20 APRIL 2015 http://www.marinemodelmagazine.com
shorter time (lead melts at 327 degrees C). I made a tray to hold
the mould out of MDF (in retrospect it would have been better to
make a tray out of aluminium – MDF doesn’t like being heated in
an oven much over 200 degrees C). The pattern, suitably polished
many times with Carnauba wax, was suspended over the tray and
the mixed two part silicone rubber was poured into the tray to form
itself to the contours of the pattern. Once the silicone rubber set
the pattern was removed from the mould (it literally popped out of
the mould - surprising me immensely as I was expecting to struggle
with its removal). The mould now needed conditioning for several
hours at an increasing temperature in the oven in order to prepare it
for the casting process.
Prior to melting the lead the mould was heated in an oven to 200
degrees C.
Now goggles, breathing mask and suitable protective clothing
were worn for the next operation which also had to be carried out
outdoors!
The lead was weighed out (including a 10% allowance for losses
in the casting process) and then melted on a camping gas stove
in a cheap stainless steel aluminium bottom milk saucepan bought
from my local Wilko store for £4 (it’s no good now for milk!). Once
the lead was molten it was skimmed quickly with a piece of wood
to remove the scum on the surface and then poured gently into
the heated mould. It took a few minutes to set and then needed a
further 30 minutes or so to cool down. It was then removed from
the mould and I now had one half-ballast. The silicone rubber mould
had also stood up well to the molten lead (so far it has made six
half ballasts and is still going strong though with some slight crazing
on the mould surface).Completed sail and rig bag which is working well for the purpose
Cutting out a sail and rig bag made from Swiftec Antinox of transporting and protecting the sails and rigThe two half ballasts were then cleaned up with a Permagrit file
and adjusted so that they weighed the same amount each. Carbon
fibre cloth (200 g per square metre) was then laminated to the flat
surface of each half and once set was trimmed to size. A slot for
the fin was cut in each half using multiple cuts on a table saw set
to a depth of 2 mm. The slot for the fin was 20 mm deep and was
achieved by setting a stop on the saw table at this position. The
slots were then filed out and cleaned up. A piece of lead sheet of
2 mm thickness was cut to the shape of the half ballast and a slot
was also cut in it for the fin. The three parts were now joined using
epoxy resin and once set the whole ballast was sheathed in a layer
of 160 g twill glass fibre cloth. The various stages of the operation
can be seen in the accompanying photograph and the painted keel
and ballast is also shown on the photograph of the Goth XP.
Now I have overrun slightly in the column this time so I must
hold over the making of a sail bag from Swiftec Antinox to next
time. However, I have included two photographs showing its
construction.RefeRences
http://www.mobilemarinemodels.com for Mobile Marine Models,
suppliers of the Euro Girl tug
http://www.cmyachts.co.uk for CM Yachts, the supplier of the MX 14
IOM yacht
http://www.mbfg.co.uk for MB Fibre Glass, the supplier of high
temperature silicon moulding rubber
Swiftec Antinox floor protection corrugated material obtainable
from Wickes and other builders’ merchants
[email protected] for John Brinkler’s email address MMIp18_MMAPR15_SailFree.indd 20 9/3/15 12:03: