a088008

I going to be attempting to design and build a 100% Sized Eagle. Nope, not a plane, but a bird. Yip, one of those things that circles your back yard hoping today will be the day you take your pet mouse for a walk.

I'd like to know if there is anybody who has information on the airfoil of an Eagle and a source for 3-views. :I know the 3-views is a long shot, but I had to ask.

-Q.

a088008

I going to be attempting to design and build a 100% Sized Eagle. Nope, not a plane, but a bird. Yip, one of those things that circles your back yard hoping today will be the day you take your pet mouse for a walk.

I'd like to know if there is anybody who has information on the airfoil of an Eagle and a source for 3-views. :I know the 3-views is a long shot, but I had to ask.

Maybe you know of someone (or website) who has attempted something like this. Please let me know.

-Q.

BMatthews

Don't know about eagles but there's been a few bird gliders done over the years. Most of them use either V tails or some sort of clear plastic vertical to make up for the lack of onboard brains....

I wonder if split rudderons ala the B2 and other Northrop flying wings could be used in place of a vertical fin? You'd need a helicopter gyro coupled into the rudder channel for this one.

And be sure the beak is rubber so it doesn't hook up on landing...

Johng

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There was an article about this exact subject published in MAN within the last six months. At least I think it was MAN. I'm pretty sure anyway. I think the guy has built a variety of species.

Birds had roll control through wingtip "feathers" and pitch control with the tail. Funny thing is, you can build them with lighter wing-loading than the real thing.

tonyc

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I read an article about a year or so ago in Model Airplane News. They were using radio control powered model Hawks to control bird population in a major airport. I can't remember the details. It was one of those "thats interesting" articles that you read but have no use for.

So what you are doing has been done. I am sure someone will have the detail's you need.

tonyc

a088008

I'm planning on putting an electric motor in the "beak" with a folding prop. This will allow me to keep up with the local population of hawks and I won't need to bugee or winch to get the thing to soaring altitude.

I'd love to see the reaction the hawks are going to have to this model. They already view my current park flier with suspicion. They swoop in and take a look (fly along side for a circuit), and then carry on about their business.

-Q.

banktoturn

a088008,

I think that if you do a Google search, you will find some papers that have some of what you are looking for. I stumbled across some related things a couple months ago. You might need to do some trial and error with your keywords. If I get a chance to do some searches, I'll let you know what I find.

banktoturn

smchale

My Feedback: (67)

http://www.modelflying.co.uk/pages/index.cgi

Click on model shop and go to the plans section. They show a plan in the slope soaring unorthadox section. 88" wingspan.

Tall Paul

It will not be easy or simple.
First you have to know -how- birds fly.
The expert on the subject lives in this area.. he's published a few articles in RCM over the past years..
Here's one of his latest from a year back...

BMatthews

You may want to put the motor in the tail with an extension shaft to drive a prop at the rear of the elevator. Rear mounted props have a little bit of fin effect that would help add to the yaw stability if you plan on not using any fin. Putting the prop on the nose would obviously be counter to this and require MORE fin or yaw stability from the gyro.

banktoturn

Prop?! I thought this would be an ornithopter!

Just kidding, but that would be really cool. I have had a few simple rubber band powered ornithopters, and it doesn't appear to be too hard to make it work, in terms of finding a wing geometry that generates decent thrust. Building the mechanism would not be a no-brainer, however.

banktoturn

Strat2003

My Feedback: (1)

One of the previous posts was right, MAN did have a very comprehensive article and plan for one a few months back. One of the guys in our club built one and, after some twiddling, it flies very nicely. It's controlled with pivoting tip feathers and an elevator and has no vertical tail at all! I wouldn't have believed it was possible, but as one of the early test pilots, I can vouch for it!
He takes it to altitude underneath a .60 size 'goat' he uses to lift parachute jumpers, 3X scale r/c paper airpanes, pop cans and other dropable stuff. Don't know if a powered version would work without some sort of vertical tail.

Ben Lanterman

Paul only a mother or your friend could love that profile. That they fly well is beyond dispute but they are ugly birds. Even a buzzard is pretty by comparison (well on second thought, maybe not). But close.

Remember a few years ago when Paul MacCready built a flying model of a pterosaur configuration. He used electric motors and seemed to solve the problems inheret with the configuration. There was also the use of some elastic bands to help smooth the flapping and aid in some energy recovery in each cycle. I believe he used the toothy part (did they have beaks?) and the head for directional control. I am not too sure the model could agressively climb from the ground. It was bungy/dolly launched and it did make enough flights of extended length to show the configuration that they had was workable.

Tall Paul

The principle problem with the flight-feather actuation is breakage when landing, the designer mentioned to me.
Very fragile.
Not something good for a sloper, for one thing.
Gulls with their more "solid" wings are also flying as models (gliding, not flapping).

Strat2003

My Feedback: (1)

Regarding the fragility of the tip feathers......we've had some trouble with them shedding if the lift plane is flown too fast. The plans call for a carbon fiber torque rod, but Chuck used either a dowel or piano wire, and that lets them flutter......

