Method: A boat was rowed over a course in Portsmouth Harbour, starting at Hardway and rounding a massive buoy that usually has a dead frigate attached to it. The first run was with no ballast, then with two bags of sand, then with four bags. Speed and course were recorded on a Nokia E71 mobile phone using Sports Tracker software.
Results:
First Lap (No ballast): Distance 0.71km, Ave speed 6.98km/h, Top speed 10.9km/h
Second Lap (Two bags of sand): Distance 0.72km, Ave speed 6.60km/hr, Top speed 11.5km/hr
Third Lap (Four bags of sand): No results due to operator error (I think I pressed the wrong button. Sorry, Sir, honest it won't happen again).
All the tracks can be seen here.
Impressions: The ballast definitely held me back when getting going, and seemed to be harder work. Also, turning seemed to be more difficult. But the extra weight really did seem to carry the boat forward during the return.
Conclusion: Adding ballast clearly slowed the boat up, but not by much. The boat sat significantly lower in the water, which was slightly alarming. All in all, the conclusion is that the extra momentum of the ballast is more than compensated for by the extra work propelling it, but more research is necessary (SRI grant please!).
After the science stuff, Martin Corrick took me round Portsmouth Harbour in his spiffy Topper Cruz:
