u00d7 lb l 0 75 np u00d7 d l 0 913 with this model tests were carried out whose results are depicted in the graphs of fig5 to 7 in the graph of fig5 the net efficiency of a traditional propeller dashed line intended to operate in full immersion is compared to the propeller used in the tests solid line according to operative speeds expressed in knots 1 knot 0 514 m s as it is apparent the performances of a traditional propeller are in principle superior to those attainable with a semi submerged propeller in this case the traditional propeller has been selected on the basis of the propeller that would have been adequate for the same model using as reference the same traditional propeller used to plot the graph of fig5 a simulation was carried out to obtain which powers would have been required to drive the craft model at a given speed as it is apparent from the graph of fig6 the semi submerged propeller offers more advantageous performances for speeds higher than 15 knot lower power required to obtain a certain speed but this plotting takes into account the raw values of the power influenced by the complex supports that are for supporting the pair of semi submerged propellers a more realistic simulation is attained when plotting anew the preceding graph eliminating the contribution of said supports as the use of this propulsion system would imply a novel stern design without.