Tech-Tip: Coring Material

Coring Material is a very important step in your fiberglass project. Coring is what takes a sheet of fiberglass and turns it into a solid panel, for decks, boats, and so much more. Coring material can give the sheet flexibility, rigidity or even insulation (which is important when making a cooler). We carry several different kinds that offer pros and cons. It’s important to find the material that works best for you.

Honeycomb –


  • PVC honeycomb with a fiber covering.
  • Very flexible and light-weight.
  • Does not rot and has great bonding properties.
  • 5lb density sheet

Diab –


  • Offers several densities (3, 4 and 5lb denisty) for different jobs.
  • Much more rigid than plain polyurethane foam
  • Tan color (used to be multi-colored).

Polyurethane foam –

Polyurethane foam

  • Great in-expensive coring
  • Light-weight
  • Does soak up resin and has a good bond.
  • Does compress if you aren’t using the proper density.
  • Greatest R-Value (insulation) of any of our options.
  • Sold in 2lb and offered in 4lb density

Kay-Cel –


  • 25lb density sheet with 18 oz Woven Roving in the middle
  • The most dense, heavy material we have
  • Perfect for transoms or pieces with a heavy load

Balsa-Core –


  • Seal-coated wood to reduce resin consumption, keeping the weight down and increasing the bond.
  • Very lightweight, and inexpensive solution.
  • Does eventually rot without proper sealing.
  • Very good compression tolerance

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