An interesting toy airplane that is launched using a catapult

Author V.ALESHKIN

You can launch a non-motorized aircraft model by hand. But it’s much more convenient to use a rubber or mechanical catapult. And the flight range will increase, and the speed will increase noticeably. At the start, for example, up to 70 m/s. One thing is for sure: when launched energetically, and even with a tailwind, the model can fly hundreds of meters away. So run after her!

Apparently, this activity was not very to the liking of the American aircraft modeller R. Simon from Dakota. He turned out to be an inventive guy and this is how he found a way out.

A non-motorized aircraft is, of course, the simplest aircraft. But why not equip it with a device that partially regulates its flight? Without resorting to electronics, Simon found the perfect solution. To implement it, you only needed an elastic band and two hooks. Let's tell you in more detail.

As you know, the flight direction of the model is determined by the tail unit. Thanks to him, she turns right, left, and can move up or down. So the inventor decided to fix the tail not rigidly, as is customary, but on the axis. In the vertical plane, such plumage was able to swing by 5 - 7 degrees, and in the horizontal plane by 1 - 2 degrees. And so that the movements did not happen at random, I strengthened the oscillating system with an elastic band (see figure).

This, so to speak, is a constructive trick, and in order to better understand the physical essence, let us turn to such a little-studied and rarely used phenomenon in technology as automotor oscillations. Let us remember how the wires of high-voltage power lines hum in a strong wind. They generate sound like strings. The tail unit of Simon's design behaves the same way. By launching the model with a high initial speed, we will ensure that the incoming air flow, like wind in wires, will force the tail to oscillate at a low frequency in two planes. Oscillations will lead to a change in its position, and therefore change the flight course. The model will either rise sharply, then go to the right, then descend, take it to the left... The flight will be exciting, and you won’t have to run far after the model.

Another fun find Simon has found are whistles. They are installed under the wings and tuned to different sound frequencies. The model “sings” during flight.

If you want to build one, we recommend using another Simon improvement - catapults for manual and mechanical launch. Rubber is the simplest. You will need a strong stick with a diameter of 1 5 - 20 mm and a length of 250 - 300 mm. The type of tree does not matter. At the upper end of the stick, a ring of steel wire with a diameter of 1.5 - 2 mm is attached, and to it a harness of 10 - 15 threads of aircraft model rubber 400 - 450 mm long. The harness ends with a steel piece, very similar to a fishing lure. The method of attaching it to the nose of the model is shown in the figure.

A more complex catapult is a mechanical one. It uses an overdrive gearbox with a manual drive and a drum. When launched, a handrail is wound around it - a fishing line with a diameter of 0.7 - 0.9 mm and a length of 5 - 7 m. Of course, such a system works much more efficiently when driven by an electric motor. But you can also launch it by hand.

As we said, the initial speed of the model when launched is very high. And so that at the final moment the “spoon” jumps off the hook, Simon uses a parachute brake. Very similar to the one used in large aviation.

Some models are difficult to throw with your hands, but the chassis is not. There is a catapult for such models. My version was created based on existing analogues, taking into account available materials.

Launch catapult built, tested, redesigned and retested FunJet Ultra.
For production you needed: 3 slats 30x40x2000; M8x1000 hairpin sawn into 3 pieces; 6 M8 wing nuts + 6 M8 locking nuts; 2 flat corners; 2 M5 bolts + 2 nuts; 4 screws.

The stand itself is collapsible. Can be folded flat and disassembled into a “bundle of sticks” state.

Next, rubber: 4 pieces of 3mm and 4 pieces of 4mm fishing rubber, 15m each. The meters are apparently also rubber, because... all pieces are different lengths. But this is not very important, because... when stretched, the difference is not visible. A steel ring is attached to the rubber on the far side, and two more rings are attached to the cord (rope) at the other end. The cord with rings is divided approximately in half and is attached to the rubber at this point.
Additionally, a main anchor is required - a large crowbar-shaped pin for driving into the ground. And a smaller pin for the trigger. I use an M12 pin with a sharpened end as a smaller pin.
The descending device is a long stick with a hole at the end and a “leg” support in the middle. From the outside it looks like a children's swing.

