| NAKAJIMA Ki.84a Hayate | 0210 |
The Nakajima Ki-84 Hayate (Gale) was under development since 1942. It was to be as nimble and easily controllable as the Ki-43 Hyabusa (Peregrine falcon), its insufficiently armed and armoured predecessor, and its performance was to be better than that of the newer Nakajima Ki-44 Shoki (Demon) (in the Allied code Tojo) interceptor. The double-row eighteen-cylinder Nakajima Ha-45 Homare (Honor) radial was chosen as its powerplant, which in its Ha-45-21 version had up to 1484 kW (2000 HP) of the take-off power. One of the specified parameters was to decrease the labour contents (i.e. the number of man-hours needed for the manufacture of a single aeroplane) in the new type. Compared to some 25 000 man-hours needed for the Ki-43 and 24 000 hours for the Ki-44 only some 14 000 were to suffice to produce a single Ki-84. The representatives of the Japanese Imperial Army were well aware that this is the sole way to increase the aircraft production under the existing spatial and manpower constraints. The need to increase the production was doubted by no one, indeed, the development of the war notwithstanding.
The Nakajima Company received the order for the manufacture of the Ki-84 prototype on 27th May 1942. The Ki-84-01 prototype was ready in March 1943, a period of a mere ten months. The maiden flight took place in April and the remaining flight tests were run at high rate. In the period between August 1943 and March 1944 altogether 83 pre-series machines were built, to test various changes and modifications. The transition to the large-scale manufacture of the Ki-84 in the Ota factory went on smoothly - utilisation of many jigs and tooling from the Ki-43 manufacture and of highly rational technological processes helped much. The Nakajima Ki-84 received the combat name of Hayate (Gale), the US intelligence allotted to it the codename Frank. Both warring sides agreed that Hayate was one of the best if not the best Japanese fighter. Its maximum speed of 624 km/h, nimbleness and relatively easy control made it an equal opponent to all modern Allied fighters.
The machine was produced mainly in the Ki-84-Ia, armed with a pair of Ho-103 12,7mm calibre machine guns in the fuselage and two 20mm Ho-5 cannon in the wings. The Ki-84-Ib was designed to kill bombers, therefore its armament was augmented by replacing the half-inch MGs on the fuselage by a pair of 20mm cannon, too. Despite the shortage of material, energy and qualified manpower and despite the bombing, the long period average production figure was over 200 Ki-84s per month. Altogether about 4500 of the Ki-84 of all versions were built.
The decal set included in the kit enables you to build one of two machines serving with the 520th Temporary Interception Regiment, Home Island Defence, Nakatsu Airfield, in the period of March-May 1945 (red stripe on the vertical tail) or the machines of the 47th Air Combat Regiment, 1st Company (blue) or 3rd Company (yellow), Eastern Defence Sector, Tokyo Air Defence, summer 1945. The spinners of these machines correspond to the colours of the tail marking.
The model is not suited for complete beginners, but its control with ailerons and elevator would not bring problems to any modeller experienced enough with elevator/rudder control models, e.g. slow-flyers. The flying qualities and performance of this scale model of the Nakajima Ki-84-Ia Hayate are close to that of much larger model, i.e. it is more docile, and flying it provides fine and substantially more colourful experience.
The model kit you have bought has several typical features:
- The semi scale model is almost finished; you only have to apply decals, install the propulsion unit and the RC equipment. You can utilise the kit's box as the transport and storage container for the finished model.
- The scale model is moulded from the extruded polystyrene foam (EPSF) with a tougher surface layer, making the model less prone to surface damage. Adding to that, all exposed surfaces are reinforced with plastic covers. Thanks to the ratio of the all-up weight and of the strength of the material used the model is quite compact, this feature reducing the danger of damage in normal operation substantially, to almost negligible level.
- When designing this model a maximum attention was devoted to its aerodynamic layout (e.g. the semi-symmetrical wing section, the symmetrical horizontal tail section), ensuring high aerodynamic finesse, with the resulting wide band of operational speeds and docile flying characteristics typical for large models.
