TOP FLITE SPITFIRE MK IX
FIELD & BENCH REVIEW
by Jim Onorato
Manufacturer: Top Flite Models
Model name: Spitfire Mk.IX
Type: 1/7 sport scale
Wingspan: 63 in.
Wing area: 687 sq. in.
Weight: 10.5 lb.
Wing loading: 35.2 oz./sq. ft.
Length: 53 in.
Radio req'd: 4- to 6-channel with 5 to 7 servos
Engine req'd: .61 to .75 2-stroke; .70 to .91 4-stroke
Engine used: SuperTigre .75G
Street price: $149.95
Features: fully sheeted balsa and lite-ply construction with basswood wing spars. Kit has provisions for installation of split flaps and retracts. Kit includes hinges, adjustable engine mount, preformed landing gear, self-adhesive decals, ABS cowl, vacuum-formed canopy and a generous hardware package.
Comments: the Top Flite Gold Edition Spitfire Mk. IX is a high-quality, sport-scale kit that looks great on the ground and in the air. Though not the easiest kit to build, this model offers a great deal of satisfaction to a patient builder with average building skills. The end result is certainly worth the effort!
- Great scale appearance.
- High-quality materials and die-cutting.
- Excellent, step-by-step instruction manual with photos.
- Labeling errors on parts and instructions.
- Wing and stab sheeting extremely fragile.
- High wing loading.
Britain's Spitfire Mk. IX was developed specifically to counter the Luftwaffe's Focke Wulf and is considered by some to be the finest Spitfire of all. When the plane entered operational service in July 1942, it had more power and fuel capacity than any previous Spitfire variant. With a total production of 5,665 aircraft, the Mk. IX exceeded Britain's expectations. As history shows, the fighter surprised many of Germany's top pilots and was instrumental in turning the tide of WW II.
Top Flite's .60- to .75-size, Gold Edition Spitfire is a fine re-creation of this historic warbird. Several modifications have been made to improve ground handling and flying stability, but the 1/7-scale kit qualifies for fun-scale and sport-scale competition.
The kit features balsa and lite-ply construction with basswood wing spars and includes hinges, an adjustable engine mount, preformed landing gear, adhesive decals, ABS cowl, a vacuum-formed canopy and a generous hardware package. Two sheets of rolled plans and an excellent 64-page instruction manual are also included. This is a typical Top Flite Gold Edition kit with the high-quality materials and excellent parts fit that modelers have come to expect. Top Flite also offers several optional scale accessories to enhance the appearance of the Spitfire; these include a scale cockpit interior and full-body pilot figure.
I had to make a few decisions before I started construction. Top Flite recommends a .60 to .75 2-stroke or .70 to .91 4-stroke. I opted for a SuperTigre .75G 2-stroke. Next, I had to decide between fixed or retractable landing gear. The Spit is designed to accept Robart no. 605 90-degree, heavy-duty pneumatic retracts.
You can use other retracts, but that would require making any necessary modifications. I went with the Robart. I also wanted to incorporate scale split flaps. The plans and instructions cover all of these options in detail.
I used Great Planes Pro CAs and Pro Epoxy for most of the construction and Top Flite MonoKote film and LustreKote paint for finishing.
Although the fin and stab retain an accurate hinge line, the entire empennage has been enlarged by 19.5 percent to give the model a solid feel in the air and enhance stability. The tail feathers have symmetrical airfoils with sheeted stab and fin, which are built directly over the plan. Neither the stab nor the fin have spars. Instead, the stab ribs, which have jig tabs, are pinned to the building board, and then a center core is glued into notches at the front of the ribs. After I attached the leading and trailing edges, I sheeted the top of the stab with 1/16-inch balsa. (The 1/16-inch sheet balsa in my kit was extremely soft and fragile. This was frustrating because I accidentally put my fingers through the sheeting on more than one occasion.) I removed the stab from the building board, took off the jig tabs and installed the hinge blocks. Then I sheeted the stab and built the fin in a similar fashion.
The elevator and rudder are not built over the plan but are made by gluing ribs and tip blocks to both sides of a center core. This required quite a bit of cutting and sanding to get the tips shaped properly. The elevator halves operate with a single servo via a supplied 1/8-inch wire joiner. Top Flite provides a strip of easy-type CA hinge material that I cut and installed after covering the model.
