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Old 4th January 2013, 06:55 PM   #81
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So...

How do you feel about boinginess?
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Old 4th January 2013, 06:56 PM   #82
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Originally Posted by quarky View Post
So...

How do you feel about boinginess?
Good for Kangaroos . . . not good for HPH's
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Old 4th January 2013, 07:04 PM   #83
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Originally Posted by ynot View Post
Good for Kangaroos . . . not good for HPH's
You must realize by now, my cheer-leading for an alternative power take off scenario. Unless you didn't read my posts in similar threads, you must be aware of my alternate takes on this essential matter.

This is the crux of my cheer-leading.

I must ask, how do you propose to supply the human power to the system, if not through approaches I've mentioned?
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Old 4th January 2013, 08:55 PM   #84
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Originally Posted by quarky View Post
You must realize by now, my cheer-leading for an alternative power take off scenario. Unless you didn't read my posts in similar threads, you must be aware of my alternate takes on this essential matter.

This is the crux of my cheer-leading.

I must ask, how do you propose to supply the human power to the system, if not through approaches I've mentioned?
I don't remember you ever explaining exactly how your boinging system would actually work on an HPH. Do that then I'll tell you why it won't work well in practice.

I propose to supply the human power to the system through approaches I've mentioned. I call it an external treadmill but that definition has slightly changed

So if I don't do it your way you will no longer be a cheerleader?
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Old 5th January 2013, 07:44 AM   #85
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Originally Posted by ynot View Post
I don't remember you ever explaining exactly how your boinging system would actually work on an HPH. Do that then I'll tell you why it won't work well in practice.

I propose to supply the human power to the system through approaches I've mentioned. I call it an external treadmill but that definition has slightly changed

So if I don't do it your way you will no longer be a cheerleader?
That's just silly. I don't even have a way, obviously, though I think there's something to be said for boing. It's the circular motion of the leg power that I question in an effort of short duration.

I'm still wearing my tu-tu, and getting my pom-poms cleaned for you.
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Old 5th January 2013, 08:05 AM   #86
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Originally Posted by quarky View Post
anyway, in my chase for the fast hp boat race, one idea I had, involving two people, was to launch an umbrella-like device, ahead of the boat, which opened up underwater...
then, the pedal-cranker pulled the boat towards that resistance; as the next one was launched.

It was a variation on the theme of having your boat tied to an anchor, far away, and winding up the line.

This has no relevance to the helicopter, thank god.

Actually, in principle, the same idea could work for an aircraft.

You start by firing a tethered furled parachute from an air cannon attached to the craft. Then you rapidly wind up the tether faster than the parachute falls, deploying the chute and lifting the craft. When you're about to run out of tether, you fire a second furled parachute, and so forth. Between firings, you have to furl the spent parachutes, unwind the tethers, and recharge the air cannon.

If you can avoid ever fouling the chutes, it's a very safe way to lift, because if your power plant fails you're just falling on a parachute. But it's sure to be way too inefficient to be human-powered.

(I think there were some very early aircraft designs that amounted to vertical conveyor belts carrying furling and unfurling winglets or parasols. With enough power they could probably lift off, but as with human-powered designs today, motors at the time were barely adequate (or not yet adequate) even with the most efficient possible designs, so simple but inefficient concepts like air screws and vertical water-wheel-like air wheels never came close to working.)

Respectfully,
Myriad
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Old 5th January 2013, 08:15 AM   #87
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Cool.
Not that it would work, but I wonder if the rules forbid such an approach?
Of course, the cannons would need to be propelled by human power; compressing a spring, or similar.

I'm surprised I didn't think of this, vertically, because I did, horizontally.
I wonder how fast 'swimmers' could go if they pulled themselves along a rope that was secured to both ends of the pool?
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Old 5th January 2013, 09:31 AM   #88
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Originally Posted by ynot View Post
Although Iím not at the wing stage yet Iíve considered long wing problems. What about having more wings of a shorter length? Iíve done some model size experiments at prestressing and cable-staying wings and the results seem to be promising. I shook my head in disbelief when I saw how the Upturn team used poles and a cobweb of lines on their wings.

ETA - This sort of thing . . .

