This model works on the same principle as the real Hafner Rotabuggy from WWII, being tethered and pulled through the air to spin the blades and create an air-catching disk which then lifts the craft into the air. Craft like the Rotabuggy, Focke Achgelis Fa330 and many others would have been towed by a truck or a U-Boat to give it speed and lift, but the model I will teach you how to build will work like a traditional kite powered by the wind.

To build this model you will need;

Scissors
A pin
Tape
String (use any string that you would associate with kite flying. I recommend thin nylon string.)
Wire and Pliers
Prestik/Blue Tac/Putty/Small coin} to use as ballast
Something to wind the string around
A windy place to fly it in
Beads
Packing/Floor insulation/other lightweight foam sheets (I used the kind used for protecting eggs when you buy a tray of 30.)

Step 1: Making the Rotors

First, cut a blade out of the foam sheet. Then trace it and make 2 others like it. To make the centre that holds them together, cut out an equilateral triangle with each side the same length as the width of a blade. Tape the blades to it as shown. Then poke a hole in the centre for the rotor shaft to fit through.

Cut 2 small circles out of the foam. These will help reduce friction. Make a small hole in the centre of each one. Then place all the parts mentioned (and 2 beads) onto the pin to create the rotor hub. The order should be like this: 0-o-O-X-O-o----------------
If 0=pin head, o=bead, -=pin shaft, X=rotor centre.

Also cut out a shape like the one shown in the 2nd last picture. This is what the shaft will be connected to the fuselage with.

Step 2: The Fuselage and Tail

Using the same foam as the rotors, we will now construct the fuselage. Yours doesn't have to look like the Rotabuggy and you could equally use any other helicopter side profile as a model.

Draw and cut out a slit in the tail end for the tailplane to be placed in.

To make the tailplane, follow the same process and measure, draw, then cut out the horizontal stabilizer. It will help to keep the craft facing in the right direction. Insert it into the slot and tape in place.

Step 3: Put It All Together

After adding tape, spike the pin into the rotor-holding piece.

Then tape it on top of the fuselage.

For the skids and ballast, I bent some wire into the shape shown below before taping it underneath the fuselage. The reason for them is that when ballast is added further out and lower down, the craft will become much more stable.
Add the ballast to the skids, it works best when placed directly below the rotor shaft.

Tape the string to the nose of the autogyro/Jeep and bend each rotor a little bit so that the leading edge is a little lower than the trailing edge.

Step 4: Take It Outside!

I apologise for the picture quality, it is a bit difficult to fly it and take pictures at the same time.

Also shown are some other gyroplanes I have built for free flight. They work the same way but don't need to be tethered.