To make one mould, the waxed wooden blade is covered on the correct side
with hard ‘outer layer’ resin. Layers of chopped strand fibre glass mat (CSM)
and additional resin are applied to build up a thick layer over the wooden
blade. The thicker this layer is, the stronger it will be. In our case this was
approximately 20 layers thick. The more expensive ‘outer layer’ resin need
only be used for the first few layers. After this then cheaper ‘inner layer’ resin
can be used. Also, to build up the mould, a mixture of resin and talc can be
used to reduce the cost of the resin and to allow even drying of thick sections
of resin.
Due to the length of the blade, this layer will not be rigid enough to be used as
a mould (it may bend). Some form of additional strengthening is required. This
must run along the whole length of the mould to stop it flexing. In this case a
long piece of high density foam was used as a former. Fibre glass and resin
were then applied around the foam to form a strong box section of fibreglass.
When dry this made a very strong beam running the whole length of the
mould. The former could also be a piece of wood – anything easily available
to give strength to the mould. (nb. The rigidity in the mould comes from the
‘box section’ fibreglass – not the material of the former).
5: Repeat for the other side of the blade.
6: Cut the sides of the two mould halves so they fit together neatly.
7: Sand the inner surfaces of the mould well so that it is smooth. Any
blemishes will appear when used to make the fibre glass blades.
WINDWARD
PAPER
PLYWOOD
MOULD
TEMPLATE TEMPLATE
BACKWARD PAPER
MOULD TEMPLATE
PLYWOOD
TEMPLATE
It is estimated that moulds made in fibreglass have a life of 50-60
manufactured pieces.
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