Ynot’s Human Powered Helicopter Attempt

[CNY_Dave]

Originally Posted by ynot

CG of hovering flight isn’t based on the CG of the craft when it‘s not flying. In hovering flight GC is related to where the lift/thrust is being applied. Like being hung from a pin from that position. Get one of those simple rod with a propeller at one end toys. Spin the rod and propeller between your hands with the prop at the top and it will hover with reasonable stability. Try spinning it with the propeller at the bottom and see what happens.

Exactly the fallacy I'm describing.

And I had several of those hand copters you describe, and would often fly them upside down.

[ynot]

Haven’t been able to get on a computer let alone this forum for a while. In my absence Team Atlas have done some more test flying. Or as they put it - “making another attempt at the AHS Sikorsky Prize” (but not official). Unfortunately their attempt ended in disaster with a rotor clipping a line resulting in two trusses and rotors being completely destroyed (pilot Todd okay). My son who also follows this said they had a photo of the wreckage on Twitter but it’s since been removed. Not a good look for the punters I guess. Really interesting thing is they claim to have “Reached approx. height of 3ms”. Won’t be able to post again for at least a few days.

[ynot]

Originally Posted by CNY_Dave

Exactly the fallacy I'm describing.

And I had several of those hand copters you describe, and would often fly them upside down.

True. I have re-remembered that I used to fly them upside down as a kid.

[Olowkow]

I wonder whether there would be an advantage for the HPH testing to be held in an inflatable building such as the one in the link. Higher air pressure, greater lift right? Also, more oxygen for the human. Would this violate the Sikorsky prize rules?

[quarky]

Originally Posted by Olowkow

I wonder whether there would be an advantage for the HPH testing to be held in an inflatable building such as the one in the link. Higher air pressure, greater lift right? Also, more oxygen for the human. Would this violate the Sikorsky prize rules?

Good point.
Or in Death Valley?


Slight derail:

Can someone explain why the dimples on a golf ball make it more aerodynamic?
It seems counter intuitive to me, though I know it is so.

[Mister Earl]

I don't think the dimples make it more aerodynamic, per se, but rather help cut down on the drag of the ball from the pocket of turbulent air that it pulls behind it by reducing the size of that air pocket.

[Olowkow]

Originally Posted by quarky

Good point.
Or in Death Valley?


Slight derail:

Can someone explain why the dimples on a golf ball make it more aerodynamic?
It seems counter intuitive to me, though I know it is so.

Death Valley is good, but a tad warm though.

I think Mythbusters or "How it's made"(?) did something on the golf balls. Reduces drag, not sure. Didn't someone do the dimples on a car and increased it's fuel efficiency?

Another twist on the HPH. How about (in principle/theory of course) doing the test inside a vertical tube whose diameter is about the same as the rotor span. Ground effect would be greatly enhanced, and the horizontal drift problem eliminated--at the expense of bumping into the sides and losing energy.

ETA: mythbusters golf ball car

[ben m]

Originally Posted by quarky

Can someone explain why the dimples on a golf ball make it more aerodynamic?
It seems counter intuitive to me, though I know it is so.

Two answers:

a) The golf ball is spinning and can generate lift via the Magnus Effect. The Magnus Effect is *stronger* (i.e. you get more lift) with a thicker boundary layer; turbulence helps.

b) A smooth sphere is a very poorly-streamlined object; at high speeds, laminar flow goes partway around the ball, then breaks off to form a turbulent wake. The whole structure does a particularly good job of causing drag. The dimples disrupt the laminar flow *earlier*, which changes the structure of the wake, and it so happens that the disrupted wake causes lower drag. This is not obvious, but it happens to work. It's also not true for all shapes and speeds. There are probably some cars that dimples would help, others it would hurt.

Note that for an airplane wing (a) there's no Magnus Effect and (b) you typically have (and want) laminar flow all the way around, so I doubt you want to dimple your wings or rotors.

[quarky]

Originally Posted by Olowkow

Death Valley is good, but a tad warm though.

I think Mythbusters or "How it's made"(?) did something on the golf balls. Reduces drag, not sure. Didn't someone do the dimples on a car and increased it's fuel efficiency?

Another twist on the HPH. How about (in principle/theory of course) doing the test inside a vertical tube whose diameter is about the same as the rotor span. Ground effect would be greatly enhanced, and the horizontal drift problem eliminated--at the expense of bumping into the sides and losing energy.

