Mechanical Summary
In keeping with our Star Wars theme, our team decided to make a Darth Vader Starfighter. The design of the boat needed to be strong but lightweight, leading us to the decision to make the hull of our boat out of fiberglass. Another advantage to using fiberglass is that the hull was continuous, with the only exception being the lid of the boat. The lid is a heat-formed piece of PETG plastic that velcros onto the hull, creating a watertight seal with the aide of a rubber lining around the edge of the opened hull.
Constructing the Hull
The boat was first designed in CAD using the Solidworks program. Two iterations of the boat design were prototyped until a final structure was determined. In order to provide balance and maneuverability in a fast boat, a catamaran style hull was chosen over a typical v-hull shape. From there, the look and design of a Star Wars Starfighter was adapted to the catamaran boat structure.
From there, the CAD boat was sliced into thirty-one 0.5" thick sections. Patterns were generated from these slices and used to the cut the various cross-section shapes out of 0.5" pink foam sheet using a hot wire cutter. The foam pieces were then assembled using guides and glued with super 77 adhesive spray. The shape was then smooth using various power-sanders and files.
Once the foam buck was completed, aluminum tape was place over every inch of foam. The aluminum tape not only protects the foam from dissolving in the presence of epoxy but also allows the foam to be effortlessly be removed from the cured fiberglass later on. Once covered, the layup of the fiberglass cloth began. A first layer of strips were placed, particularly on the pontoon sections of the boat. Once this was epoxied down, a full sheet of fiberglass was laid as the epoxy was laid down.
The fiberglass cured overnight while sitting on an aluminum plate. Before cutting out a section for the lid, the boat itself was used to the create the plastic lid. A piece of PETG was carefully hand formed using heat to create a seamless lid. Once the plastic cooled and separated from the fiberglass, the top was cut out and the foam was carved and melted out using acetone.
The Drive Train
Our boat followed the first rule of Zombies on the High Seas -- Cardio. If you want to escape the thralls of zombies, you must be able to move fast. To that end, we wanted our boat to be fast and went for a brushless motor. Even though it looks quite small, our brushless motor from hobbyking.com, packed quite a punch with 2700kv and runs at a continuous 20A. In order to control the three-phases of the motor, an electronic speed controller (ESC) was used. Both of these components required water cooling during operation. Fuel line was used to directly feed water into their cooling jackets in parallel. We found that if they are cooled in series, the motor can easily overheat if it is receiving water after the ESC. To connect the motor to the propeller, we used a flexi-shaft with a teflon liner inside of a brass sheath. In order to form the brass sheath to the right curvature, it was anneal, carefully formed to the correct geometry. It was then heated again and quickly quenched to lock in the curvature.
Rudder System
Originally, we opted for a dual rudder system to provide stability. However, we found that a single rudder directly behind the propeller provided for more maneuverability because it is in line with the thrust vector created of the propeller. Additionally, our group aimed to control the boat in reverse as well as forward. After some consultation, we discovered a single rudder provides for more steer-ability than a dual rudder system. The mount for the propeller was created within the same mounting mechanism to insure that the rudder and propeller are in line. The strut was intended to be adjustable to tweak the angle of the incoming flexi-shaft. Additionally, the intake line for the water cooling system was directly mounted to the rudder. As a result, water would be pushed directly into the intake hose by the propeller allowing for a continuous stream of water cooling.
Balloon Popping Mechanism
The most effective popping mechanism proved to be the simpliest mechanism. A piece of thin music wire (0.020") was actuated by a servo motor. Its direction was guided by the plastic tip of a mechanical pencil attached to a thin piece of brass tubing.
Searching for Controller Indicator
Just like any Star Wars starfighter, our HZV has an astromech droid to assist in its flight. Here we have R2D2 assisting our HZV to connect to a corresponding LUC. As the Starfighter is searching for a controller, R2D2 will randomly spin around until it has made a connection.