What Makes a Chopper Float?

Once again analogy between boat and chopper!

But this can be only proven with the calculations, even if it is true,

How can we define critical time?-----?

Two completely different principles are at work.

The helicopter uses thrust generated by rotating blades like a propeller on an aircraft. The prop creates a huge gradient of air pressure between the top and bottom of the blades. This gradient "pushes" the helicopter upward by the blades, not the hull. The same thing can be done with a high performance airplane going vertical.

A dirigible is a much closer analogy to a boat than a helicopter would be.

The analogy between a helicopter and a boat is very, very week. Helicopters are called rotary wing aircraft for good reason: the rotor consists of two (or more) wings, each independently adjustable for angle of attack. These wings create lift in the same way that airplane wings do: buoyancy does not enter into the equation at all, because the amount of air displaced by the fuselage is so small (a couple kilograms worth -- and that same mass of air exists inside the craft, for no net gain).

A closer analogy would be between a boat and a car: the car "floats" on the road by virtue of electromagnetic repulsion forces, the boat "floats" in the water by virtue of the same electromagnetic repulsion forces. But even that analogy is so contrived as to have no useful application for most purposes.

A hot air balloon and a boat both operate on buoyancy principals. However, the analogy is strongest if one considers a submarine for the boat. In both cases, the vessels are entirely submerged in their respective fluids, and there is a relatively delicate balancing act that has to occur to maintain a particular altitude. The load supported by a surface boat, on the other hand, can vary dramatically with only slight changes in altitude above the bottom of the body of water. An aluminum canoe, for instance, will sink about 25mm per 50 KG (1 inch per 110 lb) up to the point the where it is supporting about 700 kg (or whatever load it can support as the gunnels just submerge). At 701 kg, it heads for the bottom, not stopping at the point (.5mm below the surface) that might seem to correspond to the 1 KG overload.

Coincidentally, when amateur yacht designers build hydrofoil watercraft, they often use discarded helicopter blades (which must be retired after x hours of flight) as foils to support the weight of their boats' hulls at some point above the water. So another analogy is that between a helicopter and a hydrofoil boat: they both fly through their respective fluids, and they can even use exactly the same wings.

A chopper 'floats' because its propellers are able to provide a thrust equivalent to its weight - like an invisible rope on which the chopper hangs.

A boat floats because of Archimedes principle - it displaces its own weight!

Hi!,

Not an expert to make a comment, still one doubt: What about the effect of acceleration due to gravity, which is also pulling it down?

When the velocity of a chopper is zero, we call that situation "steady FLIGHT".

"In physics, buoyancy is the upward force on an object arising from the displacement of the fluid (i.e., a liquid or a gas) in which it is fully or partially immersed. This force enables the object to float or to at least to appear lighter. Buoyancy is important for many vehicles such as boats, ships, balloons, and airships."

If choppers could float, they could do that even... with the engine off.

So: Boats float. Choppers fly.

Ciao,

Giorgio

A basic problem with your imaginary chopper is that its comparison with a boat (in the non imaginary, non ethereal world) is based on the fallacious premise that the boat's floatingness depends upon its being "less dense" than water. However, a boat need not be less dense, and most are far more dense, than water. Yes, you might say, but, just like the imaginary helicopter, you intended that the gaseous air in the boat was to be considered as included in the boat's weight--so as to reduce the boat's density. However, the attempted comparison would again fail: as the weight of air, and air alone, bears against the helicopter's floor and walls, both inside, as well as outside, whereas the weight of air bears against the floor and walls inside the boat, but only part of the boat's walls, and none of its floor, outside the boat. Further, if you are to realistically imagine that the helicopter is buoyed upward by the surrounding air as a result of its propeller's turning, you must accordingly be able to imagine realistically that a submerged boat, with no air on board, could be buoyed upward in similar fashion through its liquid medium using only its propeller. But then, you might say, it is conceivable, that just as with the helicopter, a propeller could be made to "buoy" the boat upward in the water. Again, though, the comparison would fail: since the power plant that might drive the boat's propeller would need to run with no corresponding form of air present--only water--to use as its oxidant. To be consistent: if the copter must be power-assist "floated" only in a gaseous fluid medium, then the boat must correspondingly be power-assist "floated" in only a liquid fluid medium. So then, just as an angel must be incorporeal in order to soar like a raptor using only corvid wings, a chopper must be imaginary in order to "float" on air using only a chopper wing.

