Why build a flying machine with flapping wings?
Yes, why do it? Thousands or even hundreds of years ago, when people had the idea to build a flying machine, the only examples they had were the birds. They naturally assumed that moving flapping wings were part of the necessary characteristics they needed to emulate.
They had a big problem, how to move the wings. Early on, people like Leonardo da Vinci figured out that human muscle power wasn't going to do it. It was another 400 years later that Otto Lilienthal abandoned movable wings altogether and started us on the path to fixed wing aircraft as we have today as the dominant form.
Today however there is still a strong interest in 'flying like a bird'. Why? Why when we have aircraft that can do so much that birds can't, do we still dream of flapping our wings and flying? Or to put it another way, why are some of us interested, even obsessed with building a machine that flaps it's wings?
The first answer that comes to mind is aesthetics. There is no current flying machine that is as beautiful, graceful and capable as any bird. Not all three certainly. We have planes that can carry hundreds of tons of cargo and that can fly many times the speed of sound or even land on a dime. Still we dream and invent.
All that aside then, why should anyone try to build a flapping winged flying machine? What are the presumed advantages? From all that I have been able to glean, the one driving idea is that flapping wings for propulsion is somehow superior to fixed wings pushed or pulled by conventional systems. There are proponents who will claim that their data shows a significant advantage in thrust production from a flapping wing or surface over a rotating propeller for instance.
How do they go about implementing this flapping for thrust idea? Most often they take a conventional airframe design and try to add mechanics to it to make the wings go up and down and twist so as to produce some thrust. They have been doing this for many years with little success and lots of claims.
Granted, lately there have been some interesting devices constructed and flown that use flapping flight successfully, but the scale is well below what would be capable of carrying a man. And frankly were one to be scaled up to man sized, the ride would be intolerable. They all use some version of a single spar membrane wing that beats very rapidly. The best analogy I can think of would be trying to ride a motorcycle with square wheels.
Then, why am I interested in building a flapping wing machine? A fair question. The answer is, that flapping is not the first importance. If I could only build a machine that had the wing morphing capability of a bird without the ability to flap for thrust, I would accept that in a heartbeat. I already have machines that can cruise with and climb in lift with the soaring raptors. Machines that are capable of gaining tens of thousands of feet and covering hundreds of miles with no thrust capability at all. But they lack the fine effortless control that those birds have. They lack the ability to reduce the size of the wings to dive out of danger and then spread to take advantage of the lightest lift or set down on precisely the piece of real estate that I want to.
And the point is it is just a tiny step from that machine to one that can generate thrust by flapping.
Fascinating! I am very much "interested, even obsessed" with building a bird like structure. I hope to research this more and make something that could make man fly with limited structure. Wouldn't that be cool?!
Thanks for the comment Andrew. And keep us posted on what you create.