On the territory of the Aviation and Space Lyceum. Yu.V. Kondratyuk, Novosibirsk, there will be an open regional competition in aeromodelling sport in the class of cord models of electric flights.
Date 25 April.
Message received, we are starting to prepare.
Some time ago, a student of the School of Technical Creativity made a bench model of the Yak-3 aircraft, the hero of the Soviet Union – the pilot of the Normandie-Niemen squadron, senior lieutenant Marcel Lefebvre.
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The plane is made of gray insulation. The whole structure is cut with a nichrome string according to patterns from dense Whatman paper. The gluing was made with titanium glue.
Painted with art acrylic. All decor is made of ORAKAL advertising film.
Drawings are printed on a scale of 1:12.
This is the first model made in our circle using the “Tetris” technology.
Since there are drawings, the technology has been worked out, it was decided to build a similar model in a cordless design with a brushless motor. For participation in the competition, a half-copy of the cord will be made in the same scale.
The collected material is quite enough to compile a package of information on this aircraft. which is attached to the bench evaluation of the model.
Accidentally in the store came across a plastic model of this aircraft and that of the pilot Marcel Lefebvre! For a better understanding of the construct I bought it. Since you will have to make a half copy. I really want to win in the “stand”.
Time counts for days or even hours.
I make copies of the drawing for making templates using tracing paper.
I mark and cut the blank made of thick insulation with my wonderful nichrome cutter. By the method of gravity .. since micron precision is not needed.
At the ends of the blanks, I fix the wing templates cut from a thick Whatman paper. I rub the edges of the templates with a soft pencil lead for better gliding of the string. I fix them on the foam with needles.
I press the workpiece on top with a load, a guarantee against shear. I start cutting from the underside of the wing and from the trailing edge as it has a flatter shape. Cutting through the bottom surface. I fix the template of the upper section and again cut the foam from the trailing edge. Since the wing is tapering towards the outer edge, one half of the string must move faster than the other. Otherwise, steps will form on the cut surface. I carry out all operations in one hand. If you cut together, you need to mark the templates into equal segments and control the passage of the string along them. Speaking to a friend passing the mark, one, two, three, and so on.
The right and left fenders are cut out, transition to the tail unit. The procedure is the same, I make copies. I use them to make templates. Referring to the drawing, I will make templates for the rudder and elevator sections. I fix templates at the ends and cut through all surfaces using the technology described above. Then, under running water, I remove the makhrinka, cut it along the contour. Drying on a battery.
All bearing surfaces are ready, now you need to remove the makhrushki that remained from the melting of the foam with a string. Having picked up the grain of the waterproof skin, I begin to gently wash this hair under running water. With dry skinning, streaking may occur. Everything is sanded and cleaned. I wipe the surface with a damp cloth, finally remove hair and dust. I put it on the battery to dry.
The first day has come to an end.
We leave the model late.
For the manufacture of the fuselage, I cut insulation blocks. The first block (starting with the tail section) is 5 cm thick. This will go across in the tail area. The second block is as long as the cabin itself, a straight section. Then another one along to the engine. Several 5cm blocks for bow cross-sections. Since there are large differences in the surface. In this case, it is necessary to observe the vertical cut of all side faces of the blocks. Otherwise, when gluing, everything will go into curvature and obliquity.
I fix a couple of metal squares on the edge of the table and, according to the markings, I begin to cut the insulation strictly vertically.
Cut out templates of sections from dense Whatman paper with a margin. According to this margin, the string is set to its original position. I cut the long parts of the fuselage with a large nichrome saw. Five centimeters short with a nichrome jigsaw.
In the tail block, you need to cut the inner part to nothing. On the one hand, I fix the internal cut template, on the other, just a strip of Whatman paper. I cut obliquely.
To maintain symmetry, I attach templates focusing on already cut details.
After a while, I cut the blanks into the fuselage. I'm trying to figure out how everything will turn out.
On my mighty skin, fixed in a vice, I apply roughness to the mating parts and start gluing together in blocks. The assembly is carried out from the tail section.
I glue the details with titanium in sections, then add one to the other.
