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Chopped strand mat (CSM) will stick wellA scored surface helps polyester resin
get a better bond to plywoodSlope for shower base drain hole was formed using an orbital sander and 40-grit papernews
View from the
b oat yard
ABOut the AuthOr
Mike Pickles is a foreman at harbour Marine Services in
Southwold. he learned to sail aged four, flirted with an
Olympic campaign in his early 20s and continued with
yacht deliveries and yacht and dinghy racing until his
mid-40s. Now his knees have disintegrated, he is the proud
(and slightly obsessive) owner of an MGrS34 ¾-tonner.
n http://www.southwoldboatyard.co.ukW
e’re currently working
on a Nauticat 33 which,
having just been sold,
has been brought in to
remedy issues found
on the pre-purchase survey – and to
carry out some tLC for the new owner.
The priority job was to install a
compression post as the mast was in
danger of becoming keel-stepped instead
of deck-stepped.
I covered installation of a compression
post on a Seamaster 925 in PBO October
2017, and the solution for the Nauticat
was very similar.
However, we did have to change the
sole board layout, especially in the heads
which also doubled as a shower.
The original was plywood with a GRP
sheath and gelcoat finish on top. Sadly
the underside was never treated and was
merrily rotting away, so as we had to cut a
new-shape board to accommodate the
new stainless compression post, we tookthe opportunity to make a new shower
base too.
The base was to be made so it could be
easily removed. I don't like to make any
areas of the hull inaccessible, so while the
current vogue is to have a permanent,
nicely-moulded shower tray, this is not
compatible with easy access to the inside
of the hull.
The base itself is a strange shape, so the
first job was to create a template using 2in
strips of hardboard and a glue gun. Using
the template, the 19mm marine ply canthen be cut out – and once a decision has
been made on the position of the drain
plug, work can be carried out to make the
flat surface somewhat less flat.
We used a small orbital sander and
40-grit pads, and got creative. It's hard to
get GRP to go round tight external turns
such as sharp edges and corners, so as
this base was to be sheathed, all the
edges and corners had to be rounded off.
We were using polyester resin, and to
ensure a good bond between the ply and
the glass I tend to use chopped strand
mat (CSM) for the first layer. In my
experience, this has a far higher bond with
a plywood surface than woven cloth.
So to start the sheathing process on the
bottom face of the base we first coated
the plywood with resin using a brush.Go easy on the resin
Paint it on – don’t ladle or pour – and then
spread it about. All you need to do is wet
out the surface before laying on a layer of
pre-cut 250gm CSM. Then, using a brush,
add another light coat of resin before
consolidating the layer with a roller.
If you have any dry areas, add a little
more resin – but the trick is to use as little
as possible. Resin has very little strength
in itself, and using too much might speed
up the wetting-out process, but the
laminate will be resin-rich and as a result
will be weaker, brittle and less likely toShowered with praise
Mike Pickles builds a shower base for a Nauticat 33 and explains
how to seal it against the wet environment itÕll be facing in the heads