Introduction: Scratchbuild Discuss Launch Glider (DLG)

Definition DLG from Wikipedia: “a radio-controlled model sailplane
launched using a 'discus launch' in which the glider is held by a wingtip and rotated around the flyer by hand before release. Using this method of launching the average flier can achieve launch heights of greater than 140 feet (43 m), with the better throwers exceeding 200-foot (61 m) high launches.”

Wikipedia (ed), Radio-controlled glider, Wikipedia geraadpleegd via https://en.wikipedia.org/wiki/Radio-controlled_gl...

Our YouTube-Channel: https://www.youtube.com/channel/UCF9l8gahIavuYr9Nq...

Step 1: Intro

A Discuss launch glider contains a lot of electronics and need to be as light as possible. The lighter the better. When your glider flies its fly’s just on the air current, it doesn’t contain any motors. By throwing it like a discuss can it contain enough force to climb to a certain amount of altitude. The reason it stays in the air for so long is because It is very light.

The purpose of this project:

  • To experiment with materials
  • To stabilize it with electronics
  • To control the glider with our smartphone through Wi-Fi
  • To handcraft it ourselves
  • To glide for 30 seconds

With this instructable you can create your own DLG.

Step 2: Order Electronics

This step can take time, even up to 50 days. Most of the
electronics comes from China, because it’s a lot cheaper. You need 4 servos to control every wing control surface. It’s best to have 1 extra. The other items are 1x.

When you intent to make your own hotwire, you need a power supply (see picture).

Electronics:

Step 3: Other Materials and Equipment

Materials:

  • 3x Carbon rod: 2x a smaller one to strengthen the wings (3x4x1000mm) and 1x a bigger one for the tail (6x8x1000mm)
  • Polystyreen plates 1000x500mm
  • glue
  • duct tape
  • foam filler

  • wire in iron

  • foam plate 3mm

  • acarde robe

Equipment:

  • soldering iron
  • hacksaw
  • pliers
  • drill

Step 4: Designing the DLG

You have 3 main airframe types: Aileron, Elevon and Vtail

We chose for an Aileron. We only used roll and pitch to steer.

For the plane lift you have ‘angle of attack’ (it’s the angle that your wing is “turned” clockwise, this creates more lift but also more drag) and ‘airfoil’ (is the “shape” of your wing).

For the wing types you have Swept, Wing-position and dihedral, the above pictures are self-explaining. The purpose of those types is too difficult to explain in one step, so I will not explain it.

Finally, you have to build your wings. There are 2 types of materials: balsa wood and foam. The wood is a difficult and time consuming product to work with, but it remains very beautiful and professional. Foam is easier to work with. The 2 best ways to work with foam are: 1st technique is cutting, folding and gluing and 2th is Hotwiring, with this last way you can cut a complete wing out of 1 foam plate.

We chose to test the Hotwire technique and made our own Hotwire device, see step 5. For the Hotwire technique you need 2 equal pieces of wood, those serve as a shape for cutting out the wings out of the foam. The hot wire will rest on those 2 shapes. When you follow the shapes with the iron wire you will get your wing. Those shapes are made by drawing a drawing (see picture above) and cutting it out with a saw.

We have:

· Angle of attack: 0°

· Airfoil: see picture

· Swept: straight

· Dihedral: 5°

· Wing-position: High-wing

Step 5: Making Your Own Hotwire

Basically, you just need to clamp a filament. The easiest way is making a construction in wood in the shape of a 'H' (see picture). The filament must be well stretched, so that it cannot deform. When the wire is hot, it’s expands. So, we need a mechanism to strain it again. I used 2 robes parallel at the back, when you turn the pencil that is fitted between the robes, the robe length will be reduced and filament will stretch. To heat the filament, you need a power supply attached at both ends of the filament. You can use most types of power supplies, but if you want the same as me look at the picture. It’s that simple to make a hotwire.

Now you just need 2 wooden wing shapes. When you attach the shapes to both sides of a Polystyrene plate, you can Hotwire it in the shape of the wood. Start with you Hotwire at the back of the wing till you touch both wing shapes with your filament. Now follow the shapes till the front and go back the other way.

Now you have your wing.

For more information on using the Hotwire look at our video.

Step 6: Reinforcing Your Wing

I tried 2 methods. The first method was jamming the carbon rod in the wing. The second way making a cut/gap in the wing and glue the carbon rod in. Afterwards fill the cut with Polystyrene fill.

The second method is the best method. The first one will damage your wing too much.

Afterwards you can strengthen the wing with duct tape.

To connect both wings, we made a 3D printed piece, to which the carbon rod from the wing connects to. We glue both wings to it. If you can secure everything with duct tape.

Step 7: Electronics Configuration

This step can be difficult or easy, it depends if you miss a step. For the CC3D atom flight

controller we used LibrePilot. Because our flight controller came from China, we needed to update/upload new firmware. For this you need to do some research. When you uploaded the firmware, you can update it through the program (see picture). For connecting the parts together, you can follow my schematics.

