Mast Base
Repair Methods
Mast Base
Repair MethodsAny of the methods, ideas or techniques for mast base repair are used at your own risk. By reading and using this website you agree to hold harmless the owners of this website. BTW: The current webmaster has not tried out these personally but they appear to be well thought out.
The mast base repair listed below is more extensive than the first method. It comes to the Cal 25 Community via former Annapolis Cal 25 owner Dave Godwin.
I used 2 sheets of 1/2" marine grade plywood. This was
the wrong thickness but it was what another Cal 25 owner told
me to use. The thickness appears to be 3/8" but you may wish
to check this. It did not cause me any real problems. As far as
the marine grade vs. regular plywood usage is concerned, I don't
feel that it is much of an issue if you are going to do as you
said vis-a-vis sealing it with West System. I would just remark
that you may want to do a cost comparison of marine ply against
using the amount of West System to cover it as the West is
relatively expensive.
The factory used a bi-axial cloth on the interior ceiling side
of the plywood and I did the same. This probably gives it an extra
measure of stiffness. I used a light (approximately 10 oz.) cloth
and wetted it with West System with 209 Tropical hardener. I did
this because I wanted the interior ceiling finish to mimic the
original which was clear coated but frankly I would not do this
again. I would just paint it.
Prior to pulling the old overhead out, I made 2 templates out
of cardboard, port and starboard, split longitudinally down
the center line of the boat. These helped greatly when creating
the new overheads. I was able to do create the two overhead sheets
in my garage and have everything ready when I got to the boatyard.
It appears that the factory used standard plywood 8' by 4' sizes
wherever possible so when you go to remove the old plywood, you
will find that it is two sheets, joined on the centerline of the
boat and extending forward from the cockpit bulkhead to the bow
for 8". This places the butt joint to the v-berth overhead
somewhere around the aft end of the forward hatch. In my case
and the other Cals that I have inspected, this will almost certainly
be where your rot ends/starts. On almost all the boats that I
have looked at, when creating/cutting the new overheads, don't
go too crazy trying to get tolerances tight. Keep them wide and
use fiberglass fillet bonds and West System Low Density filler
to hide the gaps. Much easier and better looking.
When you are ready to start pulling the overhead out you will
(may) need to remove the mast beam. This is easy. Remove the chainplates.
Use a sharp chisel and cut the fillet bond on the beam on the
forward upper side. The beam will probably still be bonded to
the plywood but this can be pulled/pried away using a linoleum
scrapper. Buy one (linoleum scrapper.) If you're not familiar
with them, they can be found at Home Depot, good hardware stores
that carry real tools, etc. It is simply a triangular steel blade
that fits on a wooden handle and is used to scrape old linoleum
off of floors. Get one and put it on about a 6' handle. Keep it
sharp with a file. This is what you will use to peel the old plywood
away from the deck and will make this task much, much easier.
Prior to using the linoleum scrapper, I used a Skillsaw to cut
the overhead into small segments. This helped. The rotten wood
will fall right off, the good with a strong bond will be the hard
part. After all the old plywood was off, I ground down any ridges
in the underside of the deck. Check the sub-beam under the mast
step-up for signs of rot. If you decide that you need to replace
the beam at some point, I built a lay-up jig based on the arc
and width for the boat and donated it to the Chesapeake Cal 25
fleet.
If you haven't already, take out the windows and the forward hatch.
When you are ready to put the new plywood in, set the Skillsaw
blade to approximately 1/4" (or less) depth and score the
deck-side of the new pieces of plywood in fore and aft lines about
6/8" apart. This will help adhesion of the wood to the Fiberglas.
Mix the West System 105 epoxy with the 206 Slow Hardener (you'll
appreciate the working time) with plenty of 406 Colloidal Silica
so that the mixture is quite thick. Test it by pulling up the
stirring stick with an amount of the mixture still on it. If the
mixture runs off at all, it is too thin.
Wear a good mask! Silica in your lungs is there to stay!! <--Make it a point to actually do this!
Anyway, make the mixture thick otherwise you be wearing it.
(Your mixing stick should remain verticle if you let go) Use
a vinyl flooring trowel with ridges to spread the mixture on.
Should be just like applying flooring.
Prior to installing the overhead, you will need a large stock
of 2X4's. These need to be cut to individual lengths for propping/applying
pressure from the underside after the deck. Make them so that
you will whack them into place with a maul. I strongly recommend
cutting all the required struts and doing a dry-run with all of
these prior to putting the epoxy on. Use as many clamps as you
can lay your hands on around the windows and hatches. Tape plastic
all over and around the interior of the boat because the epoxy
is going to go everywhere. Cut square pieces of plastic to use
where ever you clamp and/or prop to keep any excess epoxy from
bonding your clamps to the overhead plywood. Get lots of rubber
gloves. I got a couple of boxes of medical Exam Gloves at $5.00/box
of 100. (Vinyl gloves are more durable. ed) Much cheaper
and better than those things that West Marine and West system
sell for inflated prices...
Anyway, when you are ready to glue everything into place, here's
a tip for applying counter-pressure on the top of the deck. Obtain
4/6 large trashcans (30 gal?). Place them strategically on the
deck and fill them with water. When you're done. just empty them
over the side. I've seen people lug cinder blocks, bags of rocks,
bags of sand onto the boat to get weight up there. I'm lazy...
That's my version of doing the deck. The other way and the way
that I was originally going to do it and still the best way is
to take everything out of the boat, flip it upside-down and set
it on two large sawhorses. Everything ends up being at waist-level.
Anyway, that's another story.
Good luck,
Dave
When constructing the jig, use the full width of the 1x6". This allows you to also use the full length of the 4x8' plywood that you will use for the beam. When the beam is done, you simply cut the ends to fit inside the boat. This is important: Save the ends from the original beam in order to duplicate the compound cuts that will be required on the ends of the new beam that you are building.
When drawing the line on the 1x6 that represents the curvature of the beam, I used a good piece of fir molding (thin). It bends on a pretty even radius. Measure the height from the bottom of the 1x6, mark it and partially drive a drywall screw in at that point. From there you can start bending the molding down to the edges in an even curvature. Scribe the resulting curve and cut with a jigsaw. Use this piece as a template for the second 1x6.
Cut the 2x4's in the appropriate lengths, place them in-between the 1x6's and orient in the direction of the force of the clamps. The 2x4's don't need to be precise, just something to hold the bottom edge of the clamp. Screw the whole thing together with drywall screws.
When laying up your beam, cover the jig with clear plastic, tacked in place with a staple gun, otherwise the jig will become a permanent part of your new beam.
Good luck,
Dave
More instructions on repairing the Beam can be found in this PDF file. You will need to go to www.adobe.com to get the reader.
The above text is also available in MS word format.