There could be rollers on the tips of the blades to reduce the friction of encountering the tube walls. That would be analogous to a specialized roadway in various bike type hpv contests. No stored energy is involved, yet, I'd imagine it isn't allowed. Pity, too, as there is much to be learned in such combinations.

I remain confused about the dimples. A dolphin's skin, for instance, is very much not dimpled.

Do the dimples somehow disturb the normal turbulence?
I am sorely uneducated in these matters, yet interested.
(I know, I should google, but sometimes I long for the equivalent of human interaction.)

Does a golf ball do much spinning in its flight?
Would it go further if it was more bullet-shaped, assuming the club could launch such a 'ball'?



Yknot?

Any progress of late?

Any news from our man Dan?

Edit:

Another thought on the subject matter...how does humidity effect the lift of a chopper?
Is there an ideal %?
I'm thinking that denser air might provide a relative advantage, yet, it would also cause more friction in the rotational force needed.

[Olowkow]

Originally Posted by quarky

There could be rollers on the tips of the blades to reduce the friction of encountering the tube walls. That would be analogous to a specialized roadway in various bike type hpv contests. No stored energy is involved, yet, I'd imagine it isn't allowed. Pity, too, as there is much to be learned in such combinations.

I remain confused about the dimples. A dolphin's skin, for instance, is very much not dimpled.

Do the dimples somehow disturb the normal turbulence?
I am sorely uneducated in these matters, yet interested.
(I know, I should google, but sometimes I long for the equivalent of human interaction.)

Does a golf ball do much spinning in its flight?
Would it go further if it was more bullet-shaped, assuming the club could launch such a 'ball'?



Yknot?

Any progress of late?

Any news from our man Dan?

The rules, as far as I know are simply:

Quote:

In summary, the requirements to win the AHS Human Powered Helicopter Competition include a flight duration of 60 seconds and reaching an altitude of 3 meters (9.8 ft) while remaining in a 10 meter (32.8 ft) square. The flight must be certified by a representative of the Fédération Aéronautique Internationale.

The back spin is essential on a golf ball to cause it to stop rolling when it hits the ground.

reposted: ETA: mythbusters golf ball car

[quarky]

Originally Posted by ben m

Two answers:

a) The golf ball is spinning and can generate lift via the Magnus Effect. The Magnus Effect is *stronger* (i.e. you get more lift) with a thicker boundary layer; turbulence helps.

b) A smooth sphere is a very poorly-streamlined object; at high speeds, laminar flow goes partway around the ball, then breaks off to form a turbulent wake. The whole structure does a particularly good job of causing drag. The dimples disrupt the laminar flow *earlier*, which changes the structure of the wake, and it so happens that the disrupted wake causes lower drag. This is not obvious, but it happens to work. It's also not true for all shapes and speeds. There are probably some cars that dimples would help, others it would hurt.

Note that for an airplane wing (a) there's no Magnus Effect and (b) you typically have (and want) laminar flow all the way around, so I doubt you want to dimple your wings or rotors.

Thanks, ben.
I hadn't seen your post when I made my latest one.
I feel better knowing that is a somewhat obscure phenomena.

Lots of science in a golf ball.
I imagine that they even figured out an optimal amount of dimples, unless there is some sort of regulated dimpling standard.
Baseballs have rules and regs.

[rjh01]

Golf balls. Did not take me long to find the information about dimples
http://en.wikipedia.org/wiki/Golf_ball#Aerodynamics

Quote:

Dimpled balls fly farther than non-dimpled balls due to the combination of two effects:
First, the dimples on the surface of a golf ball cause the boundary layer on the upstream side of the ball to transition from laminar to turbulent. The turbulent boundary layer is able to remain attached to the surface of the ball much longer than a laminar boundary and so creates a narrower, low pressure, wake and hence less pressure drag. The reduction in pressure drag causes the ball to travel farther.[7]
Second, backspin generates lift by deforming the airflow around the ball,[8] in a similar manner to an airplane wing. This is called the Magnus effect. Backspin is imparted in almost every shot due to the golf club's loft (i.e., angle between the clubface and a vertical plane). A backspinning ball experiences an upward lift force which makes it fly higher and longer than a ball without spin. (see Baez[9]) Sidespin occurs when the clubface is not aligned perpendicularly to the direction of swing, leading to a lift force that makes the ball curve to one side or the other. Unfortunately the dimples magnify this effect as well as the more desirable upward lift derived from pure backspin. (Some dimple designs are claimed to reduce sidespin effects.)

