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All techie stuff here
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By Greg Vandenberg
#369243
Greetings fellow flying humans. My name is Gregory Vandenberg and I am a 43 year old aeronautical engineer based in Johannesburg South Africa. I have been 'evolving' human powered wings over the past 6 years and it has grown into an obsession. I call it a ‘Wingbike’ or ‘Skybike’ but its technical name is a human powered ornithopter. Basically, you push the pedal with your feet and the wings flap. I have been working on the project for six years and the latest test in January of this year demonstrated positive stability, extremely responsive control, loads of lift and structural integrity (phew!). The best way to describe the feeling (besides large amounts of pumping adrenalin!) is that you have inserted yourself into a birds skeleton with all control input and response intuitive to that mind frame. In other words it feels incredible…… watch the video clip
Windsurfers have been doing what they call ‘pumping the sail’ in low wind conditions to produce thrust for years. This action is identical to flapping and I am amazed that nobody has replicated this into an aircraft yet. Imagine two windsurfer sails joined at the mast base then strapped to your shoulders where angel wings would be.
The closer I get to actually flying like a bird, the greater the urgency to complete it........ because its so simple. It is a biomimicry aircraft that adapts a human body into a birds body, or more accurately a pterodactyl body. I have spanned a modified ww U2 sail over framework of my own design. The wings, hinged at the shoulders, are flapped or 'pumped' by the legs via a pedal attached to the flying wires. Control is effected by the arms anchored in the wings, and is intuitive to replacing your arms with wings. The entire aircraft, harness and all, weighs 28 kg. Yeah…… twenty eight kilograms………….. that’s 62 pounds at today’s exchange rate 
Please check out the video clip of my most recent beach test in January of this year in Wilderness South Africa on my youtube channel. I'm not allowed to post the link here as I am a new user, but you can find it under 'Wingbike Jan 2015'
I will be flying it off the dunes in the next few weeks finances permitting. This will include pushing the pedal for the first time and effecting radical geometry change on my airframe in mid flight..……………………… Gulp!
I invite you to join me in this adventure and follow the progress via this forum and my youtube channel.
I welcome all comments and input, as well as any support :) This is my full time occupation.
By gluesniffer
#369245
:popcorn: :shock: :popcorn: looked like a good u2 at one point.... I want to see more flying Greg. Good luck!
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By tom emery
#369246
If this thing eventually works...it could be huge. Keep working and filming and....go get a parachute....just in case.
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By red
#369249
Greg Vandenberg wrote:Greetings fellow flying humans. My name is Gregory Vandenberg and I am a 43 year old aeronautical engineer based in Johannesburg South Africa. I have been 'evolving' human powered wings over the past 6 years and it has grown into an obsession. I call it a ‘Wingbike’ or ‘Skybike’ but its technical name is a human powered ornithopter.
I welcome all comments and input, as well as any support :) This is my full time occupation.
Greg,

First, please get a full helmet with a faceguard. That soup-bowl is much less protection than your head may need.

I hope you have at least Hang 3 (Intermediate) HG flying skills. Things happen very fast in the air, and you will not have time to think things over. If things are happening too fast (to suit you) as a HG pilot, the situation will be worse with the added challenge of flapping. When you can be relaxed and enjoying a normal HG flight, then you can consider flapping, in addition to your piloting.

I would like to see you get four strong friends, and position two at the aerodynamic centers of each wing, maybe 2~3 meters from the center on each side. Have them support the wings, simulating the lift of the air in flight, with you "airborne." Then, flap the wings for five or ten wingbeats.. Your wingtips may just touch the ground, on the downbeat. If you discover any problems then, you will have at least the same problems when flying.

I believe that you should consider "crash safety" now, also. In any mishap, the wings (as constructed now) will continue forward, and present a crushing hazard to any human parts which get between the leading edges. I believe it would be much safer if you constructed a hang cage around you, such as the Icarus V or Millennium uses, so you do not hit the ground in a mishap. You can easily remove the cage later, when you have some good flying time on that wing.

I am curious about pitch control, with your invention. You will need down control to prevent a stall, and up control to land safely. With both hands and feet occupied with other matters, how do you control pitch?

Please watch the beach segments of this linked video, from 3:15 to ~5:45 time. This simple tow-rope launch method should get you into the air with only moderate launch skills, and give you plenty of time to get the feet working at the mechanism.

[youtube]
[/youtube]

I do not wish to discourage you, but the most successful ornithopter I have seen used a DaVinci rig to flap, using arms and legs in concert. Back then (~1975) HGs had very poor performance, about a 4:1 glide ratio. This ornithopter could only do the same, without flapping, and with full wingbeats, the glide ratio got almost as good as a modern beginner HG. The pilot could never maintain altitude, even in ground effect; the machine always sank, either rapidly (when gliding) or not-so-rapidly (when flapping). It could never gain altitude, and it could never launch without the aid of three or four pilots running under it.

