The Naked Scientists

The Naked Scientists Forum

Author Topic: Will a heliglider work?  (Read 6413 times)

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Will a heliglider work?
« on: 22/09/2010 22:08:11 »
Would it be possible to build a small (unmanned) helicopter by joining two identical glider wings at their roots and including an electric prop on each wing to propel it?

The idea would be to produce a craft that was a helicopter with a blade that rotated very slowly and used very little power to stay aloft.
« Last Edit: 22/09/2010 22:17:56 by Geezer »


 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8128
  • Thanked: 53 times
    • View Profile
Will a heliglider work?
« Reply #1 on: 23/09/2010 03:54:48 »
The angular momentum of a pair of long glider-type wings with motors on each end will be huge.
The wings would also have to be stronger (and heavier) than standard floppy glider wings to keep the motors attached.

There are helecopters which have jet nozzles at the tips of the blades to make them rotate ...
 http://en.wikipedia.org/wiki/Tipjets
« Last Edit: 23/09/2010 03:57:01 by RD »
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Will a heliglider work?
« Reply #2 on: 23/09/2010 05:16:41 »
Bu**er! But can't I make them turn very slowly?

I'm thinking of something that looks a bit like one of those unmanned solar aircraft except that it's rotating about it's centre.
 

Offline Don_1

  • Neilep Level Member
  • ******
  • Posts: 6890
  • Thanked: 7 times
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Will a heliglider work?
« Reply #3 on: 23/09/2010 08:18:54 »
I just knew I'd seen something on lines of this some where, and here it is:- http://blog.modernmechanix.com/2009/01/06/build-a-glider-copter/
 

Offline peppercorn

  • Neilep Level Member
  • ******
  • Posts: 1466
    • View Profile
    • solar
Will a heliglider work?
« Reply #4 on: 23/09/2010 11:18:04 »
Have you been at the metal polish again, my Scots chum? >:( ... ;D

But seriously - So the whole body is turning slowly around its axis? And the electric props are there propel the 'blade' slowly around?  ???

I can just about see the wings being rotated if (as RD mentioned) there were pressurised air jets at the tips, but I feel it would need some 'non-rotating mass' slung under the wing centre (body of a helicopter, perhaps) to have any stability.
Another 'fan' could push it horizontally through the air - It would then be an enormous-span gyrocopter, I guess  :)
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #5 on: 23/09/2010 15:39:33 »
You can have helicopter rotor blades that revolve slowly, as long as all you want to do is go up and down.  However, you'll run into problems if you want any lateral movement i.e. go somewhere.

The problem is that as soon as you have any lateral movement it means that the blade that's rotating forwards i.e. into the direction of travel (the advancing blade), has a greater airspeed than the blade on the other side that's rotating backwards (the retreating blade), which means that you get unbalanced lift.  If the blades are rotating slowly enough then the blade that's rotating 'backwards' will effectively be stationary with respect to the air and will thus generate no lift at all.

This is the major limiting factor with regard to the speed of helicopters, for the faster they go, the slower the retreating rotor blade is travelling through the air, and the less lift it's producing.  This is actually a factor throughout the flight regime of helicopters but provided that the speed is low enough the difference in lift between the advancing and retreating blades can be compensated for by changing the Angle of Attack (AoA) of the rotor blades as they sweep around, reducing the AoA as they advance and increasing it as they retreat.

As it happens though, helicopter rotor blades are already more or less the same as glider wings, insofar as they have a very high aspect ratio.  A high aspect ratio wing is one that has a long span relative to the chord of the wing i.e. the 'breadth' or width of the wing.  The greatest difference between helicopter rotor blades and glider wings is that helicopter rotor blades have an even higher aspect ratio than glider wings but are designed for higher speeds, which is only possible because they're under tension; if you tried to use a glider wing that had the same proportions as a helicopter rotor blade you wouldn't be able to stop it from twisting because on a glider the wing wouldn't be under tension, which helps keep it straight.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Will a heliglider work?
« Reply #6 on: 23/09/2010 15:49:02 »
That's why I read this forum; thanks Lee - cool answer
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Will a heliglider work?
« Reply #7 on: 23/09/2010 20:22:53 »
Thanks Lee!