Two totally different physical phenomena are at work.

Boat floats = buoyancy

Helicopter fly = lift.

There is no difference between an airplane and a helicopter. They both fly for exactly the same reason and this is the generation of lift over an airfoil. Airplane being a fixed wing aircraft, and the helicopter being a rotary winged aircraft. The helicopter generate the lift by rotating it's wing, and forward thrust by tilting it.(and/or Changing the blades angle of attack) and therefor is being able to hover and move forward or sideways... Airplane needs the forward motion (laminar flow over it's wings) to create lift. So your question could very well be the comparison between a boat and an airplane, and not necessarily helicopter. What you consider as buoyancy in the case of a helicopter is Called hovering, and really has nothing to do with buoyancy this is really (Almost) the highest airspeed it's wing can get, while the fuselage is at zero airspeed.

It wouldn't make a bad idea to read a little about the subject, b4 placing the thread.

Wangito.

Just for fun...I once saw a video where a model helicopter was flown over (not touching) a digital readout scale. Of course, the scale indicated the model's weight from the downward force of the generated air flow. (By the way, some choppers float on floats... Some are small emergency inflatable units attached on the tops of the skids, while others are large fixed replacements in place of skids...)

Thanks for the thread. I hadn't ever thought to compare helicopters to boats. From the reply it would seem wise to continue that separation. Bouyancy and Lift are quite separated.

A better analogy would be "riding" a snowmobile over water. The forward momentum provides sufficient force to maintain lift, however once the speed is minimized the snowmobile sinks. Otherwise known as hydroplaning.

Regards, Delmar Schmidt
Melfi Technologies Houston
www.melfitechnologies.com

Wrong sir,

When you ride your snowmobile over water, it will do so because of what is called "surface tension" of a liquid, water in this case, and has nothing to do with lift. Lift in aerodynamic has a very precise definition. Remember being a kid throwing stones over the lake? how nicely they skidded? Where's the lift here? Sorry, no lift, pure inertia.

Wangito.

From dictionary.com: Aeronautics. the component of the aerodynamic force exerted by the air on an airfoil, having a direction perpendicular to the direction of motion and causing an aircraft to stay aloft.

Lift is the ratio of differential pressure below and above a surface. If the pressure below exceeds the pressure above, then a lifting force is exerted. I agree that airplanes apply a different type of lift by decreasing the pressure above the wing as opposed to increasing below the wing, but it's still differential pressure.

The snowmobile utilizes the pressure of the bow wake and rides up the wave. If the weight of the pile of water being diverted exceeds the weight of the snowmobile, lift is created.

OK…how about a hydrofoil that is totally submerged below the water. Surface tension will not have an effect.

You're right. Savistky developed the equations for lift in planing boats back in the 1960's. Boats that plane can accurately be described as utilizing "lift" to raise (lift) them in the water, dramatically reducing surface area. In the case of the snowmobile, surface tension would not come close to preventing it from sinking. In fact, surface tension would be no higher when the snowmobile is moving fast than if it is standing still -- under which condition it will surely sink. The force that causes a water skier to rise to the surface and stay there is also accurately called "lift".

When you say "chopper" I believe you mean helicopters with two blades on the rotor (the "Huey" as we called the UH-1 series of helicopters) as opposed to helicopters in general.

Hueys do not fly - they beat the air into submission! Hueys were the workhorse of their time - you could shoot the crap out of them and they could take it, yet they say that a strategically placed rock will knock them out of the sky every time.

A lot of other-than-federal government agencies started picking them up from the military when they sold them off - you still can't beat them for the price!

I do not believe that the small amount of volume added by including the swept volume of rotor in a given time would decrease the overall density of the copter enough to make it less dense than air.

I think you would be more accurate in saying that the rotor acts as a compressor that is compressing air below the copter to a density that is in fact greater than the density of the copter.

Good thought!

My Foreman, of some years back, a retired South African Chopper Pilot, was given the 'heave-ho' for trashing his third chopper. There is a nasty problem of a 'toroidal vortex' forming if you land at the wrong speed. The Chopper drops like a stone. There is a kind of buoyancy with the ground-effect air cushion. At altitude a chopper, especially if it landed in the cold air of the night, is unable to take off in the hot day further than this air-cushion.

