3D-printed RC Fanboat

Students

Screen Shot 2019-05-03 at 8.55.54 PM - James Palmer

Ralph Elsegood
Economics, 2019

GLLBRQAURFFGNUL.20160329182605 - James Palmer

Andrew Morgan
History, 2019

Screen Shot 2019-05-03 at 8.57.10 PM - James Palmer

Jim Palmer
Psychology, 2019

Project Description

For our project, we are creating a 3D-printed, radio-controlled fan boat. The project is inspired by our individual loves for boating, design, and engineering projects. We have all taken EPICS before, but this is by far the most ambitious project that any of us have participated in.
The hull itself is 3D printed using biodegradable PLA filament. The original design was downloaded from thingiverse.com, a popular website for sharing 3D print plans. After testing some early prototypes, alterations were made to the design in AutoCAD in order to make the hull more seaworthy (e.g. capable of supporting the weight of the electronics to be held within), the design was scaled, printed in two parts, and joined. The completed design features a sleek, attractive, and waterproofed two-tone hull and 70mm ducted fan with a 3800kv outrunner motor connected to a 5000MAH battery and controlled by 100a ESC, a waterproof servo, and a radio transmitter/receiver.
The purpose of the project is two-fold. Firstly, it is teaching us about electronics, design, 3D printing, and fabrication. Secondly, it is satisfying our individual curiosities and desires to learn and create in a team environment.

Technical Background

Developing a powerful radio-controlled fan boat required careful thought on the design of the hull, the weight distribution of the parts, and the inherent tradeoff between agility and stability.
To begin with, a simple force diagram was considered to understand the straight-line movement of the boat. On the horizontal plane, the induction fan produces forward propulsion, with air and water resistance acting as opposing forces. In the vertical plane, at low speeds, the force from upward buoyancy counteracts the downward force of gravity. As the boat speed picks up, upward thrust is generated from the water passing the hull, in a similar fashion to the thrust on airplane wing (Kandasamy et al., 2011). This was an important factor to account for when designing the model; if too much weight was distributed to the stern of the boat then at high speeds upward thrust in conjunction with the gravitational torque on the boat could lead to the nose of the boat rising too much. In a worst-case scenario, this could cause the boat to flip backward. On the other hand, distributing too much weight to the bow of the boat would make it difficult for the boat to reach high speeds in the first place, particularly if the body of water were to be less calm and the nose of the boat were to begin to dig into the water.
The second biggest concern from a boat design perspective was the stability of the boat, particularly at high speeds. Using a single hull design would allow for much greater turning capability but could be much less stable at high speeds since the rounded shape of this type of hull would not produce the up thrust necessary to plane over the water’s surface. For this reason, a flat bottom hull design was used with a catamaran style bow to optimize the boat’s planning ability (flat bottom) while maintaining straight-line stability (dual hulls in the bow which are stabilized by the passing water) (Gabrielson, 2010).

Gabrielson, Curt. Kinetic Contraptions: Build a Hovercraft, Airboat, and More with a Hobby Motor. Chicago Review Press, 2010.

Kandasamy, Manivannan, et al. “Optimization of waterjet propelled high-speed ships—JHSS and Delft Catamaran.” 11th international conference on fast sea transportation, FAST. 2011.

Design Drawings

Fabrication Process

For us, the fabrication journey began by sourcing our original design from thingiverse.com. After printing off an early prototype and conducting a simple buoyancy test, however, it became clear that we would have to make some modifications to this design to bring it to the standard we desired. In CAD, we scaled the design to a larger size and built up the gunwales so as to make her more seaworthy. We then printed the hull in two parts, glued them together, and sprayed the boat with sealant.
At this point, we began thinking about the functional aspects of the boat. After much research, we ordered all the parts we needed online, including a battery, a ducted fan, a motor, a servo, an ECF, and a transmitter/receiver. Once the parts arrived, we spent some time figuring out the electronics and making sure everything worked before moving on to assembly. Of all the phases of the process, this was the one which required us to think the most creatively. We had to design solutions to a number of problems including mounting the various electronics to the hull so they would be safe from water, designing housing for the motor/fan, mounting the fan housing to the servo, and sealing the internal components inside the hull while maintaining a system of access. Ultimately, we used velcro tape to mount the electronics to the hull on raised platforms, we designed a custom housing for the motor/fan in CAD and fabricated it using the CNC machine, we mounted the fan housing to a platform that was connected to the servo, and we cut out a wooden cover for the hull using the scroll saw, to which we mounted the servo. The hull cover was joined to the hull with velcro tape, and we included a trap door through which we can access the electrical components easily without removing the entire hull cover.
All things considered, we are very pleased with our final product. We feel that it displays a lot of critical thinking, creativity, and technical skill, much of which we learned along the way. We all consider ourselves more technically capable than we did when we started, and we are most grateful for the opportunity to take on such a challenging and fulfilling project.

Students

Project Description

Technical Background

Design Drawings

Fabrication Process

Final Result