Advantage of the newer cutlass styles

[dakardad]

OK I'm new here on this forum.
Im building a wooden boat and the plan calls for a lignum vitae stern, or cutless bearing.
Ive never used that before and it seems improvements have likely been made since this boat was designed (1924). I dont like the idea of just putting the new brass/neoprene style right into the deadwood, so Im thinking of a metal stern tube that the actual bearing goes into. But why even use the rubber style, why not use a bronze bushing?

Thanks!

[David M]

Rubber absorbs vibrations better....smoother.

[dakardad]

Ok. But wouldnt it be better to address the vibration at its source?

[Sailmonkey]

Originally Posted by dakardad

Ok. But wouldnt it be better to address the vibration at its source?

Sure, but first you must find the sewing machine smooth auxiliary Diesel engine.

[dakardad]

Hahahaha Fair enough.

But there is no reason beyond vibration NOT to use say, a bronze bushing?

[Sailmonkey]

Lignite and rubber bearings are all softer than the shaft to preserve it from wear. I don't know what wear you could expect from a bronze bearing, but I think it would be far greater than that seen with rubber.

[River Cruiser]

Just off the top of my head water will work as a lubricant between the rubber & SS shaft but may not work as well on a metal to metal close tolerance fit. A lot will depend on the rpm the shaft turns.

[scoobert]

a common rail engine is butter smooth. say a 2012 VW TDI engine.

[NahanniV]

Had a bronze bushing on my last boat (English built trident voyager) the stern tube was filled with grease which would leak out at the bushing. Had to put a turn on a greaser every so often while motoring. Also the bushing had a spiral groove machined in it; I think that was to collect crap and give it a path to exit. It worked well, never wore out in 4 years and over 20Kmiles.

I did have some noise that may or may not have been related ?

New boat has rubber cutless with water lubrication. It was badly worn when I got the boat, now replaced, will see how long it lasts.

[dakardad]

what is the best material for the stern tube? I am considering a thick walled carbon tube.
I will have a 1" SS shaft.
I plan on micro polishing the shaft where it contacts the bushing at the prop end. A bronze oilite style bushing to do the chores.
I have an 8hp farryman.

[Sailmonkey]

Originally Posted by dakardad

I have an 8hp farryman.

That certainly wont be addressing the vibration at it's source

[scoobert]

Originally Posted by Sailmonkey

That certainly wont be addressing the vibration at it's source

at 3600 RPM they are very smooth. lol

[SV Maclas]

We have a composite cutless on our aluminum boat for the obvious reason of reducing corrosion. Sure is easy to get out!

[boden36]

Also a bronze hush is much less forgiving of minor misalignment.

Regards,
Richard.

[dakardad]

Originally Posted by boden36

Also a bronze hush is much less forgiving of minor misalignment.

Regards,
Richard.

Yes l was wondering about that too.
Just have to get it right.