Beardmore Inflexible
The pattern for the sheet balsa sides of the nacelles (above right). The top paper pattern was cut from the plan. Two balsa sides are below; the bottom one shows the scoring needed to bend the curve in the rear of the nacelle. Crimping,
Off to the bench Wings: Just a note before you start. Each
wing half is built with two stiff wires that plug into aluminum tubes in the fuselage. To guarantee wing alignment, the wing join- ing part of the fuselage is constructed sepa- rately and the aluminum tubes are glued into that structure with the wings held at the correct dihedral angle. Alignment is pre- cise. After the fuselage sides are joined, the structure containing the wing mounting tubes is added to the body. Pin down the leading edge, lower spar
and the ¹⁄₈ × ¹⁄₂-inch trailing edge stock for each wing panel. Make six wing ribs from ³⁄₃₂-inch sheet balsa, ten from ¹⁄₁₆-inch sheet and six from ¹⁄₃₂-inch balsa. Cut ³⁄₃₂-inch square notches at the upper rear of only two ³⁄₃₂-inch and two ¹⁄₁₆-inch thick ribs for the stub spars that will brace the aileron counterbalances. Cut two fuselage formers “A” from ³⁄₃₂-inch
sheet balsa. Mark the location for the .062 wing wires on a rib. Stack the two fuselage formers, four ³⁄₃₂-inch wing ribs and two ¹⁄₁₆-
or scoring, the inside face of the balsa (above right) behind the last former allows the wood to bend in an even curve. The ¹⁄₁₆-inch square stringers are scored as well to produce their smooth bends.
inch ribs with the bottom edges aligned. Drill through the stack. Glue the wing ribs in place, canting the
root ribs as shown on the plan. Add the ¹⁄₄ × ³⁄₈-inch balsa between the leading edge and
the lower main spar of each wing for the up- per mounting point of the wide landing gear struts. Add the upper wing spars, including the stub spar, to each wing half. Glue ¹⁄₃₂ inch sheet balsa, with the grain vertical, to the rear face of the spars in the first four sec- tions of each wing. Glue in the ¹⁄₃₂-inch sheet balsa between the third and fourth ribs. These plates will provide the gluing surface for the rear half of each engine nacelle. Add the ¹⁄₄ × ¹⁄₂-inch balsa gluing blocks for the wing strut connectors. Cut four lengths of .062 wire to 3⁵⁄₈ inch-
es. Grind one end of each wire to remove any burrs, rounding the ends slightly. This will make inserting the wires into the aluminum tubing much easier. Slide the wires into the ribs of the wing and tack glue them in place. Add sheet balsa between the ribs to support the wires. Glue the wires to the sheet balsa.
Make two rubberband hooks from .025
wire, slip one through a small hole in each root rib, then glue them to the vertically grained balsa webbing between the first two ribs in each wing. When the model is assem- bled for flight, a small rubberband between the hooks will hold the wings to the fuselage. Remove the wing halves from the building
board. Add the aileron counterbalances, cut from ³⁄₃₂-inch sheet balsa, to each wing tip. Align them with the bottom edge of the tip rib. Make the wing strut connectors from ¹⁄₁₆×
¹⁄₄-inch spruce. Drill a small hole in the face of the rounded end of the wood to accept the wire of the wing strut. Glue the spruce con- nector to the balsa mounting block in the wing, then put ¹⁄₃₂-inch sheet balsa around the block and the connector to make a sur- face for gluing Japanese tissue when the wing is covered. Shape the leading edge and sand the rear of the trailing edge round. Join the two fuselage formers “A” with ³⁄₃₂-
inch sheet balsa that is the full depth of the formers. With the four-piece fuselage struc- ture pinned firmly to the work surface, press
The engine nacelle on each wing is built from ¹⁄₃₂-inch sheet balsa sides and formers (above left). Balsa stringers and a nose block complete the shape. Only the bottom of the nacelle is covered with tissue. The use of a small, unpowered
42
propeller spins at the front of each nacelle to give the illusion of a working engine in flight (above right). The two-hole socket for the top of the landing gear strut can be seen at the right of this nacelle.
MARCH 2012
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