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WING

As the wing is one piece, I find it easier to make up a simple wing jig from pieces of 5 mm thick lamiboard (masonite) 40 cm wide and cut to length to suit the dihedral and polyhedral joints. Off-cuts of this material can be picked up for nothing from most cabinet makers.

Set these up with the correct dihedral and polyhedral (dimensions as shown on the plan), cover with gladwrap and you are ready to start building. For securing the spars, TE and so on, I use a small drill in my Dremel, which is slightly smaller than the pins being used so that I get a nice tight fit using a small hammer to tap the pins in.

Pin the trailing edge in position, and then the lower 3 x 6.5mm main spar, which has to be packed up by a strip of 1.5 x 6.5mm balsa.

As the centre panels of the wing are constant chord, the 1.5mm vertical grain balsa shear web is a constant height, so glue up the shear web separately, cut it to the correct size, then glue it to the bottom spar after the 2.5mm ply dihedral brace has been glued in place. Make sure that it is not crooked and that it lines up with the centre of the top spar.

Cut a nice tight slot for the 1.5mm ribs using two fin-tooth hacksaw blades clamped or taped together. To do this, obtain a hardwood cube with sides of approximately 50mm and line this up against the spar at a rib location. Using the hacksaw blades, gently cut a slot in the shear web at the rib location, using the block of wood as a guide. Repeat this at each rib position, then slide the ribs down into the slots and glue them in position. This is a very fast, easy and accurate technique. Don't forget to slide the rear spar into the ribs as you go.

Use the same technique to do the outer panels, cutting the shear web with the correct mount of taper.

After all the ribs, spars, leading and trailing edges have been glued up, added the 1.5mm triangular gussets, and the riblets (top surface only). On either side of the 3mm ribs at the polyhedral join, glue 3 x 3mm balsa ribs (made using metal templates). This is done to increase the surface area for attaching the covering material.

Make a sanding straight edge by gluing a strip of medium grade sandpaper to a nice straight piece of hardwood approximately 300 x 40 x 20mm. Gently work the sanding straight edge backwards and forwards in a chordwise direction to remove any high spots. It doesn't take much effort, and you end up with a nice straight wing.

Gently remove the wing from the building jig, and clean it up, removing any excess glue. Using your straight edge sanding tool, lightly sand the lower surface of the wing.

Remove the 1.5 x 6.5mm packing strip from under the main spar and replace it with a 0.8 x 6.5mm strip.

Add the under surface of the leading edge of the wing sheeting first, using 0.8mm sheet balsa. Before you sheet the upper surface, make sure that neither the jig nor the wing is twisted, because once the upper sheeting has been glued in place it is not possible to correct any unwanted twists. You can build a 6.5mm washout into the outer panels of the wing if you so desire.

After the wing has been completely skinned, remove it from the jig, glue on the 12.5mm balsa tip blocks and shape as shown. Give the whole wing a gentle sanding as required.

Feather the 0.8mm sheet leading edge skins to the leading edge. The 0.8mm sheeting will sit proud on the main spar so cut strips 0.8 x 1.5 x 75mm and, using cyano, glue these strips onto every rib, top and bottom, butting the strips up against the 0.8mm leading edge sheeting. Using the straight edge sanding block, feather these strips so that there is a nice flowing contour from the leading edge skin to the trailing edge of the wing.

I used Solarfilm for the covering, because it is reasonably light and durable. Covering material is important, because it is easy to add a lot of weight if you use a heavier one. For example, clear Solarfilm is approximately half the weight of coloured Solarfilm, and Litespan is half that of clear Solarfilm. I guess it's a compromise between appearance, durability and weight. The choice is yours, but the lighter the model the better it will soar.

When the model has been completely covered, and the radio installed (a standard receiver fits fine), check that the balance point is in the correct position and add weight if required. Use the length of wire that was left in the fuselage to pull the radio antenna through. It exits at the base of the rudder leading edge, as shown on the plan.