Structure of the aircraft consists of the mainspars, running through the wing at constant % of chord, coming together at the firewall. There the tunnel for the mainwheel is also attached. This tunnel goes all the way through to the rear spar. At the end the tail wheel is mounted.
The rear spar runs straight from tip to tip, however with hinges for folding the wings.
Therefor also the mainspars have divisions, the stringers of centre section and outboard wings are connected with brackets and inner hex.socket bolts.
Frame centre section
The cabin floor and 2 ribs, acting as cabin side walls complete the frame.
The building sequence is as follows: first the frame has to be built. Then per outboard wing section 3 foam ribs are glued in. Over these ribs the 2 parts of the top skin are glued, going over the nose until the bottom of the main spar. After this the rest of the ribs are put in, this allowes to make good glue joints and a straight skin. The nose ribs are put in from the centre side.
For completion the ribs are sanded straight at the bottom and the lower skin is glued on.
Frame turtle deck
The turtle deck is made of a structure of stringers from foam and aluminum strips. In this way the inner space is kept clean and at the same time a strong structure is built.
A roll bar is installed at the front side of the turtle deck, also to make the centre section torsion stiff.
Now the D2 has its final shape and the rest can be built on and in, like fairings, sandwich structure of the cockpit floor elevon hinges etc etc.