- The range of proven power units offered enables to build a scale model possessing a flight performance corresponding to that of the best slow flyers, as well as to the fully aerobatic models.
- When choosing the battery, check please not only the nominal voltage, but also the available current drain (NiMH, LiPol).
- To control the model you need the RC equipment suitable for controlling the slow-flyers - it would enable you to fly majority of the aerobatic figures (with the possible exception of those that require the rudder control).
- One of the decisive factors, affecting the flight performance and behaviour of the model, is its weight. Due to the multitude of possible combinations of the RC equipment, motors and power sources (battery packs) it is impossible to exactly state the final weight. In any case, the weight of the model without the battery pack should not exceed 320 grams. With a double-cell LiPol 1500mAh battery would probably weigh in at 380 grams, with the six-cell 500mAh NiCd pack about 420 grams. The specified maximum weight should in no case be exceeded - the flight behaviour of heavier models deteriorates accordingly.
Finishing the model
It is a simple task, yet we ask you to read and follow the subsequent text thoroughly.
When opening the cockpit canopy, use the following procedure:
- Lift carefully (about 5 mm) the rear part of the canopy ( I )
- Slide the canopy rearwards ( II )
- Once the front lock is released, lift the front part of the cockpit canopy ( III )
- Slide the released canopy forward and remove it from the fuselage. ( IV )
The decals
The model is sprayed with colours making up its basic camouflage scheme. The codes and markings consist of the waterslide decals. Their primary advantage is the negligible weight and the minimum risk of damaging the model during application. They require, however, an attention and care. Therefore we recommend that you follow the subsequent instructions:
- The larger decals that are to fit to a double-curvature surface need to be cut radially at several places around the circumference.
- Cut-out the decal from the sheet with its backing paper, dip it briefly (for about 5 seconds) into a lukewarm water, then leave it to soak throughly on a flat non-absorbent surface (glass plate, plastic sheet etc.);
- You may increase the adhesion of the decal to the model's surface substantially by applying wallpaper glue to the area where the decal will be placed. However, ensure in advance that the glue would not create blotches or lumps when it dries - this is why the white (PVA) glues are usually not suitable.
- Once the backing paper is sufficiently soaked (i.e. the decal moves easily on its backing paper), slide the decal over the edge of the backing paper about 5 mm out, keep it with your finger in required place on the part to be decorated and pull the paper from beneath the decal. If the decal does not slide easily enough, apply some more water around it with a paintbrush; it would help you to replace a wrongly-applied decal if need be, too.
- Using a soft cloth or, rather a polyurethane foam roller, carefully smooth out the decal, gently squeezing the excess glue and any air bubbles from the centre to its outer edge. Do not squeeze out all of the glue - the decal would adhere badly and some light blotches could appear under it! Once the glue dries, i.e. in a few hours, the decals would shrink somewhat and adhere snugly to the surface.
- To increase the adhesion of the decals, try to use the setting solution used for the plastic scale kit decals. Check beforehand whether the solution does not etch the extruded polystyrene and then follow the attached instructions for use.
- The model could be oversprayed with a thin layer of a transparent gloss or semi-matte (in the latter case, avoid spraying the transparent cockpit canopy!) acrylic or synthetic varnish to suit your ideas regarding the surface finish of the real aeroplane. It is absolutely necessary to check that the varnish does not attack the polystyrene foam. To keep the weight down, spray varnish very sparingly.
A) RC equipment
The general layout of the electrical connection is on the diagram. We strongly suggest that you assemble and connect the RC equipment outside the model and check its function. Observe the recommendations of manufacturers as listed in the directions of use for the respective components. Check the compatibility of the receiver with the crystal used - the over-the-land range test of the transmitter, albeit it may seem unnecessary nowadays, may save you much more than it would cost…
B) Power unit ( motors with the MP Jet gearbox or MP Jet outrunner 28/7…)
- The power unit 1 is attached to the motor bulkhead by three screws 2.
- The engine cowling 3 could be tack-glued to the fuselage by the epoxy or PU glue or by a piece of adhesive tape. If you find that the motor heats up excessively in operation, it is mandatory to improve its cooling. Cut out additional openings for the cooling air where motor cylinders are. Cut also the cooling air outlet at the bottom of the rear fuselage, e.g. around or in place of the tail wheel cover.
