Model blimps can be easily built to fit any shape desired. Faster to build, lower in price and easier to operate than other model aircraft, an RC blimp is little more than a helium balloon with an attached engine. These qualities are what make them a common sight in large indoor areas for model aircraft flying, and also what attracts DIY model makers of all skill levels.
In order to make your RC blimp, you'll need a few basic materials. The primary part you should look for is the blimp envelope. This is basically a helium bag to which you attach the control mechanism. You can choose an envelope of any size or shape, but the larger the envelope, the larger the engines necessary for moving your blimp. Most indoor blimps of 1.25 m (50 inches) or smaller can use ready-made remote-control blimp gondolas, while a larger one will require you to create your own motor/propeller system.
You'll also need a three-channel radio transmitter and receiver for controlling the blimp, a channel each for the three propellers that control movements, both left and right and up and down. Buy a tank of helium and a nozzle for filling the blimp before flying it.
Assemble the blimp by filling the envelope with helium gas. You should use a nozzle created for filling Mylar balloons and unlikely to do damage to your blimp envelope during the filling process. Fill the blimp envelope until the surface of the envelope is firm, but still has a bit of give when poked with a finger. Too much helium and the blimp is likely to pop, especially if the gas inside expands due to warmer temperatures. You can tell it's growing overfull when the seams of the blimp begin to gather as if ready to separate.
Control the blimp through the use of an attached blimp gondola. Most gondolas are designed with three propellers, one to the left of blimp centre, another to the right, and a third in the centre of the gondola. The left and right propellers are pointed forward, and when power is applied will turn the blimp to the left and right as well as provide forward and reverse momentum. The propeller in the centre is pointed directly downward and provides altitude adjustments for your blimp.
Connect the gondola to the blimp's bottom using either a harness strapped around the body of the blimp, or by taping it to the body of the blimp with two-way tape. Attach the gondola at the balance point of your blimp, which is determined by holding it at the bottom by a seam and checking the front to determine whether the front of the blimp rises or falls. Adjust your grip until you reach the point where the blimp lies level, which is the balance point. The propellers are driven by a radio receiver attached to an engine for each. For even finer control, you can attach fins to the rear of the envelope using two-sided tape as stabilisers.
Operating the blimp
Once the blimp has been assembled, you can operate it by placing the batteries into the gondola and bringing the blimp to a neutral state of buoyancy. The neutral state is one in which the blimp remains level when no power is applied to the propeller, neither losing nor gaining altitude. Add ballast to the blimp in the form of lead modelling stickers if the blimp gains altitude, and add air to the blimp if it loses altitude. Once neutrally buoyant, you can fly your blimp using the controls to raise it to your desired altitude and then manoeuvre it about the space.