METHODS

To estimate the total resistance of the shells in this study, we use Michell's (1898) integral for the wave resistance, the standard 1957 ITTC line for the skin friction, and a simple empirical formula for the form drag, Scragg and Nelson (1993). See Tuck and Lazauskas (1996) for further details.

In the following figure, we compare our computer predictions of the total resistance of the Donaratico eight with Wellicome's (1967) experimental results. The agreement seems very good but it is difficult to see exactly where and by how much they differ.

In the following figure we show the same results, but plotted as Ct vs the volumetric Froude number, Fnv. Here,

Ct = Rt/(1/2 rho U2D2/3)

where Rt is the total resistance, U is the boat speed, and D is the displaced volume. The volumetric Froude number is:
Fnv=Ug-1/2D-1/6

The differences between the predicted and experimental results are now more apparent. The figure shows that the predictions are in excellent agreement with experiment at the higher speeds, say for Fnv from about 1.5 to 2.0. For this hull, this range of Fnv corresponds to a speed range of approximately 4.5 ms-1 to 6.5 ms-1. In their study, Brearley and de Mestre (1996) showed that for rowing eights, the boat speed during the rowing stroke cycle varies from about 4.6 ms-1 to 7.0ms-1. Thus our predictions seem to be most accurate for normal racing speeds.