I don't believe they can be ever be considered to be floating for the same reason. In the case of the boat, floating is passive (no input required). The boat can continue to float as long as the hull is intact.

However, regardless of the integrity of the shell of the chopper, it requires fuel to keep the engine running. When the fuel runs out, the chopper sinks.

As Christmas is soon upon us, keep the lads away from the Model Shops, Radio Controlled Battery Operated Copters get cheaper each year. No need for 'fuel' to run out. just recharge the battery. I always thought a copter was just two wings going round and round. I built a Groupner Bell 212 in 1974, it could lift a 15 pound payload. and held the world model helicopter altitude and speed record. Happy Days. The Instructions had a picture of a broken broom handle...with a warning...keep children clear of the rotor blades. have an insurance policy, etc.

comparing apples with oranges

I have been onboard several hueys and hughes for modification validation flight tests that included validation that autorotation could still be performed safely. To demonstrate this the clutch is disengaged from the rotor, leaving it to spin freely with nothing driving it except its inertia and the air blowing through it as the helicopter descends.

Let me tell you categorically that helicopters most certainly do not float, although a good pilot can make the transition from powered flight to autorotation feel reasonably smooth, and can even make the eventual inevitable contact with the ground pretty gentle. That contact with the ground is not avoidable without power. There's no buoyancy at work in a helicopter excepting maybe the buoyancy of whatever I had for breakfast that day as it tries to 'float' back up my esophagus and out into the environment again. The principle at work in operation of a helicopter is very much flight, not float.

8>/ David W

I fitted an in line, reserve fuel tank to the Graupner Bell 212(post #18), and a 'Cavan' Auto-gyro, so that the radio control was less unpredictable. I did not fancy doing an 'Auto-gyro Descent' but the motor had a centrifugal clutch, just in case the motor cut out. with enough altitude, the flying instructions advised that it was possible to make a soft landing by altering the blade pitch at the last moment. but I never risked it. The fuel sensor was optical, when there was fuel in the pipe, it was a lens, empty it was not.... LED + photo-transistor at 'sweet-spot'.(two warning lights came on)

Well, maybe it's time for conclusions?

1. It is not a chopper it is a helicopter.
2. It doesn't float. It flys.
3. 4. it is not buoyancy. It is lift.
4. It is not displacement of liquid. It is laminar flow.
5. And as one of us already said, these are apples, and the others are oranges.

Think it is time to wrap it up. what say you?

Wangito.

Does a Shuttle float like a boat?!?!?!?

Giorgio

I think chopper or helicopter not a big deal.

But this new theory given by R-S is quite convincing.

R-S You mean every helicopter have an imaginary ballon conneted with blades.great!

Yes exactly,

And this means every chopper/copter is running with a leaky (inefficient) balloon supported by overrated propeller, and if we use's the real (efficient) balloon the size of propeller can be reduced significantly.

Although it is fun to imagine such an arrangement, air is essentially non-compressible for sub-sonic flight. (You can calculate the differential pressure required to lift a 2000# airplane with 100 square feet of wing area, and see that the differential pressure is very low: thus the amount of positive and negative compression is similarly low.) There is no vacuum above and compressed air below. Even in supersonic flight, the compressibility effects do not relate to buoyancy in any meaningful sense.

If you are thinking of a craft in which both buoyancy and lift come into play, then you should calculate the required volume of low pressure or low density gas required. Although the Goodyear blimp looks small when seen on TV over a football game, it is in fact, huge, capable of swallowing many helicopters. Because of this huge size it is also very slow for the horsepower consumed. To give you perspective on the effects of buoyant air travel, volunteer to crew for a hot air balloonist. When you see the huge size of the balloon required to lift just a basket and a couple people, you will appreciate the volumes required. (A pleasant side effect of this exploration is that after you've crewed for a while, you will be asked to join the people in the basket.)

Actually, there are many differences between your imaginary balloon and a real one: the most dramatic being that a real balloon cannot contain a gas at lower pressure than the surrounding atmosphere: to demonstrate, just suck the air out of a party balloon, and see if it maintains its inflated shape. Further, your imaginary balloon is not just slightly leaky... it is 100 % leaky: as soon as you draw air out, more flows in instantly to replace it.

