Fairey Firefly, The

Model Airplane News, Mar 2003 by Mosher, Vance

CONSTRUCTION

A .25-size British fighter-bomber

The Fairey Firefly was a British-built, two-seat fighter-bomber from the WW II and Korean War eras that had a very long service career aboard aircraft carriers. The Firefly shown here is a later, Mk. IV variant, with wing-mounted radiators, a radar pod and a long-range fuel tank. Several Firefly models were flown without pods and guns. Because It had such a long service life, the Firefly had several distinct color schemes; the one shown is the late-WW II green and gray "disruptive" scheme.

I designed the model to meet several goals. It had to be suitable for both electric and glow power, it had to be easy to transport, and it had to be affordable. I wanted a project that even a reasonably new scale modeler would be able to build. And, of course, it had to fly well. I am pleased to say that the Firefly met all of these requirements.

The principal design challenge was to keep its weight down so that it would fly nicely and could be electric powered. With flaps, guns, wing pods, engine cowl and canopies, the painted airframe weighed 2 pounds, 12 ounces, and its finished weight was 4 pounds, 12 ounces. The airplane flies well with a plain-bearing O.S. .25 FP turning a 10x6 prop. An engine that's 2 or 3 ounces heavier would also be OK; to balance correctly, my model (with a very light muffler) needed 2 ounces of lead in the nose.

This model is really scale, and all of the parts and jigs are shown on the plans. Servo locations and control-actuation setup are shown in detail. Control-surface hinging is scale and simple.

The Firefly had patented Fairey Aviation flaps known as "Fairey-- Youngman Area-Increasing Flaps." The flaps moved down and rearward before they tipped downward. For long-range cruising, pilots could extend the flaps only partway to create a sort of "biplane" effect that increased the wing area. Using balsa, plywood and a dowel, the scale flaps are simple to build. Optional, simplified flaps (and a no-flap wing) are shown on the plans.

CONSTRUCTION

Simple jigs help keep the model straight. To minimize weight, the fuselage is basically a "tub" structure with a few formers and curved top and bottom sheeting. The wing uses "egg-crate" construction for straightness and building ease. The tail is a mix of jig-- built and half-shell pieces. The ailerons and flaps are built flat on the bench. Most of the construction jigs are made of ordinary balsa sticks.

Egg-crate wing construction means that the spar webs are cut to shape and have half slots cut into them for the half-- slotted ribs to fit into. This accurately positions the ribs and holds them in place during construction. The spar also acts as a shear web and makes the wing stronger. The 1/8-- inch-square balsa main spar caps are glued onto each side of the web. To build in washout and to keep everything straight, the wing is built with a balsa stick placed under it as shown on the plan. The top sheeting should be glued on while the wing structure is still pinned to the workbench. The wing panels are then removed from the board and set upside-down into the cardboard jigs. While the wing is on the jigs, install the bottom spar caps, the flaps and aileron controls and the retracts. Sheet the wing bottom before you remove the wing from the jigs. Note: the rib slots have the washout built in, so you don't have to twist the spars out of shape.

The fuselage is built around the deck sheeting, and formers are added (above and below it) to produce the fuselage's oval shape. To make sheeting the structure easier, 1/8-inch balsa (glued on edge) is added to the outer edges of the deck sheeting. This provides increased thickness so that this area of the fuselage can be sanded to shape. The fuselage bottom is sheeted while the fuselage is attached to the workbench. After the sheeting is in place, the fuselage becomes stiff enough to be removed from the bench. This makes control installation much easier. You can see what you are doing through holes in the deck.

The tail surfaces all have the correct airfoil shape and taper. The fin and rudder blend nicely into the rear of the fuselage. The rudder is film-covered, and the plans show the correct number of ribs. You could probably save half an ounce by installing fewer ribs. The ribs are rough-cut balsa triangles which you then sand to shape after they have been glued on the top and bottom of the 1/32-inch balsa-core sheet. This is simple to do and saves a lot of fussy parts cutting. There are only four ribs in the stabilizer and four in the fin. The control surface hinging is also scale and is simpler to make than commercial hinge installations.

Using the bench top as a measurement reference, place the wing on top of the upside-down fuselage. With the fuselage deck sheeting laid flat on the bench, make sure that the measurements between the bench top and each wingtip are equal. Install the tail surfaces in the same way. Install all of the tail controls and servos before you install the fuselage top. Attach the fuselage top after all flight surfaces have been installed and aligned, and the control rods have been attached to them.