Spitfire MkIIa (oz4647)

About this Plan

Vickers-Supermarine Spitfire MkII A. Control line scale model, from 1972 American Aircraft Modeler. Scale is 1/8. This is a low resolution plan, scaled up from the magazine print.

Quote: "Vickers-Supermarine Spitfire Mk IIA. Plane on the Cover. Model that won the '71 CL Nats and was 6th at the '72 CL Scale World Champs is patient project of a great plane. Has many operating features and flies quite well.

Every Scale builder has a favorite airplane or type of airplane; I've always been inclined toward World War II military aircraft. After moderate success in local scale contests, I decided to build a ship for entry in the 1971 Nationals. To do this, I needed a subject which inspired me to invest the amount of time required to complete a competitive scale model. Retractable landing gear - an operating feature having good spectator appeal and a high scoring flight demonstration option - was a must. Another point relevant to selecting a subject was additional operating features such as flaps, sliding canopy, navigation lights, drop tanks, etc, which could be incorporated. Also, I wanted to stay away from subjects which had been overdone.

One aircraft kept coming to mind, the Supermarine Spitfire. It was one of the most famous World War II fighters, plenty of reference material was available and, despite its fame, it didn't enjoy much popularity with modelers. The Spitfire had enough operating features to insure a respectable scale flight score, and it featured very simple retractable landing gear which could be easily adapted to Bill Johnson's efficient, lightweight Centrak gear retraction unit. Using this system would eliminate the mess of batteries, extra control lines, electrical wiring, and other assorted headaches which go with retractable gear in control line models. Also, the simplicity of the landing gear would make it fairly easy to machine scale shock absorbing gear struts for added realism.

While considering the positive and negative aspects of the Spitfire as a flying scale project, one nagging thought kept coming to mind: The extremely short nose moment, small empennage areas, and fore and aft placement of the landing gear on the prototype could make the model's flying characteristics less than satisfactory. However, after reading a very scientific conclusion that "anything will fly on control lines," I decided to proceed with construction. The resulting model did fly satisfactorily, but it is definitely not a beginner's ship-the Spitfire demands the flier's undivided attention from takeoff to the end of the last taxi lap.

Which variant of the Spitfire to build was the final problem. The solution was dictated by the availability of reference material, and I settled on the Mark HA depicted in Profile Publication, No. 41. Several variants of the Spitfire shared a basic airframe; it is simple to convert the Mark IIA to a Mark I, III, or V, and substitution of four 20mm cannons for the inboard .303 caliber machine guns converts the model to a Mark IIB.

Before beginning construction, study every available publication on the Spitfire to become familiar with details of the prototype. I found the following references to be particularly helpful: Bruce Robertson's Spitfire: The Story o f a Famous Fighter, and Aircraft Camouflage and Markings, 1907-1954 both available from Harleyford Publications; Profile Publications, Nos. 41 and 166; Aero Publisher's Supermarine Spitfire; and Willis Nye's excellent drawings of the Spitfire. These publications contain many drawings and photos invaluable for detailing the model and preparing the proof of scale presentation which must accompany it in competition.

Construction may be greatly simplified with installation of conventional non-retractable gear. However, the satisfaction of seeing the wheels disappear into the wings shortly after takeoff makes the extra effort worthwhile. If you use the Centrak installation, contact Bill Johnson, 2504 Charwood Charles, Mo. 63301. Bill is familiar with the model and can supply the retract unit and complete instructions for installation and operation.

Construction: The landing gear is the most complicated component and is a good place to begin. The gear struts are turned from aluminum stock and a 7/32 in diameter bore drilled and reamed for the oleos. Drill holes for the oleo retaining pin and the gear support rod, making sure the centerline of each hole is at the proper angle (see plans). This is necessary for correct tracking of the wheels and for maintaining correct gear geometry during retraction.

The oleos are machined from mild steel (I used 5/16 steel bolts). and the axles are 1/8 music wire threaded on both ends and silver soldered into tapped holes in the oleos. Exercise caution when drilling the holes in the oleos to insure correct alignment of each component. File the top of each strut to the shape shown, and assemble the struts and gear support rods, keying in place as illustrated in the plans. Fabricate the spacers, bushings, and mounts from brass tubing and sheet and the gear actuating arms from mild steel; assemble, making certain that the gear mounts rotate freely on the support rods and that the actuating arms are silver soldered in place at the correct angle. Selection of springs for the oleos depends on the final weight of the model and the amount of shock absorbing action desired. The oleos can be removed easily, so experimentation with various springs presents no problem.

One further note on the landing gear: If the Banner wheels shown on the plans are used, the aluminum hubs must be faced off on each side to give a thinner contour and allow the gear to retract fully into the wheel wells.

The wing contains almost all the gear, flap, and other control operating mechanisms and is the next component to build. Cut ribs R-2, R-10, and R-15 to shape and drill 1/8 holes in each one at the location shown on the plans. Stack the correct number of 1/8 balsa rib blanks in sequence with the pattern ribs, using 1/8 dowels to maintain alignment. Shape the stack of ribs in the usual manner, with one exception: The stack should show a curve, top and bottom, from the root to the tip rib. This is because the upper and lower wing surfaces are curved as viewed from the front.

Join the balsa wing spars and plywood doubler, and glue the ribs in place on the spar. Use two 20 in lengths of 1/8 doweling in the holes previously drilled in each rib to maintain rib alignment until the glue dries. When dry, notch the ribs and install stringers for the flap wells and aileron cutouts.

The bottom surface of the outer wing panels should be sheeted next. Leave the bottom center section open until the wing is in place on the fuselage and all control linkages are hooked up and operating properly. The flap and aileron wells should not be cut out until the tops of the outer wing panels have been covered and the wing sanded to shape.

Cut the openings for the landing gear wells in the bottom of each wing and remove sections of ribs as required. Then line the wells with 1/16" balsa. To install the landing gear, it is necessary to cut a small hole in the wing bottom sheeting between the leading edge and front spar. Before final gluing of the plywood landing gear mounts, check gear alignment carefully both in the extended and retracted position.

Mount the Centrak unit with the Roberts Flight Control, control line leadouts, and control linkages attached. Bend and install the 3/32 music wire gear actuating arms. Be certain that the rods are the correct length to actuate both gear simultaneously-they must both be full up and full down at same time..."

Direct submission to Outerzone.

Supplementary file notes

Article pages, scanned and OCR'd thanks to StuartBurling

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction