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Crowdfunding hope for human-powered helicopter project

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March 23, 2013

Kenneth Huff and his team believe that rotor efficiency improvements will allow their desi...

Kenneth Huff and his team believe that rotor efficiency improvements will allow their design to fly using a fraction of the power needed by other Sikorsky competition contenders

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Last September, the Gamera II team from the A. James Clark School of Engineering got so close to claiming the Sikorsky Prize of US$250,000 for human-powered helicopter flight that the American Helicopter Society must surely have been preparing to pull the dust covers off the safe and hand over the cash. Gamera II features a huge cross-shaped frame with enormous rotors at each of its four points, which are powered by sustained hand and foot pumping from a pilot at the center. It's a design that's been used by many of those attempting to nab the elusive prize (including AeroVelo's Atlas), but Georgia's Kenneth Huff has a rather more compact vision for success.

The project began in the spring of 2010, when Huff stumbled across some information about the Sikorsky competition while researching the building of an engine-powered single-seat helicopter that he was hoping to build after graduating from Middle Georgia State College.

"I am not sure how most people react to the question of human-powered helicopters, but I thought that it would be easy after reading about the competition," Huff told Gizmag. "I really didn't know what I was in for and after looking at Da Vinci III and Yuri I, I began to understand the nature of challenge."

A year later, he enlisted the help of two friends/fellow classmates (Neal Fischer, William Edwards) and requested a US$5,000 development grant from the College to work on a prototype and test the feasibility of building a human-powered helicopter that was much smaller than either Da Vinci III or Yuri I. At this point, the team had not come across the efforts of the University of Maryland's Gamera team, and AeroVelo hadn't yet embarked on its Atlas project.

Unlike other Sikorsky contenders, the pilot of Huff's human-powered helicopter will be sea...

Happily, the research proposal was accepted and work began on the first prototype. The aim was to develop a small coaxial human-powered helicopter that had the potential for reliable and practical recreational use, something that certainly can't be claimed for Gamera or Atlas. Banking on improvements in rotor efficiency allowing for a substantial reduction in the size of both frames and blades needed for lift, an additional grant in the spring of 2012 (along with a personal cash injection from Huff himself) allowed important design modifications to be made, along with the construction and testing of a new set of rotors.

The specs for the current prototype (and the next model) include a frame made of 6061 T6 aluminum, a 1:1 gearing ratio, and stacked rotors sporting a carbon fiber spar and S1223 airfoil with a weight of 15 pounds (6.8 kg) and total length of 12 feet (3.6 m). The total empty weight of the craft is 110 pounds (49.8 kg).

"The basic premise behind this design is that when the speed of an airfoil doubles, the lift quadruples," explained Huff. "We knew that we could reduce the area of the rotors by 75 percent when we doubled the speed. Take Yuri I for example, which had eight rotors all rotating at approximately 20 RPMs. If they had been able to double the RPMs to 40, then they could have eliminated six rotors or 75 percent of their rotor area."

"However, any aerodynamicist will inform you that drag also quadruples when the speed of airfoil doubles so there would be much more drag, which is completely true," he continued. "So we knew that our primary focus had to be to reduce the drag of the rotors (other teams are focused on reducing the power required by increasing the span of the rotor, which allows them to reduce the speed of the rotor needed to lift off of the ground). By using smaller rotors rotating at 60+ RPMs we knew that our rotors had to be as efficient as possible. So our efforts over the past two years have been to design the most efficient rotors that we possibly could without relying on previous designs or foregone conclusions about how a rotor should be designed."

Huff and the team now feel that they have developed one of the most efficient rotors ever designed, but have not been able to fully test it due to a lack of funds. They have another grant request in with the College, but impatience has got the better of them and they've headed to Kickstarter to both generate interest in the project and hopefully provide the cash injection needed to get their human-powered helicopter off the ground.

Though rotor testing has produced positive results, the simple aluminum frame topped by a pair of two-bladed rotors has yet to make it into the air. The maximum lift generated so far is 80 pounds (36 kg), while the minimum lift needed to get the craft to fly has been calculated at 240 pounds (109 kg).

