On Tue, 24 Apr 2012 11:55:25 -0400, "Flying Pig"
wrote:
If you've been paying attention, you know I've dropped my rudder and have
been removing prior attempts to epoxy pits in the shaft - done in a
convoluted, upside-down manner, inside the boat - which turned out badly.
With the rudder out, I have access to it conveniently, to do it up right
(well, as best as possible in that it can't be sent off for grinding,
rewelding, and machining to round again).
I believe I have all the prior epoxy out. Some of the pits have tunnels up
or down, too, which, as I worked them out with the pick, displayed remnants
of prior packing material. Not so good. The good news is that nearly
everywhere I managed to pick off shows very bright under the old epoxy, so
it's clean (or will be when I use a brush and acetone to remove all solubles
which may be hiding on the surface, and which would impede bonding).
The area covered by the packing gland has minimal reduction in diameter -
mostly 2-5, and at worst, ~8 thousandths of an inch (out of 2"). However,
I'd like not to have even that, if I can avoid it...
Ed. Note:
I started this last night, but abandoned it for a while so I could run up to
Vero to take my wife out for dinner on our 9th anniversary. In the
meantime, I THINK I've answered my own question, below, which I'll show at
the bottom, but in case there's a better answer, leave this he
Which leads me to ask about how to - in this group's collective wisdom -
best sand the Devcon Plastic Steel Epoxy I'll put on, using the top and
bottom of (up and down from) the newly epoxied area (Plastic Steel is touted
as machinable, drill-and-tappable and otherwise as hard as steel when it's
fully set) as a guide, to build that back out, but still maintain roundness.
Any variance wouldn't do the packing any good, I don't think, regardless of
whether it's smooth. Sanding the epoxy when it's green should allow me to
have minimal, if any measurable, impact (from sanding away good metal) on
the unpitted sections of the shaft, I believe. Even if that weren't true,
it is of no consequence in that those areas do nothing related to water
intrusion, and that amount isn't relevant to strength.
Firstly, regardless of what "they say" devcon is not as hard as steel.
True it is machinable, tapable, etc., but then so is nearly any other
solid material - you could cut threads in a pound of butter, if you
keep it cold enough.
As for sanding green epoxy, essentially what you are doing, it has
never seemed very effective to me. the yet to fully harden epoxy balls
up, clogs the sand paper, and generally results in me stopping the job
and waiting until tomorrow. I think you will find that waiting until
it fully hardens will result in an easier job.
What I would suggest is to make up some flat "sandpaper boards" by
gluing strips of, say 80 grit, sandpaper to a wooden backer to make a
hard, stiff, "sandpaper file" device. I'd also make some in 180 grit.
Then sand away, across the shaft, with the 80 grit and when you start
touching the shaft then switch to the finer grit and finally finish up
by sanding "around the shaft" and finally, using strips of sand
paper/emery cloth, by sanding across the shaft like shinning a shoe.
This should give you no problems with sanding away appreciable amounts
of shaft and should result in a reasonably round surface.... remember
that the packing in a stuffing box is not a hard material but in fact
a rather flexible material and will seal quite happily on a shaft that
is not absolutely, perfectly, round.
Fortunately, after I re-install the rudder and shoe, I have complete access
to the rudder tube/packing gland before I reassemble the steering gear
(which, of course, will require the packing nut be slid on before that).
I'll use feeler guages to exactly (well, as exactly as I can) center the
tube in the shaft, using a jack stand to support the weight of the rudder
itself, hanging off the shaft (which would put pressure on the aft portion
of the shaft), but without raising it from the shoe. That will allow me to
use the very substantial steering setup (see "drop it" in the "third try"
section of the rudder gallery for the disassembly of that), with its two
heavy delrin bushings, to keep it centered. My steering is Scotch Yoke,
which is two arms (push-pull), so I won't have any leverage to the side when
applying turning forces. So, my repair should be under the least possible
stress on the packing gland when it's finished - or, at least, that's my
story, and I'm sticking to it :{))
So, I have my repair sequence thought out. Any ideas about how to manage
sanding of the epoxy excess from a perfect 2" round outcome?
Pix to this point start at
http://justpickone.org/skip/gallery/...+Old+Epoxy+Out
Ed. Note:
So, that's what I'd had last night. In the meantime, I came up with various
sorts of pipe solutions - 2" PVC, a 2" nipple, and, today, as I was
wandering in the yard and happened upon the welder here, I realized that he
probably used 2" aluminum pipe in his work. He confirmed that he did, and
that 2" dimension was ID, and has offered me a cutoff.
I don't think that I can get it down the shaft, and if I could, there
wouldn't be room for sandpaper's thickness, even if I could figure out how
to adhere it. I'd first test it to see how exact it was, of course; if it's
very slightly oversized, that changes matters, as, of course, its being
slightly undersized would, in my thinking.
However, I believe that if I cut it lengthwise at slightly less than exactly
half, I will have a small section which I can carefully ram/wooden-hammer
(lengthwise) over the shaft, thus expanding it slightly so as to allow for
sandpaper's thickness.
This would solve both the straight line challenge I posed above, as well as
enhance the ability to end up with a round finished product, by going not
only up and down the shaft, but around it with this slightly-more-than-half
pipe. If I can't make it expand enough, I could use the
slightly-less-than-half-pipe nearly as well to the purpose. Both would be
amply stout to preserve a straight line, my original thought/challenge, from
good material over pit repair to good material on the other side, but would
have the advantage of a curvature closely matching that of the shaft.
So, back to all my begs in one ask-it, are there any better ideas? And, if
this idea is da bomb, what's the best way to manipulate this sanding shoe to
achieve the best results, in your collective opinion?
L8R, y'all
Skip, working on the boat
--
Cheers,
Bruce