Ola Fremming's homepage

Canopy of carbon and epoxy.

There may be several reasons for wanting to exchange the original translucent canopy with one made of carbon-fiber.  My own reasons are the following :

• Weight reduction, a typical translucent canopy is 30-40g heavier than one made from carbon-fiber. 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-fiber it's OK.   

• Looks. Some find a shiny carbon-fiber 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/m^2. 

	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 carbon/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 into 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 little rough to get it out of the mould.  The mould is also flexible that helps the de-moulding.  Put it back into the mould and let it harden properly.

=== DONE ===