"There is much more uncertainty about the feasibility our rotor design because it runs contrary to the design of all other successful human-powered helicopters," said Huff. "This uncertainty is compounded when coupled with the fact that we have been working on it for two years and have yet to have a successful flight. Furthermore, some aerodynamicists and human-powered helicopter enthusiasts may swear to the impossibility of our design but we believe that there is always room for improvement in any design and truly believe that practical human-powered vertical flight is possible and has the potential to one day be a recreational activity similar to hang-gliding, and we hope to prove it."

The aim of the project is to develop a small coaxial human-powered helicopter that has the...

The developers are convinced that, with funding, the helicopter will be capable of lifting 300 pounds (136 kg) using 300 watts or less of power – a fraction of that needed by other Sikorsky contenders. Direction of the current model will be controlled by shifting the weight of pilot, but plans are afoot for a cyclic control system that should offer more precision.

Kickstarter backers can pledge support for the project in return for various rewards (including framed posters, a 48-page book or a brass S1223 airfoil cutout), or can take a giant leap of faith and promise $10,000 or more, which will secure a fully functional, full-scale replica of the finished helicopter.

In the event of another team beating Huff and friends to the elusive Sikorsky Prize – which requires a craft to stay in the air for 60 seconds, stay within a 10 meter (32.8 ft) square and rise to three meters (9.8 ft) at some point during the strictly human-powered flight – development on the project will continue.

The Kickstarter pitch video is below.

Source: Kickstarter

About the Author
Paul Ridden While Paul is loath to reveal his age, he will admit to cutting his IT teeth on a TRS-80 (although he won't say which version). An obsessive fascination with computer technology blossomed from hobby into career before the desire for sunnier climes saw him wave a fond farewell to his native Blighty in favor of Bordeaux, France. He's now a dedicated newshound pursuing the latest bleeding edge tech for Gizmag.   All articles by Paul Ridden
33 Comments

I'm going to have to side with the physicists who have been working on human-powered for nearly a decade and say this is doomed to failure.

Racqia Dvorak
23rd March, 2013 @ 11:02 am PDT

The amount of data that they have seemingly overlooked is enormous. It's like someone trying to reinvent the wheel and starting out with a square. The "discoveries" they've made could have been learned through a simple Google search and saved them money to be used on a more efficient design.

Dennis Roberts
23rd March, 2013 @ 01:00 pm PDT

So what would the effect of coaxial counter balance rotors be? I was waiting to see that on the vid. looks pretty cool tho.

Rob.
23rd March, 2013 @ 05:18 pm PDT

Snicker, polite snort SMH

Bill Bennett
23rd March, 2013 @ 08:53 pm PDT

Well, of course this design runs contrary to currently accepted aerodynamic principals! Very few 'innovative' designs don't.

Rob, you answered your own question. The co-axial driven rotor eliminate the need for a tail rotor by counteracting the inherent torque rotation of the entire vehicle.

Dennis, you are assuming that this design team hasn't 'Googled' the concept. The nature of the competition limits the scope of information a team will admit to have in its possession.

Noel Frothingham
23rd March, 2013 @ 11:42 pm PDT

When Bell Helicopter modified the 212 model into the 412 the important change was that the replaced the two bladed main rotor with a four bladed main rotor, this gives about a 20 knot speed advantage to the 412. However the four bladed rotor's diameter is only two feet less than the two bladed rotor on the 212. Obviously most of the lift is generated at the blade tips. Therefor it appears to me that the rotor should be designed to minimize drag and weight near the center and maximize lift at the outer few feet of rotor blade.

Slowburn
24th March, 2013 @ 03:57 am PDT

A conceptual improvement is possible. The tip vortices spiral inward towards the shaft, to some extent. Those from the top rotor will therefore interfere with the flow at the tips of the bottom rotor thus increasing the drag and decreasing the lift. To prevent this reduce the diameter of the bottom rotor and, to keep the same torque at the same tip speed, increase the number of blades in the bottom rotor to three of four.

F. Tuijn
24th March, 2013 @ 11:21 am PDT

@Noel Frothingham- Silly me, of course you're right. There're just pretending to not know about basic concepts of aerodynamics to throw the other competitors off! When no one expects it they'll show up with the real design and win the contest! I should have known they couldn't be that uninformed.

Dennis Roberts
24th March, 2013 @ 12:06 pm PDT

This reminds me of those crazy days when men dreamed of flying through the air, over 100 years ago.

www.youtube.com/watch?v=iMhdksPFhCM

At $19,700 short of their goal with seven days to go, I think it's a pretty safe bet they won't get the money. About as safe a bet that they'll never get off the ground.

Gadgeteer
24th March, 2013 @ 02:30 pm PDT

Noel, what I meant was 2 single blades counter balanced running co axial .

Robert Timmins
24th March, 2013 @ 04:02 pm PDT

Human powered helicopters are urgently needed by humanity. Most urban cycleways are becoming dangerously clogged with speeding lycra-clad commuters.

nutcase
24th March, 2013 @ 08:58 pm PDT

They refer to possible recreational uses like hang gliding ... I for one would prefer the risks of hang gliding to pulling a hamstring at a few hundred feet in one of these! If you lay still in a hang glider without chasing thermal updrafts, you just slowly sink along your glide path, if you stop pedalling in a helicopter, your reaching the ground, at the very least, is going to be a fair bit faster and probably of a more vertical nature.

The Skud
24th March, 2013 @ 09:32 pm PDT

Launch it off a cliff, and you'll fly alongside that hang-glider, without even touching the pedals - same as any other gyrocopter can.

My paramotor produces 90lbs of static thrust, and it launches me no problem off flat ground. These guys are producing almost that same amount of thrust, without having to carry that extra motor and fuel.

The only thing between them and the prize, is getting the aerodynamics right. If a 160-square-foot paraglider and 120cm prop pushing 90lbs flies, all they need to do is figure out the correct shape of their lifting surfaces, and so can they.

christopher
25th March, 2013 @ 01:35 am PDT

Adjustments are nothing more than dividing up the power. Without enough power - it will never work. Even the strongest of men have never had enough power. Sorry guys!

donwine
25th March, 2013 @ 09:54 am PDT

Not off the ground in 2 years? Maybe tubercles would help.

Bruce H. Anderson
25th March, 2013 @ 10:00 am PDT

Why is no one considering the power source? The seated position is very efficient in bicycles, however not when the intent is solely power production. A more vertical position would allow use of the cyclists weight in producing power and the angle of the leg during the power stroke is most efficient with less knee bend.

Jerry Peavy
25th March, 2013 @ 11:11 am PDT

Compressed air jets at the the tips of the rotors. what would be needed is a efficient Air compressor and light storage tank.

this would allow pilot to rest during flight without the nasty side effects.

Jay Finke
25th March, 2013 @ 11:12 am PDT

Pretty basic stuff. If they tried to make the blades more efficient, like a whale's fin, then it'd work better. A whale's fin isn't just straight like the blade shown, but with points on the leading edge that help it cut through water better to reduce drag. This feature can work in air applications as well.

Artem Down
25th March, 2013 @ 01:02 pm PDT

Sikorsky correctly calculated that no human powered vertical take-off and landing vehicle could overcome the lift burden unless materials and muscle mass weighed much less than they do.

It seems that the only way to achieve this somewhat silly goal is to achieve relatively high RPM and feather the otherwise thin air-slicing lift surfaces. If there were also balanced & weighted tips, the flywheel effect might help delay the inevitable descent...

Mirmillion
25th March, 2013 @ 02:14 pm PDT

Great. That's all we need now. Some people pedaling along, high above our cities. I see trouble in the making ... What about leg cramps!

Peter Davila
26th March, 2013 @ 04:58 am PDT

These two seem to have this stuff covered UNLIIKE EVERY OTHER UNIVERSITY TEAM.