Attachment 27395
It seems unlikely that many lower aspect ratio blades will be more efficient than two. You should look up "momentum theory". This treats the rotor as a black box "actuator disk", that accelerates air above the disc to some finite velocity below the rotor.

It's almost always the case that accelerating a large amount of air a little is more efficient than accelerating a smaller amount more.

I think the difficulty you'll find in building a long wing is not so much strength as stiffness, both along the spar and in torsion.
That's why I suggested the biplane idea.

Still, if you're going to have a control system (I'm not sure there is one on Gamera, since the pilot's arms and legs are both busy), you may need to have more blades.
If the rpm is, say, six, and you're drifting right, and the rotor is fore-and-aft, you probably don't want to wait two and a half seconds for the rotor to swing 90 degrees to be in a position where it can apply maximal roll torque. Or even the second and a quarter it would take to rotate 45 degrees.
Flying close to the ground, a second is a loooong time.
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Old 5th January 2013, 10:02 AM   #89
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Originally Posted by TjW View Post
It seems unlikely that many lower aspect ratio blades will be more efficient than two. You should look up "momentum theory". This treats the rotor as a black box "actuator disk", that accelerates air above the disc to some finite velocity below the rotor.

It's almost always the case that accelerating a large amount of air a little is more efficient than accelerating a smaller amount more.

I think the difficulty you'll find in building a long wing is not so much strength as stiffness, both along the spar and in torsion.
That's why I suggested the biplane idea.

Still, if you're going to have a control system (I'm not sure there is one on Gamera, since the pilot's arms and legs are both busy), you may need to have more blades.
If the rpm is, say, six, and you're drifting right, and the rotor is fore-and-aft, you probably don't want to wait two and a half seconds for the rotor to swing 90 degrees to be in a position where it can apply maximal roll torque. Or even the second and a quarter it would take to rotate 45 degrees.
Flying close to the ground, a second is a loooong time.
Not sure that I can see that a biplane configuration with shorter wings above and below would be significantly different or better than the same wings forward and aft. Perhaps the biplane configuration would give the wings more clean air? Iím figuring at least 4 wings per wing-set if not 5 or 6.

Do you think any stability can be gained by having the wings on a slightly raised angle from the body so they spin in a conical shape?

What are your thoughts on prestressing and/or cable-staying the wings as I indicated in the drawing?
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Old 5th January 2013, 11:20 AM   #90
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Would being able to alter the pitch of the blades, mid flight, be worth-while?
It doesn't seem like a major investment in weight of mechanical stuff.
Do any of the contenders have this capability?
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Old 5th January 2013, 01:40 PM   #91
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Originally Posted by quarky View Post
Cool.
Not that it would work, but I wonder if the rules forbid such an approach?
Of course, the cannons would need to be propelled by human power; compressing a spring, or similar.

I'm surprised I didn't think of this, vertically, because I did, horizontally.
I wonder how fast 'swimmers' could go if they pulled themselves along a rope that was secured to both ends of the pool?
I think that the compression would count as illegally stored energy. After all, what is the real difference between that, say, and sitting there for a couple of hours generating enough compressed air to run an engine?

As for swimmers and a rope, I don't think it would be too hard to set up. My uneducated guess as a swimmer is that you could not pull your way any faster than you can swim. Viscous resistance is a huge factor here, and although I may be wrong, I can't think of a position you could put a rope that would combine with the best position for getting through the water.
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Old 5th January 2013, 02:07 PM   #92
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Originally Posted by ynot View Post
Not sure that I can see that a biplane configuration with shorter wings above and below would be significantly different or better than the same wings forward and aft. Perhaps the biplane configuration would give the wings more clean air? Iím figuring at least 4 wings per wing-set if not 5 or 6.
The historic advantage of biplanes (aside from looking cool) is that you can build a very lightweight, rigid biplane structure if you allow a few struts and cables.

Sailplane wings, for example, are very efficient, and they're very long and narrow and thin. Unfortunately, "long, narrow, and thin" is not a good starting point for "light and strong."

