Since the canopy’s die is ready, we had „plenty“ of time to work on the details of the cabin. To the most prominent details count probably the spar joiners and seat. Somehow the pilot’s weight has to be lead to the spar joiners and finally to the spars. The idea is to make a spar on which the seat is installed and the weight of the pilot rests. Before we start to work on the shell of the center section, it’s better to make a proof of concept. We have the mock-up spar joiners made by Siggi, and we made a proof of concept with cheap popplar plywood:
We recycled actually the seat of the wooden mock-up:
For the first time we could seat comfortably in the center section:
The cabin offers plenty of space and a very good sight:
The view angle corresponds roughly to the angle of attack at cruise speed. On the ground the angle will be somewhat higher (roughly 8° against 2°).
You probably haven been asking how hard it is boarding the wing. Well, boarding is easy, but getting out is harder. At the moment it’s even harder than necessary, as the shell does not offer the stability and stiffness which it will have later. So, we have to take really care when we entering and exiting the cabin at this stage:
Not that easy but doable. Later, when the shell is completed, we’ll be able to walk on it and the border of the cabin will offer a natural handle to pull up yourself.
The true material for the seat spar is ordered: 8 mm birch plywood of 12 layers (Thoma Balsa GmbH) and plenty of pultruded carbon profiles (R&G Faserverbundwerkstoffe GmbH). This plywood is in combination with PVC structural foam (GRM Systems s.r.o) the core material of the spar. Bending stresses will be taken up by carbon spar caps and everything will be wrapped in ±45° carbon fabrics. The stresses in the caps are quite high and will reach up to 400 MPa (58’000 psi). The spar will be joined to the steel spar joiners with an integral piece of CNC machined aluminum (EN AW 7075), and it will be cemented to the shell of the center section.
Having found a solution to the seat spar, most open questions regarding the spar joiners are answered. Hence, the design and drawings can be slowly finalized:
We are about to order the material (1.7734.5 steel tubing). If everything goes as expected, the joiners will be ready this winter.