Don.
Page 78. Running one diesel at full ahead on one shaft using the generator to power the other shaft by E motor at half the propeller rpm as of the "diesel shaft" was a very seldom configuration. You would get an unequal load on the propellers requiring a constant correction by the rudders, resulting in a increased hull resistance. Depending on circumstances as when you had to be at your destination and your battery charge, you choose the configuration. I guess normally I would have run both diesels at 3/4 load if no charging was required. If charging was required, as was very often the case, I would put on the battery charging on both diesels, and adjusting the load and rpm at the lowest specific fuelconsumption of the diesels. But we did not often made to much theoretical speculation around the matter, it is so many variables like hullresistance which varies with the maintenance, optimal variable specific fuelconsumption of the diesels, weather, sea etc. A long story on these matters in an explanation of the daytank would possibly be confusing for the reader and take the focus from the daytank.
There is one fringe benefit with the water compensating system which we have not touched upon, the hot water sanitary system. From the headertank you have a fourth connection (drain)supplying warm seawater to the galley and the lavatories, see the image below, which I guess is self explanatory. Although the water consumption is fractional it is nevertheless worth while to mention.
Tore