See also this which contains some interesting facts http://www.racecar-engineering.com/a...s-reduce-drag/

[TjW]

Originally Posted by ben m

Two answers:

Note that for an airplane wing (a) there's no Magnus Effect and (b) you typically have (and want) laminar flow all the way around, so I doubt you want to dimple your wings or rotors.

Well, you'd certainly like laminar flow all the way around, but there's typically a transition from laminar to turbulent flow somewhere. On some sailplane wings, this can be as far back as 95% of the chord.
The difficulty can be -- particularly at low Reynolds numbers -- that at the transition the airflow separates from the surface in a "laminar bubble', which has even greater drag than attached turbulent flow.
You can tell where this happens by painting something like used motor oil on the wing. The oil will flow in a thin layer back to the separation point, be a little thicker there, then thin out again when the now-turbulent boundary layer reattaches.
So on some older sailplane airfoils, the boundary layer was deliberately "tripped" into turbulent flow with a turbulator. This is usually something like Dymo labeling tape that's been cut lengthwise with pinking shears. It's put on the wing points forward just before the separation point.

Since a car, like a wing, has a preferred orientation, you shouldn't have to use dimples all over.

A higher density for the air will result in higher lift, but it will also result in higher drag. I don't think it takes more power to fly at high density altitudes, it just takes more speed. There's less power available from an air-breathing engine, so it takes longer to accelerate to the higher speed, so required runway lengths go up.

A higher oxygen partial pressure doesn't seem to be covered by the rules, but I would guess that increasing the oxygen content to, say 25% in a volume big enough to fly a HPH in would be hideously expensive. Death Valley in the winter can be very nice, though.

[dasmiller]

Originally Posted by TjW

A higher density for the air will result in higher lift, but it will also result in higher drag. I don't think it takes more power to fly at high density altitudes, it just takes more speed.

But if we ignore Re and compressibility effects, the L/D for a given shape at a particular attitude should be constant. Suppose we had a 1000 kg airplane with an L/D of 10, and flew it at sea level and at high altitude. It needs 1000 kg of lift (okay, 9800N . . .) at both altitudes, so it has 100 kg of drag and needs 100 kg of thrust, so the force part of force x distance is good.

However, as the density drops, the speed has to increase as the square root of density to maintain lift, so power will have to increase.

Of course, if you're interested in actually going somewhere rather than simply staying aloft, then altitude is probably your friend, but that's a very different problem.

Anyway, if you worked in some hyperbaric environment, the minimum power required should drop, though it's hard to imagine an affordably-priced hyperbaric chamber that would make any real difference to the aerodynamics.

If you went to really extreme pressures, the air would be sufficiently dense that the pilot would become almost buoyant, and could simply swim up to the required height, if the various physiological effects didn't kill him/her first (I'm not optimistic on that part). But it would allow a much smaller chamber.

[quarky]

You guys are teaching me lot, and I thank you.
The golf ball stuff was great. I'm not a golfer, and the back spin on the ball hadn't occurred to me.

Any opinions on optimal humidity for the hph?

[dasmiller]

Originally Posted by quarky

Any opinions on optimal humidity for the hph?

offhand, I'm not seeing any meaningful aerodynamic effects* unless the humidy is so high that you're getting fog over the wing. And even then I'm not quite sure what the impact would be, but it sure seems like there should be something.

If the humidity is too low, I suppose you'll start running into static electricity effects, but that's not aerodynamic (unless you're having stray bits of plastic stick to your rotors . . . )

*I have a distant memory of a term named 'R' for gas properties, and it had to do with the degrees of freedom of the individual molecules. Having more H2O would bring the average R down slightly, but IIRC R was relevant for specific heat, which matters for compressible fluid dynamics, but HPH is a long way from what we'd consider compressible flow.

