Livin' the Dream...rudder repairs in exotic locations

TQA

Super Anarchist
1,208
35
Caribbean
How much would a new rudder shaft cost?

Split the rudder, cut off tangs, weld tangs to new shaft, reassemble rudder. All simple jobs. 

A proper job compared to gooping the shaft up then hand scraping.  Also you could stop worrying about crevice corrosion. 

 
Not entirely sure in the dwg, is that collar a thrust bearing?  If it's only retaining the seal and serving no other purpose and it sounds like you have plenty of time and the whole thing is below the water line...  I would look into putting in a mechanical dripless seal like PYI.  You would only need a collar installed for the bellows. The seal has a water port so you could supply with engine cooling water or pull into raw water intake.  This ensures a regular turn over of water. Or just vent.

This is all assuming that the above conditions are as stated.

 

Ajax

Super Anarchist
14,586
2,877
Edgewater, MD
I think BJ should unscrew the diesel deck fill cap, drive the boat out from underneath it, and drive a brand-new boat under the deck fill cap, and screw it back on.

It's really the only way to be certain.

 

Not My Real Name

Not Actually Me
42,929
2,767
How much would a new rudder shaft cost?

Split the rudder, cut off tangs, weld tangs to new shaft, reassemble rudder. All simple jobs. 

A proper job compared to gooping the shaft up then hand scraping.  Also you could stop worrying about crevice corrosion. 
It's 80mm stainless post, maybe two meters long, max?

Simple jobs, it's still a lot of labor.

 

Not My Real Name

Not Actually Me
42,929
2,767
Not entirely sure in the dwg, is that collar a thrust bearing?  If it's only retaining the seal and serving no other purpose and it sounds like you have plenty of time and the whole thing is below the water line...  I would look into putting in a mechanical dripless seal like PYI.  You would only need a collar installed for the bellows. The seal has a water port so you could supply with engine cooling water or pull into raw water intake.  This ensures a regular turn over of water. Or just vent.

This is all assuming that the above conditions are as stated.
We thought about a PSS seal, but we don't think there's enough room above the shaft to fit it. We'd  need to put a collar on it, too.

 

Not My Real Name

Not Actually Me
42,929
2,767
So more IS going to happen on this in the next week before we leave. I'll be a happy camper if we can make that happen.

 

savoir

Super Anarchist
4,907
195
I think BJ should unscrew the diesel deck fill cap, drive the boat out from underneath it, and drive a brand-new boat under the deck fill cap, and screw it back on.

It's really the only way to be certain.


I dunno.  There are downsides to that maneuver. 

Sounds like the new boat might be full of at best warm beer and at worst no beer at all.

 

cje

Member
497
66
I don't understand why any of this is an issue and normal within many industries. Older Swans are similar and included masses of needle bearings within those lip seals. Push any heavy grease from a nipple above forcing it out thru thru the lower seal, keep it full of grease and water out. It does work.

Repairing that shaft is time consuming but usually most cost effective. First hit with TIG you will immediately know if that parent material is worthy of salvage, no experienced welder would dive any deeper if any faults found. Addressing each divot individually before moving on is critical, keep the shaft true and always referenced. With proper welding / filing techniques in field and eyelashes removed it will pass for lip seals.  A seal can always be raised or lowered to get them off that wear / corrosion rut or ditch. 

 

DDW

Super Anarchist
6,315
1,011
I'd replace the lower bearing with plastic by overboring the existing hole. It will outlast metal, isolate the bronze from SS, and be easily replaceable in the future if needed.

One thing to watch out for if you weld up the shaft is there is likely to be precipitation, even if done very carefully, in the heat affected zone. You have no opportunity to normalize it with the rudder blade attached. That might make it more susceptible to corrosion in the future. Just something to discuss with the welder. 

 

cje

Member
497
66
DDW, agree on all of those comments. If it's stuffed with grease with no salt it may survive a poor environment even with those repair deficiencies.

