Lavotchkin La-7 0203
	La-7 was the wartime summit of the development line of single-engined fighters that started in 1940 by the LaGG-1 - the first and last joint design effort of Semyon Alexeyevich Lavochkin, Vladimir Petrovich Gorbunov a Mikhail Ivanovich Gudkov. The main design feature of this family of fighters was the utilisation of birch veneer strips, the so called ”delta shpon” or ”delta drevesina”, laid-up in layers with grain at 45 deg. angle, laminated with resin into moulds. The moulds were then heated and this laminate was pressed and cured to final shape. The resulting shells were both strong and light and made up majority of airframe outer structure. These machines were consequently simple to manufacture, resistant to damage and easily repaired, with little demands for the strategic aluminium alloys such as the dural. While the LaGG-1 prototype reached 605 km/h, the maximum speed of the series-built LaGG-3s dropped to 535 km/h. This was caused by weight increases and by the inferior finish of the series-built aeroplanes. Installation of the heavier, but also much more powerful Shvetsov M-82 air-cooled radial in place of the M-105 Vee-twelve gave rise to the LaG-5, that reached a maximum speed of 554 km/h. Further, this time a more substantial redesign of the LaGG-3 airframe for the radial brought the La-5, armed with a pair of ShVAK 20mm cannon; its maximum speed reached 603 km/h, almost the same as the original LaGG-1. The ultimate La-5 version, the La-5FN, had a direct injection engine, automatic slats and some 160 kg less weight. The total La-5 production reached 10 599 machines, majority of them of the La-5FN version, manufactured since March 1943. Further development offered several directions to follow. The first of them was to install a more potent powerplant - the one at hand was the M-71. Unfortunately, this engine was not yet mature. This, combined with the other non-technical reasons - was the cause of the failure of N. N. Polikarpov’s I-185 fighter, which in 1942 exceeded the performance of all its Soviet contemporaries including the La-5. Another direction was lowering the weight and/or drag. A certain lightening of the La-5 airframe took place, but the ultimate yet realistic method of increasing the performance was the improvement to the aerodynamics of the aircraft. The first measurements took place in the TsAGI wind tunnel in early 1943; the proposed modifications were expected to increase the maximum speed of the series-built fighters by up to 35 kph without need for increase of the engine power. Further detailed measurements took place in November 1943 on the La-5 ”206”, which was subject to modifications proposed by the TsAGI scientists and technicians. The measured performance data were confirmed by the flight tests of the same machine, that took place between 14th December 1943 and 10th February 1944. The machine reached 630 kph. Based on the first successful flights the construction of another prototype was ordered, under designation ”La-5 etalon 1944”. In May 1944 this fighter was put to series production as the La-7. The most notable changes compared to the La-5 were moving the oil cooler beneath the belly at the wing trailing edge and the carburettor and compressor air intakes to the wing root leading edges. The aerodynamics and performance of the La-7 was markedly improved by modifying the flow through the engine cowling, by general sealing of the airframe, complete retraction of the undercarriage and by other inconspicuous modifications. The first machines were handed over to the military in June 1944, but the troop tests were conducted as late as between 15th September and 15th October 1944. These tests did not only prove the excellent characteristics of the La-7, but also shown some serious shortcomings. One of them were the engine seizures in flight due to dust ingestion. It was caused by the transfer of air intakes from the top of engine cowling to the wing root leading edge. Plenty of foreign matter was ingested to cylinders during operation on unpaved airfields - a phenomenon understandably not encountered during the winter tests. The solution was provided by installation of supplementary dust filters. Another change was the installation of three Berezin B-20 aviation cannon of 20mm calibre. There were only 368 of the three-cannon machines manufactured, the remainder of the total of 5753 La-7s produced had the same armament as the La-5. To enthusiasts interested in more detailed information about development, combat operation, markings and colour schemes of the La-7 fighter we heartily recommend the Lavochkin La-7 monograph, published by the MBI publishing house, Kocianova 1588, 155 00 Praha 5, Czech Republic, which served as the base source for preparation of this kit. 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 of this model of the Lavochkin La-7 are close to that of much larger model, i.e. they are more docile, and provide fine as well as colourful experience in the air. The model kit you have bought has several noteworthy features: It 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 more resistant to surface damage. Added 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 substantially the danger of damage in normal operation. 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 of flight performance corresponding with that of the best slow flyers, as well as with the fully aerobatic models. 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). Finishing the model It is a simple task, yet we ask you to read and follow the subsequent text thoroughly. 