Jack Norris book

http://www.propellersexplained.com

Betz Goldstein Theodorsen BGT

I understand only a small amount of the idea.

My takeaway from Norris (may be wrong) - end of blade goes to a point for drag reduction.

http://en.wikipedia.org/wiki/Charles_M._Olmsted

Charles Morgan Olmsted (Jan. 19, 1881 – 1948 ) was an American aeronautical engineer.

... Charles Olmsted then formed the CMO Physical Laboratory and continued to manufacture and sell the

ultra-efficient propellers on his own for another seven years.

Article link On C.M. Olmsted Patent number 1019078 of March 5, 1912:

https://docs.google.com/viewer?url=www.google.com/patents/US1019078.pdf

click view or download PDF upper right of page.

My takeaway from Olmsted - equal thrust from all sections along the blade.

See the lovely propellers on the Horten Ho 5. (5a~5c)

http://ufologie.patrickgross.org/aircraft/horten5.htm

I can't recall the google hit that disclosed who designed the propeller, it was an interview of one of the Horten living in Argentina, The prop was not attributed to Olmsted & and it was not the Horten's idea, I did

find this:"The propeller manufacturer Peter Kempel produced the propellers from Lignofol (beech wood impregnated with synthetic resin)." and "Peter Kumpel, who also made the "Habicht" propeller"

I too would like to see some whale turbicles on a prop, looks sexy.

http://en.wikipedia.org/wiki/Tubercle_(anatomy) "... they are also found on the leading edge of Humpback Whale's flippers, improving fluid flow over the flipper's surface."

Maybe some winglets at the end, (winglets idea came about by investigation of the spread feathers at the end of soaring birds wings, the end result in drag reduction is the same as if the wing were longer, but it's not.

http://en.wikipedia.org/wiki/Wingtip_device

Oops, per wiki they already do winglets on propellers - on existing aircraft.

A propeller is a rotating wing, how about a propeller with leading edge slats,

http://en.wikipedia.org/wiki/Leading-edge_slats

Maybe some vortex generators. to keep the flow stuck to the wing.

http://en.wikipedia.org/wiki/Vortex_generator

Maybe some golfball dimples?

http://entertainment.howstuffworks.com/sports/golf/basics/question37.htm

Ok, so dimples too tough to do, use burlap for the covering fabric.

Maybe a biplane propeller like on this powered submarine built by some Italian guy in Barcellona Spain the Ictenio II of around 1860 or so.

http://farm1.staticflickr.com/34/72988074_fbb4a6d067_z.jpg

Well water is 1000 times thiker than air, so Reynolds number factor would need to be applied.

It can be worse. The nautical crowd, may be way the ahead of the aeronautical crowd, maybe they got more time, since they have a lesser burden by two whole syllables:

http://www.torqeedo.com/us/

http://www.torqeedo.com/us/technology/propeller-technology

http://www.torqeedo.com/us/technology/propeller-technology/modern-optimization-calculation

Translate some of the jibber-jabber through that Reynolds Number magic

http://en.wikipedia.org/wiki/Reynolds_number

My personal dumb-down of the Reynolds Number is that air to tiny things is de-facto a lot thicker than the same thickness air is to large things, and attibutes to the fact that bumblebee flight does not defy the laws of physics.

Copy paste portion of my post Gamerea 1 - Things to consider:

Ergonomics & drive - Add arm & back muscles to leg muscles

http://rowingbike.com/site/EN/Home/Introduction/

http://www.concept2.com/indoor-rowers/training/technique-videos

http://www.concept2.com/

Which brings to mind something about helicopters, forward flight dynamics are different, and require far less energy than hovering helicopter flight dynamics, the rotor "disk" functions as one giant wing in forward flight.

http://en.wikipedia.org/wiki/Vortex_ring (hovering flight realy sucks)

http://www.skybrary.aero/index.php/Wake_Vortex_Generation_by_Helicopters

http://www.me.berkeley.edu/fml/projects/helicopter_wake.html

And while I'm on a roll, how about some holes or fipples in the wing so it will "whistle" opposite in motion to the vortices that would otherwise be shedded, so thier is no turbulence.

http://en.wikipedia.org/wiki/Fipple

It could then be called the hovering Ocarina.