[ynot]

Haven’t been able to post for some time or even do any work on my HPH attempt. Here’s a photo and info of Team Atlas almost reaching 3 metres. Would like to see the video - “Video data taken during this flight indicate that two rotors and the lowest part at the center of the aircraft (below the bicycle) were all above 3 m (9.84 ft), but two rotors were slightly below this threshold”. - http://www.vtol.org/news/aerovelo-reaches-3-meters

[quarky]

Originally Posted by ynot

Haven’t been able to post for some time or even do any work on my HPH attempt. Here’s a photo and info of Team Atlas almost reaching 3 metres. Would like to see the video - “Video data taken during this flight indicate that two rotors and the lowest part at the center of the aircraft (below the bicycle) were all above 3 m (9.84 ft), but two rotors were slightly below this threshold”. - http://www.vtol.org/news/aerovelo-reaches-3-meters

cool.

any idea how long they stayed up in the attempt?
i.e.; how close do you think they are?

has this at all dis-heartened your quest?

[ynot]

Originally Posted by quarky

cool.

any idea how long they stayed up in the attempt?

Not sure for that particular "high-flight" attempt but I think the longest they have been up for is 40 seconds

Originally Posted by quarky

i.e.; how close do you think they are?

Obviously they're a lot closer than they were and maybe now on a par with Gamera. Think both teams are planning more flights next month.

Originally Posted by quarky

has this at all dis-heartened your quest?

No. My attempt isn't that emotional.

[quarky]

i've noticed a lack of emotion on this forum.


but what about the quarter-mil?

i'd bet if you managed to win it, you'd be teary-eyed.

[quarky]

Any word from the contestants?

Is Ynot still with us?

[batvette]

I may be mistaken/this may have been mentioned in these 11 pages already.... and may even be irrelevant, BUT:

Isn't 3 meters altitude well within what would be considered merely ground effect hover?

(for the uninitiated, kind of like Moller's Skamcar- err, Skycar- you can push off the ground "x" number of feet, in free air it drops like a rock)

If so, we aren't really operating a helicopter at all, BUT if accomplishing the task is the goal, is there a way to exploit this lessened standard that the other designs may have designed to surpass and wasted weight or lift?


Youtube has a great piece on that HPV plane they did in '79, the Gossamer Albatross. I think Discovery produced it? Watched it recently, one amazing and important thing was how they were able to performance test athletes and precisely calculate the amount of work output they could sustain vs the weight of the craft, the drag of head (or assist of tail) winds, the speed required to make the distance goal (across the channel) before it got dark or a storm formed.
They tried a very fit woman, taught her to fly, then a very fit male grad student who knew how to fly, finally settling on a team of well seasoned competition cyclists to pool from and teach to fly.
Plane weighed about 70 lbs.

[quarky]

Originally Posted by batvette

I may be mistaken/this may have been mentioned in these 11 pages already.... and may even be irrelevant, BUT:

Isn't 3 meters altitude well within what would be considered merely ground effect hover?

(for the uninitiated, kind of like Moller's Skamcar- err, Skycar- you can push off the ground "x" number of feet, in free air it drops like a rock)

If so, we aren't really operating a helicopter at all, BUT if accomplishing the task is the goal, is there a way to exploit this lessened standard that the other designs may have designed to surpass and wasted weight or lift?


Youtube has a great piece on that HPV plane they did in '79, the Gossamer Albatross. I think Discovery produced it? Watched it recently, one amazing and important thing was how they were able to performance test athletes and precisely calculate the amount of work output they could sustain vs the weight of the craft, the drag of head (or assist of tail) winds, the speed required to make the distance goal (across the channel) before it got dark or a storm formed.
They tried a very fit woman, taught her to fly, then a very fit male grad student who knew how to fly, finally settling on a team of well seasoned competition cyclists to pool from and teach to fly.
Plane weighed about 70 lbs.

Though it's a thankless task, you might enjoy catching up with the thread so far.
You aren't far removed.

[ynot]

I’ve gone about as far as I can with my HPH build in my relatively small workshop. Unfortunately the wing structures require more room than I currently have so I will need to find a much bigger workshop space to continue further. Might be some time before I can make any more progress. I’ve built both double and single pilot frames.

Not sure if Gamera and/or Atlas will be attempting to win the prize this month. Upturn seems to be out of the race (as does AmDan).

[ynot]

Originally Posted by batvette

I may be mistaken/this may have been mentioned in these 11 pages already.... and may even be irrelevant, BUT:

Isn't 3 meters altitude well within what would be considered merely ground effect hover?

(for the uninitiated, kind of like Moller's Skamcar- err, Skycar- you can push off the ground "x" number of feet, in free air it drops like a rock)

If so, we aren't really operating a helicopter at all, BUT if accomplishing the task is the goal, is there a way to exploit this lessened standard that the other designs may have designed to surpass and wasted weight or lift?


