One of the last items on Starr's pre-departure checklist was an inclining test to determine the boat's stability. Even though Starr has successfully crossed the Atlantic Ocean once and the Pacific Ocean multiple times, Don has always wondered just how stable she really is. How far can Starr heel over before she doesn't come back up? This is something the naval architects can calculate by doing an inclining test. They move known amounts of weight across the deck, measure how the boat heels as a result, and from that data, the boat's displacement, and the shape of the water plane can calculate Starr's vertical center of gravity. They've got Starr's exterior hull shape modeled in their computer, and the computer can then calculate the vertical and horizontal center of buoyancy for any angle of heel. The computer calculates the boat's righting moment, the tendency to return to vertical, for any angle of heel. At some point the righting moment goes negative. That's the point of no return - when the boat becomes more stable upside down than right side up. You don't want to go there....
This morning we powered Starr across the canal to Pacific Fisherman Shipyard where the naval architects came aboard. We loaded thousand pound test weights onto the upper deck and constructed a ten foot long pendulum that hung off of Starr's mast to measure our angle of heel. The pendulum construction took the most time. We had to find a wooden 4x4 in the yard, put a nail in the end of it, and tie it to the mast. At the lower end of the pendulum ten feet below, the naval architects constructed a soap bath to dampen the movement of the weight hanging at the bottom...... All this was done to accurately measure the change in the boat's angle of heel as a result of moving the weights. The whole process took about four hours, and then the naval architects went back to their office to work their magic.
I was a Naval Architecture major at UC Berkeley forty plus years ago, and I participated in a few inclining experiments on vessels. We always used a water level to measure the change in heel, and it worked just fine. We'd take a long length of clear PVC tubing, fill it with water, run it across the boat, tape the ends vertically to the bulkhead on either side of the boat, measure the horizontal distance between the ends of the tube, and the change in the levels of the water in the tube as the boat's heel changed due to moving the weights. It takes five minutes to set up. Calculating the boat's change in heel angle was the same simpIe trigonometry as using a pendulum. This morning I asked one of the naval architects on Starr why we weren't measuring heel the easy way with a water level instead of doing it the hard way with a pendulum. "That's not how they taught us to do it in school," was the answer.
"Where did you go to school?" I asked.
"Alexandria, Egypt", he replied. Hmmmm.
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