PRACTICAL
Is ventilation a viable alternative
to dehumidifiers? According to
Richard Hare, it remains so
To vent or
not to vent
I
was as nervous as the
next man when it came
to leaving upholstery,
cushions and curtains
aboard Keppel during
long, damp UK winters.
But then during Keppel’s 10
years wintering in various mainland
European locations, I had no
alternative but to do so. And when
that edgy moment arrived each
spring, as the washboards were
unlocked after seven long winter
months, we were always relieved
to find her dry as a bone within.
From the first night onwards we
slept well in dry sleeping bags on
dry berth cushions.
But that was ‘there’, then. What
about ‘here’, now? Would it be the
same after a UK winter? Would
ventilation be enough to keep
interior furnishings and electrics
damp and mould-free? Ventilation
alone had always kept my former
boat sweet. She was, and remains,
a clinker-built Finesse 24, ventilation
being the norm for a wooden boat.
In Kilter’s case we did remove the
entire contents of the cabin, and
raised some sole boards and
locker bin lids. Left with her boat
cover open both fore and aft, a
...the inner forehatch set on
‘vent’, plus two open Ventlites...albeit with an open
washboard vent, and...With a rainproof but breeze-friendly cockpit tent (and watertight
windows), Keppel weathers all the UK can throw at her...March 2015: The upholstery that was stored in the forecabin during
the UK winter was ‘drizabone’
steady breeze blew though her
innards – yes, some snow too –
but she was invariably as fresh as
a daisy come springtime.
But let’s return to the GRP-hulled
and wooden-topped Keppel. Last
winter I put my money where my
mouth is. I left almost all her
upholstery on board, in East
Anglia. My aim was to demonstrate
to myself at least that ventilation, a
free force of nature, could work just
as well in northern latitudes as is it
did in the more southern ones.
During her time abroad Keppel
had overwintered in two locations
with winter weather not dissimilar
to Suffolk – Rochefort on France’s
Atlantic coast and St Jean de Losne
in Burgundy. The good results
achieved at both boosted my
confidence. So, with her cockpit
tent rigged we left Keppel to breathe
on the hardstanding at Robertsons
Boatyard. As before, we left her
with the aluminium forehatch on
the ‘vent’ setting, two open Ventlites
(one above the hanging locker, the
other above the heads) and then
there’s the washboard grill that’s
permanently ‘open’. Although the
cockpit tent is weatherproof insofar
as it excludes rain, there are plentyof places for breeze to whistle in. It
is by no means hermetically sealed.
And at the end of the winter? All
the soft furnishings were as dry as
ever and there wasn’t any mould
anywhere, other than some very
small traces of it on the curtains.Med venting
Although the cockpit tent is rigged
during northern European winters,
we used to leave the cockpit
uncovered during the five
Mediterranean years. This was as
much to do with savage winter
wind damage as anything else: the
Golfe du Lion mistral is merciless.
Here, although Keppel’s interior
remained very dry, her iroko cockpit
seats did attract mould, but less so
in Ionian Greece, this being a part
of the Med that is notorious for
prolonged winter rain. With
hindsight, this surface mould
problem could have been avoided
with the simple expedient of
brushing bare wood with a
fungicide wood preservative once
every two or three years – Cuprinol,
for example. (See ‘Keeping mould
at bay’, PBO February 2013.)How does it work?
The usual cause of excessive
relative humidity below decks is the
accumulation of water within the
cabin, most obviously in the bilge.
This is commonly caused by leaks,
be they from windows, hatches,
failed deck fittings, dripping stuffing
boxes etc. In our case, leaks are
very minimal, if at all.
For boats that suffer from a steady
ingress of water into their interiors
we need to ensure that it is
removed. Failure to do so leads
to soaring relative humidity in the
cabin, moisture contents going up
as a result, and mould everywhere.
So, the water/humidity cycle has
to be broken. Automatic electric
bilge pumps can be deployed to
remove liquid water, and electric
dehumidifiers will keep relative
humidity under control. However,
both rely on electricity and both can
fail. If a boat is left unattended for
seven or eight months a year it
almost goes without saying that
this is far from ideal.
Alternatively, Old Ma Nature can
take care of the whole shebang for
free. Every picture tells a story.