Or maybe design to excite flutter, then you could have a ornithopter-helicopter, might sound like a giant kazoo, too bad if it works.

Gotta go, white coats coming, not lab coat white coats either, it's the attendants, again.

Whew, I think they should have structured their pledge amounts differently:

4 Decals $25, naw, one decal & paper (not brass) airfoil - $10.

48 page book -$100, nope. How about $50 post paid, $80.autographed, $25. ebook on amazon

$500 ~ $1000 - Video of you peddling their existing version for 10 ~ 20 minutes.

$10,000 or more - One of them marries your X-wife, and you pay them 5% of the alimony you were paying her.

I love thier project, I'd like to see them win.

Dave B13
26th March, 2013 @ 11:45 am PDT

Doh, I had'nt read:

"Direction of the current model will be controlled by shifting the weight of pilot, but plans are afoot for a cyclic control system that should offer more precision."

You all need to take a long hard look at how the existing helicopters with counter rotating rotors are controlled, tip spoilers for yaw is the big item you need to address, If you go with something like the Snek bicycle instead of regular peddle power, maybe have some twisted elastic with a clutch that locks things up so it can be loaded by some rowing (or peddling, also not so even), then keep winding one end while the other end unwinds to power the rotors. Hopefully the rules don't disallow some small battery powered widgets to manage stability, or lessen control difficulty. The russians were way bigger on counter rotating rotors than the west, as you'll find googling.

Dave B13
27th March, 2013 @ 10:15 am PDT

From the video it is apparent that the pedals are not far enough out for the rider - his knees have significant bend in them throughout. This greatly decreases efficiency (try riding your bike with the seat too low).

Harry Slocum
28th March, 2013 @ 02:10 pm PDT

Hey my friends,

Your results were misleading because the test with high angle of attack was conducted with only a fraction of the power used in the second "zero-angle" test. Horse power (and human power) is a result of torque times RPM. You have to change the gear ratios and redo the bench-mark.

Good luck.

Paulinator
31st March, 2013 @ 02:01 pm PDT

Another idea came to mind from 1987 TV news article on America's Cup Yacht race, or Chicken McRiblets, not sure which:

http://www.ncbi.nlm.nih.gov/pubmed/1922842

Drag Reductions in Fluid Flows - Techniques for friction control

"... The use of streamwise microgrooves, or riblets, for turbulent skin friction reduction originated at NASA Langley for aerodynamic applications. ... providing a decrease in skin friction of about 8% ... " (... 6.8% max for marine...)

Riblet Technology.

http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html

http://www.safl.umn.edu/featured-story/featured-research-project-reducing-wind-turbine-blade-drag-using-riblet-film

http://oracleracingblog.blogspot.com/2010/04/3m-riblet-technology.html

Dave B13
2nd April, 2013 @ 07:33 am PDT

The fact that despite their extreme aspect ratio helicopter blades manage to support the weight of the whole craft at the rotor's center is due to the centrifugal pulling force generated at typically high rotor speeds.

So the problem with Kenneth's design (like with all other competitors') is one of too low rotational speed with consequent cantilever construction, i.e. weight penalty, i.e. insufficient blade aspect ratio, i.e. poor aerodynamic yield.

Hence, without increasing rotor diameter, blades with much higher aspect ratio would allow for substantially higher tip speed yielding in turn substantially higher lift -- though along with a collateral problem arising from the higher loss factor of a multiplication gear needed to spin the blades.

However, blade tip speed would thus come way closer to the air speed of modern gliders at their best sinking rate -- which might turn out a distinct advantage over state-of-the-art human powered fixed and rotary-wing aircraft bound to fly at very low speeds because of their huge and relatively low aspect-ratio cantilever airfoils.