How it works: we measure at least 4 lengths of rubber between the pins along the line of the wind (launching against the wind), hammer them into the ground, stretch the rubber, first put a stick with a hole on the trigger pin, then a ring. To descend, you just need to step on the other end of the stick. Simple, cheap, quick to manufacture. Next, we install the catapult and the plane so that the second ring fits onto the plane’s hook.
The towing hook was made from a 5 mm rod (electrode), a thread was cut, a hole was made in the plane, reinforcement was glued from a piece of carbon plate on the outside and a piece of wooden ruler on the inside.
When starting the RV to the maximum up.

I sketched out a diagram. The yellow stuff is the trigger device. I didn’t bother to draw the catapult stand itself, everything seems to be clear.

One more remark needs to be made. The closer the hook is to the CG of the model, the more the nose will turn up at the start. Gliders launched with rubber generally fly vertically upward, but this is no longer a catapult.

I did it at random, the distance from the hook to the CG is quite large, more than 100mm. It flies horizontally, accelerates to a decent speed, at which it becomes controllable.

I made 3 more starts over the weekend, all went well. I took a little look at what was happening; before this, emotions and jitters did not give me. While acceleration is in progress, the model does not react in any way to the fully raised RV. Then it sharply goes up and the hook unhooks. Gas can be supplied somewhere at this transition stage. Once again I was convinced of the reliability of such a start.

Fast delivery: sending goods from warehouses in Russia

Gliders for FPV flights have become especially popular lately; their sizes are becoming increasingly impressive. Pilots also do not ignore impeller models. There are not always convenient conditions for launching models, and not all models have a chassis. Launching is often done by hand without an assistant. The solution may be a catapult. The Internet is replete with diagrams and options for its manufacture, but it’s not so often that you see modellers launching from catapults in the field. So, the line of products of the Dear-Fly air club has been replenished with an easily assembled catapult - a collapsible catapult with foot control for launching FPV gliders and impeller models.

Manually starting models can be a challenge; most pilots have difficulty starting models. This wonderful launching system is easy to transport (loosen 6 screws and it assembles in half) and will allow you to independently launch models at the required starting speed! Everything you need for this is already included in the kit (metal locks, 2 meter shock absorber cord, nails, bolts, nuts, etc.).

Characteristics:

Dimensions when assembled:

Length - 1060mm

Rear height - 240mm

Front height - 460mm

Guide rail width - 470mm

Material:

Frame - fiberglass pipe with plastic connectors

Foot launch system - plywood with rubber band (2 meters)

Typical catapult layout:

When launching using a catapult, follow the safety rules:

1. When driving the crutch into the ground, tilt it in the direction opposite to the pull vector of the tourniquet.

2. Make sure that the spike is securely driven into the ground to a sufficient depth and that the soil can withstand the tension of the rope

3.Fix the catapult and pedal firmly to the ground

The throwing model is a semi-copy of the Su-24 aircraft. The model was developed and manufactured in the aircraft modeling laboratory of the Center for Children's and Youth Technical Creativity in the city of Rybinsk for beginning aircraft modelers. The prototype was the modern supersonic bomber with variable geometry (sweep) wing Su-24, which is in service with the Russian Air Force. Launches of such models always arouse interest among both circle members and spectators. And thanks to the ease of manufacture, the model of this jet aircraft was a great success in suburban children's centers.

The materials for the half-copy will be the most accessible: a sheet of foam plastic PS-4-40 (300x210x3 mm), 3 mm plywood for the spout, aircraft model rubber and PVA glue. And the only tools you will need are a scalpel, a marker, a pencil, a ruler, scissors and pins.

Making the model. Most parts are cut from foam plastic. Only the spout is made of plywood. It is best to process foam plastic with a thermal cutter, the cutting element of which is a nichrome wire heated by electric current.

It is most convenient for novice modelers to mark the contours of parts using pre-made templates made of thick cardboard, but older children can use the method of transferring the configuration of parts from the drawing to foam plastic and plywood using carbon paper. To prevent the drawing from deteriorating, it makes sense to protect it with plastic film.

The production of the model begins with marking the contours of the model parts on a 3-mm sheet of foam with dimensions of 300×210 mm. This work must be carried out with maximum precision - the flight qualities of the semi-copy depend on this. The bow part is marked on a sheet of 3 mm plywood. It should be noted that the model requires a double set of wing consoles and fuselage sidewalls and six sets of weapons suspension pylons.

1 - wing console; 2 - sides of the fuselage; 3 - upper part of the fuselage; 4 - lower part of the fuselage; 5- halves of stabilizer; 6- keel; 7- partition; 8- gargrot; 9 - forward part of the fuselage; 10 - weapon suspension pylons (6 pcs.)