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 a 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. Dip the decal cut-out from the sheet with its backing paper into a lukewarm water for about 5 seconds, then leave it to soak through on a flat non-absorbent surface (glass plate, plastic sheet etc.); You may increase the adhesion of the dried decal to model 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 will help you to replace the wrongly-applied decal, too. Using a soft cloth, 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! Once the glue dries, i.e. in a few hours, the decals would shrink somewhat and adhere snugly to the surface. The model could be oversprayed with a thin layer of transparent gloss or semi-matte (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 much more than it would cost… B) Power unit 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 cyano or epoxy glue or by a piece of adhesive tape. The cowling could be also attached to the fuselage permanently; the motor with its gearbox could be removed through the front cowling opening if needed. To facilitate this, it is advisable to enlarge the opening slightly by sanding. If you find the motor overheats, it is necessary to increase the flow of the cooling air. Cut out the air intake slits in the front louvres and the outlet for the heated air on the rear side of the belly oil cooler. Take care when cutting into the hard surface plastic - once the resilient surface foil is cut through, the resistance to the cutting pressure suddenly decreases and a serious damage to the model or even injury may result. Slide the propeller back plate 4 to the gearbox 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 powerplant set), and tighten the complete assembly with the nut 8. Snap the propeller spinner front part 9 to the rear part of the spinner 6. Doing this, hold firmly the propeller and the rear spinner, not the model. To disassemble the spinner, press the rear edge of the rear spinner part 6 until the front part of the spinner 9 gets loose. 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 the thin oil, such as the WD-40. Place the connector 10 into hole in the servo single arm, at the distance of about 8 mm from the axis of servo arm’s rotation. If the opening in the servo arm is too large, it is better to drill new one of 1 mm diameter rather than bushing-out the old ones. I Into the connector opening, insert a 6mm long piece of the tube 11. 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 can 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 deflection of the control stick (fig. C3) - check the correct sense of their deflection! If they are not moving correctly, and you could not program the 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 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. 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 to the hole in the servo arm that is placed about 6 mm from the axis of the servo output shaft rotation. Drill a new hole if needed. Insert piece of the plastic tubing 16, about 6 mm long, into the connector hole. Insert the assembly to the elevator control rod and insert 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 tube to the cut-out in the control rod support. 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 8 millimetres (fig. D2). Note! Ensure that the sense of aileron deflection corresponds to the 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 unconnected, using the spring washer 14 inserted from below (the servo arm is outside the model), or by gluing a piece of tube. Secure the servo arm itself by 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). Accumulators are attached to the base plate using a self-adhesive Velcro strip. The receiver is attached to the plastic bed for the wing in the fuselage with a self-adhesive Velcro strip. The receiver antenna may be lead out of the bottom fuselage behind the wing and taped to the fuselage with an adhesive tape or left freely streaming behind. It is recommended to check with the motor running (especially at the maximum power) that no interference (jamming) of the RC receiver takes place - it would manifest itself by oscillating of servos. In that case move the receiver to the fuselage sidewall forward or even better rearward of the cockpit, as far from the battery pack and power leads as possible. 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. If you want to fit the pilot into the cockpit, you have to carefully remove the cockpit canopy, tack-glued in the corners, place and glue an assembled and painted pilot in and glue the canopy back in place. 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 CG 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 level position or slightly nose-down. For the first flights the CG may be moved some 5 millimetres forward, but absolutely no rearward shift of the CG is 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. Devote special attention to the magnitude of elevator deflection. It should not exceed the prescribed 8 millimetres. In flight, avoid very quick movement of the elevator to its maximum deflection as, even at higher flight speeds, this can bring the model to an accelerated stall/spin. Hold the model at the wing trailing edge/fuselage junction, supporting it by the oil cooler with the fingers, or at the front fuselage/rear engine cowling. 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 50 % both for ailerons and 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. 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. When flying the La-7 model, always bear in mind that the wing of the full-size aeroplane was designed to allow for maximum speed - to this purpose served also the sharply tapered wing planform. This wing shape however has a less-than-optimal behaviour at high aerodynamic loads (lift coefficients - CL) - such as low speed, abrupt changes of the angle of attack etc. In these cases a flow separation at the outer wing panels may easily occur (in most cases in an asymmetric way - one wing earlier), causing the machine to drop a wing and, if left unchecked, to develop a spin. In the real life this behaviour of the tapered wing was mostly cured by the automatic slats, which, for understandable reasons, are rather impractical on the model of this size. On the La-7 model we therefore used an aerodynamic solution less radical than the slats, to give it a good behaviour. The landing speed of the La-7 model is similar to other models of this category produced by our company, and its flight behaviour is pretty much normal. However, in the stalled or too tight turns such as the half-turn-and-roll (Immelmann turn), even at quite high speeds, you may reasonably expect to meet with the wing drop or snap roll behaviour- therefore we recommend you to execute these manoeuvres at safe altitude. You will soon find that if you want to fly the well adjusted La-7, 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 Lavochkin La-7. We wish you many happy landings. A list of parts and tools necessary for finishing the model that are not supplied in the kit: Polyurethane (PU) or 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 tested recommended 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.