- Slide the propeller back plate 4 to the gearbox (motor) shaft, install the propeller 5 to the back plate, the rear part of the spinner 6, and the washer 7, respectively (use the washer from the model kit, not from the power unit set), and tighten the complete assembly with the nut 8.
- Tack-glue (Epoxy) the front part 9 to the rear part of the propeller spinner 6. Apply the glue to the contact surfaces, not to the rim. To disassemble the spinner, carefully cut away the spinner front part 9 at the line joining it with the rear spinner part 6.
- Check that the propeller rotates freely, without binding between rotary and stationary parts.
C) Aileron control
The aileron servo should be powerful enough to overcome the friction in the control bowdens - we recommend utilising a servo of more than the 0,15 Nm minimum torque. The friction in the bowdens could be reduced by removing the push-pull rods from the tubes and lubricating them with a thin oil, such as the WD-40.
- Place the connector 10 into hole in the servo single arm, at the distance of about 9 mm from the axis of servo arm's rotation. If the opening in the servo arm is too large, it is better to drill a new one (of 1 mm diameter) rather than bushing-out the existing ones. I
- Insert a 6 mm long piece of the tube 11 into the connector opening.
- Insert the connector to the control rods, first to one, then to the other (fig. C1).
- According to the dimensions of your servo, modify the opening in the top surface of the wing. It should fit tightly; the best way is to cut the opening somewhat narrower than the servo width and then to push the servo in carefully. Insert the servo into the wing opening and place it so that once the servo arm is inserted on its shaft (the axis of the servo arm should be parallel with the longitudinal axis of the servo) the control rods would make a smooth curve and that the set-screws 12 and 13 could be tightened (fig. C2). If the servo protrudes above the wing surface, it has to fit into the opening at the bottom of the fuselage centre section. If need be, you may enlarge the wing opening even in front of the servo, but always take utmost care when cutting into the hard surface of the plastic.
- Devote maximum attention to the correct positioning of the servo - only that way you would ensure the proper function of the controls. Secure the servo against movement by applying a thin layer of PU or Epoxy glue at the place of contact of the servo housing with both wing surfaces - in case a servo needs to be removed it is easy to pry it loose without damage.
- Tighten lightly the screw 13 so that the aileron trailing edges would be some 1,5 to 2,0 millimetres above the wing trailing edge (fig. C3) .
- Check function of ailerons: they should be at their maximum deflection of about 10 mm at the maximum displacement of the control stick (fig. C3) - check the correct sense of their deflection! If they are not moving correctly, and you could not get the proper sense of servo throw by the RC set programming, change as necessary either the position of the control rods in the control circuit arms or of the connector on the servo arm. Only then secure the connector against becoming unconnected by the spring washer 14 inserted from below (the servo arm is outside the model; use a thin tube such as the ball point pen refill), and then secure the servo arm itself by the screw 12. Readjust the correct position of the ailerons and tighten the screw 13. Secure the control rods against disconnecting from the control arm by gluing (CA) a piece of tubing onto it (fig. C4) .
- In place of the spring washer 14 the connector could be secured by a plastic tube, glued with CA. If done properly, this simple securing method works very well; if need be, the disassembly would be much simpler - the tube would be simply cut away.
D) Elevator controls, accumulator pack placement
A servo of more than 0,07 Nm minimum torque is recommended for the elevator control. Both moving surfaces are interconnected by a glued-in coupler. If one of the elevator halves deflects excessively (outside of the recommended angles), the coupler may become loose and the deflections (especially the maximum ones), may differ substantially. Restore their stiffness by gluing (Epoxy) a "U"-shaped connector made of steel wire of 1,5 mm diameter.
- Glue (CA, PU, Epoxy) the servo into the opening on the starboard side of the servo base plate so that the screws 13 and 15 could be tightened.