People have experimented with vacuum based flight, an idea that was conceived many centuries ago. If you have a very rigid, very light sphere that is also very light, it would be possible to evacuate it and have if float in air. As it happens, no one has accomplished this, because materials are not yet light enough and strong enough to resist implosion.

Coincidentally, the name of one of the respondents (half rho Veesqrd) by his moniker alone, gives you some answers. In aero calculations for lift and drag, the term "½ rho V^2" shows up all the time. If you google that, you'll find all sorts of info, not the least of which is that rho, the mass density of air, is only .0024 slugs/cu ft. Because of this very low density, it requires a very, very large quantity of a light gas to do any meaningful lifting. Follow enough of these aerodynamics links and you will come to understand that helicopters do not "float" in any way whatsoever. (In fact, many fixed wing pilots would argue that helicopters are nothing more than inherently unstable machines bent on self-destruction, with a propensity for taking the pilot along in that destruction.) Do the calculations, and you'll find that you cannot explain helicopter flight on principals of buoyancy.

Rakesh, a word, literally a= one Word.....'Tautology'

Oxford Dictionary:- Saying of the same thing twice over in different words, esp. as fault of style.

OK, then all birds fly because they are buoyed up by an imaginary ballooon....cool

Thanks all, for so many good comments,

Think an imaginary big balloon fixed on the top side of propeller and propeller is sucking all the air from the balloon making air inside less dense or even vacuum,

Isn't it floating now?

The only difference between imaginary and actual balloon is, later one is air tight and former is leaky.

Speaking of beating the air into submission, it appears that is what has been done with this thread! Happy Holidays

Slanch Eva, From the Heather Perfumed Hills of Scotland, on this the Patron Saint's Feast Day, Saint Andrew the Apostle Fisherman. May the 'NET' bring forth wonders to you all

Halleluyah and Amen!

Wangito.

Not related to the original question, but ever wonder why helicopters can't go very fast relative to an airplane?

It is due to dissemetry of lift between advancing blades and retreating blades. As the helicopter builds airspeed, a greater amount of air is hitting the blade moving forward than moving aft. Since both blades are mechanically moving at the same speed, the speed of the chopper is added to blade speed on the advancing side, and subtracted from the retreating side. Obviously, this creates more lift on the advancing blades. If you attempt to go too fast the retreating blade will stall and the aircraft can pitch over to that retreating side. To compensate for dissemetry of lift, the retreating blade "flaps" (at least in a Huey) which means it hits the air at a higher angle of attack by starting out higher near the front and descending as it moves to the rear of the aircraft. If you go too fast, the retreating blade angle of attack increases too much and the blade stalls.

So next time you are watching a F1 race, you will note that helicopters are getting left in the dust by the cars below. Speeds decrease even more at higher altitudes and in hot conditions, or when carrying heavy loads. Flying helicopters in Afghanistan is a particular challenge due to the high altitude of the mountains coupled with the summer heat.

[Quote: Answer by Guest2]....To compensate for dissemetry of lift, the retreating blade ...hits the air at a higher angle of attack by starting out higher near the front and descending as it moves to the rear of the aircraft.... [end quote]

Very good, you get a B+ on introductory copter flight dymanics. But here's the bonus question: how is the "flapping" of the blade accomplished? Hint: it is a mechanical assembly which has a name; what is the name?

Swash plate. And for god's sake,when will you stop calling helicopter flight "float"?

Wangito.

Flight instructor CPL/CFI/CFIH, TH-269, R-22, Bell 47, 206 . (Ticket #79.)

A big round of applause for "Wangito's first century. Fabulous Comments.

Happy Days and fond memories. Kenya Hil Country, High & Hot needed this little beauty wangito, ever flown one?

http://en.wikipedia.org/wiki/A%C3%A9rospatiale_Alouette_II

Darn blades rotate the wrong direction. Can't the French do anything like everyone else? I'm loving all this internal Islamic insurrection and A380 incompetence at the moment. Talk about an aircraft in search of a mission at the wrong time and place. Kind of like NASA, isn't it Wangito?

