How to Shape Dow Blue Core Foam

Written by dakota wright
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How to Shape Dow Blue Core Foam
RC planes can be homemade from Dow Blue Core foam. (rc aeroplane, image by Greg Pickens from

Dow Blue Core foam is a closed-cell polystyrene foam product used to make "foamies" or foam models. Blue Core is commonly called "fan-fold-foam" or "FFF" on modelling forums because it's packaged with a technique similar to folding a paper fan. Each sheet within the fan measures 2-foot wide by 4-foot long. Blue Core foam is popular among modelers because it is lightweight and one of the only types manufactured between two plastic skins. The plastic skins add durability to the finished product without hampering assembly.

Skill level:

Things you need

  • Template
  • Permanent marker
  • Double-sided tape
  • Utility knife
  • Hot knife

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  1. 1

    Lay a template atop a sheet of the Blue Core foam. Carefully mark around the template with permanent marker.

  2. 2

    Cut the excess foam from the template using a utility knife. Doing so makes the foam piece easier to handle. Cut multiple pieces at one time by layering more Blue Core foam under the top template. Attach the pieces together using double-sided tape to prevent movement while cutting. This trick is helpful when you need to cut wings or other parts exactly the same.

  3. 3

    Drag the hot wire foam cutter (hot knife) into the edge of the Blue Core foam. Position the cutter as you would a pencil. Drag the cutter along the lines of the template, as if you were drawing a new template. Remove the excess foam.

  4. 4

    Pierce the foam slowly with the hot knife to create windows, doors, and other shapes from the centre of the template. Drag the cutter around the outline until you meet the entry point again.

  5. 5

    Tilt the hot knife to produce an inner or outer bevel. Holding the foam cutter at an angle produces a bevelled edge along your product. Allow the tool to do the work, instead of forcing a cut.

Tips and warnings

  • Start and finish a cut, even if you must exit the foam, removing small sections at a time.
  • Toothpicks will stabilise the foam in place of double sided tape.
  • Don't use large pieces of double-sided tape; pieces the size of a finger tip are sufficient.
  • Blue Core foam takes longer to cut because of the plastic skin, however this doesn't detract from its popularity.
  • Leaving the foam cutter in one spot for too long will melt the surrounding foam.
  • Hot wire foam cutters damage a work surface if they are left on.
  • Cut foam in a ventilated area.

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