Lets agree to meet half way on this.. averaging the bending moment of the wing loading puts the centre of pressure about 1/3 of the half-span away from the shoulder.. just above the elbow. I couldn't rest on my outstretched elbows for long either. And then of course birds have a large distal panel outboard of their wrist, that puts the centre of pressure closer to the outstretched wrist again. Now after hanging there for a few minutes try heaving yourself up and down...

The comparison with birds gets a bit silly, but remember my original point was about a human powered ornithopter with wings several meters long operated directly by outstretched arms. If anyone still thinks this is a good idea they can buy their own life insurance.

Murray.

A few minutes is way better than about 1 second, which is all the time I think I could mange to hold myself using my hands on outstretched arms.
I agree but some more sillyness: Could we hold (and control) 50 Kgs on/at each elbow? I think some of us could, but an ornithopter is going nowhere with only several meters of wing.

Ok, I agree with this LoL.

Jessica

Even your well-built mate would have had a hard time holding the wings down with the bending strength of his arms and shoulders; in this case he was probably holding the hang glider yoke uprights together by tensile force in his arms, an altogether easier exercise ( but still impressive).

To illustrate the problem for those who don't analyse structures, our challenge is to support half the aircraft weight, say 100kg /2 at the half-wing's centre of pressure which for a hang glider would be about 1/4 of the half-span from the centreline, say 6m /4 or about 1.5m. The root bending moment is thus 50kg*1.5m = 75 kg.m.

At the end of the 1m yoke uprights this bending moment of 75kg.m requires a tensile force of 75kg, a manageable pull on straight arms.

Lets suppose instead that this bending moment were to be imposed on a man's arm 180mm diameter ( Jon did say he was built like a brick sh* house) with the bone in the middle. The bone carries compression force, coupled with tensile force in the muscle underneath, lets say 75mm from the bone. To withstand a bending moment of 75kg.m on this lever arm of 75mm, the coupled forces of tension and compression would each have to be
(75kg.m)/0.075m = 1000kg or 1 tonne weight.
Not manageable.

Murray.

Thanks Jon, I do appreciate that. My over-analysing was aimed at the misunderstanding that crops up in the forum from time to time about how much force is applied to a bird or ornithopter wing and where it acts. Pardon my pedantry. It was initially triggered by discussion of Dennis Curry's arm-waving flapper but I'm not sure that the full realisation has set in even now.
Murray.

Have a look guys. http://www.ltair.com/products/model/Ornithopter.htm

Like a Bird,
Your fascination with building a hovering ornithopter And sharing with this
forum has produced some results. Earlier this month I e-mailed Nathan and explained to him how a Vtol ornithopter could be built,,, this was based on your idea, good work Ronn.

E-mail to Nathan>>
Forgive the crude sketch but it will best explain how to accomplish the task. This craft would be designed to hover, forward/backward/left right movement and will not fly like a conventional ornithopter.

Two Graupner 300 motors, one 20amp speed control, one RX, one hyperon 1400 mah 20c poly battery and my pull-cable wing warp system on both wings along with two main wing servo's for control. Their will be no tail empennage, since the CG will be just beyond the trailing edge of the wings', gravity will provide some stabilty and the pull-cables' will provide the rest. Since half of the radio system' has been eliminated, the second wing is devoted entirely to lifting thrust. By lengthing the con-rods, the wings can be adjusted to just miss one another on downstroke but yet close enough to use the clap and fling technology the Mentor used.
The two 32p-80t main gears will mesh allowing for posi-phaselock. Two reasons for this; Their may be a need to advance or delay the counter-phased wings for unforseen reasons, possibly trimming the craft to hover properly and second, in case of a motor failure, the good motor should allow for a emergency landing.
Of course the idea may not work at all, but with the new outrunner motors available along with these high capacity poly batteries the craft has a pretty good chance of flying. Willi >>End

The second photo is the craft coming to realization.

gettin closer
 

the blue arrow reminds me of the ovirc. would like to know the pros and cons of its tail (v shaped) verses the flat tial on other models. nice to see more and more robot birds on the market and flyin. i think companys are gettin closer to realizin the possabilitys of flappin wings. i think its just a question of how long it has takin for the strength to weight ratio of man made materials to catch up to the that of a bird. i am tickled to know that in my lifetime i will see humans be able to experiance the world as birds do. i still say you give one of those birds a 20 ft wing sp., and a motor, youll flap into the air tommorrow. i dont know what there waitin for. maybe there broke like me. yeah!!! 2006, i say we fly.

Wow, very impressive work Willi and Nathan there will be lots to learn from this design even though it may not fly like a conventional ornithopter. It will most definitely inspire and teach us more on the subject of flapping wings. Seeing this kind of progress really pushes me on, I design and build every day. I am currently finishing a Lego based flying ornithopter that I was building in my spare time waiting on parts delivery. Thanks for the compliment Willi but you guys were the ones that got my creative juices flowing. Have you guys decided on what Hz it will be run at ?

Getting closer is the correct term Gweedo, I plan to do my first full size testing in spring of 2006. It will just be a taxi acceleration test to determine proper gearing and power requirements (got to get those numbers right). No tail on this test though, but I will be running a V tail configuration when all is said and done. I do not know if there is any concern-able differences in performance between the conventional tail and the V tail. But I like the look of the V tail on my ornithopter.

Willy , it is funny,
having built Meganeura http://ovirc.free.fr/ornithopteres_ovirk.php , i made, last year, the mecanique of a flapping VTOL.
I arrived at a design identical in your, but with a single engine.
This prototype has not yet flown, for lack of time.
I am curious to know the results of your machine.
Good luck!