Things being glum over the hill at the 'Shed' i.e. the Trent for the A380, Rolls-Royce may have to diversify into "Underground Wind Turbines" Helicopter Size Turbines in a Reinforced concrete tunnel, and 'wings' lofted to direct the airflow down to the entrance of the underground tunnel. The sums look good for both power output and return on investment. A few hundred of those would put RR back on it's feet.

Why underground?

Maybe RR could get into the above-ground wind turbine business since you all have lots of wind over yonder. Or maybe you folks are more pragmatic about nuclear energy and don't need to bother.

I was glad to see Boeing opted to use both GE engines and the Trent 1000. That should give you a healthy share of the $40 billion potential for 787 Dreamliner business over the next 25 years.

To answer your earlier question, the Russians tried that with the KA-50/52 Hokum before they went broke. The Israelis considered buying a version of it, but perhaps the cost, complexity, maintenance headaches, single-pilot cockpit of the 50 or lost payload of the 52, and limited speed advantage (217 mph?) were not worth it.

Check out:- http://www.monkeyhanger.com/angel/angels.html

Antony Gormley's Angel of the North, just outside Gateshead. OK not to everyones taste, but wind can be 'directed' into a spiral and 'down' like a tornado.

Wind direction is unimportant, and a thing that works well, is usually a thing of beauty as well. We shall wait and see.

Thanks for high altitude complements Alastair, you really write beautifully! How do I know? Simple, Whenever I read something I solidly don't have a clue what's all about, I know it is of high culture and must be beautiful!

BTW: No, I didn't have the honour of Flying the Alouette, I was close to, but the French boycotted our air force at the time, So I had to fly those with the incorrect blade rotation. and yes, I did fly in hill country, we flew bulldogs et al at Wilson air force base. How did you know? amazing.

Wangito.

My brother in law just returned from Iraq where he flew C-123 Sherpas with the Pennsylvania National Guard. He is a CW4 about to make CW5 and is also qualified in just about every Army helicopter except attack ones. He also is a Standardization Instructor Pilot and Instrument Flight Examiner and works for our Federal Aviation Administration.

I was thrown off by your TH-269 mention until I realized it is our TH-55 which is what I learned on many years ago. That was always interesting to fly since you had to manually adjust throttle for increased or decreased collective pitch. With the newer helicopters, even the tail rotor need not be adjusted for increased collective. Lazy youngsters, also flying around with GPS/INS instead of map only.

I'm imagining you would not venture too far into the mountains of Chile in any of the aircraft described. But I bet it is probably kind of hard to get lost as I imagine you can probably see/find the ocean from just about anywhere if you look/fly west. My only mountain time is in the Sinai in a Huey. Is that hot enough for you.

Yap, TH-55=TH-269. Flying with permanent governor failure...But after a while, your wrist and arm goes fully synchronized. No, with 7000' of OGE you wouldn't want to venture too deep into the mountain,As a matter of fact I can see them from my house, and at that distance, about 17-20 miles they are already at 13MFT. Lots of airplanes are resting there...deinitely not for beginners.

Who did you fly for at the Sinai desert? what sort of work? guessing some sling work for Moses? (what else?) I am sure he'd love it, these stones look damn heavy to me... Just plain curiosity.

Wangito

I'm frankly surprised that even a Bell modern 206 can hover out of ground effect (OGE for others) at that starting 7K altitude...and maybe you don't.

On that assignment, I flew for the US Army in the Multinational Force and Observers, an 11-nation peacekeeping force established by the Camp David Accords in I think 1979. I was there in 89-90, leaving just prior to Desert Storm. We flew troops and supplies to observation posts scattered about, to include on a couple of pinnacles and on one island. We also flew observer civilians up north everywhere from the Suez to the Israeli border. We even crossed into Israel to pick up their officers and fly over Gaza and within 3 km of the border on the Israeli side all the way down to Elat.

Nothing heroic like our guys now, but some of the more challenging flying for a Huey at the time.

The Moses reference was interesting as the place claimed to be Mt Sinai is greatly disputed. I saw a recent show where an Israeli was trying to apply scientific principles to the Exodus. He claimed the parting of the Red Sea was caused by an Earthquake and tides in already shallow waters that returned when the Egyptians crossed. The claim was that similar quakes brought on by a huge Volcanic eruption in Greece released CO2 gases that rose from underground, duplicating a semi-recent incident at an African lake, and suffocating first born Egyptians who slept low on the ground floor while others slept in lofts and survived. He also cited the same African lake incident turned the lake red from iron deposits or some such, thus explaining the Nile turning red. Interesting show.

