I haven't made any new models last winter. I mostly repaired and renewed the old stuff. I also had bad luck breaking one of my little model favorites - "orange" Yak-3. The fault was mine: I hurried and failed while configuring the remote control. Despite the confused controlling I managed to save the plane from a full-force nosedive, but the foam wing spar didn't survive such treatment...
Was there any sense repairing it? It would require a new wing though, besides the replacement traces would be noticable. And where there is a wing, there is everything else...
Such thoughts led me to make a relatively similar but new model.
I took the old Yak-3 "Electric Orange technology" drawnings, which I decided to change a little, in order to make a new model. The choice was between the Yak-1 and Yak-9 of different modifications. The earlier model of Yak-1 with high fuselage fairing required too many fuselage changes. Yak-9 was very similar to the lighter Yak-3, except the recessed panel lines of cabin canopy - the change insufficient for full remake. There was only Yak-1b (the one that "gave birth" to Yak-3") and earlier modifications of Yak-9 left, but I liked Yak-1b more for its smoother and not that angular airscoop contours. So, let's build Yak-1b!
What is the difference between Yak-1b and Yak-3 looks?


First of all, under the motor we can see the "beard" of an oil cooler and a smaller water radiator tunnel. They tried to introduce a one-piece windshield to Yak-1, but managed to get the required quality of materials only when Yak-3 appeared in the series. Among the minor differences: Yak-1 had greater wingspan (10m against 9.2 with Yak-3 and 9.74 with Yak-9). There were yet some other differences, but I ignored them, as I didn't plan to make it a serious copy.
So, the prototype was chosen and the construction begun.

Day 1.
I started my work with the fuselage construction. I copied the fuselage framework stencils to a piece of a ceiling tile. It's better to use ceiling tiles and the thicker it is - the better as the airframe becomes harder and not that twisted while being covered. It gets heavier of course but not much, all the framework details fit in a half of a sheet:


After carving all the details I piece it together like a puzzle. As opposed to the drawing I do double-size D frame because the junction of the frame parts will cross it. I also glue up foam stripes after the frame F and to the sides of battery compartment from motor mount to the third lower partial bulkhead to make the covering process easier and to strengthen the nose. The motor mount itself is glued of three plywood layers. It may seem as extra-weight but such thickness allows hiding the long tail of propeller adapter and enlarges the gluing area of motor mount to the foam, so it won't come apart from minor vibration.


While glue is drying, I glue light foam bars underneath. They add neither weight nor strength but make it easier to conjoin the cover edges. The absence of these details on the drawing makes it significantly harder to fit the parts of a cover together.



Then I make the blank part for the battery compartment lid:



While I can reach all the corners which will become inaccessible after covering I mount the motor, speed controller and receiver. The motor used is the old Turnigy C2410. Many times did it hit the ground, bent and was rewound, its bearings replaced not once. The latest rewound left it with capacity 1300 RPM instead of 840, yet it works quite well. The speed controller - HK SS 15-18A. The receiver - FrSky VD5M with a self-made adapter from micro-connectors to standard ones. Even though it was designed for in-door models, it works well for little park-flyers: its range is good enough to make you lose sight of the model. All of this was left from the predecessor.


Before covering I decided to make some shape to a cockpit. I cut out a part of the stringer between C and D frames and glued walls of the prospect cabin inside:


I decided to make covering parts not in one piece, as it was suggested in the original, but in two separate pieces. I think it's way more convenient. I didn't do cutouts in the tail part: the gray laminate flooring underlayment I used for covering is quite soft and elastic. It allows for covering surfaces of sophisticated shapes. I marked the nose cutouts, but didn't cut them right away - it's better to do on place, so that they coincide with the frames.


Next step was naturally covering. I started with the tail as it was the easiest part. I covered the airframe with glue, then with a cover piece, cut off the excesses underneath and fixed the edges with pieces of masking tape. The same I did for the front part, but prior to that I glued the cutout on top and fit the joint with the tail part:


Day 2.
It took a night for the glue to dry, we can take the masking tape off, putty and sand the cover joints, cut the battery compartment lid out:



While the putty is drying up, I start working on the wing. To expand the span I added a 4cm wide stripe (i.e. 20mm each panel) to the center. This time I made the spar out of a wooden ruler: it is a bit heavier than a foam one, but in case of some hit there's a chance of getting away with some minor dents. The rest of the construction doesn't differ from the original, except for the central rib, that serves for assembling the upper part of cover.