Proper support around the that mid shaft seal is perhaps the cause of the issue, how did it get wet?

 

Moonduster

Super Anarchist
4,823
229
Ha, I'd go double or nothing for the guy who claims he can finish to 3 microns by hand.

The really pathetic thing here is that there's no reason to fill those divets at all. Just grind them out and polish them smooth. There is no application for a lip seal here, so refinishing for lip seal is a huge waste of time and money.

The solution here is a packing gland. Total repair cost should be less than NZD$2000.

 

Not My Real Name

Not Actually Me
42,929
2,767
Ha, I'd go double or nothing for the guy who claims he can finish to 3 microns by hand.

The really pathetic thing here is that there's no reason to fill those divets at all. Just grind them out and polish them smooth. There is no application for a lip seal here, so refinishing for lip seal is a huge waste of time and money.

The solution here is a packing gland. Total repair cost should be less than NZD$2000.
It's not quite as simple as you make out, as there would need to be some re-building of the area to have something to put a gland onto. The present setup isn't really capable of having anything put over it, there needs to be a collar, which would need to be stuck in there somehow. There's no protrusions above the hull to clamp on to.

 

Fah Kiew Tu

Curmudgeon, First Rank
9,853
3,120
Tasmania, Australia
Ha, I'd go double or nothing for the guy who claims he can finish to 3 microns by hand.

The point I was making was, your 0.003" tolerance is piss easy to meet - that's ~0.075mm or 75 microns in the units all the First World except the USA uses - and there'd be no need for anything better. Yet you seemed to think this would be difficult to achieve, which suggests to me that while you may be an engineer of some sort, you certainly aren't a machinist or toolmaker. My toolroom lathe turns parallel to 0.0003" (yes 3 tenths of a thousandth of an inch or roughly 8 microns) over 8 inches. To spot that shaft I'd turn & bore a spotting master to the correct diameter, split it and then use Dykem blue or similar to pick up the high spots on the shaft and carefully grind them down, finishing by polishing. This is old tech.

That's assuming it couldn't be fitted onto my Kearns horizontal boring mill and re-machined as in the previously linked YouTube vid. That'd depend how far down from the top of the rudder the affected area was as my HBM only has 400mm of quill travel before I need to get creative.

Problems like this are interesting because they're a bit out of the normal run of the mill stuff.

I still don't like the design. Too many unknowns including, as has been commented, possible future corrosion problems in the heat affected zone if TIG welded. I'd rather a design that kept water out of that area using grease for example.

FKT

 

Fah Kiew Tu

Curmudgeon, First Rank
9,853
3,120
Tasmania, Australia
It's not quite as simple as you make out, as there would need to be some re-building of the area to have something to put a gland onto. The present setup isn't really capable of having anything put over it, there needs to be a collar, which would need to be stuck in there somehow. There's no protrusions above the hull to clamp on to.
Yeah I got that impression from the early pix you posted. There'd need to be some sort of flange/spigot created and glassed in before anything else was done. Would that cause interference problems in that space? NFI so the guys and you on the spot are the best judges of how to proceed. I'll look forward to the final solution with interest.

Off in transit back to Tasmania in another day or so via a long swing out west so won't be looking in very much for a while. Time to plan on my summer sailing season.

FKT

 

Not My Real Name

Not Actually Me
42,929
2,767
Yeah I got that impression from the early pix you posted. There'd need to be some sort of flange/spigot created and glassed in before anything else was done. Would that cause interference problems in that space? NFI so the guys and you on the spot are the best judges of how to proceed. I'll look forward to the final solution with interest.

Off in transit back to Tasmania in another day or so via a long swing out west so won't be looking in very much for a while. Time to plan on my summer sailing season.

FKT
That's the trouble, there are a arms on the rudder post for the steering and autopilot, and not a lot of room above it. But we'd have to put some sort of lip flange on there to make it work.

 
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