Giant-Scale Tiger Moth

Model Airplane News, Jul 2004 by Allen, Gary, Davisson, Budd

A 30-percent, precision classic

Derived from the highly successful D.H. 60 Moth series of civilian aircraft that included the famous Gypsy Moth, the de Havilland D.H. 82A Tiger MOth is the quintessential British biplane trainer. The Tiger Moth has long been popular with modelers, and a comucopia of "Tiggie" models is available today in the form of backyard flyers, ARFs, kits and plans. Few full-scale aircraft offer the available range of paint schemes (including military) from a dozen countries. Couple this with classic lines and docile flight characteristics, and the allure of this vintage biplane is easy to understand.

I flew a 1.20 glow-powered �-scale Tiger Moth for many years and enjoyed the experience immensely. These days, my preferred power source is gas, and I wanted a model suitable for the Zenoa G-45. A 30-percent-scale version seemed perfect. I tried to keep its construction methods and field assembly a practical as I could without compromising scale fidelity; the only intended deviation from scale is a slight widering of the cowl nose to accommodate the G-45 fifted with a Bisson Pitts-styie muffler, a 90-clegree carburetor bend and a 2-inch prop-drive extension. The plans show an absolutely scale cowl nose section for those who might use a narrower engine/muffler combo.

Many configurations of Tiger Moths are evident today, including all possible additions and omissions of retractable top-wing leading-edge slats, anti-spin strakes, navigation lights and a tailwheel as a tailskid substitute. My subject aircraft included all these extras, so they are atso on the plans. There are, however, many attractive, easily documented examples of Tiger Moths that have none of these extras.

Detailed step-by-step construction notes are available on the Model Airplane News website "Click Trip," so I'll give only a general overview here. Construction materials consist of balsa, aircraft plywood, basswood, spruce, tubes of brass and aluminum and a multitude of small nute, bolts and screws (all available from Micro Fasteners).

CONSTRUCTION

* Fuselage. The fuselage consists of four major subassemblies: the engine box, the upper-wing-tank center section, the landing gear and the main fuselage structure. The fuselage uses basic box construction and follows full-scale practice; spruce and balsa are substituted for the welded tubes of the original. The tank center section with its corrugated metal covering is one of the Tiger Moth's defining characteristics. It also represents probably the most tedious portion of construction. It is constructed around an 1/8-inch-ply framework, which is sheeted and glassed with 2-ounce fiberglass cloth and epoxy resin. The corrugations are duplicated with half-rounded balsa strips, which I soaked in ammonia and very carefully glued to the tank structure. After I had sanded them smooth, I brushed three to four coats of thinned epoxy over the "corrugations." The results are very realistic.

I fabricated the cabane struts using 1/8׽-inch aluminum stock. The critical alignment of the center-section tank with the fuselage is achieved by working directly over the plans as you install the struts. Access to the rudder and throttle servos and the receiver and battery pack is through a hatch just behind the cowl. A bottom hatch just behind the cockpit provides access to the elevator servos.

The engine box is assembled out of �-inch-ply parts using epoxy and screws. It contains the tank mount and is attached to the fuselage with aluminum-angle stock, 6-32 socket-head bolts and blind nuts. The entire engine and tank assembly can be removed as a unit for servicing and access to the radio compartment. While the landing-gear outline and cross-sections are scale, their functionality is not. Shock absorption is provided by a traditional rubber-band/spreader-bar method instead of complicated-to-build Oleo struts. The main portion of the landing-gear structure is constructed of �-InCh music wire and the rest of 1/8-inch music wire. Balsa and basswood fairings complete the unit.

Another defining characteristic of many Tiger Moths is the distinct D.H. logo-bearing wheel cover. A simple method of fabricating and mounting versions suitable for standard Du-Bro wheels is shown on the plans.

* Engine cowl. The cowl follows full-scale design, and its side panels are hinged to provide access to the engine for fueling and to make carburetor adjustments. The side panels are secured for flight with scale-like fasteners. The cowl is built in situ (i.e., in place) around a ply framework. The top is balsa planking, the bottom is a thick balsa sheet, and the nose is a combination of balsa blocks and planking. The hinged sides are fabricated around 1/32-inch-ply cores. Everything is then glassed with 2-ounce cloth and epoxy resin.

* Tail surfaces. The stabilizer/elevator and fin/rudder, which contains the tailwheel assembly, are easily removed from the fuselage. The stabilizer features a laminated-balsa leading edge. The trailing edge and capstripped ribs are 1/8-inch balsa stock. The ply portions of the center section provide the attachment points to the fuselage and the slot for the rudder assembly. Note that functional struts are attached between the fuselage bottom and the stabilizer's leading edge. The elevators are fabricated around a sheet-balsa framework. I made the scale-like elevator control horns by carefully trimming standard hobby items to size.