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Jun 21, 2019, 01:30 PM
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Build Log

I made my own efx racer

Let's get started
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It's been over a year since I've been in this hobby. First with static models due to the lack of components to fly them and then more recently, and thanks to a visit of my wife to switzerland, I've been able to get the electronics I need to start building my own planes. The first model I built was a replica of the Cessna 182, with which I learned the basics for a successful flight. But in this world, it is never enough, there is always a next step.

We've all probably seen a model and said: I want this model in my hangar for sure! That was my reaction when I first saw Durafly's EFX Racer. Maybe you guys are thinking, why do it instead buy it? I live in Cuba, and here we don't have access to any hobby shops, and we can't shop online either. So, we just have to resign ourselves? No, there are thousands of ways to build models with conventional materials. All you have to do is want it and make an effort.

With the objective fixed, it only remains to start building, and all good construction begins with a good plan. As usually happens with most commercial models, there are no plans, so you just have to do it yourself. The level of detail of the plan will depend on the construction technique we use. In my case, I used a basic construction technique, using EPP. So I only needed the plan profiles of the different views of the model and some more details. After several hours of work, I obtained the basic plan following the images provided in the assembly manual of the original model. All that's left is to print and start cropping the templates.

Characteristics of the model
  • Wingspan: 110 Cm
  • Long fuselage: 76 Cm counting the cone

Electronics to be used:
  • Motor: Turnigy L3010C-1300kv (420w)
  • ESC: HK 60 A
  • Batery 3s 2200mA
  • Servos: HXT900
  • Prop: 8x8.

The construction technique
The construction technique used for this project is simple and affordable for most. In this thread of the spanish blog Miliamperios, each of the steps is illustrated in great detail, so in this writing I will only mention the steps vaguely. For the construction of the fuselage the first step is to cut the templates of the upper view of the model. Once trimmed, it is necessary to glue them to some material strong enough to pass the hot wire without deforming the template. In my case I will use a cardboard that is used to make false ceilings and by architecture students in their projects. You have to make two copies of each template.
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Description: Templates cut out and ready to be glued on the cardboard

For the construction of the model I will use a 10 cm thick EPP block which is used as a lightweight cover here in the construction. The next step is to fix both templates above and below the block correctly aligned, for this we can use small drops of glue, or as in my case, sewing pins. Once we have the templates well aligned and attached, we pass the hot wire cutter.
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Description: Cutting the fuselage using the top view

We repeat the process using this time the lateral templates, one for both sides.
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Description: Cutting the fuselage using the side view. The cabin and the vertical stabilizer have been removed from the template.

Finished these steps, we will obtain the fuselage cut with a square form. At this moment we have two options to follow, or we round the fuselage from now on, or we keep it square. In my particular case, I keep it unrounded to be able to locate the wings and tail group more easily and accurately.

The tail
For the tail group, I will use high-density EPP obtained from a TV box. Using the hot wire cutter, I obtained several 1 cm thick sheets on which I marked the tail templates and cut out using a sharp blade. Then I cut the control surfaces and proceeded to sand and round the edges to improve the aerodynamics of the whole. Both the horizontal and vertical stabilizers were reinforced with a 5 mm thick pine crossbar.
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Description: Tail group cut and not yet sanded

The wings
For the construction of the wings we follow the traditional method of ribs and hot wire. After obtaining the two half-wings, it is sanded to smooth the possible defects of the cut.
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Description: Wings cut and not yet sanded. You can see the flaws of the cut with the hot wire.

Then cut the templates from the plane and cut the tips of the wings with blades following the shape of the model.
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Description: The tips of the wings trimmed according to the plan

Once they are ready, they are glued and when the glue dries they are reinforced. In my case I used formica as recommended by my friend Jorge who has been building and flying for a long time. A reinforcement is glued all along the wings and then another ribbon for each wing.
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The ailerons are trimmed and beveled checking that the movement was correct.
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Description: Cut and beveled ailerons

The wings have two small pins made of hard wood, which are used to attach to the fuselage, which is also secured with two screws to a wooden base.
The original model does not have a landing gear, but doing some researching, people who have bought it, say that it is complex to throw by hand. Likewise, several have also taken on the task of modifying it. So I decided to include this modification in my model. The main train is fixed under the wings and on the tail, a skate.