- Insert the connector 10 into the hole placed about 9 mm from the axis of the servo output shaft's rotation in the one-sided servo arm. Drill a new hole if needed. Insert piece of the plastic tubing 16, about 6 mm long, into the connector hole. Slip the assembly over the elevator control rod and put the servo arm to the servo output shaft so that the arm's axis would be roughly perpendicular to the elevator control rod axis (fig. D1) . Glue (Epoxy, PU) the control rod outer tube to the inside fuselage wall.
- Tighten slightly the connector screw 13 - the servo arm and the elevator are both in neutral position.
- Check that the maximum throw of the servo corresponds to the maximum elevator deflection of about 10 millimetres (fig. D2) . Note! Ensure that the aileron deflection responds to the sense of control stick movement! If they are not moving correctly, and you could not set the servo throw by the RC set programming, change as necessary either the position of the control rod in the control arm or of the connector on the servo arm. Only then secure the connector against becoming loose, using the spring washer 14 inserted from below (the servo arm is outside the model), or by gluing on a piece of tube. Secure the servo arm itself by tightening the screw 15 . Readjust the correct position of the elevator and tighten the screw 13 . Secure the control rod against disconnecting from the control arm by gluing a piece of tubing onto it (fig. D3) .
To facilitate the transport and storage of the model the wing is made detachable. The wing and the fuselage are joined with the bolt 17 - tighten carefully!
You can insert and glue an assembled and painted pilot into the cockpit from bellow, after opening up appropriate hole in the decking.
E) Flying the model
Balance the complete assembled model by shifting the position of battery pack along the base plate. The prescribed position of the centre of gravity is marked on the wing bottom surface by transverse lines (fig. E) . Balance the model supported at the lines by your fingers, as sharp items may damage the polystyrene surface. The model should remain in a level position or slightly nose-down. For the first flights the centre of gravity may be moved some 5 millimetres forward, but absolutely no rearward shift of the centre of gravity would be allowed! Mark the correct position of the battery pack on the base plate; it is best done at leisure at home, as is the check of the RC equipment, i. e. the sense and magnitude of deflection (throw) of the ailerons and elevator and the operation of the controller.
Hold the model at the wing trailing edge/fuselage junction. It is important that the model, once launched, flies without vertical or horizontal rotation (yawing or pitching). If you can, do not hesitate to turn to an experienced fellow modeller for help, at least with the first few launches.
First, glide-launch the model over higher grass to cushion its eventual falls and check its reaction to controls. If you can, set the non-linearity on the transmitter to around 50 % both for the ailerons and the elevator. The powered flight will differ according to the power unit - the "280" will make the start just a bit more lively than with a slow-flyer, the AC motor will try to jerk the model from your hand - be ready for a pronounced torque from the propeller in slow flight when the controls are less effective. There is no need to use full power during the launch!
Once the model is trimmed in the powered flight, try the marginal regimes - especially the slow flight and stall behaviour of the model. Once you become accustomed to the model, you may return the ailerons to normal zero setting. The model of the Nakajima Ki-84-Ia Hayate has - thanks to wing outline - excellent flight properties and would stand a lot of abuse. But it is no slow-flyer/fun-fly machine or an aerobatic special and you have to adjust the piloting to this fact. You could be surprised by the reactions to the excess movement of the elevator, so please try these figures at higher flight altitudes.
You will soon find that if you want to fly the well adjusted Nakajima Ki-84-Ia Hayate model, you need not to wait for a calm weather. The model handles well and has a broad range of speeds, behaving like a much larger aeroplane. It will be only up to you when you feel like going out to fly the Nakajima Ki.84a Hayate.
We wish you many happy landings.
ALFA MODEL Ltd.
A list of parts and tools necessary for finishing the model that are not supplied in the kit:
- Polyurethane (PU) glue, five-minute Epoxy glue, cyanoacrylate glue.
- Modelling knife, screwdrivers, transparent self-adhesive tape, 1mm dia. drill bit.
- Power unit with the controller and propeller, battery pack etc.; some of the recommended t combinations are listed below.
- At least a three-channel RC set with two micro servos (up to 10 g weight) and a miniature receiver (up to 10 g weight).
- Extension cable (150 mm) to attach the aileron servo to the RC receiver.
- Battery charger.