A biplane configure will let you make a nice, rigid box that will resist twisting and bending, at the price of some additional parasite drag (cables and struts) and some mutual interference between the wings. It boils down to a normal engineering trade.
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Old 5th January 2013, 02:26 PM   #93
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Originally Posted by dasmiller View Post
The historic advantage of biplanes (aside from looking cool) is that you can build a very lightweight, rigid biplane structure if you allow a few struts and cables.

Sailplane wings, for example, are very efficient, and they're very long and narrow and thin. Unfortunately, "long, narrow, and thin" is not a good starting point for "light and strong."

A biplane configure will let you make a nice, rigid box that will resist twisting and bending, at the price of some additional parasite drag (cables and struts) and some mutual interference between the wings. It boils down to a normal engineering trade.
A bi-wing design is definitely on the list of things to consider if for no other reason than I respect TjWís advice. I believe I can see the bi-wing advantages and disadvantages however. As I said earlier Iím nowhere near the wing stage yet but I certainly donít mind it being part of the discussion. I need to satisfactorily complete the ďtransmissionĒ before anything else. I know what I want to build for testing but I donít have much spare time at present.
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Old 5th January 2013, 02:48 PM   #94
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Perhaps this is taking cable-staying too far in the pursuit of the rigidity of a single wing?

cswing.jpg
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Old 5th January 2013, 03:15 PM   #95
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Biwings certainly do seem to have some advantages, but I note that most human powered flight attempts have bypassed them. I suspect that there are reasons for this, one of which might be that although the struts and braces seem economical of weight normally, the weight requirements for an HP craft are so radical that they add too much. The other possibility is that HP craft rely so intensely on ground effect, at least for initial takeoff, that even if a biwing works best when you're aloft, it might be hard to get off the ground.

All guessing, though.
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Old 5th January 2013, 03:43 PM   #96
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Originally Posted by bruto View Post
The other possibility is that HP craft rely so intensely on ground effect, at least for initial takeoff, that even if a biwing works best when you're aloft, it might be hard to get off the ground.

All guessing, though.
I'd also suspect the ground effect advantage main reason. Another reason may be that even though the biwing structure is better at handling force vectors in all directions, that really isn't needed in this case. No gusts, and no dogfighting.
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Old 6th January 2013, 09:52 AM   #97
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Originally Posted by ynot View Post
Not sure that I can see that a biplane configuration with shorter wings above and below would be significantly different or better than the same wings forward and aft. Perhaps the biplane configuration would give the wings more clean air? Iím figuring at least 4 wings per wing-set if not 5 or 6.

Do you think any stability can be gained by having the wings on a slightly raised angle from the body so they spin in a conical shape?

What are your thoughts on prestressing and/or cable-staying the wings as I indicated in the drawing?
Aerodynamically, biplanes are less efficient. No question about that.

Structurally, it's easier to make a biplane stiff because the depth of the truss is so much larger than the depth of an airfoil. The outer fibers are much further apart.
With simple wire bracing, the further out on the span you go, the shallower the angle, and the more compressive load on the spar per unit vertical force applied.
On an airplane, this may be a wash, because as you go further out on the span, there's less lift generated, and so less force. (Ideally, it's an elliptical lift distribution.)
On a rotorcraft, because the outside portion is moving faster, this isn't true. The majority of the lift is generated further out.
Because the inner part is moving more slowly, the additional drag of a biplane/wire bracing there is a smaller penalty to pay for increased stiffness there.
You'd probably still want to go with a monoplane on the outer section for the better efficiency.

By staggering the top airfoil forward of the bottom, and adjusting the decalage, you could have the inner biplane work something like a sloop rig, where the jib (top airfoil) actually speeds up the air over the main (bottom airfoil).

I think wire bracing of some sort will be necessary. I'm not sure how well small scale testing will work.
For example, the Gossamer Condor's spar could be crunched like a soda can. I'm not sure what you could work with at small scale that will accurately represent something like that.

As for prestressing, I'd recommend something like the Gossamers used:
Deliberately make the wire a little short, and terminate it in a thimble.
Loop a piece of Dacron leech line several times through the thimble and the attach point. The multiple loops work like a teeny "come-along" to apply tension. Tie a square knot.

With coning, I think the main difficulty will be to limit it to some reasonable value.

