Polystyrene

 3 November 2020

Making a lightweight slab-sided fuselage

• Draw the fuselage profile on the polystyrene sheet and cut it out roughly.
• Draw the cut-out on the foam blank but remember to leave a perimeter of foam around the cutout.
• Carve and sand, round the edges of the foam blank before making the cut-outs.
• Do not cut across the perimeter foam around the cutout because glue is heavier and does not add strength.
• Insert and glue foam formers in the cutouts if the cutout is too long or too large. The idea is to ensure sufficient foam for the odd knocks without breaking. The foam will retain its shape.
• Cut 2 pieces of paper to cover the cutout hole.
• The 1st piece of paper is just about 3-5mm bigger all round then the cutout hole. 3-5mm is enough, anymore is just extra weight without adding strength.
• The 2nd piece is the same shape and size as the 1st piece except that if there shall be a hatch, for example, to allow battery or receiver removal, then cut a hole to the shape of the hatch on the 2nd paper piece. The hatch cover shall be 3-5mm bigger then the hatch.
• After gluing the paper pieces to both sides of the foam fuselage, it is time to cover the fuselage, perhaps with tissue. Remember to cover the hatch cover too.
• Devise how the hatch cover is hinged and held in place. Tape, loops, magnets can call be used.

To have a 'proper' cross section of the fuselage, just add blocks, formers and stringers before final shaping/sanding and covering. This adds weight.