RC Blimps March 19, 2008
Why RC Blimps Float
A remote controlled blimp is a lighter than air aircraft that relies on the principle of buoyancy. Buoyancy is the effect that causes less dense objects to rise when immersed in a denser substance. As long as a similar volume of one material is less dense than another, it will rise. RC blimps, airships and flying saucers make use of this buoyancy effect by using a lighter than air gas to fly: Helium. Because Helium is less dense than the air the blimp will float. The idea behind a blimp is to have the lifting force of the helium exactly cancel out the downwards pull of gravity. This is called neutral buoyancy. In order to rise or descend, the blimp fills or empties different compartments (ballonets) with air. Because air is heavier than helium, this will cause the blimp to decend. Emptying these ballonet compartments will make the blimp lighter and cause it to rise.
The First Blimps
The first rigid airships (also called Dirigibles or Zeppelins) were constructed in the early 20th century. Back then blimp aircraft consisted of a metal frame, covered with fabric and filled with a lighter than air gas like Helium or even Hydrogen. Below this balloon assembly was the gondola. The blimp’s gondola housed the pilot, crew, passengers, and engines. These airships were used for both war and civilian travel during the 20th century. A famous example of such a zepplin was the German Hindenburg airship, which was destroyed on May 6th, 1937. The Germans, who were unable to obtain helium gas for the airship, used hydrogen as the lifting gas. Hydrogen is explosive where Helium is inert. The Hindenburg disaster played a huge role in ending the use of huge blimps for passenger travel.
Modern blimp airships are non rigid, meaning that there is no internal structure to support the envelope. Modern blimps are filled with Helium, a safe inert gas, to make them float. Like the old rigid airships, modern blimps still rely on the principle of buoyancy to fly. Modern blimps are used primarily for advertising rather than passenger travel. If you’ve ever attended an NFL football game, NASCAR race, or PGA golf tournament you’ve probably seen the popular Goodyear blimp.
Remote Control Blimps
Radio controlled blimps are an excellent choice for someone new to RC and appeal to all ages. An RC blimp is just a smaller version of a modern blimp airship, except for a few differences. Instead of relying on ballonets (air-filled bladders) to change the weight of the blimp to rise or descend, neutral buoyancy is achieved by adding small weights or ballast putty to the blimp until it hovers. The RC blimp’s gondola is equipped with small electric motors with propellers used to propel the blimp up and down. Most electric rc blimps use a tri fan design, to provide directional control in every direction: up/down, left/right, and forwards/backwards. A good example of this are the Mach III Indoor RC blimps at RCToys.com. These R/C blimp aircraft are for indoor use only. Flying them outside will lead to them getting lost, or blown away. Remember, these aircraft are really helium balloons with motors and a radio, so make sure that you fly them where they cannot get away.
RC Blimp Balloons
RC blimps come with a super lightweight mylar balloon. These mylar rc blimp balloons are both durable, refillable and replaceable. For customers at altitudes greater than 4000 ft above sea level, a larger capacity high lift balloon is available. This white high-lift rc blimp balloon is also great for applying advertising stickers. This can be necessary because, as altitude increases, the density of air decreases, lowering the lift generated by the balloon.
Where to buy Helium for RC Blimp Balloons
Helium for the rc blimp’s balloon envelope is easy to obtain at wedding & party supply stores, flower shops, most grocery stores, and welding supply shops. Filling the rc blimp is also easy, the person selling you the Helium should be able to do it for you, if they have a mylar nozzle. After filling the envelope with Helium place a small piece of tape over the hole to keep the Helium in the balloon.
How to achieve neutral buoyancy so your RC blimp hovers
Chances are, after you have filled your blimp with Helium, it will try to climb. You can use either the weights included with the blimp, or some modeling clay (ballast putty) to correct this. Hang the weights on the rods supporting the engines, making sure to keep the weight equal on both sides. If you decide to use modeling clay, place it in the gondola, near the batteries. Using clay instead of the included weights will allow fine tuning the airship, so that it will maintain the altitude that you want it to. Add just enough weight so the rc blimp neither climbs or sinks.
Where to buy RC Blimps
Draganfly Innovations Inc. sells a huge selection of RC blimps and flying saucers. The most popular blimps are the RC Goodyear Blimp, the RC Airship America and the RC Blimp Bomber. Replacement r/c blimp parts, balloon envelopes and 3V lithium blimp batteries are all available at www.rctoys.com.