Canopy of carbon and epoxy.
There may be several reasons for wanting to exchange the original translucent canopy with one made of carbon-fibre. My own reasons are the following :
-
Weight reduction, a typical translucent canopy is 30-40g heavier than one made from carbon-fibre. In addition the cockpit interior is not visible saving weight of pilot etc. and the cockpit floor can be removed to save another 30-40g.
-
More room inside fuselage. Some models with one-piece wings have limited space between wing and cockpit floor. To make more room for fuel-tank in CG-area the cockpit floor can be removed. With a translucent canopy this will not be pretty, with one of carbon-fibre it's OK.
-
Looks. Some find a shiny carbon-fibre surface more beautiful than a translucent plastic canopy. Some models comes with a totally clear canopy, in air this is invisible making it look like a part of the plane is missing.
First of all, I use the inside of the original translucent canopy as a mould. The carbon-cloth that I use is of weight 200g/m2.
The
interior of the original translucent canopy are waxed and polished a
couple of times. After that the interior is sprayed with 2K clear
paint. I have been using old and trusty K&B-poxy since it bites good
to epoxy. With Acrylic's a second thin coat must be painted immediately
before the carbon-copy is made. If not the clear paint will not stick to
the corbon/epoxy matrix.
A
suitable piece of carbon-cloth is cut.
The
carbon cloth is put inside the 'mould' and shaped to get a good fit inside the
mould. Some stretching must be done.
The
carbon is wet'ed with epoxy using a brush. Work with the epoxy using the
brush, to remove any air-bubbles that can be seen from the outside of the
'mould'.
To
get the epoxy thoroughly int the carbon-cloth it's clever to heat it with a
heat-gun and work even more with the brush. Take care to not over-heat as
this can destroy the 'mould'. The heating decreases the viscosity of the
epoxy and also 'boils-off' most of the tiny air-bubbles that tends to get
created in the crosses in the carbon-cloth.
To
get the canopy out without generating 'cracks' in it, remove it from the mould
after 10-12 hours (using 24h epoxy). It's still a little flexible and can
be treated a litle rough to get it out of the mould. The mould is also
flexible that helps the de-mouldig. Put it back into the mould and let it
harden properly.
=== DONE ===