The frame is constructed of 2x4s for the initial prototype with a field quality prototype being constructed from 1in (1/16th in) aluminum angles. A simple plastic storage container functioned as a waterproof housing to protect all necessary electronic components. This was done using a simple container and waterproofing it with silicone glue on the seams. The chosen container is a Sterilite 25-quart modular latch box. A rack to hold the ultracapcitors in the waterproof housing was designed using UniGraphics NX 7.5 and printed using a reprap machine. The profile for the part can be seen below. The final product was printed to a thickness of 1/2in.
The .stl file can be found here – Maxwell 3,000 Farad ultracapcitor holder.
Each mechanical component was modeled using UniGraphics NX 7.5 and is shown in the image below.