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Carbon/balsa sandwich preparation
carbon fibre sandwich sheet
I have not found any sources of ready-made carbon/balsa sandwich in the UK, so I make my own. There are many suppliers of sheet carbon fibre in the UK, with different quality and prices.  Wet-lay carbon fibre is cheapest, and "pre-preg"  the most expensive but stiffest and best looking. I have only found one supplier of end-grain balsa sheet.  The suppliers I have used are listed at the end of the document
Tools
Flat hard surface larger than the carbon and balsa sheets
Flat 15mm MDF panel larger than the carbon and balsa sheets
Newspaper/packing paper to cover the carbon/balsa panel with two layers
100+kg of weight, e.g. bags of sand, gravel, salt
Materials
½"  end grain balsa sheet, 500x500mm
1mm thick 500x500mm rigid carbon fibre sheet
Structural epoxy 50ml
Epoxy gun and mixer nozzle
Construction
Construction time: 2 hours
Lightly abrade the non-shiny side of both sheets
Wash both sides of both sheets of carbon fibre
Prepare a hard level surface e.g.15mm MDF square on the floor, cover with a sheet of paper
Lay balsa on surface
Spread epoxy in an even pattern on the balsa surface
Place one sheet of carbon fibre, shiny side up, on the balsa, and press down slightly off-centre. Slide into position to smear the glue around.
Carefully lift and turn over the balsa/carbon sheet, and place carbon side down on the surface
Spread epoxy in an even pattern on the balsa surface
Place remaining carbon sheet on the balsa, repeating the press and slide operation
Cover the panel with another sheet of paper, and place the MDF panel on top
Pile 100+kg of weight evenly on top of the MDF panel
Leave for at least 24 hours.