What I don't understand is why all projects heading for the Sikorsky prize are managed by students -- as if the best of inventions had always come from students, and not from experienced self-taught senior experts...

IMHO, the most promising perspective is to be seen in the cycloidal rotor concept (no cantilever blades, no wing-tip vortices, evenly distributed air speed along the blades) -- which leads me to just another wondering*: why are so many student teams working on reduced scale cycloidal rotors, and no one on a human powered one?

* Old-age pensioner's wondering...

euroflycars
3rd April, 2013 @ 09:30 am PDT

"What I don't understand is why all projects heading for the Sikorsky prize are managed by students -- as if the best of inventions had always come from students, and not from experienced self-taught senior experts..."

euroflycars, you have a point.

http://en.wikipedia.org/wiki/Paul_MacCready

"...designer of the human-powered aircraft that won the first Kremer prize ...'

http://www.bloodhoundssc.com/

http://www.bloodhoundssc.com/education

There may not be a lot of ability to make money (other than the prize) from a human powered helicopter.

Senior Experts, need to eat, pay alimony , and so work on stuff that comes with a paycheck.

Or at least the possibility of a paycheck:

http://en.wikipedia.org/wiki/Burt_Rutan

For students - one huge problem solving / learning exercise , almost incidental if they achieve their goal, and they can get grant money.

Ref:

http://www.isrsubrace.org/

http://en.wikipedia.org/wiki/Concrete_canoe

The below started out as a joke, became a routine assignment for students, then a Soviet State secret, then decades of routine frustration for those attempting to bring it to market, Got Money?

http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=740

One of the ultimate self-taught senior experts:

http://en.wikipedia.org/wiki/Charles_F._Kettering

Dave B13
3rd April, 2013 @ 12:16 pm PDT

@Dave B13: ultra-light aircraft are a highly sensible political and strategic issue, e.g. being even totally prohibited in both Switzerland and North Korea (as the only countries in the world to ban these aircraft of the future) -- and please note that according to Swiss rule, Piccard's Solar Impulse, with less than half of the required 20kg per square meter of wing area should be prohibited in his own country!

Instead, it has federal backing through engineering services provided by Swiss high schools -- because the Swiss government's message is the following: "As you can see, ladies and gentlemen, solar flight needs a monster with a 60-meter wing-span, so forget about your ultra-light personal solar aircraft...". That's probably why, a few years ago, Piccard claimed boldly (and wrongly) in the Swiss magazine AeroRevue that he was going to build the first man-carrying solar aircraft, thus ignoring (or rather dismissing), McCready's 163-mile flight from Paris to Manston Royal Air Force Base in the UK performed 20 years ago with his sturdy Solar Challenger taking off and flying on solar cells alone without batteries and with less than 15m wing span -- but now you may also know why it was a one-off headed straight for the Smithsonian...

For the same reason (i.e. because it has tremendous potential as an ultra-light electric VERTOL personal aircraft) the DARPA refused funding of Sikorsky's X2 -- so it might be interesting to take a closer look at the rules of the student challenge to see if there are any symptomatic conditions or restrictions set to prevent a civil break-through in ultra-light rotary-wing technology.

After all, if any one of the teams came up with a genuinely practical concept in the vein of the Solar Challenger, nobody would object to electrical assistance for mass-use -- as witnessed by the booming electric bicycle market!

euroflycars
3rd April, 2013 @ 02:43 pm PDT

Another project that would be fun,would be to try to make a short flight by using some type of wind up mechanism,using large rubber bands or spring and flywheel.You pedal the mechanism real tight and release it,making a short flight.How about a small multirotor using /jobi motors 4 of them,like E volo but with a pod below the rotors,keeping it cheap and simple.Good luck,I'm sure you have you hands full.

Thomas Lewis
3rd April, 2013 @ 02:54 pm PDT

Since the surface swept by the inner two thirds of the blades doesn't contribute significantly to total lift, rotor lift has to be optimized for the high-speed area defined by the surface swept by the blades' outer third. Hence, in order to compensate for the inner area's low yield, the upper rotor should be scaled down to two thirds of the lower rotor and made to spin so much faster as needed for torque compensation at the driving shaft of its multiplier gear.

