Through hulls - intentional holes in the boat

Not all holes in a boat are bad. Cruising yachts need to intake and discharge water in various forms to run their engine and interior subsystems. Arabella ended up with 9 through hulls in all, 1 for the depth/velocity transducer, 2 to intake sea water below the waterline, 2 to drain seawater from the cockpit, and 4 to discharge wastewater and exhaust gas. At each of these points I fabricated white oak backing blocks to reinforce the planking around the hole. Satchell and I match drilled the blocks and planks, bonded them together, and installed copper rivets to secure the connection. The ductile copper yields as the oak planks swell, preventing failure of the fasteners or crushing of the wood.

Inside the boat, each through hull has either a check valve or a vented loop to prevent water from being siphoned backwards into the bilge. Because a sailboat can heel over to the point of dipping either rail, there’s no section of hull guaranteed to be above water at all times. Therefore, anti-siphon features are critical to preventing flooding. Per ABYC code, I fitted all through hulls near or below the waterline with a seacock valve, used to shut off flow in an emergency.

Watermaker - desalination system

Arabella uses a reverse osmosis watermaker to produce drinkable water from seawater. It’s by far the most complicated fluid system outside of the engine with a variety of pumps and filters supporting the core reverse osmosis membrane. Through careful planning and a little bit of luck, I was able to package all the components in a tight area of the head that would otherwise be of minimal value. The watermaker is now being used every day to produce drinkable water for people sailing onboard.

Engine cooling - water heating

Internal combustion engines in boats get to use the water around them for cooling. This offers 2 distinct advantages. First, the denser medium allows you to use a much smaller heat exchanger than you would need with air cooling. Second, raw water coming out of that coolant heat exchanger can be further put to use to cool exhaust before it exits the boat. I installed the series of strainers, through hulls, valves and lines that make up the raw water cooling system, and modified the engine side coolant loop to extract heat for shower water in a separate heat exchanger.

Sealing the water tanks

The stainless water tanks were already installed in the boat by the time I arrived, but hadn’t been filled yet. I was suspicious of the combination of a thin flange and stiff gasket used to seal the inspection ports, and my doubts were quickly proven correct when I filled the tanks with water. Fortunately, switching to a softer closed cell foam gasket solved the leakage without having to take more drastic measures. Even though the inspection ports are nominally above the water levels within the tanks, the flanges will see water when the boat is heeled over hard to one side or the other.