Wing Joining.

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Some aircraft kits are supplied with a wing joining kit which consists of a 100mm. (4") band of heavy glass fibre and some (very!) thick epoxy resin for reinforcing the wing centre section. These reinforcing kits can also be bought separately if you're building from a plan.

There are two drawbacks to this. One is the rather obvious and unsightly bump where the reinforcing ends on the wing. The other is that from an engineering point of view, there is a marked difference in the wing strength at the wing/reinforcing boundary which is made worse by the fact that the load on the wing is highest at the centre section. This is techno-speak for "If the wings gonnna break, it's gonna break at the edge of the reinforcement!"

There's a real nice way round this problem which is to "feather" the wing reinforcing. All that's required is lightweight woven glass cloth (½ ounce) and 24 hour epoxy resin (the thin stuff!). Both are readily available from your local model shop.

The example shown below is for a wingspan of around 1.8m (60").

  1. Pencil mark lines parallel to the wing centre joint at 38mm (1 ½"), 63mm (2 ½"), 88mm (3 ½") and 100mm (4") on both wings, top and bottom.
  2. Apply masking or self-adhesive tape to the outer lines, top and bottom to prevent the resin speading too far over the wing.
  3. Cut three strips of the glass cloth whose length is twice as long as the centre section chord plus about 100mm (4").

The widths of these three strips should be 75mm (3"), 125mm (5") and 175mm (7").

  1. Mix the resin in accordance with the manufacturer's instructions and apply between the masked off area of the wing with a 20mm (¾") paintbrush.
  2. Carefully apply the 75mm (3") wide strip of glass cloth between the inner two lines, top and bottom. Trim as required.
  3. Carefully apply the 125mm (5") wide strip of glass cloth between the next two lines, top and bottom and over the first glass strip. Trim as required.
  4. Carefully apply the 175mm (7") wide strip of glass cloth between the next two lines, top and bottom and over the first and second glass strips. Trim as required.
  5. Remove any excess resin - kitchen towels are very good for this!
  6. Carefully remove the masking strips.
  7. Allow the resin to harden - this can be "triggered" with the careful use of a domestic hair drier as well as aiding the flow of the resin itself.
  8. Rub down the fibre glass carefully.

Building Tips
Introduction Wing Joining Wing Ribs Graphics Thrust Angles Manifolds Exploding the Myth