This might also help to explain why I could never get those blinking rubber band powered balsa and tissue paper planes to fly more than about two feet  ;D. I better stick to electronics.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Will a heliglider work?
« Reply #8 on: 24/09/2010 12:45:19 »
I just knew I'd seen something on lines of this some where, and here it is:- http://blog.modernmechanix.com/2009/01/06/build-a-glider-copter/

Sitting in that I would feel like a stone tethered to an idiot, or possibly someone meaning me real harm. :)
Incredible idea, and even more incredible in that it seems to work..
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #10 on: 25/09/2010 16:53:47 »
Yeah, that was interesting.  It looks like they had to initially tow the aircraft into the air but the pilot then sustained the flight.

It wasn't too surprising that the team came from the University of Toronto Institute for Aerospace Studies (UTIAS) - the institute's Professor James DeLaurier has done a lot of work on ornithopters and is credited with designing the first one to be able to take off under its own power (the original intention was to derive all of the thrust from the flapping wings but the original pilot had to be replaced by someone who was a bit heavier, very late in the project, which meant that a bit more thrust was needed, which in the end was supplied by a small aeromodelling jet engine).
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Will a heliglider work?
« Reply #11 on: 25/09/2010 17:24:55 »


It didn't lift under its own power though?
Not in the movie at least, but it sure looks beautiful, almost ethereal.

It won't need much thrust to get airborne I guess?
Would it be able to lift 'straight up' too?
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #12 on: 26/09/2010 13:06:00 »
Would it be able to lift 'straight up' too?

No; you need airflow over the wing to generate lift.  Well, that's not strictly true; the pilot was able to sustain flight at an average speed of just under 26 km/h so if it was facing into a similar headwind it would generate the same amount of lift - this is how kites work.  However, it would either have to be anchored against the wind, like a kite, for once the wind lifted it into the air it would then be blown backwards, reducing the effective airspeed and reducing the lift again, or the pilot would have to supply the power to keep it in place against the wind.

In practice it would much more tricky though; a ~26 km/h wind blowing over the ground will be quite turbulent whereas there will be little turbulence in flying forwards at ~26 km/h through stationary air, and you wouldn't want to fly that sort of aircraft in any degree of turbulence.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Will a heliglider work?
« Reply #13 on: 28/09/2010 06:39:25 »
.


Maybe I could use two rotors like this?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Will a heliglider work?
« Reply #14 on: 28/09/2010 12:38:05 »
Thanks LeeE.

I know this isn't the place, but looking at your vehicle Geezer I come to think of that guy that was building a 'flying saucer' in his garage (England?) planning it to be able to lift on the 'magnetic field lines'? or similar. Whatever came of it?
 

Offline peppercorn

  • Neilep Level Member
  • ******
  • Posts: 1466
    • View Profile
    • solar
Will a heliglider work?
« Reply #15 on: 28/09/2010 12:43:43 »
I know this isn't the place, but looking at your vehicle Geezer I come to think of that guy that was building a 'flying saucer' in his garage (England?) planning it to be able to lift on the 'magnetic field lines'? or similar. Whatever came of it?

Better to ask about that on the 'That CAN'T be true !' board, me thinks!
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #16 on: 28/09/2010 19:21:12 »
Geezer: yes, that would provide uniform lift, as the advancing and retreating blades would be mirrored.  At higher speeds though, you'd only be using half of each rotor, which is a bit inefficient.

Some effort (and money) was spent (unsuccessfully) on trying to get stop-rotor helicopters to work.  These aircraft were to use the rotor conventionally for takeoff and landing but then, once enough forward speed had been achieved, the rotor was to be stopped and used like a conventional wing.

have a read of: http://en.wikipedia.org/wiki/Boeing_X-50_Dragonfly and http://en.wikipedia.org/wiki/Sikorsky_S-72
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #17 on: 29/09/2010 23:06:59 »
I wasn't aware of the one in this article:

http://www.theregister.co.uk/2010/09/29/eurocopter_x3/
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Will a heliglider work?
« Reply #18 on: 29/09/2010 23:16:04 »
Thanks Lee. That's the one that led me to the Sikorsky pic! The Sikorsky claims to be a bit faster too and, to my mind anyway, a heck of a lot better looking  :D

I'm thinking the contra-rotating rotors will permit higher speeds, albeit at the expense of some nasty transmission problems.
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Will a heliglider work?
« Reply #19 on: 29/09/2010 23:18:17 »
Yup, as the article points out, the main attraction of the Eurocopter X3 is that it's simpler = cheaper to operate and maintain.
 

The Naked Scientists Forum

Will a heliglider work?
« Reply #19 on: 29/09/2010 23:18:17 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums