PHOTO ABOVE : GRAHAM SNOOK/YMTECHNICAL
76 http://www.yachtingmonthly.com MAY 2016
more problems: crevice
corrosion, lack of backing
pads and small washers.’
On solid GRP decks, it’s
best to tighten fi ttings
down onto a large a marine
plywood backing pad – at
least one and a half times
the footprint of the fi tting,
with large washers under
the nuts. On some boats you
may fi nd just penny or even
halfpenny washers.
The core problem
Balsa or foam cores make
for lighter, stiffer decks
but through-bolting deck
fi ttings, besides crushing
the core, may also allow
water to seep in. This can
rot a balsa core and saturate
a foam core causing
delamination.
In modern yacht
construction the foam
core stops before most of
the deck hardware and
aluminium or stainless steel
backing pads are glassed
in during manufacture. If not,
cutting out the foam around the
holes either by making the hole
larger or by putting the long end
of an Allen key in a drill chuck
and the smaller end in the hole,
moving it around before carefully
starting the drill to mash up the
foam core, then fi lling the voids
with epoxy. For non-GRP decks,
backing pads like those for solid
GRP are recommended.
If installing your own fi ttings,
always gently countersink holes
drilled in glassfi bre. This helps
prevent stress cracking roundthe hole and allows the
bedding compound to form
an O-ring when the bolts
are tightened. Use locking
nuts, cut off excess lengths
and burr the ends to ensure
the nut won’t work loose.
Never put sealant on the
below-deck backing pads.
Under-deck sealant holds
the water in the core, or the
glassfi bre laminate itself,
without you being aware of
a problem. A combination
of metal, water and
confi ned spaces is a great
recipe for rotting cores and
encouraging corrosion.
Bolts, even of stainless
steel, can rapidly corrode.
You may not even see a
rust mark before they fail
and the deck delaminates.
A quick inspection with a
digital camera or camera
phone can help you see
hard-to-get-to places.
Do not rely on an
anchor windlass to hold
the cable fast, all windlass
manufacturers recommend tying
or cleating it off – the windlass
clutch isn’t designed to take the
loads. If your cable is all chain,
use a long snubber that passes
out through bow roller; this
lessens the snatch load on both
cleat and roller and will alsogive those in the forecabin a
quieter night’s sleep.
After the bow roller, the fi nal
possible weakest link are the
cleats themselves. The loads on
them are very high when the
boat’s moored in a blow or if
they’re used for towing, made
worse by snatch loading.Sizing cleats
The rule of thumb for sizing
cleats is 25mm of length for every
1.5mm of warp diameter. A 15mm
diameter warp needs cleats
250mm (9.8 inches) long. Many
boats come with undersized
cleats. There are always problems
providing decent backing pads
to fi ttings on the toerail or close
to the edge of the sidedeck,
including chainplates. Even using
penny washers can be diffi cult.
Even though they have no
moving parts, deck fi ttings
are not maintenance-free. If a
fi tting is pitted, it is suffering
from electrolysis. If it has rust
streaks, it’s leaking. Likewise,
dampness below decks warns of
leaks. Smearing sealant around
never really works, and besides,
wouldn’t you want to check the
bolt now, before it’s too late? The
only real solution is to remove the
fi tting and its backing pad, clean
everything thoroughly and then
refi t and reseal it properly. WThis cleat is the right size for the
thickness of rope being usedThis cleat is too small as it’s
already swamped by linesA 260mm cleat has a maximum diameter of rope of around 15mmPHOTO: ALASTAIR BUCHAN PHOTO: ALASTAIR BUCHAN PHOTO: ALASTAIR BUCHANYour bow roller
might have to
withstand the
loads from many
different uses
PHOTO: BEN SUTCLIFFE-DAVIESPHOTO: BEN SUTCLIFFE-DAVIESStainless steel bolts can corrode rapidly. If
they do, reseal the fi tting and replace the boltsThis wooden backing plate is completely
rotten due to a leak through the stem fi tting