Once the hull was off the building board and well coated with epoxy on the inside and polyurethane varnish on the outside, I did some buoyancy testing to get a sense of how stable this rather extreme hull would be. As expected, without any ballast, it floated high and turned turtle quickly. I added ballast to the bottom of the hull to increase stability and to also get a measure of how much weight it would take for the hull to float at about the proper waterline. I determined that 4 to 5 pounds would be the approximate capacity of the hull. Later, I re-tested the hull floatation with the motor, drive gears, ESC, and battery in place and used paper-wrapped rolls of 25 copper pennies as additional ballast. These rolls fit snugly between the frames and against the keel. Eight such rolls seemed about right, but I will re-adjust later in the process as needed.
The next steps included installation of propeller shafts and the drive system. Because of the weight limitations and the need to keep ballast low, I decided to power the model with a single 550 brushed motor linked through gears with about a 2:1 reduction in speed to the two propellers. Power will be from a 7.4 volt LiPo battery, again a weight saving feature.
This view shows the drive in place. The gears used at standard Dumas gears fitted into a piece of aluminum L-channel. The motor mount is made similarly. The ESC is in place, and you can see some of the paper-wrapped penny rolls used for additional ballast in place.
The prop shafts were set as low in the hull as I could manage and still clear the gears. They emerge from the hull through a long stuffing box and then pass through struts at the very back of the hull, just before the rudder. The result is a sort of Jules Verne looking rig, which seems right for the era of the vessel and is pretty consistent with the original plan. The propeller shafts are made up from 3/16 ” brass rod, and the stuffing boxes are 7/32 ” brass tubing. The boxes are also built up with telescoping 1/4″ and 9/32″ tubing where they emerge from the hull to better duplicate the original. The stuffing boxes were then epoxied to the hull with marine epoxy inside and out.
Prop shafts, struts, and stuffing boxes in place and epoxied
For props, I used plastic props of 2 inch diameter. I cut them down to 1.5 inches and also sanded the blade edges to make them less modern in appearance and more consistent with what I thought the original vessel’s propellers may have looked like. The propellers are notched and fit against pins soldered into holes in the shafts. They are then held in place with 3/16″ collars anchored with set screws.
At this point, I also installed the rudder stuffing box. I drilled through the center plywood of the keel between the additional material on each side of it and epoxied the stuffing box in place. The rudder post will be 1/8″ brass rod, so the stuffing box was made from 5/32″ tubing. The sides of the stern at this point were also built up with additional wood, wood filler, and epoxy on the sides.
After the preliminary assembly, above, I decided to further modify the propellers to more resemble what I thought the props on the original vessel might have looked like. With the heavy stuffing boxes and the large diameter prop shafts, and the struts holding the props away from the hull, the ship was taking on a Jules Verne look, so I modified the props to fit with that.
This snap shows the props modified for the Vesuvius. The original is on the left, painted bronze, and the modified props to the right. They will be also painted bronze prior to final installation.