Getting a bit off topic now but ...
Wot I don't unnerstand is.. surely the surface level of the water in the ballast tanks lay at the same level as the surrounding water? And therefore has no weight?
The ballast therefore only comes into play when the boat is heeled and the ballast (water) is lifted clear of the surrounding water, it's weight then comes into play and it tries to maintain equilibrium and keep the boat upright.
A container of water submersed in a tub will only weigh the weight of the container - only when you lift it out will you feel the weight of the water plus the container?
Get rid of the water (ballast) and we are left with just the weight of the container (boat) which, of course, is what makes our boats such perfect trailer sailers.
My thinking is therefore - and my own experience seems to support this - that the boat sails (or motors, or rows) as well, if not better, with the ballast tanks full. Of course there is the effort required to get the weight of the water ballast moving in the first place - but if there is no weight, then the effort to move it must be minimal? Unlike conventionally ballasted boats, where the ballast is heavier (denser?) than the surrounding water and takes a lot more effort to get it moving?
Now I am confusing even myself! There must be better minds out there than me who can explain the physics behind water ballast?
I recall sailing with Jonathan on Caledonia last year in my old BR20 with empty tanks, the (notorious) short steep chop on Loch Ness was hitting us on the bow just as we were tacking, the weight of the waves kept knocking us back into stays - I am convinced this would not have happened if we had the weight (but not weight!?) of water ballast to give momentum to carry us through the tack. Indeed, in the recent discussion about raising the main underway, single handed, I always would maintain having the tanks full to give the boat momentum to carry the bow through waves intent on knocking it off your hoped for course.
Maybe worth a library article if someone can explain in words of one syllable the physics behind water ballast!
Andy
Baycruiser23 No.25 'Equinox'