Main details of the model(the numbering of parts corresponds to the positions of the assembly diagram)

The next operation is cutting with a sharp scalpel to mark all the foam parts. In this case, it is advisable to use a metal ruler. For novice modelers, it is better to perform this operation with scissors. The ends of the cut parts must be smoothed with sandpaper.

The most complex and time-consuming part of the model is the bow: it is cut out of 3 mm plywood with a jigsaw and processed with a file and sandpaper. The groove for engaging the model launch catapult rubber band should not have sharp edges, otherwise the rubber on them will quickly fray.

The assembly of the foam parts is carried out using PVA glue using ordinary tailor's pins to temporarily fix the parts relative to each other. This is how the stabilizer is first glued to the top of the fuselage. If the glue is thick, then before work it should be diluted a little with water to better coat the surfaces.

The sides and upper parts of the engine nacelles are connected with pins, after which the joints are coated with glue from the inside. Glue is applied to the ends of the lower parts of the engine nacelles, and they are glued between the sidewalls, securing them together with pins.

Next, you need to select the required sweep of the rotating (on the prototype) wing consoles and glue them to the center section, inserting their root parts into the slots in the sides of the fuselage, and then glue the jumper into the middle of the rear fuselage.

After the glue has completely dried, the technological pins that secured the parts to be glued are removed, and the nose element of the model is joined to the fuselage box and the joints are carefully coated from the inside with PVA glue.

The keel is glued to the rear of the fuselage and temporarily secured with the same pins. A gargrot, also cut from a foam strip, is glued on top of the model fuselage. After the glue has dried, the weapon suspension pylons are installed in their places in accordance with the assembly diagram of the model.

Model finishing. As already mentioned, the throwing model is a half-copy of a modern supersonic bomber, so it is advisable to paint it in accordance with the coloring of the prototype aircraft. We recommend using indelible markers for this purpose, with which you can draw the contours of ailerons, flaps, rudder, technological joints, air intakes, as well as stars and side numbers.

For greater copyability, you can paint the model with light blue nitro enamel using an airbrush. It is best to do this in a special ventilated room or outdoors, away from fire. When using an airbrush filled with nitro enamel, it is recommended to keep it at a distance of 150-200 mm from the model in order to prevent the foam from dissolving; The paint should be diluted only with acetone.

Balancing the model. The assembly diagram of the semi-copy shows the position of its center of gravity (CG), which guarantees stable flight of the model, which has a wing sweep of 35°. When the sweep changes upward or downward, the alignment is selected experimentally using plasticine added to the nose or tail of the aircraft.

Adjustment and launch of the model. Before launching from a catapult, the model should be adjusted in gliding test flights by hand. If the model glides steadily and the flight range is 10-15 m, then it can be launched from a catapult. The catapult is a ring made of rubber thread with a cross-section of 2×1 and a length of 400 mm. After tying the ring, pinch the knot with your fingers. With your other hand, grab the model by the tail section and, pulling it back, release it. If the model is well assembled, then immediately after a successful launch it should make either a Nesterov loop or an “Immelmann-semi-peggle” and land spectacularly.

Possible planning deficiencies are eliminated by bending the trailing edges of the fin and stabilizer. By changing the wing sweep and the angles of deflection of the tail edges, you can make the model perform aerobatic maneuvers - such as “barrel”, “loop”, “Immelman”, “bell” and others.

A - when diving, the trailing edges of the stabilizer blades bend upward; B - when pitching up, the trailing edges of the stabilizer blades bend down; B - bending down the trailing edge of the wing of the left console will help get rid of the left roll; G - in normal flight, the model glides steadily at a distance of 10-15 m; D - the adjusted model is launched using a rubber thread catapult

Based on the Su-24 model, our laboratory developed and manufactured propellant semi-copies of the MiG-29, Su-27, MiG-25, R-18 and R-16 aircraft. All of them have different sizes and weights, but they are united by spectacular flight, attractive appearance and ease of manufacture.

To develop the design abilities of novice modelers, experimental copies of various designs can be developed on the basis of these models: tailless, flying wing, canard and others.

In competitions between modellers and semi-copy models, replicability, flight time, cleanliness of aerobatic maneuvers and originality of design (for experimental models) are assessed.

