Inside the mind of an engineer
by Mario Chapa
If you know me from college you probably know me as “Chapa-Rocket” thanks to my rocket building skills. My family has a long history in relation with the aerospace industry and it’s no surprise that’s why I love rockets, planes and yes bees too. My great uncle was one of the founders of Mexico’s first commercial airline. My grandfather, father, mother and brother are all private pilots. I myself used to fly a Cessna 172 and my younger brother was a national RC aerobatics champion. We’ve been building and flying RC airplanes quad copters and rockets for longer than I can remember. Professionally I have taken part in the design of Mexico’s first Unmanned Autonomous Airship and also Mexico’s first UAV. I have designed the fuselage for amphibious quad copters, and the single seat experimental “BD Jet” that uses a demilitarized Tomahawk missile jet engine as its main propulsion system. Yes that’s very cool!
It was in the early 2008 when my brothers decided to go pro. They launched a startup named Skymedia. The plan was to design build and operate an autonomous airship (which we did) and sell ad space in crowded events as well as other services such as traffic monitoring.
I had just finished my aluminum boat building contract and had all the shop’s capacity to do something fun, so why not a blimp. I also worked there as an aerospace engineer designing the blimp vectoring system, landing gear and altitude valves among many other components.
When it was time to inflate the blimp, we looked for a place to setup our hangar and we eventually ended in the Coahuila desert in a place that we naturally named Area 52!
Any flying object has to generate enough force to counter its own weight. Airships or Blimps as opposed to bees fly thanks to a combination of lift, thrust and buoyancy. Our blimp was filled with helium. Helium is lighter than the air it displaces. The difference in weight from such displaced air and helium weight is the buoyant force the blimp generates. Now air doesn’t weigh much, so you need a very large displacement volume to be able to generate just enough buoyant force to almost counter the blimp’s weight. We decided that the buoyant force should be just shy of the airship’s weight, so in case of an engine failure, the airship would slowly and safely descend. The altitude valve was also designed to give the airship an operating “ceiling” and to avoid the balloon exploding due to high internal pressure.
The little “remaining” weight of the airship can then be countered with the engines’ thrust and the blimps’ lift. The vectoring mechanism which I designed helped rotate the engine’s propellers so that its thrust would push the blimp almost vertically up during takeoff. As the blimp generates speed, the air passing along the blimp’s body accelerates and thus reduces its pressure (Bernoulli Effect) generating lift, this same effect is how airplanes’ wings generate lift. The fat body of the blimp is a combination of the need for a large helium volume with as little air drag as possible. Hence the papaya shaped blimp body.
Bees on the other hand fly thanks to a combination of drag and lift. We’ve all heard that famous Forbes article “According to Science Bees shouldn’t fly, yet they do anyway” (May 2018). If you try to apply the lift equation to a bee’s wing, it turns out that theoretically bees’ wings generate only half of the lift needed for the bee to fly. Well, it turns out that rapid wing flapping has more in common with paddling than with flying. Although the complete fluid dynamics of ornithopters (flapping wings) is not yet completely understood, it is clear that in the case of rapid flapping wings such as bees, drag is more important than lift. Just like paddling, bees wings generate vortexes that generate a suction force (drag) that pull the wing in the direction opposite to the relative wind speed. It was also found that bees actually generate lift (and upward drag) in both stroke directions, hence the missing lift!
Bees’ body shape is the result of the big flapping muscles in their thorax. The need for their breathing organs as well as their honey pouch shapes their abdomen. The fuselage shape of the bees’ abdomen may also be the result of the need to reduce air drag while on forward motion. In case you wondered, bees flap their wings up to 230 times per second and they have a payload equivalent of their own weight!
BeeEO | HiveGenie