This is the ballast system to control the buoyancy of the boat. It has a ballast tank with two large holes in the bottom to allow water to freely flow in and out. The vent valve,which you can see mounted on the left of the tank allows the air to escape on command and water flows into the tank thus changing the displacement of the boat. DOWN SHE GOES!. To come back to the surface,you close the vent valve and operate the blow valve which you can see mounted on top of the battery on the far left hand side.Liquid Air, stored in the pressure vessel is then pumped into the ballast tank, forcing the water back out through the holes in the bottom. UP SHE COMES! We hope.
The pressure vessel sits in a pvc tube mounted in the middle of the ballast tank.
The blow and vent valves are operated mechanically from one servo in a push pull set up using bowden cables from a mountain bike.