The fuselage is assembled and heroically dried on a battery.
I turn to the wings.
The wings were glued together on a slipway. Pre-neatly cut along the length and glued in a spar of 4 mm plywood, cut at the desired angle. On the side member, there is a place for attaching the control rocker for the elevator. Standard model rocking chair for fighting wings. Glued with titanium and fixed with masking tape on both sides.
A comb for attaching the control cables is glued to the end of the wing.
While the wing is being glued, I come to the glued fuselage. With the help of sandpaper and water I grind the entire contour, smooth out and straighten out irregularities.
Yes, it turned out quite smoothly. There was no need to putty.
Using a simple device made of skewers and a strip of cardboard, I made a device for copying the wing contour in the area of intersection with the sides of the fuselage. I drew a couple of templates along this contour. Marked the position of the wing on the fuselage. Using the fixed templates, I cut out a seat under the wing with nichrome. Everything went well enough, despite the wet fuselage after grinding. On the battery to dry!
According to the drawing I made templates for inserting the rudder and elevator. I fixed the templates on the fuselage from above and below with needles and cut a hole with a string to install the rudder.
I pasted the rudder, cutting off the moving part. I glued it at an angle. On cord lines, this is done so that the model flies out of the circle and pulls the control cords with its inertia. For strength, I also installed the steering wheel on toothpicks.
Using the templates I made, I cut a hole with a string for installing the elevator in the side surfaces of the fuselage.
Cut off the moving parts on the halves of the elevator, reinforced the mating points with 3×5 mm balsa strips.
Before gluing in the elevator, I connected the two halves with an aluminum plate with a hog. This device was assembled from two plates glued with cyacrine.
I hung the movable part of the elevator on homemade plastic hinges, cutting through the balsa reinforcements with a scalpel. The hinges were glued with cyacrine. (They were cut from a protective film from a new monitor. It was attached to protect it during transportation.)
I installed a landing gear wheel on the tail of the fuselage. The stand is made of 2 mm spring wire.
The mounting platform is made of two plates of fruit plywood, everything is glued to titanium. A structure is installed in the body into a niche cut out with nichrome. Filled with 5-minute filled epoxy.
The landing gear is installed in the wing. The struts are made of aluminum, on which wheels are mounted with axles of 3mm bolts. The thread is fixed with cyacrine. In the wing, a niche is cut out with nichrome for the embedded pads, which are glued into the wing and the spar using a five-minute filled epoxy. The racks themselves are bolted to the base plate with four screws 2 mm in diameter.
Then the fuselage is installed on the slipway, belly up, and wings on titanium are glued into the cut-out hole. Air intakes are glued into the space between the leading edge of the fuselage and the wing and fixed with masking tape. For loyalty, everything is crushed by weights.
Everything dries heroically until tomorrow. There is very little time left before the competition, you have to hurry.
The second day of work is over.
The third day.
We begin to detail the airplane, this is almost half of the work.
First of all, I remove the contour to install the fairing between the wing and the fuselage .
I make templates from a dense Whatman paper, once again I adjust them in place. For fairings, using horizontal nichrome cutting, I prepared strips of insulation 1.5 mm thick. With the help of screw-in bolts with a fine thread, I set the required cutting thickness, taking into account melting and forward.
Recently I wrote an article on this device.
After making the strips, I grind the hairs remaining after the cut with nichrome wire.
I roll each strip with a metal pipe. After rolling and crumpling, the foam becomes plastic and easily takes any curved shape.
Using templates I cut out the parts of the fairing between the wing and the fuselage on the right and left sides and stick them on titanium.
After that I make templates for fairings in the area of the rudder and elevator. I cut out parts from crushed polystyrene and glue them onto titanium. I apply glue, wait five minutes and carefully apply the workpiece to the right place. Adheres almost instantly. I press a little with my hands along the contour, for clarity. The crushed polystyrene lends itself like plasticine.
I turn the airplane upside down, it is necessary to mount the air intake tunnels.
According to the drawing, I make templates from a thick Whatman paper and use a thermal jigsaw to cut out a couple of tunnels from the insulation. Air intake in the bow and under the cockpit.
