The Effect of Deadweight

© 2001 Atkinsopht (02/15/03)

Increasing displacement weight reduces speed owing to the increase in wetted surface at the higher displacement and, further, increasing deadweight reduces speed owing to a reduction in the shell velocity excursion - which reduces the available external momentum work delivered to the footboard.

Below is a table of the pertinent data from the model ROWING for a coxed eight:

                               Case 1    Case 2    Case 2a: @ equal power
                               ------    ------    ------
Displacement weight, Ww, kg       805       885   * V2= V1 [Ww1/Ww2]^0.167
Deadweight, Wd, kg (non-sliding)  220       225     V2= V1 [Wd1/Wd2]^0.500
                                -----     -----
Shell speed, V, m/s             V1: 5.85  V2: 5.76      5.71
                                -----     -----     -----
Rating, 1/min                      30.1      30.1      29.5
Peak oarhandle pull, N            630       630       630
Shell w.l. length, m               17.85     17.91     17.91
Shell w.l. beam,m                   0.58      0.59      0.59
Reynolds' number                    8.7E7     8.6E7     8.6E7
Block coefficient, Cb               0.42      0.42      0.42
Prismatic coefficient, Cp           0.53      0.53      0.53
Hull resitance factor, N-(s/m)^2   12.74     13.28     13.28
Oarlock work, J/stroke           4344      4323      4306
Ftbd. momentum work, J/stroke     800       792       796
Shell friction work, J/stroke    5144      5115      5103
Total rower power, Watts          525       540       524
System efficiency                   0.615     0.594     0.599
* Agrees with the "Effect of Weight in Rowing", Section 7. Effect of Deadweight on Boat Speed.

The speed penalty for added weigt is slightly greater if the comparison is made at constant total rower power (Case 2a) in which case the stroke rate is necessarily relaxed slightly.


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