Mast Step - Cutout?

[ebb]

The depth of the mortise(s) would match the two square protrusions
of the mastbase casting -- which is 1l/16" -- mortice might be 3/4".
{LATER EDIT: This is wrong. See post #6 below here. The fore
and aft thru hole is where the tenons of the mast base fit.}

There is in my original base casting, which is essentially an aluminum
bowl with two cube-like tenons, an open 1 1/4" diameter hole dead
center through the bottom.
This used to have a piece of pipe extended into the mast, obviously
to lead mast wiring through a matching hole in the mast step and
a matching hole through the cabin top. Condensation & rain water
leaking thru these holes have caused a lot of grief over the decades.

Many have closed off the thru-holes when the mast was removed, and
have lead their wires through a watertight deck fitting near the mast
step, wires lead out the side of the mast 6 to 10" above the bottom.
Assume your original 'wire' holes are closed off one way or another.

Assume like almost everyone else you will not be able to remove
the casting from the bottom of the mast without violence. Corrosion
has welded it to the mast extrusion. Imco it should be removed and
something else put in its place, but it's a lot of work. Only my opinion,
but a G-10 insert could be made machined to engage the original
maststep mortise. You would need considerable thickness, but G-10
can be glued with epoxy and tapped for machine screws.

The top of a new G-10 insert would be flat. The insert will be bedded
in with something like Dolfinite, so that it can be taken out again in
the future. The mast inside will be sealed, altho you will see light
through various holes, and the main sheave open 'box' at the top.

You want a drain hole through the mast wall at the level of the insert.

The original casting includes a 5/16" ledge for the mast extrusion to
sit on. The casting used screws to fasten it on to the extrusion. On
A338 it all corroded (and actually expanded the mast) into a single
mass. Sacrificed about an 1 1/2" of mast height by cutting it all off.
Made it up with a taller maststep.

IDEA (to completely seal the inside of the mast from leaking below.)
If you have the mast off the boat, have access to the casting, and
have closed off the original wire access holes into the accomodation
through the maststep. And are able to, maybe , bondo shut the
center hole between the two cubular tenons in the casting... I'd
be considering, if I was not willing to remove the casting, a way to
fill up the bowl completely. You discover that the base casting is not
a solid block but a thick walled bowl about 1/2" at its top to 3/4"
where the ledge under the extrusion is seen at its very bottom.

When the mast is back up and vertical again, drill a couple 3/8"
holes through the mast wall (port and starboard), just above where
you're sure the top of the casting terminates -- about 1 1/2"above
the end of the mast extrusion, where you will find the 1/8 mast wall.
Or predrill those holes while the mast is down and the step is not
in the way. The thought is, to use these holes to inject liquid rubber
into the casting bowl and fill it up to the level of the holes.
This is just an idea. Have not actually done this.*

You certainly can drill holes lower down, but the thickness of the
casting will make it difficult to inject liquid rubber. You will use a lot
more rubber to fill the whole cavity. 8 to 10oz I guess, but more likely
to fill to a known level because your fill holes on either side of the
mast will end up as topping drains for the rubber plug.
Theoretically the liquid will not fill above the two holes if you have
placed them level with each other. I would choose liquid rubber
rather than epoxy because it is least likely to leak out. Epoxy would
be easier to inject. But also more likely to glue the mast to the step,
get out of containment within the mast.
And if you ever have to cut it out, you'll wish you used rubber.

In the interest of later mast removal, make sure you do not glue the
mast to the boat. Amazing what damage a crane can do if the mast
does not readily lift off the step.

Littlegull has a forward lowering mast with a removable G-10 insert
with a slope inside. Where there's a hole to let any water out.
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* Plasti-Dip $7, 14.5oz, may be the cheapest liguid rubber around.
It's for dipping tool handles for a softer grip. It weathers fairly well
exposed. Internally it should last a long time. Used it enough to
know that if you try to save a partial can, it'll be hard by the time
you get back to it. When the mast is vertical: use 2oz TAP Plastics
Syringe Applicators from TAP $3.10. You can dip the nozzle into
the rubber, pull back on the plunger to load the tube, wipe off the
excess, jam it all the way into a fill hole in the bottom of the mast
....and push the plunger! You want to be quick reloading. If you use
white you might see what's going on by shining a light through the
2nd hole. Just an idea...