ROBART HEAVY-DUTY PNEUMATIC RETRACTS
The Top Flite Spitfire is designed for Robart's no. 605 heavy-duty 90-degree pneumatic retracts. The gear weighs approximately 5 ounces and features 3/16-inch tempered-steel legs with positive up- and down-locks made of tough nylon. The straight legs are cut to length, and then a bolt-on axle is attached.
To fit into the wing properly, the retracts have to be disassembled and the air cylinders mounted so that they are opposite the legs. This requires the use of two small bushings that are available from Robart for two bucks. To give the wheel more clearance in the wheel well, the right and left struts are swapped during reassembly.
I used a Robart Deluxe Air Control Kit (no. 188VRX) to operate the retracts; it includes the air-fill valve and chuck, T-fittings, variable-control valve, tubing, retaining nuts, air tank, quick disconnects and an onboard pressure gauge. The only additional items needed are a servo to operate the air-control valve and a hand pump. I did not use the onboard pressure gauge because space was somewhat limited in the Spitfire fuselage. The variable-control valve allows you to adjust the speed at which the gear is raised and lowered, without the need for separate air restricters. I set mine to rise slowly and come down fast!
Installation of the retracts is quite simple. The plywood landing-gear rails for the retracts are installed during the construction of the outer panels. The rails fit into die-cut notches in the ribs so that the wheels will be at the correct angle and position when the gear is extended. The retracts are attached to the rails with four screws. As in the full-size Spitfire, the landing gear pivot outward toward the wingtips. The most critical step in the installation is to make sure that the legs are positioned with the coil parallel to the ribs and that the axle is parallel to the spars when in the down position. After I had done this, I filed a "flat" on the leg so it wouldn't rotate.
When I first installed my retracts, the wheels splayed outward too much; to reduce the angle, I installed a washer under the outboard mounting screws.
The retracts worked perfectly at the field. On one occasion, the engine quit as I was setting up for a low pass. With the plane only 5 feet off the ground at the time, a quick flip of the retract switch had the gear down and locked quickly—just in time for a pretty wheel landing. That kind of reliability surely builds confidence!
The Spitfire's elliptical wing is, by far, its most distinguishing feature. Since I had decided to go with split flaps and retractable landing gear, I knew the wing would also be the most complex and time-consuming part of this project. Fifteen pages of the instruction manual are devoted to the wing. The construction isn't particularly difficult; there's just a lot of it.
The wing, which is fully sheeted with 1/16-inch balsa, has a Selig airfoil and is built directly over the plan in three pieces: the conventional framework construction consists of die-cut balsa ribs with jig tabs, two basswood spars and balsa shear webs. Plywood landing-gear rails for the retracts are installed during construction of the outer panels. Die-cut notches in the ribs allow the rails to go in at an angle to ensure that the wheels will be in the correct position when the landing gear is down.
During construction, I found that the labeling of the forward and aft dowel plates was reversed on the die-cut sheets. The forward plates are the narrow ones, and the aft plates are the wide ones.
After I sheeted the top of the center section, I removed it from the building boardand temporarily installed the flap servo and pushrod. The outer panels are joined to the center section while the wing is upside-down. A couple of unique plywood jigs are provided to keep the whole assembly straight and ensure the proper amount of dihedral. This worked out really well.
At this point, I trial-fit the retracts into the wings, installed the flap bellcranks and servo-hatch rails and prepared the framework for sheeting. The outer wing panels use 16 sheets of 1/16x3x36 balsa. I sheeted the bottom of the wing and cut holes for the retracts and aileron servo hatches. The aileron servos are attached directly to the hatches and then held in place with six flat-head wood screws. This is a neat installation. The top of the wing is sheeted while it is cradled in another set of jigs. Even though this was my first attempt at making split flaps, the detailed instructions made things fairly easy. There are four, 1/16-inch, die-cut plywood flap skins; two are glued to the wing's top sheeting, and the bottom two are attached with four pivot-point hinges in each flap. The hardest part of the whole procedure was getting the hinge holes aligned accurately. Though not perfect, my flaps have only a 1/32-inch gap when closed—close enough for me!
