Article 1.003 – What is the best method to cut holes and openings in the fiberglass?
Holes up to 5mm in diameter can be simply drilled, but large holes (exhaust pipe & cooling shroud exit) should have a pilot hole drilled first and then using a grinding stone attached to a Dremel or equivalent rotary moto-tool, open up the hole to the desired size. In many cases, a drafting circle template can make a perfect guideline to follow. If the cut-out is not round, then use the same approach to drill pilot holes near any curve inflection points and use the moto-tools cut off disks (usually stone or composite) for straight lines and the grinding stone or sanding drum to link together curved sections. Always start smaller working your way up to an outline that you have created at least 2-3mm inside of the final size. Final sanding should be done by hand using sanding blocks (flat, square and round) to achieve a perfect result. As a reminder, if you are cutting holes in a painted fuselage, the edges should be painted with a compatible and generally fuel proof paint to ‘seal’ the
