Energy cost and efficiency of Venetian rowing on a traditional, flat hull boat (Bissa).

The total net metabolic power output (E, kW) required to scull a traditional, flat hull boat--the "Bissa", 9.02 m long and weighting about 500 kg including the crew-was assessed at different constant speeds (nu) ranging from 2.44 to 3.75 m s(-1). E increased with the speed: E = 0.417 x e (0.664v ); r (2) = 0.931. The amount of metabolic energy spent per unit distance (C, J m(-1)) to move the "Bissa", calculated by dividing E by the corresponding nu, was a linear function of nu: C = 0.369 nu -0.063; r (2) = 0.821. The hydrodynamic resistance met by the boat in the water--drag (D, N)--was estimated by analysing the decay of the reciprocal of nu as a function of time measured during several spontaneous deceleration tests carried out in still water and by knowing the total mass of the watercraft plus crew. D increased as a square function of speed: D = 12.76 v (2). This allowed us to calculate the drag efficiency (g(d)), as the ratio of D to C: g(d) increased from 8.9 to 13.7% in the range of the speeds tested. The "Bissa" turned out to be as economical as other flat hull, traditional watercrafts, such as the bigger Venetian gondola, and her g(d) was similar to that of other modern and traditional watercrafts.