How to Make a Fiberglass Cowl

Written by jay kurz
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How to Make a Fiberglass Cowl
Fibreglass is commonly used in model aeroplanes. (aircraft model 6 image by Alexey Kuznetsov from

A cowl is the front section, or nose, of a model aeroplane that is commonly constructed using fibreglass. In order to have a surface to apply the fibreglass to, you must build a mould for the cowl. You can build a mould out of anything that can be formed into the shape you need, such as clay, wood and plastic. Another material that can be used for a cowl mould is a dense foam that can be found at all craft stores. This is the cheapest and easiest way to mould a fibreglass cowl for an remote control plane.

Skill level:

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Things you need

  • Dry foam brick
  • Marker
  • Compass
  • Coping saw
  • 100-grit sandpaper
  • Masking tape
  • 56.7gr. fibreglass mat
  • Razor knife
  • Rubber gloves
  • Polyester resin
  • Catalyst (methyl ethyl ketone peroxide)
  • Small bucket
  • Paint stir
  • 4-inch felt roller
  • Air roller

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  1. 1

    Determine the diameter you need the cowl to be. Using a dry foam block that is larger than the cowl will be, draw a circle to that diameter on the bottom or base of the foam block with a compass.

  2. 2

    Carve the foam block into the shape you want by using a coping saw and 100-grit sandpaper. Start by trimming the foam the long way into a bullet shape, staying on the outside of the mark you made for the diameter. When you get close to the final shape with the saw, begin sanding it smooth and rounding all edges off.

  3. 3

    Cover the entire foam mould in masking tape. Avoid any inconsistencies in the tape such as creases or bunched up areas.

  4. 4

    Cut a total of four layers of 56.7gr. fibreglass mat that will cover the entire mould using a razor knife. Make relief cuts in the mat anywhere it might bunch up or not lay flat such as on the nose of the cowl mould.

  5. 5

    Fill a small bucket with polyester resin and add one to two per cent catalyst. Thoroughly mix it in using a paint stir. Saturate the surface of the mould with the resin using a 4-inch felt roller.

  6. 6

    Cover the mould with the first complete layer of fibreglass mat and saturate it with resin using the felt roller. Work out all the wrinkles and air bubbles in the mat by going over it with an air roller. Apply the next layer and continue this same process until the four layers of mat are on the mould. Let the fibreglass harden for a couple hours or until it's hard and cool to the touch.

  7. 7

    Remove the foam from the inside of the fibreglass cowl. Sand the cowl smooth using sandpaper.

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