Just wonder: your water tanks, which can be filled with sea water - do they significantly contribute to stability and/or heel or are they too small to make a real difference - water ballast tanks on dedicated racers are usually much larger and further on the sides of a boat (with large pumps to move watter left or right). Of course you could not sacrifice the living spaces for that - so do you use them as ballast tanks ?
Tomaz, the tanks are on the bottom of the boat, and transfer between them is done with 2 pumps and 2 valves. It takes aproximately 1 minute to transfer.
What you do is fill the tank half level, (that's the weight we calculated to help reduce heel), then transfer from port to stbd as needed. I wish we could have higher tanks, but.....you're right..the space. Still since the beam is so wide the bottom tanks do a pretty good job. Note that the boat was built to be sailed hard without ballast, the ballast helps in certain conditions. The day we made the 15 knots on that video I had the balast on...and it helped. Last week returning home they were also ballasted.
At the stern, I have a hole, that dumps all the water out of the tanks with another pump. It empties the whole boat in 4 minutes.
I am talking with the builder to be able to not only transfer form port to Stbd, but also forward and aft. Which will help downwind if the water goes aft, and forward for beating.