The fuselage
Now is the time to retake the fuselage. With the tail group ready and the wings, we proceed to measure where exactly each piece fits. Using templates of the same material we use to cut the fuselage, the hot wire is passed to free the space to house the horizontal stabilizer.
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Description: Horizontal stabilizer housing cut using cardboard template

Likewise, using a negative template from the wing top, the lower part of the fuselage is cut to place the wings. It is time to shape the fuselage, first with a blade to remove the thick and then with medium sandpaper to mold and smooth the surface.
Once the nose section has been sanded, we cut approximately 5 cm from the tip, and paste a block of the same size of EPX.
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Description: Templates mounted and ready to pass the cutting wire
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Description: Sliced 5cm nose section

This piece is glued with little glue (only a few drops) because it will be removed later, just by the joint. The new nose tip is then moulded following the shape of the plane and guided by the reference photos to achieve the most realistic finish possible. When we finish, we cut just by the union, separating the block with the shape of the nose. Next we will glue a sheet of approximately 1cm of thickness for the part of the contact with the fuselage, and we give form to follow the continuity. This piece obtained will be the mold that we will use to replicate the hull of the motor in plastic. You can use any other material such as wood, but I use the EPX without any problem and without deforming the mold.
Using a bottle of conventional soft drink (preferably transparent), we cut the bottom and introduce the mold into the shoes with a wood or other object that resists heat. Using a hot air gun, or some other heat source (in my case, the electric stove), we shrink the bottle slowly trying not to burn the plastic. Little by little the material gives way and takes on the shape of the mould. Once the process is finished, all that remains is to carefully cut the plastic using scissors or knives. The hull obtained should fit under pressure on the fuselage, approximately 1cm inside. If this is not the case, sand the mould and repeat the process once more.
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Description: From left to right: initial nose cut from the fuselage, piece of EPX in pink colour and the carene obtained from plastic. Note how the EPX mold is approximately 1 cm higher than the original.

The electronics
With the fuselage fully sanded, we can proceed to open the patient in half on two symmetrical sides. With great care and patience we remove the polyfoam from the spaces intended to house the variable speed drive, the battery, the receiver and the servos.
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Description: The cut was made with a well sharpened blade. The interior is not perfect, but it doesn't matter, it will be modified later.

The engine mount is attached to the front of the fuselage, in my case has 3 screws that will hold the engine. The screws are embedded in the wood and glued with crazy glue to allow easy removal of the engine for use in other models later.
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Description: Engine bed. The screw heads are glued on the back.

The inverter is housed on the wings of the model taking advantage of the incoming air flow through the orifice under the motor bed and an air inlet just through the wings. The air outlets are on both sides of the fuselage.
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Description: The ESC is housed in the lower part of the fuselage on the wings.

The receiver, battery and tail servos are housed in the compartment accessible through the top cover. For the control rods, I used the wires of the aluminium electric cable. Each cable has 7 wires approximately 1mm thick. They do not weigh almost and in short distances they do not bend.
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Description: Servos, receiver and battery compartment accessible from the top hatch

One of the most captivating parts of this model is, in addition to its shape, its outstanding finish. Before assembling the pieces in their final place, we begin the decoration of the parts separately. Thanks to a shipment I received from my father, I have in my possession different colors of seals, which provide an almost perfect finish.
With patience and using glass to support, we can make curved cuts with ease, first by gluing the tape onto the glass and then using the blade to cut the shapes. Then we peel and glue over the material. Another variant for more complex shapes is to stick the tape on a paper, cut to taste and then under water, remove the paper by rubbing with the fingertips. Once all the paper is removed, dry gently with a towel (avoiding lint) and then glue on the material.
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Description: Custome sticker made from packing tape

For complex stickers, or those shapes that are difficult to cut out, say model names, numbers, or logos, etc. We use a technique that allows us to transfer the ink from a sheet to a transparent seal. We print in color or black and white the image we want. We glue transparent tape on the print taking care not to leave bubbles and we pass a plastic palette or something like that, making sure that the ink is well fixed to the tape. Once again, we remove the paper soaking it in water, and we have a sticker ready to stick on our model. If it is true that a total sharpness is not achieved, with time and practice, it is possible to superimpose two stickers with the same image achieving total sharpness.
Using these techniques I decorate the wings, the fuselage and the tail group.

Final touches
Ready the decorations, it only remains to assemble the model trying to achieve the correct angles between each piece. Also glue the cabin and the details of the nose, as well as fixing the top hatch with magnets. Install the servos and control rods and adjust the control surfaces.
The truth is that it is a precious model, and this technique of the tape and stickers, gives a different touch to our models. It is not yet in the air, but I hope it will be a pleasant experience once it does. I have enjoyed very much the construction of this model and it has been a good project for the exploration of new techniques that I am sure will serve for future works. Here I leave you with the final result of the work.
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Last edited by HardWork91; Jun 21, 2019 at 02:01 PM.
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