How they make propeller shafts on large vessels like ocean liners or aircraft carriers waterproof considering the intense water and mechanical pressures that come into play?

Question

It seems like a grommet-type seal would fail in no time. Also, looking at an image of one of the propellers for the Queen Mary, it hit me that this is decades old, and would have to go to dry dock to be serviced, and there is no way they are doing that so… How is that even possible? I’d figure dry rot would set in somewhere along the way.

In: Engineering

Answer 1

Well, with small boats, you pack tight around the shaft with a special oiled rope that’s water repellant. It still leaks some (or, rather, if you pack it tightly enough to not leak at all, it will make enough friction to ignite the rope, so you deliberately leave it a bit loose and leaky), but it’s nothing a bilge pump can’t handle. I imagine there’s something similar going on when you scale it up