a)

6 CONCLUSIONS
One important conclusion is that the numerical procedure is extremely powerful for the preliminary
choice of the hull form. The possibility to choose the optimum stem wedge angle and the position of
the bilge keel are useful design tools. For the absolute estimation of the ship's resistance it is necessary
to make use of experimental results however, the use of the correction factor, of the same magnitude
for both vessels, permits a first estimation. The experimental procedure compare favorable with
previous results and it is hoped that future test will include a broader speed range.

Acknowledgements

The authors would like to thank Mr. A. A. B. Lleyda for the help in the computations, Mr. L. F. P. de
Castro of the Navy Engineering Department for the interest on the research. We are also grateful for
the support given by the Research Foundation of S5o Paul0 for the construction of the models. Finally,
the numerical computations were based on the results given by the software SHIPFLOW of
FLOWTECH, without it the comparison with the experimental results would not be possible.

References
Couser, P. R., Molland, A. F., Armstrong, N. A. and Utama, I. K. A. (1997). Calm Water Powering
Predictions for High Speed Catamarans, Proceedings of the Fourth International Conference on Fast
Sea Transportation -FAST'97, Baird Publications, 765 -772.
Karafiath, G. and Fisher, S. C. (1987). The Effect of Stem Wedges on Ship Powering Performance,
Naval Engineers Journal ,27-37.
Tanaka, H. ; Nakatake, K. ; Araki, S. ; Nakato, M. and Ueda, T. (1990). Cooperative Resistance Tests
with Geosim Models of a High-speed Semi-Displacement Craft. Journal of the Society of Naval
Architects of Japan Vol. 169, 55-64.
Sahoo, P. K. ,Doctors, L. J. and Renilson, M. R. (1999). Theoretical and Expenmental Investigation of
Resistance of High-speed Round-Bilge Hull Forms., Proceedings of the Fifth International
Conference on Fast Sea Transportation -FAST'99,803-8 14.