 Fiat @-@ San Giorgio " was wary about using heavy oil Diesel engines and hesitated to guarantee the success of such engines of the power required . At the same time Laurenti prepared a design with geared steam turbines having a speed of 18 knots on a surface displacement of 856 tons . " His design was modified by Scotts Shipbuilding and Engineering Company , Greenock , to include guns . Swordfish kept the same main dimensions as Laurenti 's original design , but had a greater displacement and less endurance . 