BMatthews

The "100% Eagle" thread from "Scratch Building" forum has been merged into this thread for your continued reading enjoyment.

ThankyouverymuchyourewelcomeImsure,
The Management

Isn't there a phrase about those "that soar with eagles"? All I know is that this is a totally BIRD BRAINED idea

a088008

Thanks for all the info so far.
I see that this topic has many enthusiasts.

I see that most models try to exactly match the wing tips of the bird. I don't intend doing this as they are so fragile.

I was thinking of creating a tail with elevator and ailevator combination. I don't want true ailevators as the radio I will be using does not have mixing capability. I'm not sure how effective it's going to be. I need to put on my thinking cap and crunch a few numbers. I need to find some formulas for calculating force from moment, area and deflection. This is going to mean even more aerodynamic reasearch on my part.

I plan on keeping things similar to the "real" version, so I'm not going to be adding a fin. It would just look ugly if I did that. Besides, how does the real thing create yaw stability!?

I've included a picture of the tail with control surfaces.

-Q.

Strat2003

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The way I understand it, the complicatd, fragile tip feathers are what gives the one we're flying its yaw stability. They're set at different angles, and the whole assembly took some fiddling to get set right. I think you'll need a vertical tail of some sort if you don't use them.

a088008

Are the wingtip feathers creating drag (a kind of brake on each wingtip), or are they acting like tip-plates?

I must confess that I thought that the tip feathers were only used for roll control.

-Q.

a088008

Does anybody know why a lot of birds seem to have a swept forward inner wing section with a swept back wing tip? Why is this configuration not seem in aircraft?

I have some theories on this, but none of them seem to make any sense when I try to write them up here. So, I'm going to take my foot out of my mouth and leave it at that.

-Q.

Tall Paul

It's really a requirement ot go out and observe birds!
Out here in the desert the ravens in particular enjoy flying. They will "slope soar" off anything that creates lift, and while they're beating back and forth in the lift anywhere from 2 feet off the ground using a drainage ditch to 100 feet up along the face of a building, the primary -steering- control is the tail! It twitches up and down independently on each side to maintain the heading the bird wants.
The wingtip feathers are not used for steering.
Pitch control is more difficult to detect..
Go out and observe!

Strat2003

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Wilbur Wright said "Trying to learn to fly by observing a bird is like trying to learn the secret of a magic trick by watching a magician."
They just do it too subtly and well for us to pick up the 'trick'!

I've noticed the tilting of the tail, too. On the model we're flying, however, all the roll control is by the tip feathers. The angles involved seem to create more drag on the downgoing wing, rather than the adverse yaw you get from ailerons.

Regarding the forward sweep on the inner part of some bird wings.....maybe it doesn't serve any purpose, aerodynamically, maybe it's just a result of how the wing is 'constructed' out of the assortment of arm, wrist, and finger bones nature had to work with? Stephen Jay Gould, the evolutionary biologist, said that some traits (like nipples on men) have no functional significance, they're just artifacts of the way things develop...

Ben Lanterman

There are some interesting pictures at this site

http://www.ornithopter.org/flapfligh.../birdsfly.html

There are a host of sites that discuss bird flight including some that put trained birds into wind tunnels to study their flight.

On the forward sweep thing. It is a compromise. The wings need to fold completely into the body to protect the flight feathers when hopping about the ground and to retain some body heat. There is the necessity of folding the wing on the upstroke to reduce the drag during that portion of flight. With those requirements and given the limitations of an organic bone joint/ligament system a compromise of that angle verses aero effectiveness of the wing produces what we see. Each reduction of angle between the bones allowing the wing to be straighter makes the complete folding of the wing that much harder. Forward sweep angle effecting stall is not a factor with the dynamic flight system that the birds possess.

The tip feathers depends on the type of flight. Two extremes are the albatross and the buzzard. Dynamic soaring flight based on the wave motion of the ocean (which is fairly constant) which is what the albatross uses seems to be most effective with a very aerodynamically clean high aspect ratio flight. The buzzard doing thermalling flight in which the magnitude of the thermals may vary from a little to a lot uses the separate wing tip feather system. Each feather acts as a slot for the feather following it. With some control over the slot action the lift characteristics of the wing can be adjusted.

In both cases the twist of the tail seems to be a primary directional control surface.

a088008

Thanks for the really helpful info, guys.

I have been studying the flght of birds for a while now. I love to watch a hawk negotiate a ridge. It's fascinating to see just how adept they are at seeking out lift.

I have noticed the movement of the tail for directional control. I seem to observe a change in the wing incidence for slight changes is pitch. This would seem to be similar to a hang-glider.

-Q.

Ben Lanterman

As a kid I had dreams about flying where I could run and jump and feel the lift in my arm pits holding me up. Later on I discovered this is the way some of the early hang gliders were working. About the time I discovered hang gliders I realized I had severe issues with height. So much for flying with the birds that way.

The height problem is not there in any form when in an airplane of any kind that has a full fuselage around the bottom. Maybe it is my butt that has the height problem! Strange.