Manufacturing & Assembly
The preliminary design phase focused on selecting a pontoon geometry that balanced buoyancy, stability, and manufacturability within the constraints of a scaled catamaran platform. Early in the process, the decision to 3D print the pontoons imposed clear size and build-volume limitations, which motivated an evaluation of common pontoon cross-sections and their associated hydrodynamic tradeoffs. Buoyancy requirements were translated into volumetric constraints based on a target operating draft, while the catamaran layout constrained pontoon spacing and overall geometry. A symmetric configuration with a V-shaped lower profile was selected to promote directional stability, and the upper geometry was shaped to maximize volume and buoyancy within manufacturing limits. In parallel, MATLAB-based analyses were used to size the articulating pod geometry and suspension interfaces, ensuring sufficient resistance to immediate deflection under applied thrust loads. Together, these analyses defined a manufacturable baseline design that informed subsequent fabrication and testing efforts.
Early in the design process, the decision to 3D print the pontoons turned buoyancy requirements into volumetric constraints. Based on a target operating draft of 40% by volume and a maximum vessel length of four feet, mass volume calculations were performed to determine the displacement required to support vehicle weight while maintaining stability within this draft limit. These calculations directly informed pontoon sizing, ensuring the final geometry remained within length constraints while fitting inside the available 9 in × 9 in 3D printer build volume.
3D printing was selected to enable in-house fabrication without the need for outsourcing, allowing rapid iteration, greater flexibility in producing irregular geometries, and increased control over the build schedule. The pontoon geometry incorporates a V-shaped lower profile with irregular radii that would be difficult to manufacture using rolled sheet metal without adopting a more complex rib-and-skin construction approach. Additive manufacturing provided an efficient way to realize this geometry while maintaining consistent mass properties. TPU was chosen for the pontoons to replicate the “squishy” behavior of the air-filled floats on the full-scale Minion platform, while PETG was used for the propulsion pods to provide higher stiffness and reduced deformation under the structural loads imposed by the thruster assemblies.
The thruster assembly was designed to enable servo controlled azimuthing while supporting two Blue Robotics T200 thrusters per pod to provide increased thrust and maneuverability. The assembly incorporates a concentric shaft arrangement, in which an inner rotating shaft transmits servo-driven motion within an outer structural housing. Thrust bearings were integrated to provide low-friction rotation and reduce wear between the shafts under load, while washdown collars were used to secure the assembly and limit axial movement. This configuration enables precise angular control of the thruster pair while maintaining structural robustness and reliability under sustained thrust loading.
Foam Inserts
Firstly, the Foam Insulation boards needed to be cut. Based off of the dimensions pulled from the CAD model, templates were made to cut the boards to the right size before being glued together. After curing and drying, the boards were then fit tested and lightly sanded where needed
Outer Shell
After the Foam Inserts were dry, they were inserted into the back piece of the pontoon. Then one by one each subsequent pieces were inserted over the foam boards and glued together. After all the pieces were assembled a ratchet strap was used to compress the pieces together.
Final Coating
Once the outer shell was done curing, a putty like epoxy was placed on all the seams to fill in any gaps that still remained.
A coat of Bondo was then applied to the entire outside of the outer shell then sanded smooth to remove any 3D printing artifacts left behind like layer lines.
Coats of primer and spray paint were then sprayed over everything to give the pontons a nice uniform color.
Finally each pod and pontoon received a generous coating of silicon conformal coating to guarantee the plastic was protected from the outdoor UV rays and waterproof seal it one last time