Youtube has a great piece on that HPV plane they did in '79, the Gossamer Albatross. I think Discovery produced it? Watched it recently, one amazing and important thing was how they were able to performance test athletes and precisely calculate the amount of work output they could sustain vs the weight of the craft, the drag of head (or assist of tail) winds, the speed required to make the distance goal (across the channel) before it got dark or a storm formed.
They tried a very fit woman, taught her to fly, then a very fit male grad student who knew how to fly, finally settling on a team of well seasoned competition cyclists to pool from and teach to fly.
Plane weighed about 70 lbs.

Don’t think there is much effective ground effect at three metres for an HPH but I agree (and have said before) that it’s more a hovercraft rather than helicopter competition. Makes it easier to win so I’m not complaining.

[ynot]

Team Gamera are planning "flight tests" on April 25 - 28.

[ynot]

Team Atlas (Aerovelo) have finally reported on their “roughly 3 metres” high flight and resulting crash - http://www.aerovelo.com/2013/04/24/3...3-metres-down/

No mention of when Atlas will try again but Team Gamera now say –“Team members are in overdrive preparing for this weekend's flights”

[Marcus]

It won't be long now with two teams being so close. I'm sure either team could convince a world class sprinter to participate if all they needed was more power, but I suppose control issues are paramount at this point.

[Olowkow]

Lance Armstrong is probably available.

[TjW]

Originally Posted by batvette

I may be mistaken/this may have been mentioned in these 11 pages already.... and may even be irrelevant, BUT:

Isn't 3 meters altitude well within what would be considered merely ground effect hover?

(for the uninitiated, kind of like Moller's Skamcar- err, Skycar- you can push off the ground "x" number of feet, in free air it drops like a rock)

If so, we aren't really operating a helicopter at all, BUT if accomplishing the task is the goal, is there a way to exploit this lessened standard that the other designs may have designed to surpass and wasted weight or lift?


Youtube has a great piece on that HPV plane they did in '79, the Gossamer Albatross. I think Discovery produced it? Watched it recently, one amazing and important thing was how they were able to performance test athletes and precisely calculate the amount of work output they could sustain vs the weight of the craft, the drag of head (or assist of tail) winds, the speed required to make the distance goal (across the channel) before it got dark or a storm formed.
They tried a very fit woman, taught her to fly, then a very fit male grad student who knew how to fly, finally settling on a team of well seasoned competition cyclists to pool from and teach to fly.
Plane weighed about 70 lbs.

Quite a number of people flew the Condor after its Kremer flight at Shafter, including a 59-year old grandmother of ten, Maude Oldershaw. As far as I know, that was the first woman-powered flight. But Bryan Allen was the primary pilot for most of the development of the Gossamer Condor (Tyler MacCready did most of the early piloting) and all of the Gossamer Albatross. He was already proficient in hang gliders and bicycle racing. There was no pool of bicycle racers.

You may be thinking of the MIT group that wound up doing the Daedalus flight in Greece. Their first airplane, the Light Eagle, was piloted by a woman.
They did train with a group of bicycle racers. In the event, they picked the Greek.

[Marcus]

Originally Posted by Olowkow

Lance Armstrong is probably available.

That should bring some publicity to the event Seriously though, even in his prime with chemical assistance, Lance couldn't compete in a sprint , those guys are optimized for a very large power output for a short length of time. The differences in output for an effort lasting a minute or two are substantial even over a power like Lance, compared to a regular athlete they would be huge.

[ynot]

Team Gamera have completed their test fights. Seems they still have problems with "drift" as well as structural problems. They seem to have spent more time fixing than flying. I guess that's what test flying is often about.

[ynot]

A video of team Gamera's test flights - http://www.youtube.com/watch?v=GLflx...outu.be&t=1m2s

[WhatRoughBeast]

Originally Posted by quarky

Any opinions on optimal humidity for the hph?

0%, absent static electricity effects.

http://www.ihst.org/Portals/54/insig...y_Altitude.pdf

dasmiller

Originally Posted by dasmiller

However, as the density drops, the speed has to increase as the square root of density to maintain lift, so power will have to increase.

is exactly correct. Particularly for helicopters, altitude ceiling is set by power/lift considerations, and not by reduced power from the power plant.