[Public-List] Cockpit deck core job

[Gordon Laco]

Hello friends - 

This past weekend I completed a long postponed job replacing the deck core
in SURPRISE¹s cockpit sole.  It was much easier to do than I anticipated and
I am very glad it is done.    This is a long email... Only those interested
in core jobs need read on...

The problem was first identified several years ago by an unauthorized
visitor at our winter marina who took it upon himself to go over my boat
with a moisture meter and reported to me that I had a problem developing
around the rudder head in the cockpit sole.  I should have been grateful for
the early diagnosis...but being human was miffed at the invasion of privacy.
Oh pride.

Over the next several seasons I began to notice movement in the sole toward
the after end... Which year by year crept forward.  During the last two
years visitors were making jokes about the Œnice¹ feel of the soft deck on
bare feet... And the creeping trouble was half way to the wheel¹s pedestal.
This spring I decided that I had to take action, mostly out of fear of
having to dismantle the steering gear as part of the fix.

So, Friday morning last weekend I removed the bronze rudder head and
addressed myself to the contortions required to unbolt the bronze plate
holding the top of the rudder shaft.  Much to my surprise only one bolt when
all the way through... The other three were very short and didn¹t penetrate
the sole.  Oh Whitby Boatworks... Good builders, but not fine builders!

With six Dremel cutting blades on my vert axis electric tool (anybody know
what they are called?)  I cut a rectangular section around the sole... I am
glad I bought the hardware store¹s whole stock because I broke five and the
last one was likely on its last legs when I finally completed my
circumnavigation of the sole.  I laid the tool aside and began prying up the
top surface.  Very much to my surprise it came up intact and solidly stiff
with the only resistance being the more forward and edge areas where the
balsa core was still good and adhering to the top skin.  I achieved
separation in those areas by pounding a hatched head in as a wedge.

The bad core was sopping wet and black.... That came out easily.  The merely
wet and the Œgood¹ core was tougher to scrape and chisel off but not really
hard to do.  I was surprised at how thin the remaining lower surface of the
lamination was.  I was also surprised at the area where the rudder shaft
came up through the sole.  The hole was large and very irregularly cut with
not trace of any protection for the exposed balsa.  Once the caulking got
old around the rudder head plate and water started getting in...the balsa
core had no defence whatsoever.

I dug under the edges of my opening, pleased that I was digging out nice dry
balsa (except one area but decided not to worry about it too much) and
sanded the top surface of the lower skin.  I then scrapped and sanded the
lower surface of the top skin, and beveled the upper edges of the top skin
and the rim of the cut all around.

For the new core, I decided to use marine plywood, which I cut to fit the
core I had removed and further cut with a close matrix of 1 1/4² holes with
a hole saw.  I mixed up a thick paste of West Epoxy and pushed it into the
cavity I had dug all around the perimeter of the excavation.  After painting
the lower surface with raw epoxy I covered it with a mash of the thickened
version, and pushed down the new plywood core.  (I had also painted its
lower surface and all edges with unthickened epoxy).   The surface of the
lower skin was not quite flat so I piled bricks on the plywood to keep it
down.  (despite that precaution I lost my nerve late that night and drove
over to the boat to reassure myself that the plywood had not Œfloated¹ up on
the epoxy!)

The reason I drilled the holes in the plywood was to create Œreservoirs¹ so
that I could make sure there were no voids under the ply.  After pressing
everything down I squatted patiently and kept adding epoxy to the holes
while monitoring which ones were draining.  Eventually all the holes were
full and overflowing, telling me that the under surface was filled with
epoxy both thickened and unthickened.

The next day I went to the boat and cleared away the bricks... Oh joy the
new core was absolutely solid.  I belt sanded off all the upwellings of
epoxy and my joy was increased when I confirmed that the old top skin fit
perfectly; the new core was at just the right depth.

I painted the top of the new core and the bottom of the old skin with
un-thickened epoxy...then smeared the top of the core with a thickened mix.
I toweled the thickened stuff into the space around the edges...then
carefully positioned the top skin on so that the imprint of the bronze
finishing fitting for the rudder shaft was in the right place.  Back on top
went the bricks.  I again squatted over the job pouring epoxy into whatever
voids appeared around the edges.

I then turned my attention to installing the new bow pulpit bought for me by
the marina to replace the one mangled by a truck in the fall... Discovered
that it had been made of sub-grade 7/8² tubing instead of the much stronger
1².  Not wanting to make a scene about it I went ahead trying to talk myself
into accepting it while the complications making it fit grew.  The final
straw came when I discovered that the base plates were much smaller and
barely covered the old holes in the deck.  I didn¹t want six holes at every
base... So since I would have had to re-epoxy all the old holes I went and
talked with the Marina.  Much to my relief they immediately agreed to have a
proper spec¹d pulpit made.  They are good people.

After the epoxy cured I sanded the edges... Replaced the plate around the
rudder shaft and Voila... New solid cockpit sole done.  The only part of the
job I am not so happy about is the finishing of the Œwound¹ where I made the
cuts.  Because I will never be able to make them invisible I have
concentrated on making them smooth and covered them with white paint.  This
has resulted in a bright white rectangle on the cream coloured gel coat but
I guess I can live with that.  If it really bothers me, I will cover the
whole sole with the fake teak Œplasdeck¹ material.

I have trouble brewing in the core around the chainplates and some of the
life line stanchion bases... That will keep till next year.  I am not afraid
of this job any more.

The best part is that it is still only the beginning of April!  We have had
such a mild winter here that but for a few weeks I could have kept my summer
car on the road all winter.  I still have three weeks before my intended
launch date and all the big jobs on the boat are under control.

Gord SURPRISE #426