The most successful ornithopter (that I have not seen) is in the video below. It certainly reeks of efficiency, but again, it can not climb out of ground effect. Please note, it is tow-launched, also.

[youtube]
[/youtube]

Best wishes in your research.

:mrgreen:
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By Nicos
#369251
That looks like a REALLY interesting concept, thanks for posting and best of luck developing the idea — I hope it comes to fruition.

Red has some VERY good advice about protection and learning how to fly a regular HG before testing your bike untethered... please listen to Red.
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By Greg Vandenberg
#369256
Thanks Red for the input, I have been flying HG for 25 years now in Europe and Africa. Well spotted on one of the main concerns with the frame design. The wings have steel cable limiters on all axis' of freedom. I would like to post some photos of the construction for your perusal, can I do that on this site? As to pitch control, that is effected thru collective sweep of the wings, roll thru differential AoA and yaw thru differential sweep, that is what I am doing in the video. I'll post another one that shows it better. The arms are fully and exclusively dedicated to control, yet they do contribute to total energy of the system by guiding where the brute power of the legs goes thru AoA variation in the flap cycle. The rowing analogy comes to mind. I am familiar with the ornithopter you mentioned. In that case as with the snowbird the approach taken has been to build an aeroplane and then insert the human as the power source. With the skybike I have literally made prosthetic limbs. Weight is roughly half that of the snowbird with the same power source. Control is infinitely greater and it is made to fly in the kind of wind that makes take off much easier. (10 kts+) Moreover the action and physics of flap propulsion we are only now beginning to fully understand, and I am of the opinion that the efficiency increase gained by flapping over generating a little tornado behind you (propeller) will surprise many. No two species of bird flap the same way and the method is as varied as walking animal gates. With the kind of control inherent in the Skybike I believe that efficiencies in the order of bipedal (two legged) perambulation will be achieved, where an inherently unstable system is constantly 'caught' by the action of the limbs (as with walking), and a harmonic periodic oscillation is achieved, which indeed would look very similar to the human powered hydrafoil action (well spotted Aldpal :) Who would have thought a decade ago that a human could power a hydrafoil !!
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By haddieman
#369288
The video is extremely intriguing and I have subscribed to your channel. Best of luck to you, and the best of safety as well.
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By brian scharp
#369315
It looks like a lawn dart if you go negative.
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By red
#369330
Greg Vandenberg wrote:Well spotted on one of the main concerns with the frame design. The wings have steel cable limiters on all axis' of freedom. I would like to post some photos of the construction for your perusal, can I do that on this site?

As to pitch control, that is effected thru collective sweep of the wings
Greg,

Right now, you will need ten posts (which can be anywhere here, on any thread) before you achieve "pilot" status, as opposed to being a drop-in, or a spammer. These posts do not have to be prize-winners, just some input on topic. Then you can post links and pictures here. I suggest that you post your photos to your ISP account, or maybe a hosting service like PhotoBucket, as you may see fit. Single images can be posted in the Photos section, but I do not know about entire albums. After ten posts, you can post pictures here using these procedures:
http://www.hanggliding.org/wiki/Posting ... ge_Threads

Collective sweep controls pitch? I would guess that forward sweep will be a "pitch up" command, with weight going behind the centers of lift, is that correct? In general terms, drag increases at the square of velocity. As airspeed increases in a dive, it would take more and more arm strength to command a pitch up of the craft, correct? At some point, once you reach the limits of arm strength, drag will continue pulling the wings rearward, commanding a steeper dive, is that correct? If I have understood your pitch controls, I see the real possibility of the craft locking into a terminal dive. Your video does not seem to address this issue.

I would strongly suggest that you work through the control issues (and soaring flight) using unmanned RC models, before attempting a manned ornithopter flight. As stated earlier, you seem to have no pilot protection there, in any mishap. Once you can soar your craft, it will be a "minor" matter to add the flapping to your flying, with the manned version. These HG models are a good size for your research, and they can fly with radio control. If you build your models to a similar size, you should have some reasonable test vehicles.
http://www.aviationproducts.de/e/scale/scale_3.html

Please believe, it would be good to see your model wings soaring (gliding, not flapping) at your favorite HG sites, and demonstrating good control in flight. I would not recommend a manned attempt until the controls are proven, and some measures of pilot protection are incorporated.

:mrgreen:
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By jyoder111
#369347
Not to be a downer, but....

Have you done the math? How much force can a human create continuously for several minutes vs how much force is required to successfully power your ornithopter? They've been trying to build human powered helicopters and such for a while now and even with a professional cyclist going all out for ~30 seconds they can't really get out of ground effect. The human powered hydroplane bike linked above only works because of water's density. You're just not going to get that from air.

But please prove me wrong. Would be freakin sweet!

