Prop shafts - a warning

[Norman_E]

The off centre prop shaft thread reminded me that on a few boats it is possble to completely withdraw the prop shaft without fouling the rudder. My own boat is a case in point.
When I bought it I noticed that an anode had been fitted to the shaft inside the boat as well as the one outside, and asked why. The answer was that the charter company found out the hard way that the shaft can come right out. On one of their their first Jeanneau 45.2s the shaft coupling had not been properly fitted and the whole shaft and prop fell out. The boat was in harbour at the time and they saved it from sinking. After that they fitted a spare shaft anode on the inside in each boat so that even if a coupling comes undone, the shaft stays put.

 

[Mudplugger]

A jubilee clip works as well!

 

[David2452]

[ QUOTE ]
A jubilee clip works as well!

[/ QUOTE ]

Provided you put two on with the screws at 180 deg.

 

[VicMallows]

Do you really think the slight imbalance close to a support point will be significant at the revs in question /forums/images/graemlins/confused.gif

Vic

 

[Porthandbuoy]

For the same reason you put two clips on every hose.

You do put two clips on every hose don't you?

 

[Searush]

[ QUOTE ]
Do you really think the slight imbalance close to a support point will be significant at the revs in question /forums/images/graemlins/confused.gif

Vic

[/ QUOTE ]

Or is it just that the two screws at 180 increase the effective diameter?

 

[VicMallows]

But I don't expect the shaft to part company in the first place ... so it's a back up; just like the second clip on a hose /forums/images/graemlins/grin.gif

Vic

 

[Porthandbuoy]

And if both clips fail, and your propshaft slip out, do you have a tapered softwood plug of just the right diameter tied to the stuffing box? /forums/images/graemlins/wink.gif

 

[VicMallows]

Of course! .... and by the way those plugs they sell in the chandlers are much too hard! What about some well designed rubber bungs?

Vic

 

[Porthandbuoy]

The trouble with rubber bungs is they rely on compression to keep them in place. They will only ever be as secure as when you've driven them into place. A softwood plug, on the other hand, will become tighter as the wood absorbs water and swells.

 

[Norman_E]

I am glad I am not the only person who thinks they are too hard. I actually made a couple of extra ones in large sizes and used some soft pine.

 

[abbott013]

I bought some plugs last year from a chandlers, he stocked hardwood and softwood types. Not sure why they make hardwood plugs, these particular ones were to hard to be pushed home by hand.

 

[thalassa]

[ QUOTE ]
A jubilee clip works as well!

[/ QUOTE ]


No, it doesn't in many cases. They can shred the seal to bits, causing massive water ingress.
I went for the inner anode solution as well, after the shaft once parted from the conical coupling, but I couldn't get a good grip on the greasy shaft. With an anode, it's very easy to pull back the shaft at sea, good grip - and this is not theory, but experience...

 

[Superflid]

One of the commercial fishermen in Boston told me of it happening to a friends boat, luckily in the river near the mooring.
My shaft coupling is drilled and bolted through the shaft, the rudder would stop it falling out completely but something would be damaged.

I might make up a collar to fit on the shaft to do the job properly.