In conclusion, it should be noted that larger models can be made, increasing the linear dimensions by one and a half times. In this case, you can use 5-mm plates prepared using a thermal cutter from quite affordable packaging foam.

Technical data of the semi-copy model of the Su-24 aircraft
Wing span, mm;
at a sweep angle of 15°…. 280
at a sweep angle of 68°….. 210
at a sweep angle of 35°….. 260
Length, mm……………………………. 285
Height, mm…………………………….. 80
Model weight, g……………………… 20

S. KOLONSKOV, teacher of additional education of the highest category, CDYUTT, Rybinsk

!
In this article, Bob, the author of the YouTube channel “I Like To Make Stuff,” will tell you about his rather bold and unusual project to create a catapult.

Materials.
- Pine board 50X100 mm
- Silicone hose
- Plastic ties
- Perforated steel strip
- Aluminum profile
- Steel stud, nuts
- Self-tapping screws for wood.

Tools used by the author.
- Clamps
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- Miter saw
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- Square, pencil, tape measure

Manufacturing process.
First of all, the author cuts the material, bars 50X100 mm in size, and begins building the frame.
Several bars are cut in half in order to make racks and several diagonals from them.

Since the vertical post will be subject to significant force from moving back and forth, the author attaches a diagonal crossbar to strengthen the connection. He uses clamps to hold the structure together. The master sets the disc at an angle of 45 degrees and cuts the timber on both sides. Now it should fit perfectly here.

After some thought, the author came to the conclusion that the easiest way to hold this entire structure together, without bothering with joints and pocket holes, would be to use steel strips. They are strong enough to withstand the load. True, their strength is not functional in all directions, but for this particular “machine” they are the best solution.

Then the author makes the same second half and temporarily fastens them with a metal pin.
In addition, he wants to use a similar rod as a support for the arrow arm. This is the maximum distance at which these elements can be removed from each other.

He cuts a few more pieces of wood to hold the base together. Once again, the author resorts to the “quick join” technique: he uses long wood screws and drives them from the outside of the frame into the very middle so that they go deep into the fibers.

The craftsman figures out where to drill holes in order to pass the metal rod through them. This will be the central axis of the structure, so that the entire lever arm will have its fulcrum at this location.

He places the arrow on top of the shaft and lifts it vertically to figure out where the fulcrum should be.

The master marks it and drills a through hole. The lever arm is nothing more than an aluminum profile. It is extremely light, but at the same time quite strong.
Well, now the rod will go here.

Excess studs are cut off with a grinder. Now the rod is fixed in both parts with nuts.

On both outer sides, the author screws the cuttings of the board so that the rod does not slide back and forth.

The base of the frame is sufficiently fastened, but the top is somewhat shaky. So the author screws on a few more additional spacers.

The time has come for testing. The craftsman screws a wooden round piece to the arrow. It will act as a hook for the rubber hose to hook onto.

The hose is temporarily fixed on the racks with clamps. This is a regular medical hose. It is very elastic. And the attempt was a success. Small objects fly far, and with decent acceleration.

The transverse partition had to be removed; it interferes with the full movement of the boom.

The negative point was that during launch the support struts bent somewhat and “extinguished” part of the kinetic energy. The author is going to strengthen them by screwing these plates to the outside of the bars. In this case, the structure will not tilt.

Instead of a crossbar, the master pulled an elastic band - an arrow catcher. One more check... the arrow is not touching the frame - that's what you need!

In his project, the master will use these locks to hold the arrow.
Thanks to them, the whole thing will be kept cocked. If the latch is pulled back, it releases the catapult boom.

The screws in this place must be long enough to withstand the force that the lever will create.

To launch the catapult, you need to open both valves at the same time. And it is advisable to do this from a safe distance. The author connects both latches with a short rope, quite loosely, and ties a long one to it.

Now you need to make a place for the hose that would twist around the hook at the back of the lever. For this, self-tapping screws with an eye will be used. It is fixed to the profile using a wooden block.

Now you can pass the hose. The author does not yet know how long it should be.
Everything will be tested experimentally.

The ends of the hose are wrapped in this way; this will create additional friction and prevent the hose from coming undone. In addition, you will need a few more zip ties. The tails of the ties are cut with scissors.

The rubber damper is attached in the same way.

For the “spoon” itself, where the projectile should be loaded, the author will use this spatula, purchased at a hardware store. He will secure it to the profile again with ties. If there are not enough of them, electrical tape will be used.