Mould manufacture
In order to create the fibre glass blades, an original sample must first be
produced. A mould is then made from this sample. The mould can then be
used to make numerous ‘copies’ of the original sample. This was the basic
mould manufacture process used.
1: Firstly, a wooden wind turbine blade sample was built. The process to make
this blade, along with its size and shape, is given in ‘How to build a wind
turbine: the axial flux windmill plans’ guide.
This blade must be very accurately made as, once a mould is created, any
imperfections will be repeated in all subsequent blades.
2: The outer surface of the wooden blade sample was given a layer of resin in
order to create a hard surface. See ‘Blade half manufacture’ chapter for the
resin mixture required. ‘Outer layer’ resin mixture was used. This was left to
dry and then sanded down. Another layer of resin was then applied, again
sanded down when dry. (Varnish should not be used as this may react with
the resin).
Note: This step may not be necessary depending on the type of wood used
(tests could be done on a scrap sample of wood first).
3: Once dry, a number of coats of wax must be built up on the wooden blade
sample. At least five coats should be applied, buffing the surface after
applying each layer. A good quality mould release wax should be used to do
this (‘Durawax’ used in this case).
4: Now the actual mould can be created. This is made in two halves, with the
joining points along the two edges of the blade (leading edge and trailing
edge). This is to allow the easy removal of the pieces from the moulds.
Note: The blades could be manufactured with a stand to ensure they will sit
horizontally. This was not done on the moulds we produced and this caused
some problems.
Strengthener
Stand
(to keep the mould horizontal)
‘Outer layer’
resin mixture
on these surfaces
Windward blade half mould
Wooden blade
Backward blade half mould
Strengthener
Stand
(to keep the mould horizontal)
This image shows the cross section
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