Thinking about control, I'm wondering if the conventional tilting of the disk will work. At these low speeds, you'd be accelerating an enormous volume of air. The Gossamer Condor and Albatross were difficult to roll because of this. They were steered by twisting the wing on the inside of the turn down. This is bassackwards from the way most airplanes operate. The additional drag of the increased AOA caused them to yaw in that direction, and the turn rate was fine-tuned by tilting the canard.
I don't know that there would be an equivalent cheat for rotorcraft.

One goofy thought is a completely separate set of vertical airfoils, set up as a cycloidal rotor. It would provide a little translational thrust without having to roll the rotor disk. That's really blue-sky, though. I think the additional drag and weight would be too much.
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Old 6th January 2013, 10:59 AM   #98
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Originally Posted by TjW View Post
Aerodynamically, biplanes are less efficient. No question about that.

Structurally, it's easier to make a biplane stiff because the depth of the truss is so much larger than the depth of an airfoil. The outer fibers are much further apart.
With simple wire bracing, the further out on the span you go, the shallower the angle, and the more compressive load on the spar per unit vertical force applied.
On an airplane, this may be a wash, because as you go further out on the span, there's less lift generated, and so less force. (Ideally, it's an elliptical lift distribution.)
On a rotorcraft, because the outside portion is moving faster, this isn't true. The majority of the lift is generated further out.
Because the inner part is moving more slowly, the additional drag of a biplane/wire bracing there is a smaller penalty to pay for increased stiffness there.
You'd probably still want to go with a monoplane on the outer section for the better efficiency.

By staggering the top airfoil forward of the bottom, and adjusting the decalage, you could have the inner biplane work something like a sloop rig, where the jib (top airfoil) actually speeds up the air over the main (bottom airfoil).

I think wire bracing of some sort will be necessary. I'm not sure how well small scale testing will work.
For example, the Gossamer Condor's spar could be crunched like a soda can. I'm not sure what you could work with at small scale that will accurately represent something like that.

As for prestressing, I'd recommend something like the Gossamers used:
Deliberately make the wire a little short, and terminate it in a thimble.
Loop a piece of Dacron leech line several times through the thimble and the attach point. The multiple loops work like a teeny "come-along" to apply tension. Tie a square knot.

With coning, I think the main difficulty will be to limit it to some reasonable value.

Thinking about control, I'm wondering if the conventional tilting of the disk will work. At these low speeds, you'd be accelerating an enormous volume of air. The Gossamer Condor and Albatross were difficult to roll because of this. They were steered by twisting the wing on the inside of the turn down. This is bassackwards from the way most airplanes operate. The additional drag of the increased AOA caused them to yaw in that direction, and the turn rate was fine-tuned by tilting the canard.
I don't know that there would be an equivalent cheat for rotorcraft.

One goofy thought is a completely separate set of vertical airfoils, set up as a cycloidal rotor. It would provide a little translational thrust without having to roll the rotor disk. That's really blue-sky, though. I think the additional drag and weight would be too much.
Quite like the inner bi outer mono concept. Donít like the cycloidal rotor. Busy now so will get back later on the rest.
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Old 6th January 2013, 12:15 PM   #99
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Such a gift, to have a TjW here with us.

Just had to say it...

what a gift.

thankyou, all.
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Old 6th January 2013, 12:37 PM   #100
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Originally Posted by bruto View Post
I think that the compression would count as illegally stored energy. After all, what is the real difference between that, say, and sitting there for a couple of hours generating enough compressed air to run an engine?

As for swimmers and a rope, I don't think it would be too hard to set up. My uneducated guess as a swimmer is that you could not pull your way any faster than you can swim. Viscous resistance is a huge factor here, and although I may be wrong, I can't think of a position you could put a rope that would combine with the best position for getting through the water.
You are absolutely correct, as per loading the spring.
Not sure about the swimmer's rope.

Surely it's been done?

