Drilling through fiberglass hull

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Tips and tricks[edit]

Fiberglass and gel coat are easy to work with, but difficult to work with properly. Screwing into fiberglass and gelcoat or drilling into fiberglass and gelcoat often results in cracks. A few tips and tricks to prevent this:

  • Use masking tape over the area that you're drilling. This is the single biggest thing you can do to prevent cracking
  • When drilling a pilot hole for a screw, ensure that the drill bit barely is sufficient for the girth of the screw and well less than the threads.
    • Cracking often occurs when screwing in a screw because the hole was not large enough for the screw body so the screw exerts outward pressure to force itself in creating stress and cracks. The hole should be snug, but not force the screw to create it's own space in the material.
    • Stripping often occurs when the hole is too large for the treads to have adequate gripping power on the fiberglass core. While you don't want to small of a hole, a too large hole is equally dangerous.
  • Put a touch of 3M 5200 or 4200 - if below waterline - or 4200 or 3200 - if above the waterline - over the hole before inserting the screw to prevent water entering and rotting the surrounding glass or wood.