....How kind of you to say so. Whenever I see a bottle of wine with the word 'Chile' inscribed on the Label, I know I am in for a treat. I am sure Merlin Hay, The Rt. Hon. Earl of Erroll would love to hear of any wine tips from your native Chile, Secret Somellier is an expert panel. you can listen to Merlin's podcasts. The Butler of Scotland is expected to know his wines. Wikipedia will fill you in on the details. They call the organisation over here "The Firm"..... very nepotistic one at that.

My Great Grandfather Mr. Fraser. was the Civil Engineer who built most of the Railways through the high Andes. The track from Ticlio to Morocoocho, altitude 15,8068 feet, is the worlds highest railway. The British had a great need of Chilean Nitrates. among other things.

Check out:- http://mikes.railhistory.railfan.net/r022.html

Everybody said it would be 'impossible'. A word that is a challenge to any red blooded engineer, especially a Fraser. Grandfather teamed up with Andrew Carnegie....another tale....suffice to say the youngsters from Clan Carnegie and Clan Fraser, were introduced in style....hence me. etc. They were men of 'vision' and saw a very bright future for mankind, and dedicated their last drop of sweat and blood to achieve the impossible dream. Knowledge shared and disseminated, was in their view, the key to success. The Sky is not the limit

Gulp. Andrew Carnegie as in:

"Entrepreneur and philanthropist ANDREW CARNEGIE (1835-1919) was born in Scotland and emigrated to America as a teenager. His Carnegie Steel Company launched the steel industry in Pittsburgh, and after its sale to J.P. Morgan, he devoted his life to philanthropic causes. His charitable organizations built more than 2,500 public libraries around the world, and gave away more than $350 million during his lifetime."

Impressive pedigree! They could have used both relatives in Afghanistan where presumably due to mountains, they never built ANY railroads. Of course the British probably weren't in a very accomodating mood to help the Afghans given their history together, and the Soviets only helped them create roads to help themselves. Too bad so many use those roads now to smuggle opium to Europe.

I gather from your mention about the sky not being the limit, and an earlier comment by Wangito contrasting NASA budget meetings vs those in the Pentagon that he works for NASA in Chile. Seems like an ex-NASA autocrosser I know mentioned being stationed there once upon a time at a tracking station. He did something to irritate the boys there, something about ratting out a $50K misappropriation, and was reconciled to running a small Triumph/Jaguar shop in Tallahassee, FL to utilize his PhD skills thereafter. Bummer, but nice guy who fortunately has an equally nice lawyer wife.

No Sir ,I Never worked for NASA, nor did I write Murphy's law.

But before I answer in greater details, I have to make an informal comment about your PhD friend.:

It is a common old understanding: "In Rome, Be a Roman",

If your friend , with all his skills and high education didn't understand that some of those 50K's (percentage is negotiable) were bound to him, that is, if he would have acted like the Romans in Rome, (or in Santiago for that matter,) He'd most probably be still there and maybe even a little bit richer. However, next time you see him, PLEASE ask him if I get him those 50K's will he let me work with him on those Triumph/Jags in Tallahassee?

Wangito.

Can't say I disagree with you too much, particularly due to it being only $50k, which wasn't that much even 25 years ago when this supposedly occurred. He has been a happy camper as near as I can tell, all this time, and the bit about the lawyer wife was not to imply litigation, but rather a source of additional income. They tried to get a Mini dealership but that didn't work out. See what happens when globalization occurs and Germans are running (and restoring) a proud old English company?

As for doing as they do in Rome, I tried that semi-successfully when stationed in Germany, but not so much on one occasion in Egypt. While travelling home midway through my tour there for the birth of my son, I learned that I would need a new passport to leave Egypt since they had made us turn ours in so WE would not lose them....they lost it for me instead.

So I get a replacement from the embassy in Cairo, no problemo, but the catch is I will need an entry visa stamp on the new passport to exit the country which required visiting the Egyption visa office across the street. That place was, as you can imagine, somewhat a zoo, but I was making OK progress until getting to one official who clearly had an attitude. But when told to wait, I politely did so outside his office for an hour and a half while he appeared to do next to nothing. I finally asked if there was a problem of some sort, and he went off on a tirade about Americans losing their passports or selling them to Egyptians. About that time I remembered being told about "little gifts" being a traditional in some Arab lands, so I inquired if there was anything I could do to speed the process along, reaching for my wallet.

