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I wasn't quite correct here. Camber IS necessary for ADEQUATE lift. A flat board will give you zero lift at zero angle of attack, and some deflection lift if you give it a little AoA, but it won't take much AoA without stalling.curvature (camber) IS necessary for lift
Yes, that is a stall.So if I make the wing from a flat board and increase the angle of attack, the air above the board will stop flowing "nicely". That's the problem?
That is what they do in wind tunnels. There are numerous videos on the internet showing this and allowing you to see how the air behaves at various angles of attack and speeds. Way better than a verbal description.It makes sense, although I would like to install a colored smoke generator above and below such a wing and see what happens to the smoke.
A lot of the paper airplane examples use flat wings .
Well, because the A-4 was a carrier airplane, Heinemann knew very well that the wing would have an slatted moveable leading edge and flaps on the trailing edge.
If you build a paper model that flies right first, and then transfer the pattern to the thin sheet metal or thin wood, you will be more than half way to getting the balance of forces right. Hope this helps.
" The leading edge slats might be used during hard maneuvering, such as in air combat. The flaps, probably not.
Don't confuse weight and density. Metals are generally "heavier" than paper because they are dense and the applications we have for metals and papers mean we can pick up most things made of paper but many things made of metal need a crane to lift them. Aluminium cooking foil is very "light" which you may think is because aluminium is light, it isn't, it is because you can roll aluminium foil very thin. Gold is much more dense than paper or aluminium but can be rolled so thin one ounce (25.4g)of gold can cover 300square feet (28 square meters).I get the impression that a model made of heavier materials needs a bigger lift.
Yes, they were used in various phases of flight. In climb, descent and level flight, all these "high lift devices" would be retracted. In any high angle of attack situation, such as a high G combat turn or an approach to landing, the automatic leading edge slats would deploy whenever the AoA exceeded approx 3/4 of the the critical (stall) AoA. The flaps would be extended during the approach to landing and partially extended for a heavyweight takeoff.But these elements were probably not used during the flight?
The leading edge slats on the A4 were free floating and would be held retracted by aerodynamic forces at normal operating angles of attack In flight. When the AoA approached the the critical angle, the stagnation point would drop below the leading edge of the slat, and the "reverse flow" of air over the curvature of the leading edge would cancel the pressure of relative wind holding them shut, and they would start to "fall" forward on their curved rails which ran on ball bearing rollers, opening a "slot" that allowed the airflow to follow a more moderately curved path to the top surface of the wing.The leading edge slats might be used during hard maneuvering, such as in air combat. The flaps, probably not.
From the AoA and the camber of the airfoil. The A4 had a rather small wing for the weights it was capable of operating at, and flew in a pretty pronounced nose-high attitude at just about anything less than never-exceed speed. An A4 carrying a maximum ordnance load looks like a caricature of a tiny toy airplane strapped to a huge cluster of bombs. Lightly loaded, it had the thrust to weight ratio to be a startling performer for its time, much to the chagrin of the occasional unwary Vietnamese MiG pilot.So, during the flight, where did the lift come from?
Lightly loaded, it had the thrust to weight ratio to be a startling performer for its time, much to the chagrin of the occasional unwary Vietnamese MiG pilot.
What people often do not realize is that a flat or symmetrical wing still uses Bernouli because when it is at a suitable angle of attack a wing still creates a situation where the air has to go faster over the top than it does the bottom .
After the Blues switched to the A4 (due to a series of fatal accidents, more than the fuel issue), the Thunderbirds came to Key West (on Navy Day, no less) to rub the Navy's nose in what their spanking new F4Es could do. This was only two weeks after we had been treated to The Blues first rather tentative public show in their A4s, which I must admit was not very impressive.And the A-4 was even used by the Blue Angels, for a while, due to the oil crunch in the 70's, which made it embarrassing for the military aerobatic teams to be flying the F-4. The USAF switched to the T-38 in that same timeframe.
Your cardboard is too stiff and heavy and your relative wind (your breath) isn't strong enough. Try a facial tissue or a piece of toilet paper and see what happens.BTW I don't understand something about "Bernoulli". Air should go faster over the wing than under the wing, right? So if I take a flat piece of cardboard (zero AoA), take air in my lungs, and blow over that cardboard, should it go up? But - nothing like that happens.
Try this. Use your light, stiff material for the bottom surface of your wing and cut ribs of some very light, stiff material to your desired airfoil shape and glue them to the top surface of your wing bottom. Now glue some kind of light, strong, flexible material such as tissue tracing paper over the curved top surface of your ribs. You have now created a wing. If you can get some thin sheets of balsa wood, it would be ideal for making ribs and making your flat bottom, or even an undercambered one, which will perform better in a glider. Be sure your glider balances at about 1/3 of the chord dimension of your wing. Good luck.It is quite light and very stiff but I have a feeling I can't make a convex airfoil out of it. If I try to bend it more, this material will probably break in two.
Unless you're a certified dwarf, your helmet-to-canopy clearance in the A4 is pretty minimal. It gets pretty narrow above shoulder height, and "headbanging" is a pretty common occurrence. Ever notice the canopy similarities between the Douglas X3, the Douglas F4D, and the Douglas A4? Ed Heineman loved that A-frame style greenhouse.I recall IDF pilots saying that the Mirage was always so smooth but in the A-4 when the slats came out, it would be "Bang!" and the pilot's helmet would hit the canopy.
Use your light, stiff material for the bottom surface of your wing and cut ribs of some very light, stiff material to your desired airfoil shape and glue them to the top surface of your wing bottom. Now glue some kind of light, strong, flexible material such as tissue tracing paper over the curved top surface of your ribs. You have now created a wing. If you can get some thin sheets of balsa wood, it would be ideal for making ribs and making your flat bottom, or even an undercambered one, which will perform better in a glider. Be sure your glider balances at about 1/3 of the chord dimension of your wing. Good luck.
BTW I don't understand something about "Bernoulli". Air should go faster over the wing than under the wing, right? So if I take a flat piece of cardboard (zero AoA), take air in my lungs, and blow over that cardboard, should it go up? But - nothing like that happens.
Okay, to do experiments like that you are going to have to build yourself a wind tunnel .
Well, because the A-4 was a carrier airplane, Heinemann knew very well that the wing would have an slatted moveable leading edge and flaps on the trailing edge. When deployed hose features largely overcome any built-in curve on the wing surface.
The F-86A had leading edge slats but on the F-86F they got rid of that in order to extend the wing leading edge in a fixed position and improve high speed turning. But they used long runways.
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The shape of the wing - its cross sectional profile - on my Ercoupe, combined with its angle of incidence as set on the fuselage, means that it goes from no lift to considerable lift with a small amount of change in angle of attack. When properly rigged - and many out there are not - you can go down the runway at full power and the airplane will sit there moving fast, with its wheels on the runway. Pull back on the wheel just a little and .. Zoom! Up you go. On landing it is the same way; you can fly the airplane "in close formation" with the runway, get the wheels on the surface, and chop the power, without fear of it ballooning up. Of course, Th proper way to land it is just like any tricycle gear airplane, MLG on first, and then have the nose come down, applying some brake when the MLG hits if there is some crosswind.