Fernando, you got my brain working again! Thank you
In multiple books and manuals on naval "tools", I've seen small knives carried by sailors for a variety of ship-board purposes. The knives were used for whittling, scrimshaw, fraying rope, sharpening fids, etc, etc. I understand that perhaps navajas were not allowed and likewise as Chris points out, not around at the early date specified, but there were definitely side knives at sea. A recent book I read concerning punishments at sea even mentioned sailors killed in knife fighting on the ship, with the transgressors being hung from the yardarm. Perhaps these knives were smuggled aboard? Come to think of it, in this circumstance, I believe it was a merchant vessel...