The aileron construction is unique; they are built using a die-cut, 3/32-inch balsa aileron base that is glued along the center of the aileron leading edge. Eleven ribs are then glued to both the top and bottom of the base. The ailerons are not sheeted, and the extra ribs give a nice scale appearance with the covering applied.
With the addition of the shaped leading edge and laminated tip blocks, the wing was complete. There's no mistaking that beautiful elliptical shape! I built two radiators and set them aside.
The sequence of fuselage construction is quite unconventional. The top half of the fuselage is built over the plan by installing die-cut formers and stringers over two main stringers. The fuselage is then fully sheeted, and the fin and stab are installed. The fuselage is then removed from the building board and placed upside-down in a support stand (not provided) while the bottom formers and stringers are attached. Be careful not to introduce any twist into the structure while sheeting the bottom of the unsupported fuselage.
There were several errors in the fuselage section: some of the parts were mis-labeled, references to parts in the instructions were incorrect, and more than one part had the same number as another one. None of these were of major consequence; they were just annoying. (Great Planes is aware of these errors and will correct future production runs.)
I attached the molded-plastic wing fillets to their die-cut, 1/16-inch plywood bases after the wing had been fitted to the fuselage. This task went very smoothly, and the large fillets really say "Spitfire"!
I installed my SuperTigre .75 and Top Flite's optional header and in-cowl muffler in the inverted position using the provided adjustable engine mount. I later discovered that the Top Flite muffler was not very effective (over 100dB at 9 feet), so I substituted a Davis Model Products Soundmaster muffler to get the sound down to an acceptable level (less than 96dB at 9 feet). This muffler has almost the same dimensions and configuration as the Top Flite, so it fit entirely within the cowl.
The two-piece ABS cowl has scale exhaust stacks molded into its sides. After I attached the cowl using four no. 4 sheet-metal screws, I found that the molded aft cowl blisters did not fit properly; I replaced them with carved balsa ones.
I installed the radio components on two trays: an upper for the throttle, rudder and elevator servos and a lower for the receiver, retract servo and retract air valve. Because of this configuration, I couldn't place the receiver battery as far forward as I would have liked. With the pack under the fuel tank immediately behind former F1, the Spit required about 8 ounces of nose weight to balance.
First flights are usually a little nerve-racking, but I must say that I was more than a little apprehensive when I went out for the Spitfire's first flight. All I could think of was that high (35 ounces per square foot) wing loading. Fortunately, it didn't turn out to be a major problem.
Takeoff and Landing
I advanced the throttle slowly while holding a bit of up-elevator to keep the tail down until the Spit was rolling. I then relaxed the elevator to allow the tail to come up and the plane to gain speed. Little or no rudder input was necessary to keep it tracking straight ahead. When I was certain the Spitfire had reached flying speed, I applied just a touch of up-elevator, and the Spitfire rose smoothly into the air with almost no rotation. The mellow sound of the Soundmaster muffler and the sight of that unique elliptical wing as the Spitfire went into a shallow, climbing right turn made my day!
Almost all of my landings have been wheel landings at moderate speed. Because the Spitfire is rather heavy, I always try to bring it in under power, and I don't chop the throttle until touchdown. The approach is usually very steady with the wing perfectly level; although the split flaps don't seem to slow the Spit very much, they certainly look great!
I really can't say a lot about slow-speed performance because I tend to fly the Spitfire like the warbird that it is—fast! However, I will say that the Spit was solid and controllable throughout all of my flights. This plane really isn't meant to fly slowly.
The SuperTigre .75 was a good choice for the Spitfire, as it hauls the plane through the sky at scale speed. Tracking is excellent, and the plane is quite stable at full throttle. Retracts really clean up a plane in flight, and high-speed, low passes with the wheels up are a sight to behold.
This Spitfire is intended for scale and general sport flying and is capable of mild aerobatics such as loops, stall turns, rolls, etc. I did not ask it to do more.
This is a nice flying sport-scale warbird with good scale appearance. If you are not already in love with Spitfires, this one could make a convert out of you.
Reprinted with permission.
May, 2000 Model Airplane News
Editor: Gerry Yarrish