build it.” Well Anton, we did build it, and
thank you once again. And we hope the
wine was OK.
Another person who was superbly
helpful was Ray Mathews, who was
commodore of the Royal Cape Yacht Club
at the time, and organised for the plasma
cutting of our hull plates.
It was incredible to see how the plates
for the whole boat were cut to shape in
about an hour: they were delivered that
same evening.
Our excitement was uncontainable as
we handled parts of our boat for the first
time. Ongemak is a hard chine boat, so
each plate is as long as the boat, although
quite narrow. The wonder, with aluminium
being so light, is that two people can quite
easily manoeuvre these long plates.
So they were dragged across the lawn
to the back, but didn’t remain there for
very long. Over the next two weeks they
were moved again, into the shed and onto
the cradle, where they were to stay for
nearly five years.
At the time of delivery we’d already built
the cradle in which the boat had to lie. It is
made out of mild steel and is rugged and
strong. But we had made it with the
utmost care, accurate to a few millimetres,
because in this the hull plates had to rest,
and it ultimately determines the shape and
symmetry of the boat.Speedy stitching
What followed was fantastic – something
close to immediate gratification: every day
we hauled one of the plates onto the
cradle, and tack-welded it to the one
underneath. Each tack-weld is only two or
three centimetres long, and the purpose is
to temporarily hold all the plates in the
right position. So, lo and behold, after
eight days we had a beautiful shining
aluminium hull next to our house.
The seam welding, however, took manyTo accommodate the depth of the keel in
the lean-to shed a hole had to be dug in
the ground!During the five years of the build the hull plates were supported in the carefully
constructed mild steel cradle
weeks. The welding on the outside of the
boat was done first. It is important to make
welds short (about 20cm) and to scatter
them along the length and also between
port and starboard. This prevents
distortion caused by built-up heat.
This took a long time because the
welding machine constantly had to be
moved, and furthermore every single weld
has a cold start which had to be cut out, in
our case with a special disc we had on the
angle grinder.
Of course, at that stage, we were still
new to the game of welding, our bodies
were not used to a whole day’s manual
labour, and much time was spent figuring
out where to do what.
Still, the boat grew, and with it our
abilities. It’s a wonderful feeling when
equipment becomes almost an extension
to your body, being used without any
great effort.
Next came the inside. It was a relief not
to weld upside down for a change, but
first all the back-cutting on the inside had
to be done. This involves cutting a groove
along the joint of the plates at the inside
so that, once welded, the exterior and
interior welds are fused without voids. The
stem was also fitted during these early
stages, a big heavy tapered bar.Building a keel
The keel is a big job and it was frankly
difficult. I have a strong suspicion that
nothing I read on aluminium keel
construction was written by someone who
ever did it themselves. Of course we now
know exactly how to build the next one!
The first step was to strengthen the hull
somewhat. So we fitted the stern plate,
deck stringers and foredeck.
Then we moved into the garage, where
the keel was constructed. It is basically an
accurately made aluminium tank, into
which the lead can be poured.
It contains vertical floors which run all
the way down for strength. The one side
of the keel can simply be welded to these
floors, but there is no access to weld once
the other side is on, so slots must first be
cut to enable welding onto the floors.
Having cut the side full of holes, they
then have to be welded up very carefully,
because if not salt water will enter, and
galvanic corrosion would occur between
the lead and aluminium.
This requirement is so strict that you
have to temporarily weld a lid onto the top
of the keel, and then pressure test it to
check for any leaks.
I should add that some aluminium boats
have normal external lead keels, with a
non-metal gasket between it and the boat,
and it is attached with normal keel bolts.
The advantage is probably that you’dPractical Boat Owner • http://www.pbo.co.uk 79BUILD AN ALLOY SLOOP
‘Our excitement was uncontainable as we
handled parts of our boat for the first time’