Context & users

Field teams needed a compact underwater recorder that stays oriented, resists pressure, and can be attached and retrieved reliably without specialist tools. Goal: a repeatable, low-profile package that extends recording time and simplifies deployment.

Requirements / constraints

• Thin form factor; smooth exterior to minimize snags/drag

• Predictable orientation (CG CB), tolerant of minor payload variation

• * no * Ingress resistance via a serviceable seal (no permanent potting for routine maintenance)

• Mounting that works on varied substrates/harnesses; protected cable/connector strain-relief

• Materials and processes suitable for short-run molding and fast iteration

Solution architecture (sanitized)

• Multicomponent molded polymer housing (main shell + cover + gasket groove)

• Serviceable seal: O-ring/gasket stack with compression stops and generous lead-ins

• Internal ballast pockets to trim CG; modular board standoffs to control stack height

• External mounting flats/slots compatible with straps or brackets; recessed fasteners

• Routed cable path with strain-relief features and drip loop

Engineering highlights

• CG/ballast tuning: Spreadsheet + benchtop tank trials to set a ballast map and trim angle; targeted neutral/slightly negative buoyancy for predictable handling

• Molding for repeatability: Draft, radii, and gate locations chosen to reduce warp; indexed features for assembly alignment; documented de-mold steps

• Seal design: Groove dimensions set for target compression; corner radii to avoid pinch; tactile check for full seating; light-grease spec to reduce stick-slip

• PCB/mech integration: Board keep-outs respected; standoffs + washers manage compression; cable gland spec’d for pull-out and bend radius

Build & validation testing

• Buoyancy & balance: Tank tests (fresh and salt) to verify orientation, trim angle, and stability during gentle tow

• Pressure checks: Pressure-pot/column to target depth equivalent; inspected for leak paths and post-test mass gain

• Hydrodynamics: Simple tow test to gauge drag and side-slip; adjusted leading edges and mounting position

• Attachment trials: Strap/adhesive/standoff options compared for install time, shear/peel behavior, and serviceability

Results (sanitized)

• Stability: Consistent orientation in tank tests; reduced roll/rocking versus prior layout

• Endurance: Packaging changes enabled longer recording time (thermal path + battery-volume efficiency)

• Repeatability: Molding/assembly steps documented; fast, consistent closes with even seal compression

• Readiness: Passed internal buoyancy and pressure checks to program targets; improved handling via protected strain-relief

What I’d improve next

• Formalize IP-style ingress tests and UV/salt-fog exposure; add debris guards at cable entry

• Tool-less latch option to speed field swaps; standardize hardware to two driver types

• Expand environmental matrix (temperature, long-duration soak, repeated deploy/retrieval cycles)