Mirage 2000 from Ojimak

[terrinecold]

Hello,
I built this mirage 2000 from Ojimak, a very simple model, took me just a few hours (evening + morning) the only difficult part was gluing the canopy to the fuselage as I had chosen 80g paper and the fuselage wasn't very rigid.
The attractiveness of this model is that like the other ones from the same designer it can fly (glide). I will try to capture it while it flies before a crash finishes it but it is quite fun.

 

[Zathros]

All Delta wing aircraft will require that you have the elevators slight lifted to keep the nose up. It is worth it on these craft to separate the elevators from the flaps, as the will greatly increase your control of the craft. The same can be said with the rudder. With the C.G. set right, it should fly like a Dart! On the trailing Edge of the wing, the inboard rectangles are the flaps, and the outer, the ailerons, you probably knew that already.

 

[terrinecold]

Didn't know about those settings. As built (no special setting) if I launch it very slowly it glides very nicely. But if I throw it with any force it goes up quickly, stalls and dives. I'll try the settings you advised this evening.

 

[terrinecold]

for setting up the plane you talk first of elevators then ailerons I am assuming they are the same?
Also you say the same can be said about the rudder, what do you mean?

 

[Zathros]

The plane nosing up means that the center of gravity is too far rearward. If you get good distance, then a slight pushing down on the flaps will push the dose down and give you a straight flight. It it still noses up when it slows down, it needs more weight. On the attached photo, the blue parts are called elevons. If the same aircraft had each blue part split at the line, the parts furthest out from the fuselage would be the ailerons, and the inboard units would be flaps, dropped down simultaneously to provide more lift at slower speed. Delta wing aircraft, in the early days, tended to "nose up". This was why canards were added. Many of these craft used elevons which would act separately as ailerons, but could also more together to act as flaps, hence, elevon. If you split them, it would give you more fine tuning and better control over the flights, making it possible to throw the plane into long sweeping turns, or loops, etc. The vertical control surface, the rudder, controls yaw of the craft. This surface, in a glider is best left perfectly in line with the center line of the glider. If the craft rolls left or right, use the elevons, lifting one, lowering the other, to straightening out the flight. This means that the craft is not set up right though as it will continue to move in one direction or the other with the controls surfaces adjusted. Ideally, all things being equal, it should fly a straight line, then nose down, pick up speed, gain altitude, and do this till it hits the ground.

 

[terrinecold]

Thanks this is clear. The plane is flying straight (or seems to be as I have only thrown it indoors for short distances). I did split the flaps and ailerons. Yesterday evening I had set the ailerons slightly up which didn't help since what I should have done is the opposite. Note again that when thrown slowly and horizontally with no adjustment the plane flies with a nice smooth and slow glide. The plane has some ballast in the nose but probably not enough. I'll tell you mor after my next test.

 

[terrinecold]

It worked great! So great in fact that I got cocky and decided to launch it from my balcony (third story). I'm sure you can guess the consequences.

 

[Zathros]

I through a plane/Glider off of Bear Mountain, New York, instead of gently gliding down, it went up on a thermal and landed somewhere in New Jersey! Yep, I know the feeling, bittersweet moments!

 

[bulldog drummond]

I printed this model & set it aside,now I'm going to build it!

 

[Zathros]

for setting up the plane you talk first of elevators then ailerons I am assuming they are the same?
Also you say the same can be said about the rudder, what do you mean?

This is worth clarifying. The ailerons are on the outermost point of the wing. They move opposite to each other. They cause a plane to bank from right to left and left to right. The rudder controls the planes Yaw motion. that is, left to right, right to left, no banking (thought in reality, when you Yaw a plane, the wing in front will cause the plane to lift that wing first and the plane will bank, if not cancelled out by the ailerons. A well balanced plane would have the rudder and ailerons capable of cancelling each other out).

The elevator(s) move in unison. The nose the plane up and down.

In a glider, if you have to adjust the rudder, that usually means a flaw in the build, a twisted fuselage or wings that are not exactly symmetrical, or a rudder that is not on an exact center line with the fuselage and not located correctly to the wings. If you have to adjust the rudder in a paper model, it will probably never fly decently, because of the drag, and the fact that it will constantly be changing the yaw of the craft.

The Center of gravity should always be done statically. On a Delta wing aircraft, their is a tendency for them to nose up if thrown hard and sometimes the elevators must be pointed slightly down.

This aircraft actually used what was called "elevons" a combination of elevator and ailerons. They could function as both. This was necessary for a lot of reasons, and books have been written on it, but basically, in a pure Delta wing craft, when a pilot pulls back on the stick, the trailing edge loses all lift, while the leading edge still has lift, the plane then noses up. This could, and often did, lead to bad situations where the planes would stall on take off or landing. They needed really long runways to overcome this, and subsequently needed a more robust landing gear.

Trimming a delta winged aircraft for level flight causes the wing to create a massive amount of drag. This is why this style wing has fallen into obsolescence, unless a canard is used up front. This of course excludes the "cranked" delta wing, which has a completely different set of aerodynamics.

Since a glider is usually climbing, then returning, a Delta wing glider can successfully be trimmed for this, achieving great height, then a safe landing. it is hard to make one "hang" in the air though, compared to the same amount of lift area on a conventionally shaped wing, or a wing with the planform of a conventional glider.