Fun With Numbers...

[marbleturtle]

Since I can't start building just yet, I've been experimenting with some computer modeling.

 

Does anyone have numbers on the required lbs of thrust to maintain cruise speed of 180mph at 10,000 ft and MSL?

 

What equation are you using to get your numbers? I've seen variations for accounting for resistance using flat plate drag coefficients... but I'm more familiar with aerodynamic drag coefficients by frontal area.

 

Any ideas?

[John Slade]

Much better, MT. Keep this up and people will start thinking you're almost normal

 

I don't know the answer to you're question, but thanks for asking it. I'll be interested in the answer myself.

[Aaron]

The parasitic drag is:

 

[Parasitic Drag]=[Coeff of P.D.]*[surface area]*1/2*[air Density]*[Velocity]^2

 

The problem is that Coefficient of parasitic drag, right?

 

Well, we know that the flat plate equiv for a Cozy is around 2 square feet, and that

 

Flat Plate Area= [Coeff. of P.D.]* [surface area]

 

Did I miss anything? I'm not used to these aerodynamic formulae, but I think that's it.

 

Still thinking about "alternate propulsion", MT?

 

http://142.26.194.131/aerodynamics1/Drag/Page1.html

[No4]

That's easy Marble, if the aircraft is in equilibrium the thrust must equal the drag.

Really easy to find the drag just use this equation

D=1/2pV2SCd+1/1/2pV2(W/b)2 1/pi e.

Are you still planning on the twin ducted fan's? or have you worked out yet that propellors are far more efficient than a jet of air until they approach high Mach numbers.

Kinetic Energy = 1/2mV2

(1/2)* 1kg air accelerated 10m/s(2) = 50 watts

(1/2)* 10kg air accelerated 1m/s(2) = 5 watts

Both have the same thrust of 10 kg.

[Aaron]

is this the induced drag:

 

1/1/2pV2(W/b)2

 

What's the definition of W and b?

[No4]

Sorry Aaron, I got myself in way too deep there. That's the induced drag calculation, so at a guess W is weight, and maybe b is a lift coefficient.

I got that from here: http://www.me.ttu.edu/faculty/oler/me4356/website/Notes/total%20drag.pdf

and you might want to also look at this : http://www.desktopaero.com/appliedaero/appliedaero.html

I'm just studying a Gas Turbine course at the moment, very interesting after our discussions on turbochargers.

Made your mind up on the cozy yet? I'm going to get started in about 3 weeks. Hopefuly my group of slaves aka Dust style will include a 747 Flight Engineer, an aircraft mechanic, and at least 5 other student CPL pilots.

 

DUST ; Cheers for the nod on the 337 pusher prop, I found a bored almost identical to this one for the Skymaster, but it's very quite, maybe we should send Marble over?

[dust]

No, i have to pop in on this one (like I rarely say anything), the slaves can and should be totally unexperienced and untrained, unless you plan on making modifications, then you might want to call nasa. he he he

 

My experience is 100 percent good with good for nothing, no nothing slaves (sorry slaves, meant as a compliment) slaves

 

John's experience, on the other hand, with a "fully trained experienced builder" caused him to have to remake the canards he was helped with.

[George Sychrovsky]

It apears the drag area is about 2.2 sq ft

 

I beleiave the thrust would be around 150-160 lb @8000 and about 200 lb @ sea level

 

Legal disclaimer

This is only one mans opinion and my contradict with experience and advice of others.

[marbleturtle]

Thanks John... but you might want to rethink the "Normal" after you hear what I'm thinking about now.

 

I found out that Moller has been smacked by the SEC for certain securities marketing practices and for making the prediction about thousands of Mollers flying around by 2003... whoops.

 

Someone must take up the torch of the Flying Car promised to us all in those Science films of the 60's. (I've never actually seen one but I hear they're neat!)

 

The way I see it... there's two parts to consider for a VTOL aircraft. The normal flying part. The transition to flying speed and back to zero again part. Now why worry about designing both when the normal flying part is already available! (That's where the Cozy would come in.) All that actually needs to be designed is the transitional part.

 

Limiting factors include finding engines strong enough to produce high thrust, but light enough to lift themselves and airframe. That's where John's turbo rotary comes in. (Sorry Dust, no Yugo engines.)

 

Another limiting factor is a control system to balance the system out of ground effect. I'm testing a few ideas with a Computer Program I'm writing to crunch the numbers.

 

This idea came to me while watching the new design VTOL jet (I can't remember if it was the Lockheed or Boeing version) that uses a thrust direction nozzle for the rear of the aircraft, and a shaft driven fan with doors that open up on the front of the aircraft in transitional flight. There are smaller nozzles on the wing tips... but the general idea is to balance the aircraft on a four legged stool of thrust.

 

I'm wondering if a variation could be made for the Cozy... a three legged stool. Two fans in the back, one on each side of the fuselage. Deflectors to route thrust down. One fan in the nose placed horizontaly with retractable doors, shaft driven to keep engine weight out of the nose... hmmm. (Can anyone tell that I'm getting tired of my 82 mile one way commute through traffic? There is a perfect place to land on the top level of a parking deck that no-one uses.)

 

Anyhoo... back to the normal. I'm putting numbers together on a twin ducted fan system. One turbo rotary or two motorcycle engine driven. I'm kicking the motorcycle engine idea around because it introduces redundancy (two of everything to break!), light weight since non-hog sport touring bike engines are designed for high power to weight, and with one fuel tank per engine maybe even a little simplicity. Reliability is a big fat question mark... but at a few thousand a piece, I could chuck one, get another, and still be ahead of the game by... oh... $20,000.

 

To answer my own original question, I think I was coming up with roughly 300lbs of thrust to maintain 180 at MSL. (My notes are at home.) Also I was getting thrust numbers of 2200 lbs with twin 140 HP engines... which could turn a Cozy balistic. Which brings me back to hovering, or the flying car idea. Maybe I should check my numbers first.

 

Well, its been a difficult day at work surfing the internet, but now that its 3 o'clock, its time to go home. @#$@%@!!! Moller... if he had his flying car ready, I'd be home in 15 minutes.

[No4]

200hp max @75%power=150hp*0.8(prop efficiency) = 120 Thrust HP

THP=Thrust * TAS(ft/sec)/550

180 mph= 264 ft/sec

120=(x * 264)/550

120=0.48x

Thrust x = 250 lb's

 

You can obtain 2000 lbs of thrust from 280hp, but it would require a rotor diameter of 35 feet, so I don't know about going ballistic.

I heard the line outside the USMC Osprey test pilot office is looking quite short, maybe you're the man for the job?

[marbleturtle]

Osprey eh... I wonder what I could buy one of those suckers for military surplus.

[John Slade]

Not normal, no, and a total dead end - but at least you're thinking.

 

IF (and it's a really big IF) you could get the sucker in the air you'd be up against the same problem as the early Harrier pilots - once she starts to tip you have to be VERY quick to bang out, or you'll be going sideways. A heard of one that went through BOTH sides of a full size military hangar still strapped to the seat. On the other hand, I guess you wont have that problem unless you can get a good deal on a used Martin-Baker.

 

As far a drive shaft running down the center of the plane - I guess that would be fine ....until you got to the nose wheel.

[JakeC]

unless you can get a good deal on a used Martin-Baker

Now those you can get surplus. I know because I saved one from being sold surplus. I found one out at the FT. Stewart surplus yard and brought it home to my unit to serve as a training aid. It sounded like a good idea but the most use it actually got was by me pretending to fly F-4's around the training room when nobody was around .

 

To me it sounds like you might be better off starting from scratch on a design MT. The reason I say that is because you would most likely spend more time trying to modify the cozy design than you would beginning from a clean slate. To take an aircraft that is very tightly designed to do one thing very well and make it do two things very well would be a monumental task.

 

Jake

[John Slade]

Now those you can get surplus.

 

Yea, but they don't give you the charges. What use is a bang seat without the bang?

[No4]

Marble : Don't listen to John bro, Go for it! Although I think what you really need is a big tank of liquid oxygen and a couple of drums of jet fuel, I'm sure a smart chap like you will work out the nozzles and the turbopump etc. I think you can pick up an Osprey for it's weight in scrap.

 

John : Don't put Marble off. When they remake "Those Magnificent Men in their Flying Machines", they're going to need some new footage for the start when the mad contraptions sh#t themselves on take off.

I heard the Harrier has the dubious record of killing more of it's own pilots than enemy crews. I saw one at Middle Wallop when I was a wee nipper, hovering about, fantastic noise, but the thought of landing one at night, on a slippery deck pitching and rolling, no thanks.

 

JakeC : Maybe you could help Marble set up some sort of launch ramp with a bit of C4 at the back to help him on his way?

 

Dust : I understand about the slaves, ignorance is bliss. The trouble is that the unskilled labour will just sit around drinking beer talking rubbish all day, whilst I might get some sweat from the aero club crew.

[JakeC]

If I learned one thing from my time in the service it's that any problem no matter how complex can be solved with the correct amount and the correct application of high explosives.

 

MT - I say go for it. One way you could go is build a 1/4 scale model and see what you can make happen. It won't tell you if it would be possible at full size but it could give you some idea about the behavior of such a craft in hover and transition.

 

John - Just take the nozzles off and fill the empty rocket tubes full of match heads then put the nozzles back on. That should work. If it doesn't let me know.

 

Jake

[marbleturtle]

I have another problem to work out... I wonder how Dobbins AFB and Lockheed would feel about me taking off and landing between all those C130's since I am only a couple of miles from the end of their runway... maybe I'll stick real close to I-75 and pretend I'm a traffic helicopter.

[Aaron]

I saw one powered by a motorcycle engine, 60mph capable, for under 10 grand (as a kit)

 

Since it's an ultralight copter, you wouln't need a license, nor would you need to file a flight plan.

[marbleturtle]

... but ultralights are not allowed in populated areas. Back to the drawing board. I could have swore I was getting 2200 lbs of thrust...

[JakeC]

Aaron might be on to something for you MT. An experimental class gyro with a hefty pre-rotator for VTOL capability. Go with a 13B Turbo and start enjoying your commute for a change. Sort of a homegrown Carter Copter. Gyros have a long history so most of the groundwork has already been laid.

 

Jake

[LargePrime]

http://www.cartercopters.com/

 

of course you have to remember to put the gear down

 

these guys have the best idea i have seen in 30 years in aviation.

 

And its glass...

 

If you want pure gyros then it's this.

 

http://www.rotorcraft.com/dominator/

 

alas not glass

[marbleturtle]

Carter Copters are spiffy... but the time frame looks like 6 years plus, and its only a two seater. The dominator? 50mph cruise is nothing I can get excited about.

[Marc Zeitlin]

Originally posted by marbleturtle

Carter Copters are spiffy... but the time frame looks like 6 years plus, and its only a two seater.

The Cartercopter seats five.