This configuration would not only increase the high-yield area of the rotor's swept surface, but also reduce the necessary volume of a streamlined central body as recommended to accelerate airflow trough the innermost swept area -- whereby the overall effect of a smaller and faster upper rotor in conjunction with a streamlined central body ought to grant almost evenly distributed air speed over the entire length of the rotor blades.

If I had the necessary resources to build a human powered helicopter of the above described type, I would of course rather not disclose my concept...

euroflycars
7th April, 2013 @ 01:16 pm PDT

I'm somewhat frustrated that no one (including, evidently, the team itself) has stepped back and actually put bounds on how much power they're going to need. Here are the back of the envelope calculations they should have done in prior to any other design work.

Suppose the vehicle is hovering with zero airspeed away from the ground such that there is no ground effect. Now consider a stream tube enclosing the steady flow processed by the propellers and assume that:

- the thrust is distributed uniformly over the disc

- no rotation is imparted to the flow

- the pressure far ahead and far behind the prop matches the ambient value.

Upstream of the propellers, the inlet velocity V0 is approximately zero while downstream, there's a jet of fluid exiting the CV with a velocity of Ve. Neglecting pressure on the side of the stream tube as it decreases in cross sectional area, the thrust will approximately be given by

T = mdot dV = rho A V1 (Ve - V0)

...where V1 is the velocity at the propeller and A is the prop area. In general, V1 < Ve, but for the sake of argument, suppose they are getting more thrust than they actually are and let V1 = Ve such that

T = rho A Ve^2

Power will roughly be given by

P = 0.5 mdot (Ve^2 - V0^2) = 0.5 rho A V1 Ve^2 ~ 0.5 rho A Ve^3

Rearranging and substituting,

P = 0.5*sqrt(T^3 / (rho A))

This is a highly simplified equation. It assumes perfect power transfer efficiencies and no drag, but it should give a ball park estimate of the minimum power that could conceivable make this thing work.

Let assume that they have a fairly light 70 kg person such that the total mass is about 120 kg. The required thrust then becomes 1.18 kN.

Using a sea level density of rho = 1.225 kg/m^3, an area of A = pi (3.6)^2 = 40.7 m^2, the required power is 2.86 kW.

Now some reference:

- A typical, reasonably fit person, is able to do between about 180 and 250 W on a bike (with the proper seat height)

- Lance Armstrong, at his training peak (not his doping peak mind you) was able to push about 350 W for extended periods of time (http://www.physics.fsu.edu/courses/Fall08/phy2048c%20Studio/CalendarSC/W12D3/LanceArmstrong.html).

- Mark Cavendish can apparently hit 1700 W in all out sprints (http://wattbike.com/uk/blog/post/sprinting_at_the_tour_de_france)

In short, this will NEVER work. A Tour de France sprinter would not even be able to make this thing hop, and it gets worse. Also accounting for the contraction of the stream tube, a slightly more detailed analysis (Sforza 2012, Gessow 1985) gives:

P = sqrt(T^3 / (2 rho A))

which means the minimum power is actually above 4 kW. Again, this will NEVER work, even before you add real world losses. I don't care how efficient you make your propellers.

ToTheNth
18th May, 2013 @ 11:42 am PDT

One last widget:

http://en.m.wikipedia.org/wiki/Gurney_flap

Which Gurney was next to last to know about.

Dave B13
12th November, 2013 @ 02:30 pm PST

29th May 2014

Good evening Gamera II Team , would it not be possible to change the propeller design , so that it does not have to be subject to high revolutions per minute , but rather obtain a low revolution count with a lower Aspect Ratio and a more pronounced Camber line to increase the lift .

I salute you for your innovation and do not give up . Best regards , Charles H .

Charles H Schulmann
29th May, 2014 @ 01:12 pm PDT
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