Eli5: How does water not get inside ships or submarines through the motor shaft?

Question

Eli5: How does water not get inside ships or submarines through the motor shaft?

In: 112

Answer 1

the device on the shaft is called the stuffing box

they have a quasi tight fit around the shaft

a common wood used is/was iron wood

[https://en.wikipedia.org/wiki/Ironwood](https://en.wikipedia.org/wiki/Ironwood)

here is some info from west marine

[https://www.westmarine.com/west-advisor/Stuffing-Boxes-Shaft-Seals-and-Shaft-Bearings.html](https://www.westmarine.com/west-advisor/Stuffing-Boxes-Shaft-Seals-and-Shaft-Bearings.html)

the general idea is if sand enters the gap the sand will sink into the stuffing and not be abrasive. if it was a metal-metal joint the sand would have nothing to sink into and would thus with metal-on-metal grind away the shaft or bearings

in some ways this is similar to Babbitt bearings where a soft metal is used as the bearing surface