In this paper the process of optimizing the propulsion efficiency a series LEG carriers, from a first batch of units to the second one. In particular the second batch of units were optimized trough modifications to the hull (while keeping constant the general dimensions), the installation of a lower speed main engine and the selection of a CLT^® propeller in lieu of a conventional one. Both batch of units were tested at model scale in the same model basin, built by the same shipyard and tested at full scale according to the same criteria and with the same equipment, thereby ensuring a fair comparison and assessment of the improvements.

Model tests and sea trials will be compared (in adimensional form?) in order to compare predicted and attained improvements. The influence of the various modifications on the attained improvements will also be presented.

Finally it will be shown that standard ITTC’78 extrapolation procedures cannot be used in connection with unconventional propellers, such as CLT^® propellers.