"It's a simple matter of weight ratios."
https://youtu.be/JHFXG3r_0B8?t=79

Full scale powered ornithopter attempt:
http://www.flightglobal.com/news/articl ... ng-208773/
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By Greg Vandenberg
#369352
Thanks for the heads up on how to post the photos, I will be doing so this evening. You are correct, forward collective sweep effects nose up by way of CoG shift aftwards. The Skybike also has a secondary nose up control through collective AoA increase. This increases the angle between the horizontal tail fin and the wing thus effecting an aerodynamically induced positive moment around the CoG. The induced drag increase is also noteworthy. Lets say stopping is not my biggest headache.
The conundrum regarding the wings being swept back by the airspeed is something I really struggled to get my head around and was the cause of much wasted structural designing in the first prototypes. This 'phenomenon simply does not exist in ornithopter flight. There is nothing causing a negative sweep moment (wing tips moving aft relative to CoG)) on the wings. in fact during flap propulsion the opposite is the case. The wings want to overtake the body. it is so ingrained in our heads that the body / fuselage must pull the wings along. This is simply not the case here. Yes when standing on the ground in wind there is a slight negative sweep moment, because the feet, attached to the ground are 'pulling the wings along. It took me two evolutionary stages to loose the bungies (elastic rubber chord, not sure if bungie is american ?) that I had installed to counteract the wings being blown back. Everytime my feet left the ground the wings would go to full forward deflection because of my bungie cords. What finally brought me around was standing in a 15 kts wind with the wings strapped on and nothing tethering the leading edges. It requires very little effort indeed to move them forward of trim, so much so that I now have bungie to stop the wings from sweeping forward of trim position. The fact that the body weighs more than the wings is more than compensated by its greater form drag and the vertical and horizontal stabilizer drag. The weight of the body pulls the wings down not forward, the wings then translate this force into forward motion, thus pulling the body along. Those little spiniing helicopter seed pods some trees produce are perfect displays of this principal.
Rest assured I have no intention of hurting myself, I am allergic to pain..... all the coming initial glide tests are happening on our training dunes, just like HG was invented.
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By red
#369361
Greg Vandenberg wrote:Thanks for the heads up on how to post the photos, I will be doing so this evening. You are correct, forward collective sweep effects nose up by way of CoG shift aftwards. The Skybike also has a secondary nose up control through collective AoA increase. This increases the angle between the horizontal tail fin and the wing thus effecting an aerodynamically induced positive moment around the CoG. The induced drag increase is also noteworthy. Lets say stopping is not my biggest headache.
The conundrum regarding the wings being swept back by the airspeed is something I really struggled to get my head around and was the cause of much wasted structural designing in the first prototypes. This 'phenomenon simply does not exist in ornithopter flight.
Greg,

My concern was not in normal flight, or at low airspeeds, and I expect no problems there. My concern is at high airspeeds, and especially in diving flight, where the body would definitely "pull the wings along." Wings in flight do create drag, both parasitic and induced.

I once (decades ago) built a rigid-wing HG from "proven" plans, and it was fine, below a certain airspeed. It did everything very well. At an airspeed not twice the cruising speed, however, certain forces overbalanced the design, and it became divergent. Nothing could be done (short of a parachute, which HGs did not have then) to stop the dive. The glider accelerated steadily, until meeting the ground. Large M&M wheels and a smooth downhill roll-out saved my bacon, although I did slightly sprain one ankle. Most HG pilots witnessing the incident could hardly believe that I walked (limping) away.

My concerns with "pitch controlled by sweep" are for high airspeeds. You may need a vehicle platform to explore this realm of flight safely. In California, and maybe other places, we have the Flight Deck:
https://www.youtube.com/user/hgflyer11/videos

Best,
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By Greg Vandenberg
#369367
Believe it or not........... but the first actual liftoff I had with the Skybike was on the back of a pick up truck............... I got tired of waiting for wind to do tests so I did a few tests standing on the back of a pick up truck going at 25 mph with my 250lb 'flight director' buddy gripping my front straps. I'll post a little clip on my channel later. To be honest it scared the living @$#@ out of me , but we got some good data and I didn't have to run my mieli off :thumbsup:
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By TjW
#369409
Greg Vandenberg wrote: Weight is roughly half that of the snowbird with the same power source.
I don't think weight is so much an issue as drag.
With two wing halves, you have 4 vortices rather than two,
As a wild surmise, I'd guess you lose more power from the gap in the middle than you will ever be able to make up for by flapping.
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By Greg Vandenberg
#369425
You are of course correct TjW. The prototype is at the moment very much a work in progress, and things like stability and structural integrity not to mention the 3D geometry of cables and aluminium poles (I think I sprained a brain cell or two on that subject :) had to be proven first. Now I get to do the 'fun' stuff, making it all sleek and aerodynamically sexy :drool:
I have posted another clip of the same test but including some construction photos and extra footage of control. Check it out ..................


Okay................that didn't work........... I cant post links yet but the clip is called Skybike update #1 and its on my channel at the link below.............. which I can post :mrgreen:

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