I have no idea, and may have to go a googling.
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Old 6th January 2013, 05:26 PM   #101
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Originally Posted by bruto View Post
Biwings certainly do seem to have some advantages, but I note that most human powered flight attempts have bypassed them. I suspect that there are reasons for this, one of which might be that although the struts and braces seem economical of weight normally, the weight requirements for an HP craft are so radical that they add too much. The other possibility is that HP craft rely so intensely on ground effect, at least for initial takeoff, that even if a biwing works best when you're aloft, it might be hard to get off the ground.

All guessing, though.
MIT built a biplane HPA that flew short distances. Called BURD. Biplane Ultralight Research Device. I think it or BURD II flew short distances.
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Old 6th January 2013, 05:50 PM   #102
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Originally Posted by TjW View Post
MIT built a biplane HPA that flew short distances. Called BURD. Biplane Ultralight Research Device. I think it or BURD II flew short distances.
As I recall the BURD never left the ground and essentially self-destructed before take-off. It was a two pilot plane.

ETA - Some info here - http://books.google.co.nz/books?id=V...iplane&f=false
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Old 6th January 2013, 07:34 PM   #103
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Has Spork left this arena?

Sure would be fun to have his in-put.
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Old 7th January 2013, 06:52 AM   #104
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Originally Posted by ynot View Post
As I recall the BURD never left the ground and essentially self-destructed before take-off. It was a two pilot plane.

ETA - Some info here - http://books.google.co.nz/books?id=V...iplane&f=false
You're right. I was probably thinking of Chrysalis. Sort of a follow on, done by different students. Still a biplane design, though. It flew with quite a few different pilots.
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Old 8th January 2013, 03:22 PM   #105
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triple post - Boy this forum is running painfully slow!
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Old 8th January 2013, 03:24 PM   #106
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double post
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Old 8th January 2013, 03:26 PM   #107
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Thought I would explain the design improvement I mentioned in an earlier post for anyone that might be interested . . .

I was designing and building an external treadmill for my one pilot designs and simply used a bike wheel with the tyre and tube removed. The rim formed a large spool on which the pulled line was wound. I put 3 evenly spaced handles on either side of the rim and they were evenly offset side to side. The handles couldnít span the rim as that would prevent the line being wound on it. The wheel was positioned between the legs and was powered by arms and legs. Even though it all may sound crude it worked quite well and was able to lift quite a heavy weight on the end of the line.

Some problems encountered were that the unused handles got in the way of the legs to some degree and because they could only be attached to one side of the rim they needed to be braced which would have increased their weight in the real thing. There was a potential problem in having to quickly remove and replace the feet from handle to handle (the hands werenít such a problem). Also exact sizing of the wheel size and positioning of the handles for different body sizes were potential problems.

I found that it was better if I didnĎt stagger the handles on either side and made them exactly opposite each other. I made them in one piece and attached them under the rim so they didnĎt interfere with the line. This meant I used both legs and both arms in unison. When one is being quickly reset the other provides the power. For much of the time both provide power. This method gave a steady and powerful output and worked very well.

Then I had a little eureka moment - Instead of fixing multiple handles to the rim I made two small bogies, each with a handle that spanned the opening of the rim (on top of it). They could now do this because they would never be used in the portion of the rim that the line was being wound on. The bogies move freely around the rim for the reset strokes and lock to the rim by means of a ratchet or sprag for the power strokes. One bogie for arms and one for legs. This meant there were no unused handles to get in the way and the feet could be fixed to their handles and the reset stroke could be made quicker and with more confidence. Different arm and leg lengths are now not a problem. The bogies can be made lighter than the fixed handles with braces.

Instead of bogies on the rim I can alternatively use levers that lock and release from anywhere on the wheel or axle. I can make these levers of different lengths so the arms can be more lower geared than the legs to more match their power output. This method also greatly improves my two pilot design and options which is now the one Iím focused on.

That was written quite quickly so hope itĎs understandable.
 
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Old 8th January 2013, 03:33 PM   #108
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I understand,yet lack credibility.
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Old 8th January 2013, 03:38 PM   #109
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Originally Posted by quarky View Post
I understand,yet lack credibility.
Explain why.
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Old 8th January 2013, 04:15 PM   #110
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If I could explain why, I would have credibility.

