[Public-list] Hard on the Rocks

Wed Nov 8 18:26:10 PST 2006

HI John,

No doubt there are a lot of variables associated with rudder shaft corrosion.  I suspect people who sail in fresh water all the time, have magnitudes less problem with corrosion than boats stored in salt.  Also I know  in earlier years, at least in Alaska, galvanic potential in most boat harbors was enormous because of poorly   designed electrical systems.  'Hot' marinas really eat up prop shafts nuts, wherever I have always been. I think Ketchikan harbor once recorded 400 + volts in the water at dockside. 

My rudder shafts dissolved over 25 yrs, so it is a slow process. I am going to try bonding the gudeon fitting to the existing hull zinc which protects the bronze prop shaft housing.  Its only  a few inches away from the gudeon itself.  The gudeon now at least has direct mechanical  contact to my new one piece lowr shaft, and bottom shoe.  In the spring I will look at it and see if anything is happening.

STill working on last layers of FG on my rudder, so havnt sent any pictures or write up yet,,, but will pretty soon.

regards

Glenn 
Dolce #318 

 -------------- Original message ----------------------
From: JohnI <a30blueteal at gmail.com>
> Glenn,
> 
> Thanks for the description. It's reassuring to see that failure of these
> parts has plenty of warning. I have issues with galvanic corrosion in my
> location. This past summer I had a prop nut zinc disappear in less than
> three months, I'm wondering if rudder protection is also a good idea, and,
> if so, what people use for zincs, bonding strategies, etc. I've also felt
> some "fluttering" of the rudder in similar circumstances to those you've
> described, so it seems a good inspection is in order.
> 
> John
> 
> 
> On 11/5/06, brooks.glenn at comcast.net <brooks.glenn at comcast.net> wrote:
> >
> > Hi John
> >
> > I noticed a lot of play in my rudder, ( original construction from
> > 1968).  Last season  there was substantial, hard vibration during certain
> > broad reach angles.This fall, turned into serious thunking below water
> > line.  I figured the rudder had broken loose and was flalling around on the
> > end of the upper shaft somewhow.
> >
> > Turns out the pin sitting in the bronze shoe at bottom of the keel was
> > corroded down to 1/4" minus and the 3/4" gudeon rudder shaft was corroded
> > down to 5/8" and bouncing around inside the gudeon/pintel assembly.   The
> > whole thing could move laterally enough to gind up against the trailing edge
> > of the keel adjacent to leading edge of rudder... very discomforting noise
> > whjilst sailing around.
> >
> > It appears a lack of cathodic protection on the lower rudder shafts ( 1 at
> > gudeon, one at foot in the rudder casting) basically ate away the zinc/other
> > materials within the silica bronze shaft leaving soft crumbly orangy copper
> > residue in the exposed strategic places.. Also the upper shaft leading out
> > of the rudder thru the full to tiller was pitted and corroded in big
> > bloches, so... out dam spot(s) and new rudder shafting overall.  I will
> > certainly put a small zinc on the rudder somewhere and bond it to the new
> > shaft.
> >
> > I have a few pictures and some construction details of the original lay up
> > and can send along early next week.  Still fiberglassing a new shaft into
> > the foam core of my old rudder...( captured some measurements as I autopsied
> > the old rudder).  Would be happy to send along in a day or so.
> >
> > Glenn
> >
> > S/V Dolce, #318
> > -------------- Original message ----------------------
> > From: JohnI <a30blueteal at gmail.com>
> > > Glen, what was the reason for the rebuild? I would appreciate seeing
> > your
> > > writeup along with some pictures. Thanks.
> > >
> > > On 11/2/06, brooks.glenn at comcast.net <brooks.glenn at comcast.net> wrote:
> > > >
> > > > Hi George,
> > > >
> > > > Yes, will write it up.  I will try to borrow a camera--mine is in
> > France
> > > > with daughter at the moment, likely not to come back for a while-- and
> > take
> > > > some shots of the internal construction of the rudder and reassembly.
> > > >
> > > > Also, my leaking bronze thru hull rudder post/packing nut assembly was
> > > > finger loose and woobly in the hull after I took out the rudder, so
> > pulled
> > > > it out and rebedded with 5200 and new glass to the hull.  I could
> > include
> > > > some details of that little routine also.
> > > >
> > > > not a big deal but going more slowly than desired, as usual...
> > > >
> > > > regards
> > > >
> > > > Glenn
> > > > -------------- Original message ----------------------
> > > > From: George Dinwiddie <gdinwiddie at alberg30.org>
> > > > > brooks.glenn at comcast.net wrote:
> > > > > > Also made some templates to capture the two angles the upper
> > > > > > rudder stock bends as it lays around the prop apperature opening
> > in
> > > > > > the top half of the rudder... A local ship yard made a new one
> > piece
> > > > > > rudder stock with 1 " silica bronze shafting, based on the
> > original
> > > > > > dimensions for around $900-including shaft material.
> > > > >
> > > > > Wow!  I'd guess cost might be the reason Whitby used separate pieces
> > > > > with no bends.
> > > > >
> > > > > If you're documenting this process and want to write it up, I'd be
> > glad
> > > > > to post it on the website.
> > > > >
> > > > >   - George
> > > > >
> > > > >
> > > > > --
> > > > >
> > ----------------------------------------------------------------------
> > > > >    When I remember bygone days                         George
> > Dinwiddie
> > > > >    I think how evening follows morn;
> > gdinwiddie at alberg30.org
> > > > >    So many I loved were not yet dead,
> > http://www.Alberg30.org
> > > > >    So many I love were not yet born.
> > > > >                 'The Middle' by Ogden Nash
> > > > >
> > ----------------------------------------------------------------------
> > > > >
> > > > >
> > > > >
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