Along the ailerones' cuts I glued pieces of ceiling tile. One layer wasn't enough so I had to glue two of them and then carefully cut off the excesses and sand these inserts. I also sanded the bottom edge on a plug both in the bottom and top cover parts. At the same stage, I glued in the ailerones' servos and put the wires to them. There won't be any access to the servos, the facade however looks neat. After giving panels reverse twist, we can close up the wing.



While the wing is drying, I do the empennage. I wouldn't make the rudder as on a previous Yak: due to the fact, that the model has no landing gears , it won't have to drive on the ground and there's no need in rudder while flying. Therefore I glued the fin at once, adding an insert of a single ceiling tile layer and sanding the trailing edge for it not to look that flat. I glued a piece of carbon into a stabilizer to strengthen it. Halves of a elevator are joined together with a check clamp, which rotates on two tin rotary joints. 6 stripes of laminator film are used as hinges:



Day 3.
The wing is glued, we can mount it, but before mounting we should glue a servo for elevator, put a wire to its receiver and create push rod. Cuffs in the original drawing are very unclear so I had to invent something of my own, fitting it where needed. The soft floor underlayment allows for that.


I cut out the air intake for oil assembly out of firm package foam. I should have made it of XPS: however firm the foam is its surface becomes too spongy after the treatment... Anyway, after puttying and painting the flaws won't be seen. By the way the air intake functions - underneath there's an opening cut which leads to the motor/battery compartment , and the wind current will give the engine unit enough cooling while in flight.




Day 4.
Now the time has come to paint, glue decal and cover the model with duct tape. The colour scheme I chose was black and green camouflage. I painted it before carving ailerons. When the paint was dry I cut the ailerons out and painted the bottom blue. While covering I hanged ailerons on duct tape. The colour scheme has no historical value - it is simply a mixture of elements from various planes. There hardly existed any Yak with such combination of colour scheme, number, rank markings, especially a guarding one. But it looks very nice altogether:



At the same time with painting I cut the imitation of a water radiator tunnel out of XPS. Given the fact that it will have to serve as a landing skid, I put a thin transparent plastic strengthener after painting and covering it. I did the same on the front air intake:



Day 5.
The process is close to its end. The model can fly already, but some decoration elements are needed.
I got to form the cockpit so for it not to look an empty hole in a fuselage. I didn't try to copy everything, so I got with the panel board, pilot chair, footplates, control stick and power lever:


I finally glued the cockpit canopy in place, carved a spinner out of XPS and made an exhaust collector imitation. Yes, I know that Yak-1 had not 6 but only 4 exhaust pipes on each side - such exhaust system was introduced in later models of Yak-3/Yak-9. But the "exhaust" here is functioning - these vents wil let the cooling air out. And 12 vents are not 8 vents...


The model is ready.



Specification:
- wingspan: 900mm
- length: 760mm (with cock)
- takeoff weight: 430g (Yak-3 was 415g - a small price for the strengthened wing of a greater span, cockpit and an extra-air-intake).

Components:
- motor: Turnigy C2410 840kv (rewound to approximately 1300 RPM, OTM)
TURNIGY Bell TR2410-9 840kv Outrunner
Product http://www.rcfair.com/en/product/6549/

- speed controller:
Hobbyking SS Series 15-18A ESC
Product http://www.rcfair.com/en/product/6456/

- servos (3ps): HobbyKing™ HK15178 Analog Servo 1.4kg / 0.09sec / 10g
Product http://www.rcfair.com/en/product/103526/

- receiver: FrSky VD5M 2.4Ghz 5CH Micro Receiver (Telemetry Capable)
Product http://www.rcfair.com/en/product/387720/

- battery: Turnigy 1000mAh 3S 30C Lipo Pack
Product http://www.rcfair.com/en/product/9491/


And in conclusion - the video of a flight. This is not the calibration one - the first time it was the camera that shifted without me noticing it. As a result the plane was on screen only occasionally. This time the camera went off earlier, must be frozen and lacked charge from the previous half-hour shot. So the landing isn't here. But you can see the plane flying under the conditions of 3-4 m/s wind and terrible turbulence caused by the houses.


This model isn't as fidgety as the previous Yak-3, especially in rolling. These 4cm of difference do their job. But the speed is the same, as expected. The flying time is also the same - 7-8 minutes. So this ia a rather nice variant for calm demonstration flights. If you increase its servo travel and set it on a full-throttle it could become a nice fighter.

P.S. Don't you think I've been doing it all days through. I devoted 2-4 hours of my time a day, nothing more ;-)))
This is the translated version. You can read the original Russian article here.