Hi, all,
Thanks for all the discussion so far. I'll try to address each of the
issues/suggestions I've seen:
Flaking/breaking off from future corrosion: I don't know. I suspect (but,
obviously, can't prove) that there might have been a bonding issue causing
the pits.
The shaft has pits only in the area of the packing contact (and slightly
above), none below. My pix show a ring at the bottom (and one fissure which
extends downward, but that's the ONLY exception on the downside) of where
the bronze tube tops out. Everything else is above that point, and ends
slightly above where the gland tops out. Having moving water below the gland
would help with no corrosion/pits there, but having the extent above the
packing gland suggests there is something more than just unoxegenated water
at work here.
As this pitting was present to at least some degree when we bought the boat,
I have no idea how long it took to get to that stage, and what, if any,
progress occurred since we have had it. We've next to never been tied up
for any extended period of time (a couple of months during our 2009 refit,
in a marina with recently new power stands being the exception), but the
boat spent most of the 15 years before we bought her at a dock in FTL.
There may have been some issue with the electricals there; certainly, the
zincs on the shaft and prop were much more worn than I'd have expected after
a short while between their haulout and spiff-up and our haulout for our
initial refit.
There was a bonding strap to the shaft which I had to remove to get the
steering gears off; I'm going to leave that off, as it goes to the ground
plane stuff, and we've got plenty of other help in that regard. The ground
plane stuff is electrically grounded, but the thru-hulls aren't part of
that, other than our keel cooler, so there's no issue there. If there WERE
some internal electrical issue, this should remove that.
Back to the question/concern of future pitting/corrosion displacing the
epoxy, if, indeed, there is any connection (pardon the expression) I'd hope
that this will remedy that. I have some difficulty believing that the level
of pitting - and the very localized nature of it - could be just salt water
and air exposure.
In any event, it took many years to get this point. My conversation with
Devcon assures me that my cleanup I've done and will do is adequate for
bonding. From Rick's frequent use, and their assurance, and the local
machine shop which uses it to do the same thing I wish I could do for this
rudder shaft with drive shafts (much higher velocity, of course), yes, I
think I trust this epoxy. As to standing back and rethinking, that's what
I'm doing by not proceeding yet :{))
Replacing the shaft or having it addressed in a shop: It's impossible to
(merely) replace the shaft, as there are massive plates welded to it
internal to the rudder. You'd have to destroy and rebuild the rudder to
replace it (I'm not comfortable with the thought of cutting it off and
welding another to it, for a variety of reasons.) I called Foss Foam, who
provided the mold to Morgan at the time of build; he was pretty sure he had
it, and the replacement was $2200. As it was new, that was what I'd
planned to do, given that I'd thought a new rudder was much higher.
However, he searched through all his molds and it was one of the many molds
which Catalina dumped when they bought Morgan, in either the bay or the
Gulf, which wasn't recovered. To make a new rudder he'd have to have mine,
and fabricate a mold from it, and an extra $1500, which was my cost; he'd
keep the mold. Between getting it to him (and the new one back here) and
the now-cost of $3700, I abandoned that thought.
I've queried all the usual suspects about the norm of my experience in shaft
repair, which is to turn or grind down to all clear, building up metal to an
excess, and removal by turning (e.g. a crankshaft). There is no place I've
asked, including asking for referrals to someone else, anywhere, with the
means to accurately remove new metal if this were to be done. Without the
means to do that, I'm stuck with what I have, and/or can do here, or a new
rudder. See above about the new rudder :{/)
Sanding green and/or flat: I'm familiar with the pilling and clogging of
the sandpaper. Sandpaper's (relatively) cheap :{)) However, getting down
to the base metal of the area of the pits, if I weren't to try to build it
back out to the original dimension, is something I'm not worried about. If
I'm not going to try to build it up or be concerned about roundness, I can
easily attack it either with a machine or with the sticky-back stuff we used
on the fairing compound, including some finer grits I also ordered, in 2.75"
width rolls. Leaving the plastic on the sticky side allows me to make a
shoeshine cloth (it's what we did the back of the rudder with, e.g., when it
got another layer of cloth, and fairing compound, but was still in the skeg
slot) style sanding setup without having it stick to my hands :{)) I'd, of
course, go through several grits before stopping. In my work on other
entirely rough (mill finish) SS, I worked my way up from 80 and stopped at
600, then used two grades of rouge on a buffing wheel in my 4" grinder. Of
course, sanding was with a power sander, and still a lot of work. If I
started with something relatively soft (the assertion that this stuff isn't
as hard as steel is agreed), I think I could make it happen without croaking
from the effort. So, I'm not afraid of the work, other than I'd like to
make it as little as possible.
However, I'd rather it were as round as possible, and also as back-to-2" as
possible, which is why I went to all the thought about a mold (slightly
expanded 2" aluminum pipe, at this point) for the sandpaper. The only
reason we're doing this is to end, once and for all, the stream of water
which has been running through our bilge; that stream is what caused all the
rust in the driveshaft bearing due to the vapors created. As it is, I'm
having to replace several clamps due to accelerated corrosion in the same
areas. If it's smooth and round I should be able to get it to as few drips
as would evaporate before it got more than a couple of feet along.
Attacking it as Bruce has suggested, with a hard flat "something", across
the shaft would, at best, yield the same configuration (as to round) as
before, because I'd be stopping the removal at the point of exposed original
(slightly undersized due to 30+ years of wear, and especially tight glands
attempting to stanch the flow for the last 5 years and perhaps before by the
prior owner) metal, but if I weren't pretty aggressive in the shoeshine
phase of it, leave lots of flats/edges. If that (the above/Bruce's
suggestion) is sufficient, it certainly would be simpler as I could be more
aggressive without concern for perfection.
Has anyone had experience in out-of-round shafts to say whether the standard
packing will do its job? If I were to do a lot of shoeshining, I think I
could attack the flats/ridges, but probably not get it perfectly round no
matter how I danced around the circumference to avoid irregularity...
Smoothing before sanding: I have coke cans, saran wrap and other
possibilities for minimizing irregularities in the surface, but no Mylar
pattern making material. Certainly, using something of that sort would
minimize excess needing sanding. However, if tightly compressed, it might
also make it such that the original configuration (however much wear-removal
was present) would likely result. Then, there's the earlier suggestion about
tapping a 2", mold-released pipe down. Getting that off is a previously
expressed concern :{))
What kinds of places would use Mylar patternmaking material where I might
obtain some scrap (I only need ~4" square)?
I really had only thought to build it out to the original 2" as a side
benefit of my pipe-sander's rigidity/conformance-to-shape. If the
experience with slightly undersized shafts (anyone??) shows that it's of no
consequence to a standard packing gland (my thinking is that it shouldn't,
particularly when the packing is 5/16" - 0.3125 but both sides, 0.625 down
to max reduction to 0.617, a 1.3% difference at worst), I'll abandon the
build-out-to-original part of my thinking.
So, who's got a measurably undersized shaft which works just fine in a
standard packing gland?
Thanks for all the ideas and troubleshooting!
L8R
Skip
--
Morgan 461 #2
SV Flying Pig KI4MPC
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