CougarTail & CUB: A General-Purpose Mast and Central Utility Board for Cylindrical Underwater Enclosures

Ben Washburn, Clayton Smith, Eli Gaskin, Brighton Anderson, Braden Meyers, Brady Moon, Joshua Mangelson · N/A · 2026

Summary

Cylindrical watertight enclosures are widely used across various underwater systems, from unmanned underwater vehicles (UUVs), to remotely operated vehicles (ROVs), to various sensor platforms.

Abstract Summary

Cylindrical watertight enclosures are widely used across various underwater systems, from unmanned underwater vehicles (UUVs), to remotely operated vehicles (ROVs), to various sensor platforms. However, electronics are typically built on rectangular PCBs arranged in horizontal stacks, which inefficiently occupy the circular cross-section volume that is critical for both payload capacity and buoyancy management. This paper presents CUB (Central Utility Board) and CougarTail, a general-purpose system designed to address this gap. CUB is a circular PCB sized for 4-inch-diameter enclosures that consolidates a Raspberry Pi Compute Module 5 (CM5) and an STM32 microcontroller, while also providing power management features and auxiliary connections. Mounted coaxially, CUB reduces the electronics stack of our CougUV from 200 mm of tube length and 709 g to 25 mm and 156 g, returning that length and mass budget to payload and buoyancy trim. CougarTail is an open-source companion sensor mast that houses a GPS antenna and two dual-band (2.4 and 5 GHz) omnidirectional PCB antennas. Both components are validated through bench testing and integration on a CougUV platform, our small open-sourced torpedo UUVs.

Key Points

Cylindrical watertight enclosures are widely used across various underwater systems, from unmanned underwater vehicles (UUVs), to remotely operated vehicles (ROVs), to various sensor platforms.
However, electronics are typically built on rectangular PCBs arranged in horizontal stacks, which inefficiently occupy the circular cross-section volume that is critical for both payload capacity and buoyancy management.
This paper presents CUB (Central Utility Board) and CougarTail, a general-purpose system designed to address this gap.
CUB is a circular PCB sized for 4-inch-diameter enclosures that consolidates a Raspberry Pi Compute Module 5 (CM5) and an STM32 microcontroller, while also providing power management features and auxiliary connections.
Mounted coaxially, CUB reduces the electronics stack of our CougUV from 200 mm of tube length and 709 g to 25 mm and 156 g, returning that length and mass budget to payload and buoyancy trim.

Custom PCB Design

The CUB mainboard was designed to consolidate bulky and wiring-intensive power and data systems onto a single easy-to-use board. A cut-circular geometry was chosen to minimize the size footprint and pass-through inconvenience while maximizing board area. The CUB mounts coaxially within commonly-used 4-inch-diameter Blue Robotics acrylic tubes.

By integrating previously separate systems onto a single board, CUB achieves a significant reduction in footprint and wiring complexity which increases reliability.

Custom PCB Design — CougarTail & CUB: A General-Purpose Mast and Central Utility Board for Cylindrical Underwater Enclosures — Fig. 3: Molex 146187 dual-band antennas (1), Taoglas AP.25F.07.0078A GNSS antenna (2), Wire clips (3), Mast housing (4), Mast insert (5), Mounting screw holes (6). Labeled render of CougarTail mast housing (left) and insert (right). The mast insert was placed in the housing and filled with epoxy. Cables were secured by clips and fed through a polyurethane tube through the base of the mast housing (not shown).

Integrated Sensor Mast

Surface operations with our CougUV platform [ 1 ] previously relied on GPS and radio antennas housed within the main enclosure. Even shallow submersion attenuated these signals enough to render them unreliable, forcing the vehicle to fully surface and orient itself favorably before acquiring a GPS fix or establishing a communication link.

To address this, we designed a custom 100 mm-tall mast that extends above the waterline whenever the vehicle is surfaced (see Fig. 3 ).

Integrated Sensor Mast — CougarTail & CUB: A General-Purpose Mast and Central Utility Board for Cylindrical Underwater Enclosures — Fig. 5: Cart-based waypoint-following test of the CUB and CougarTail. Positions were recorded while the CUB processed live sensor input and actuator commands, confirming end-to-end functionality of the sensing, control, and communication pipeline.

Testing and Results

The CUB and CougarTail were thoroughly bench tested, with deployment onto the CougUV platform in progress. The results below detail the performance of both systems and the improvements they provide to the CougUV platform. The electronics system CUB replaces occupied 200 mm of longitudinal space within the body tube and weighed 709 g. CUB occupies 25 mm and weighs 156 g, reductions of 87.5% and 78% respectively.

Sources and Demonstrations

Figures are reproduced from Washburn et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.