He told me he could have me arrested and threw the passport at me and went stoming off down the hall, and I was not sure if he was going for police or what, so I rather hastily left the building like Elvis.

Long story short the embassy flew me back to the Sinai and I crossed into Israel with a simple ID card and used the passport to exit Tel Aviv instead of Cairo...but not before raising eyebrows and getting a longer interrogation than normal from airport authorities who quiz every passenger....smart.

So is there a moral to the story? Ugly American, misunderstanding, or should I have made the offer more discreetly. Probably the latter. As a West Point grad, we were taught that all matters should be on the up and up. Yet our attempts to do so in Iraq have failed, not militarily, but due to taking too much of the high road on some occasions instead of reaching out to tribal leaders and former Sunni Army officers and officials who may have dirty hands or less than democratic ways of doing business.

Don't know. But I do know they found my original passport when I returned. Talk about Murphy's Law.

Indeed! Referring to flight as float is something I've never done...ever. Why am I being so accused?

Heh, I don't design the things....I just flew them. But it sounds like Wangito flies them a lot more.

In a two-blade Huey the rotors are semi-rigid so when one side is up, the other is down. So the left side blade is up at 300 degrees and the right side is down at 120 degrees and both swap places during the rotation with the left side descending and right side ascending. That helps the retreating left side gain lift while the ascending right side loses lift via angle of attack.

Most modern helicopters have blades that flap independently. Gotta go.

What a great post 'Guest2' This problem of asymmetric lift is not so important in a small model helicopter, I have not been reading the latest model magazines, but there are plenty of ideas for Santa i.e. http://www.hobby-lobby.com/elecheli.htm

I was in the local Model Shop and was about to ask the salesman to wrap up a model helicopter kit there and then, "quanta costa for that lovely collective pitch electric job" £379 he had told me, that included a powerful 55 amp motor with close to a full one horse output. only about the size of a large cotton reel too! "how much for a decent Radio Control & servo kit to go with this"....blah...."So that's it then, all ready to wrap up for under the Christmas Tree then....perhaps if it snows we can have her flying Christmas afternoon?"...... "Well you will need a pair of blades sir"...."and how much are those?"....."well I had better have some, and sort out an insurance package for us as well please"..........The Shopkeeper goes to the back room......"We seem to be out of stock for that model, I know I ordered them"......Mixture of disappointment and impatience, I asked if delivery could be guaranteed before the Yule, ..."NO"... but I think I detected an audible sigh of relief from my 'Plastic Card'

There are claims of model helicopter flight in excess of 100mph.

I suppose a tail wind might assist this, I have doubts that a both ways 100+ flight has been certified yet.

So here is the $64,000 question, with my poor old brain slightly in the wrong gear, what difference would a pair of 'counter-rotating' blades make to this situation, and if so would a 'collective pitch' mechanism be redundant.

Mmmmm.....I have been dismantling a few old scrap 'HARD DRIVES' and have taken note of the fantastically powerful pair of magnets in each one. Try lifting them off the magnetic shielding alloy plate and the force of attraction will snap them in half. Two projects now come to mind....A realistic 'ornithopter' perhaps a 'Hawk' of some kind? that would scare the birds away from Airport Runways. and now a new one; a direct drive motor for a Model Helicopter.....Those magnets will just fill a complete 360 degree circle.....stick them on a disk of Aluminium attached to the Rotor-Shaft and away we go, if suitable coils are wound for the 'stator'...might be able to salvage old car-boot & junk sale throw-away transformers, for the steel plate content? Mmmm?

ERATA:- "Two discs for the drive rotor. and no need to remove the magnets from the Shielding alloy, perhaps grind/lap a bit of thickness off the mag-shielding plates Glass/Nanofiber/Kevlar disks might also save weight?...A wood's metal [L.M.P. eutectic alloy] Mould to make disks that are tailor made to fit the machined Hard Disk magnets, depressions for perfect drop-in location. i.e. 'A big steel washer with trangular nicks at the right subtended angles, glued to another steel plate, with an outer bigger concentric washer much thicker to contain the poured molten L.M.P. Eutectic Alloy. "Jobs-a-Good-un" Then the Stators need only be wire coiled on a transformer steel/glassy alloy? bobbin, not much more than electromagnets stationed round the gap betwen the two 'rotor' permanent magnet drive discs. Nothing like recycling old high-tech hardware junk.

