The
plan is ambiguous on this point.
While the rudder stock itself is supposed to
pass through the keel runner, its housing tube may not be. One drawing
shows it either passing through, or at least leaving a clearance
between the rudder shaft and the keel runner sufficient to expose the
bearing.
What does this mean? Do the arrowed lines indicate an extension of the tube
through the keel runner, or a clearance between rudder shaft and runner?
As this drawing also shows the bottom of bulkhead F reaching right through
the hull to the under surface of the runner, it cannot be taken literally.
In
case the latter interpretation is correct I have made a blunder by
bringing the tube out onto the surface of the runner. But it does not
take much to correct it.
Luckily, the plug I removed
from the runner to allow the tube to pass through is intact, and can
be used to fill the hole. I bored a 20 mm. centre through it first, and
then fitted it into the runner. It is not quite the same diameter as
the hole in the runner, because of the kerf of the hole saw, but the
difference is slight, and can easily be filled with epoxy.
The blunder plug: before gluing it in it is held in position by wedges.
Actually, I am not convinced that having
a plug snugly fitting around the rudder shaft is the best solution. The
end grain of the inside of the
plug, where the rudder shaft will go, is going to be unprotected except
for a few layers of unthickened epoxy. There will be friction from the
shaft, so almost inevitably there will be water and rust getting into
the runner
at some stage. If a plastic tube were bonded there instead, it seems to
me that there would be better protection. On the other hand, if the
first interpretation is correct and there is a clearance around the
rudder shaft, friction would not be a problem, and, provided the
clearance is wide enough, when the time comes
to change the bearing, it will be readily accessible.
A compromise can be struck by using a plug, with a small but adequate clearance, so that it avoids friction, but with the expectation that the plug is sacrificial and can be bored out again when the bearing needs changing
Looking through some of the boat related newsgroups, I see that there are some builders in favour of making or repairing their own rudder bearings, by forming them in-situ around the well waxed shaft with graphite thickened epoxy. Presumably this requires the shaft to be stripped of any paint and polished up to a smooth surface. Although I do not intend to replace my UHMW polyethylene with a home made bearing, I could possibly use one within the widened hole in a sacrificial keel runner plug. That would serve to protect the exposed end grain of the runner and extend the bearing surface for the shaft right down to its final emergence. It would also stop the tube short of entering the runner, but would it be any advantage over the tube and bearing both coming out onto the surface?
UHMWPE rudder bearings for the rudder tube, and the top one sitting in the tube.
In the end I decided to use the plug, bored out to 25 mm. to avoid friction, so I glued it back into the runner on the work bench.
A compromise can be struck by using a plug, with a small but adequate clearance, so that it avoids friction, but with the expectation that the plug is sacrificial and can be bored out again when the bearing needs changing
Looking through some of the boat related newsgroups, I see that there are some builders in favour of making or repairing their own rudder bearings, by forming them in-situ around the well waxed shaft with graphite thickened epoxy. Presumably this requires the shaft to be stripped of any paint and polished up to a smooth surface. Although I do not intend to replace my UHMW polyethylene with a home made bearing, I could possibly use one within the widened hole in a sacrificial keel runner plug. That would serve to protect the exposed end grain of the runner and extend the bearing surface for the shaft right down to its final emergence. It would also stop the tube short of entering the runner, but would it be any advantage over the tube and bearing both coming out onto the surface?
UHMWPE rudder bearings for the rudder tube, and the top one sitting in the tube.
In the end I decided to use the plug, bored out to 25 mm. to avoid friction, so I glued it back into the runner on the work bench.
The plug being glued back into the runner
and with the rudder shaft in it prior to enlarging the hole for full
clearance.