First we are going to configure the ESP. You can find an Arduino program as attachment. I did not write it myself, it came from our supervisor, Mr. Lievens.

Basically, it sends through the TX, 18 channels. Those channels are in fact milliseconds for controlling analog servos. Next you need to install the application ‘app-release.apk’, this is also from our supervisor. Connect your smartphone with the ESP. When you move the joysticks in the application and at the same time type get in your COM windows in Arduino you see that the milliseconds will change. Note: if you cannot connect with the ESP, you need to go to advanced settings in your network on your phone. Now go to ‘static’ and give yourself a IP address. Type a different IP address then the ESP otherwise it wound work. Because you can’t give yourself the same IP as your ESP has. I thank Jelle B. for this idea.

The second step is making connection between the ESP and flight controller. This is through the ground and the TX. The TX goes in the RX of the main port of the CC3D, but the signal needs to be inverse. We can do this with a signal inverter. Note: the inverter has a polarity, so we lost precious hours figuring out what the problem was.

The third step is connecting the servos and everything else. Afterward: test your configuration.

I will summarize the complete schematics:

• Start with the battery

• Connect it to the DC-DC booster, this will boost the 3,7V battery to 5V

• Connect your CC3D with the booster through a channel, now your flightcontroller has power

• Connect the RX from the CC3D to the ‘in’ from the signal inverter

• From the inverter to the TX from the ESP

• Do not forget to power the inverter with the red and black wire from the main port from the CC3D

• Last is to connect the servos with the channels from the CC3D

Attachments

Step 8: Making the Tail

The tail is made of a carbon rod and foam plate, the foam plate is glued and taped to the carbon rod. The rudder, elevator, horizontal and vertical stabilizator are cut out of the foam plate. We drew a template on Solidworks and printed it with scale 1:1, it’s an easier method to cut is out. We made a typical shape and reinforced it at the rod with duct tape and glue. This is to make sure that it can’t move or rotate, otherwise your plane will have a live of its own and crash.

Now we can connect the tail and wings with each other. Make sure that they are aligned perfectly when you glue them together.

The servos of the rudder and elevator will be located at the head. So, we need to connect them. We did this with an acarde cable and some rubber bands at the control surfaces. First you need to attach those surfaces. Hold them 60° relative to the rudder/elevator and tape it together on the side where the largest angle is. Now you can move at least 60° and the gap isn’t too large. Tape 1 or 2 rubber bands at the rudder/elevator and control surfaces. Do this in the same position as described above. At the other side glue a small rob, this is for connecting cable between the servo and control surface.

When the servo pulls, the control surface will turn and when the servo returns, the rubber band will pull and the control surface will return.

We made some metal rings from iron wire to make sure the cable follows a good track.

There are also 2 servos in the wings (ailerons). To secure them without creating air resistance or break point in the wing, you need to make a gap with the soldering iron on the spot where the servos will be. Make the gap the same dimensions as the servo and make sure the servo fits well. But now you created a break point in the wing. To neutralize this you need to glue the servo in tight and finish it with duct tape. The control surfaces are taped the same way as the rudder/elevator and glue also a small rod at the other side. But the connection between servo and control surface will be an iron wire, because no rubber band should be glued. An iron wire can push and pull.

Step 9: Making the Cockpit, Prototype 1

For the first prototype we just cut a balk out of a Polystyreen plate
with the hotwire. Big enough for all the electronics. 50x50x1500 mm should be big enough. Melt a gap in the middle (40x40x800 mm should be ok) for the electronics, glue them in place (the flightcontroller needs to be aligned and leveled) and strengthen the peak with duck tape. Do not forget to connect the 2 cables from the rudder and elevator with the servo’s and make sure that 90° on the servo is equal to the middle position of the control surfaces. Pierce gently the carbon rod through the cockpit and glue it secure.

Your prototype is done for now :)

Step 10: Cockpit Prototype 2

With the test flights we had a small problem with the cockpit, the carbon rod pierced straight through cockpit prototype 1. So we designed a cockpit in Solidworks and 3D-printed it, you can find the schematics in the enclosure. It’s more sturdy this way. You can find the drawing in our As-build dossier.

Step 11: Details

This step is different with each DLG. This step is correcting the
little errors. Like as fine tuning your flightcontrollers autopilot.

Points of attention with our DLG:

· Making the control surfaces big enough

· Strengthen the control surfaces with duct tape (required if you crash)

· Reattach some parts with glue and/or duct tape (thanks to crashes)

· Don’t let your LiPo battery descent below 3,5V!! When you do your battery’s capacity will be reduced

· Make sure there are no clinks at certain degrees of steering. This is caused by a nod at the control surface or a cable that is jammed. For the first problem tray to tape again and the second problem, relocate the track of the cable.

Watch also the BOM (Build Of Materials), Manual, datasheets, blog
and technical drawings. You can find them in the as-build dossier.

Attachments