Neverthe less, I'm banging out a p.t.o. in my mind.
Hope to get back to you soon.
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Old 8th January 2013, 06:17 PM   #111
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Originally Posted by quarky View Post
If I could explain why, I would have credibility.
So if you don't or can't explain why you have no credibility?

Originally Posted by quarky View Post
Neverthe less, I'm banging out a p.t.o. in my mind.
Hope to get back to you soon.
Would rather know why you think my design lacks credibility given I said I've built and tested it to some degree. Perhaps you think I'm exaggerating or lying?

Happy to get details of any alternative system however and will readily adopt it if I conclude it's better than what I've got at present.

ETA - Just realised that you may have been saying that you lack credibility (DOH!). Funny how many ways a few words can be taken.
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Old 9th January 2013, 06:58 AM   #112
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Originally Posted by ynot View Post
So if you don't or can't explain why you have no credibility?


Would rather know why you think my design lacks credibility given I said I've built and tested it to some degree. Perhaps you think I'm exaggerating or lying?

Happy to get details of any alternative system however and will readily adopt it if I conclude it's better than what I've got at present.

ETA - Just realised that you may have been saying that you lack credibility (DOH!). Funny how many ways a few words can be taken.
totally.
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Old 9th January 2013, 11:22 AM   #113
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Originally Posted by quarky View Post
totally.
Sorry about that

Made any progress with your p.t.o. ?
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Old 9th January 2013, 12:54 PM   #114
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Hereís a video of the Atlas teams control system to prevent drifting. It uses movable small winglets on the tips of the wings.
http://www.youtube.com/watch?v=pJYIS...ature=youtu.be
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Old 9th January 2013, 01:34 PM   #115
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Some amusing attempts at HPH flight . . .

A prop powering wing attempt - http://www.youtube.com/watch?v=QXRZ6u04Dno

Test bed - http://www.youtube.com/watch?v=8TGnPTZFseE

The things some people do in their bedroom - http://www.youtube.com/watch?v=0Fkk17rtrSc and http://www.youtube.com/watch?v=_ZPUsclllUs

Beats mowing the lawn I guess - http://www.youtube.com/watch?v=BAD_e-tGpoM

Did anyone really think this would actually fly? - http://www.youtube.com/watch?v=PiMWzebn-DM

Wonder if I will have to add my attempt to this ďamusingĒ list?
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Old 9th January 2013, 04:04 PM   #116
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Perhaps FanWing is the way to go. They claim "high lift at low speeds" - http://www.youtube.com/watch?v=asJqvrikQSA

Very interesting concept. More info here - http://www.fanwing.com/
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Old 9th January 2013, 05:23 PM   #117
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I remain curious about Amishman Dan's Igor approach.

I may have missed something.

Not wanting to be disrespectful, and shy by nature, I will gradually divulge my opinions on the p.t.o of my dreams.

No joke, I have lucid dreams about this stuff. Very specific stuff.
It reeks of woo, yet I have built some interesting stuff.

I'm not sure whether I should even take myself seriously.
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Old 9th January 2013, 06:12 PM   #118
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FanWing not only claims high lift at low speeds but also lift at no speed! Apparently their model will hover from a tether. In other words merely by way of the wind created by the fans flowing over the top of the wings. So multiple wings opposing each other should mean it would hover without a tether. Not sure how well it would work at human scale however.
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Old 9th January 2013, 06:21 PM   #119
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Originally Posted by quarky View Post
I remain curious about Amishman Dan's Igor approach.

I may have missed something.
I had doubts from day one that Dan would ever post any actual details of his rotors/wings. He doesn't have to of course but it seems pointless to start a thread in this section of the forum and just say he has a dream but it hasn't gone well it practice.

Probably best if he doesn’t post details because I don’t think he could take the honest feedback he would get. He would call it something different.

Originally Posted by quarky View Post
Not wanting to be disrespectful, and shy by nature, I will gradually divulge my opinions on the p.t.o of my dreams.

No joke, I have lucid dreams about this stuff. Very specific stuff.
It reeks of woo, yet I have built some interesting stuff.

I'm not sure whether I should even take myself seriously.
Hope you do post details of you p.t.o . . . but will you? (no preasure )
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Old 9th January 2013, 07:12 PM   #120
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I will.
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