Reinforcement of ribs

Yesterday and today we laminated the reinforcement of the ribs. We used 200 g/m² non-crimpt biaxial carbon fabrics and a covering layer of 100 g/m² flax fabrics. Biaxial carbon fabrics are great when you have corners. The stiff carbon fibers have then an orientation of ±45°, so that the fibers are bent less and wrapping them around the corner is much easier. Also, this orientation is optimal for shear loads.

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You might ask why we used flax fabrics. Well, they protect the load-bearing carbon fibers from external abrasion! Flax behaves much like aramid (Nomex® and co.): It takes some energy until it is damaged. Such a covering protects not only the load-bearing fibers, but also the pilot from sharp edges.

The reinforcements are curing now in vacuum at roughly 200 mbar residual pressure. The surplus resin is taken up by breather felt. We used also a covering layer of peel ply to obtain again a rough surface.

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Two are better than one

The main ribs and those beside them have to take-up the weight of the pilot while entering the airplane: Climb from behind and walk on top of the wing. These ribs have to be doubled near the joint to the shell to distribute the pressure on a larger surface:

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After bonding, one layer of 200 g/m² biaxial non-crimp carbon and 100 g/m² flax fabrics will further reinforce the joint.

We also made a couple of small ribs to stabilize the tail:

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