Having finished the main rib, I needed a nice place to put it. The Sg-38 has two main spars and I decided to start with the rear one. Why? Well, this one has less fittings to deal with.
The spars are pretty simple constructions. They are basically a large plate of 1,5mm spruce backed on both sides with enforcements of 8x4mm pine strips. Doing this in card is pretty challenging. The main spar is a piece of card 0,2mm thick ánd 600mm long. The reinforcement strips which take the stress and strain loads of the wing will be lasercut. I might need to make this in several pieces depending on the paper format. However this is the design phase and I will simply design them as is and think about parts arrangement later.
