This ornithopter was a school project.
We were supposed to design a plane that has to fly as long as possible - without the use of motor and/or electric parts. We started off with folding paper airplanes and making the Squirrle Rubber Band Plane.
You can find the link to the blog on how I came to this design, here: http://airplanecharlottebelliard.blogspot.be/
- polystyrene U-profile
- polystyrene rod
- steel wire 0.8 mm
- balsa 10x5 mm
- balsa 5x5 mm
- balsa 5x2 mm
- balsa 3x3 mm
- tissue paper 1 sheet, ~A3
- paint (optional)
- screws, nuts & washers M2(x10)
- cyanoacrylate glue
- rubber band - since this is a rubber band-plane
- paper tape (TESA)
- ball pen
- utility knife
- needle-nose pliers
This DIY will take you ~1day to make.
This DIY is based on the Orly Ornithopter.
Step 1: The Body
Cut the 10x5 balsa-rod in pieces of:
- 1 cm 
- 2 pieces of 13cm  - I afterwards changed one length in 13+15 = 28cm
- 40cm 
Cut the 5x5 balsa-rod in pieces of:
- 13cm  -Here also, I added 15cm, so that you ned 28cm
- 2 pieces of 6cm 
Cut the steel wire in 2 pieces of 7cm
Bend the steel wire as shown, you'll need the needle-nose pliers for this.
Stick the wires through the balsa wood, at the shown positions. Be carefull when you push the wires through, the balsa may break. I recommend you to first make a whole in the balsa with a needle.
For the lower rod, after bending the wire, you should cut off the extra wire. Glue the wires in place and use some paper tape to strengthen the whole. Your result should look like this.
Glue all the parts together, as shown. Make sure to glue in steps and not the whole thing at once, so that the glue has time to dry.
Remember that I changed the lengths. You only have to add 15cm to the upper balsa rod, and 15cm to the lower balsa rod. Other than that, nothing has changed to this image.
If you want, you can paint your model now.
For this part, you'll need 3 tubes (beads) of ~1cm through which the wire fits. If you don't have any beads, you can roll a piece of paper around a wire (make sure the hole is big enough, yet not too big) and glue it together like a tube.
You'll need to glue one tube at the bottom piece of balsa of 1 cm. I recommend you to let the tube exceed the balsa-piece a little bit (on the inside of the model).
The other two tubes are supposed to be glued next to eachother on the top corner. (The other end of the vertical rod, on which you glued the first tube).
This is your end result.
Step 2: The Tail
This is an easy step. You can do this one, while you wait for your glue to dry on other parts.
You'll need a piece of tissue paper, the size is shown on the picture, and the balsa rod of 3x3mm which you'll have to cut in two pieces of 25 cm.
If you want to paint your model, I recommend you to paint these pieces in advance, before glueing them together.
Glue the balsa rods in a T-shape, and glue on top of that the tissue paper.
You can use the CA-glue to glue the tissue paper to the rods, but the paper is very fragile and rips easily. It's 'safer' to glue the tissue paper to the rods with a glue stick.
Tip: Be carefull not to glue the paper to your desk.
Step 3: The Wings
You'll need a piece of tissue paper, cut to the size shown on the picture, two pieces of balsa 3x3mm with a length of 35cm and 2 pieces of wire of 7cm. If you want to paint your model, it's easier to paint these rods in advance.
As I changed the lengths afterwards - see the previous step - The tissue paper should not be 70x15, but 70x28
Bend the wires as shown in the picture.
Stick the wires -with the 2.5cm-end - through the balsa rods, be careful because the rods break easily. Make sure that the 2cm-end exceed the basa rod, or else your wings'll have trouble flapping. Glue the wires in place and strenthen the ends with paper tape.
Tip: Wait to glue the whole together, until the next step. This'll prevent the risk of accidentally ripping the tissue paper.
Step 4: The Crank
Cut the polystyrene rod into pieces of:
- 12 cm, with a 2mm hole at 1cm from the end. I know the picture shows two holes, but this is a mistake.
- 10 cm, with a 2mm hole at 0.5cm from one end and one at 1.5cm from the other end. 
Cut a 4cm-piece from the polystyrene U-profile 
Cut a 4cm-piece from the 10x5mm-balsa rod 
Cut the 5x2mm-balsa rod into:
- 2 pieces of 10 cm, with a 2mm hole at 0.5cm from one end, and a 1mm hole at 1.5cm from the other end 
- a piece of 6cm, with a 2mm hole at 0.5cm from one end, and a 1mm hole in the middle. 
Cut a 4.5cm-piece from the wire 
You'll also need a tube (bead)  or will have to make one, as explained in a precious step, and 2 screws with nuts and washers 
Tip: First make all the holes, before painting your pieces.
Glue the polystyrene U-profile to the 5mm-side of the 4cm-balsa rod. And bend the wire as shown in the picture.
Glue the 4cm-piece from the previous step to the Body, as shown in the picture. Put the wire through the inner end of the bottom tube on the body and put the tube on the outer end.
Now you have to see if, when you place the 6cm-balsa rod on the wire, the wire will come through the rod. If so, your wire is too long and you'll need to cut a little piece of it! Thus: Your wire should not go entirely through the rod! Notice that, between the second tube and the balsa rod, there should be a 1-2mm gap so that there wouldn't be too much friction. If you've cut your wire into the right length, you can glue the wire to the rod. Make sure that you glue your rod perpendicular to the body!
Beware: Take your time to correctly glue the rod to the wire. These two pieces should turn as one piece and not seperately!
Remember to imagine +15cm to the lengths :)
Mount the following pieces in order on the screw: 12cm-polystyrene rod + 10cm polystyrene rod + 10cm-balsa rod + washer + 10cm-balsa rod + washer + nut.
The result should look like this.
Slide the 12cm-polystyrene rod through the u-profile and mount the 10cm-polystyrene rod on the 6cm-balsa rod.
Notice that the bottom sequence consists of FIRST the balsa rod followed by the polystyrene rod. If you'd invert this, the crank won't turn.
Step 5: Finshing Touches
Use a glue stick to glue the top balsa from the body on the center of the wing-tissue, as shown in the picture.
Use a glue stick to glue the wing-balsa rod on the wing-tissue, as you slide the 2cm-wire end in the corresponding tube. Do the same for the other half.
Your result should look somewhat like this.
Your result should look somewhat like this.
Put the end wire (at the end of the 40cm-balsa rod of the body) through the beginning - at ~1cm - of the tail. Make sure the body and the tail are aligned, or else your model won't float straight. Glue the wire to the balsa and bend the wire a little upwards, so that the tail makes a 15° angle.
Notice: The balsa-side of the tail is the bottom side!
Step 6: Result