I cut the first tunnel obliquely and run it in the bow under the hood. At the second, I cut off the space for the sashes and mount it from thin foam. Then I glue everything assembled in place in accordance with the drawing.
BOOOT first problem.
As a result of the rush, I forgot to install the thrust from the control rocket to the elevator inside the fuselage …
This contraption had to be installed when the wing was still I did not glue it.
I made the rod from a bamboo skewer with a diameter of 5 mm. At the end I tied a wire continuation with a diameter of 2 mm.
I sit thinking, the clock is ticking.
The first movement is pushing the sword through the bow, where the motor is. The wire goes through the cut channel exactly in the area of the elevator hog. I bend the tip with the letter “Ge” I put the pig into the hole and fix it with a piece of tube with cyacrine. I solved half of the problem.
To continue the operation, I need one more hole in the fuselage. According to the drawing, I make a template for the cockpit and, having marked, I cut through the cockpit in the upper part. And also the hood, the hardware and the battery will be installed in this cutout. The holes are just in the area of the installed rocking chair.
Putting the pliers into the cockpit, I bite off the thrust sword in the right place. From a strong wire, I bend the second end and install it in the hole of the control rocker. Fiddling with nippers with tweezers and a set of the necessary phrases (mentally reciting spells on the great and mighty, the children are nearby), was crowned with success. He connected the wire and the end of the rod with heat shrink clamps on cyacrine. I very carefully seated the rings with a soldering iron.
I am laying the floor of the cabin and small detailing completes its interior decoration.
I set the cockpit canopy down from a milk bottle on a dummy left over from a past project. I glue the moment to the body with glue. It dissolves the foam. But there is one trick. I apply glue to the surface of the plastic lantern. I wait about ten minutes. And the dried glue behaves quite peacefully in relation to the foam.
From the same crumpled strips I form the cover of the cockpit canopy. The binding was glued with the same glue using the same technology.
I cut off the nose of the aircraft in the right place and glue the motor mount made of 4 mm plywood at a slight angle of the motor to the right. He, too, must pull the model out of the circle with his thrust, pulling the control cords. I chase the cut off part of the nose and glue it to the motor mount. From the top of the hood, everything is smooth. I install a 2836 1400 kV motor. Regulator for 30A and battery 1300mA 3S.
All elements are fixed inside the body with Velcro, and the battery has enough room to move when looking for the center of gravity. The receiver is also installed with one control channel only for gas.
The rules of our competition are such that the transmitter is at the pilot's side. He can control in flight only through the throttle channel.
There are suggestions for setting a timer.
Let's say the mechanic turns on the timer for 4 minutes and starts the model “at full throttle”. This time is enough to fly off the complex. Then the timer turns off the engine and the pilot lands.
This option is more like “real” aerobatics of models with a gasoline engine.
While these proposals are under consideration.
Sorry for the retreat.
Then, from suitable heat shrink tubes, I form the engine exhaust pipes.
With a well-polished plate along the ruler, I apply all the connections of the hood and the division of the body. Hatches and other details. I imitate the rivet by poking with a ballpoint pen. True, the rivets are obtained inside .. but this is a half-copy.
The fuselage is painted with artistic acrylic. Initially, it was covered with acrylic white primer and then with the main color. When accelerating drying, he warmed his hair with a hairdryer.
Stars and other decor is made of advertising film ORACAL. Since the film does not adhere very well to acrylic, I slightly painted over all the places of gluing with a matte varnish. After drying with a hairdryer, I glued the whole decor.
What is the result.
We managed to leave the circle at nine o'clock in the evening the night before the competition.
The competition was organized on the territory of the Novosibirsk Aerospace Lyceum.
18 athletes took part in the competition. And of course, our main competitors were the pupils of the lyceum.
We won at the stand!
On flights in third place.
Since we did not have time to fly around the plane, all our the settings were purely speculative.
In the first flight, we suffered fear when the pitch began to swing.
Applause to the young pilot Maxim .. in such a stressful situation he managed to keep the plane on course, flew off the program and landed without damage.
The second and third flights after adjustments and settings were in a good picture, but there were not enough points.