A thought, Only a few doors down Winewall Lane, Winewall, Colne, Lancashire, (my Address)is !3 Hawley Street + above + BB8 8BY) is Roger's (Finnis) weekend pad.....cool, he is the Grand Prix Guru who organises and fits the onboard cameras, mmmm..120 mph? more even? ..Maybe have a chin wag about counter-rotating model helicopters & onboard video cameras to follow a race.

That 100 mph speed record.....A double direct-drive-recycled-hard-drive-magnet-rotor-paired-twin-disk & electromagnetic stators (on second thoughts, 4 machined Aluminium disks & just screw the magnets on after altering the mag-shielding plats to suit).....mmmm...Think this calls for the services of the Wee Dram Company.....What are we going to use for 'Lubrication'?......23 year old cask strength Talisker. The Scotsman's Return From Abroad. J.L.Stevenson wrote:-

"The King o Drinks, as I conceive it, Talisker. Islay, or Glenlivet." Merry Christmas CR4 Team & Thread Contributors from Bonny Colne Lancs. & Bonnie Scotland.

last e-mail received here; "Alastair Carnegie replies to Alastair Carnegie," reminded me of the very old question, often asked: "What is the difference between a monologue and a dialogue?"

In a monologue, one person is talking to himself, while in a dialogue two persons are talking to themselves. Gotcha?

Wangito.

It will be a 'Trialogue' when the two Doctors come to certify me and take me away to the nice warm ward with padded walls.

http://www.secretsommelier.com/public/

Hi wangito, with those qualifications,(how useful).....Have a blog with my Boss. The Butler...(of Scotland,Earl of Erroll)..... Fine Fellow, Colonel also of a cadre outfit of Red Beret Stooges AKA the RMPTA. I have never jumped from a motorised kite, so as Chaplain aforesaid only entitled to a Yellow Beret. (Coward)

Pancake flat 'high torque electric motors' mmm? bicycles...lot of wasted space in that conical nest of cogs that if a Chaplain is not wearing bicycle clips will cause a lot of darning!......The 'little cog' .....small is always beautiful.....why not have an internal-big-cog-supporting-high-torque-pancake-flat-salvaged-hard-drive-magnet-electric-motor-linked-2-small-cog?

Then those mountain pass 'up-n-down' slogs could be accomplished with less pedal power. Why waste braking energy, if a battery could be recharged?

Thank Goodness we don't have to judge, That's God's job (RIP)......I was thinking about placing a few shrines to our 'Queen of Heaven' on the way up those steep climbs. Perhaps lit by 'solar & wind' any spare juice could contribute to a 'Battery Exchange' affair.....No need to charge, Queen of Heaven would attend to that.....More chin-wags needed with my Bishop. (Brain of Salford, Greater Manchester)

Not exactly. A monologue (monolog) would be a person speaking (generally to others) who do no speak back. A dialogue is two persons speaking alternately, usually to each other but not necessarily. A special form of monologue (perhaps this is the term you were grasping for?) would be a soliloquy, in which one person speaks, usually to the speaker's self, but also to others present, but not knowingly known to the speaker, the same listeners who are concealed behind a virtual veil of suspended disbelief--that is, an audience. However, a soliloquy would also require a certain degree of poetic or literary merit to be so named; hence Master Carnegie's pronouncements on the board would also not constitute a soliloquy. As to your provision of the answer to the bonus question posed to Guest #2, the answer is correct, but no bonus, even if you are guest #2. It would be misapprehension of the importance of the invention not to realize the importance of the swash plate in the development of the helicopter--for, indeed, it was, and is the sine qua non invention which made the helicopter possible after decades of experimentation with various kinds of vertical flight contraptions...the break through invention. While Guest #2's description of the effects of turning a propeller axis at right angles to the direction of flight is a tortured one, it does give an interesting (and original) perspective on the problems encountered during the development of stable helicopter flight up until the invention of the swash plate.