My dream for many years was making something fly and, at the same time, being able to controlling it.

With a cheap RC car and a self-made balloon of a condom (got mine for testing purposes at school for free, it also is dry, has no lube) and, of course, any light gases I could make this dream come true!

Supplies

cheap RC car
condom, the dryer the better
plastics from old food container
light gas (Helium or Hydrogen)
sticky tape
scissor
screw driver

Step 1: Stripping the Car

Take a cheap RC car (I got mine for € 9,-) and loosen the screws under the car. Carefully take away any plastic parts, we won't need them. Pull the two motors out of their plastic gears. Take the small PCB and the batteries (in my case, there are two) together with the motors and the antenna cable and put everything in front of you, taking care of the tiny, fragile cables.

Step 2: Making the Propellers

Take some plastic packaging (from a piece of cheese, in my case), it should be stable. Cut with a scissor two small stripes from it, about 1,5 × 5 cm. The following steps do twice because we need two propellers, one for the acceleration and the other for the steering of your Zeppelin.

Heaten the stripes up with a candle or lighter in the middle for a short time. It should get soft but not liquid :-)

Bend the two ends of each propeller slightly around their longitudinal axis until they are slightly twisted.

Use a hot needle to pierce a small hole in the center of the propeller or drill in with a small drill (~ 1.5 mm).

Stick the propellers to the motors axises with a very small drop of hot glue or two-component adhesive.

Step 3: The Motor Base

Again, cut some plastic packaging into a stripe. This one is about 2,5 × 14 cm. Bend it in the middle around a sharp corner, it should look like a "V". Bend it's sides the opposite way, about 1 cm. In the end from the front view it looks like a bird (like the gull in children's pictures).

Step 4: The Balloon

A typical condom has the perfect shape and size for being a model Zeppelin, but it needs to be filled with gas that's lighter than air because the Zeppelin will have to carry itself up in the air, the load of motors, batteries, electronics, propellers and some stabilizing stuff as well. For this reason we have two possibilities: Buying balloon gas, that's Helium (He) and relatively expensive, or using Hydrogen (H2). that's relatively cheap and can be produced at home. There are advantages and disadvantages, of course...

Although Helium has no molecules, it's atoms are bigger than the molecules (H2) of Hydrogen. So, the Hydrogen can more easily escape through the thin balloon coat. Helium will stay longer inside. Also, Hydrogen is a dangerous gas because of being highly flammable and making explosive mixtures with air or Oxygen (O2) (For security reasons or just interest, have a look at the "bang-gas" reaction).

I'll later here go into detail of the production of Hydrogen with only a plastic bottle, razor's edges, some wire and an electric power source.

Now, fill up your balloon with that gas of your choice and keep it down while making a knot into it's "neck". From now on a second person could be very helpful!

By the way - when you look closely at these pics, you'll find out the balloon had been pumped up with my breath but not with any Hydrogen or Helium yet ;-)

Step 5: Putting It Together

With a bit of sticky tape put the motor with the propeller, that was for the acceleration of the RC car, in the middle of the long plastic stripe. Also, put the stripe with some tape somewhere in the middle of the balloon. Where you put it will be the lower side of the Zeppelin. Now put the whole electronics, cables, batteries with some tape on the balloon, directly behind the motor holder.

Cut a stripe of the plastics, about 1,5 × 7 cm long. Bend 1 cm on both ends to 90 degree. On one end fix the car's steering motor (with propeller) with tape, the other side stick to the Zeppelin's bottom, perpendicular to the Zeppelin's and the other motor's axis. This'll be your left-right turning thing. (In my photos this motor is not yet installed. I first wanted to keep the weight low)

Step 6: Balancing

A good and necessary thing is balancing out the behaviour of the Zeppelin when flying in slow air, e. g. in a room. Does it steer too much to the left or right, you can make some fine tuning on the transmitter in your hand. Although it's cheap, it has some fine tuner knobs. So, you can adjust the speed and especially the accuracy of the steering propeller which makes the Zeppelin either go left or right.

A bit more tricky is balancing out the front and back of the Zeppelin for a stable flight parallel to the ground. For doing this, you can stick small plastic parts to the Zeppelin's front or back. For heavier load a few small coins stuck to the Zeppelin's bottom will do a good job.

I'm sorry for maybe missing some detailed pictures in the description here. Some steps I had already done before and didn't have another toy car to destroy. Also, I'm gonna add the steps about the production of hydrogen or Oxyhydrogen with cheap and simple stuff you have at home.

Now, have fun with building and playing with your DIY RC Zeppelin! Because of being light but very huge it would instantly be outdoors the wind's victim. So, better keep it indoors! And, please let me know any questions and share your successfully built Zeppelin!