Marine-Grade Cable Design for Decks
Twenty meters of cable damaged by a tire is not a sensor problem — it is a cable problem. Here is what we learned about specifying for the environment.
In v1 we under-spec'd the cable. Standard CAT 6A in conduit looked fine in the lab and survived 11 days of sea trials before the first run was crushed by a wheel arch during loading. The replacement program was educational.
What ended up working
- Stranded conductors over solid — flex cycles matter more than peak attenuation.
- PUR jacket over PVC — survives diesel, hydraulic fluid, and salt spray.
- Aramid braid for crush resistance in unconduited runs.
- IP67 connectors at every node — not a strain reliever, an actual seal.
Questions, answered
Why does cable specification matter so much on a vehicle deck?+
Because twenty metres of cable crushed by a tyre is a cable problem, not a sensor problem. In v1, standard CAT 6A in conduit looked fine in the lab and survived 11 days of sea trials before the first run was crushed by a wheel arch during loading. The environment, not the lab, sets the spec.
What cable design choices ended up surviving the environment?+
Stranded conductors over solid (flex cycles matter more than peak attenuation), a PUR jacket over PVC to survive diesel, hydraulic fluid and salt spray, aramid braid for crush resistance on unconduited runs, and IP67 connectors at every node that act as an actual seal, not just a strain reliever.
How much did the better jacket spec cost?+
The jacket change moved the bill of materials by only a few cents per metre but extended service-life expectations by years — a cheap change with a large reliability payoff.
Continue the thread
Salt Mist, IP66, and the Coating Spec
The first conformal coat passed lab spray tests and failed in service. The second passed in service and failed thermal cycling. The third one stuck.
Why EtherCAT Ring Topology for Marine Sensors
Star-topology fieldbuses fail open when one run is damaged. A redundant ring keeps the segment master talking to every node, even with a cut cable.
Redundant Power for the Segment Master
A segment master that loses power loses a whole deck. The redundancy story has to start at the supply rail, not at the network port.