simplified structure using rigid struts

A simpler fuselage using thick, rigid struts to take the principal flight loads in positive and negative G. The fairing is the same, it's just not shown in these images

straight line fuselage

The fuselage has been modified. It's still a 60 mm wide box section but it's all made out of straight lines. The material is carbon reinforced wood and we had two reasons to migrate to a straight line shape, one is simplicity of construction (each straight segment can be a rectangle of 1mm plywood, overlapped with the next)  and also ease of reinforcement by straight carbon fiber rods included inside the structure seams. In this layout, the pilot is also lying down a bit more, to reduce frontal area and interference with the wing.

Project Rendering

Leading Edge D-Structure: 2.3 kg

3 meter long leading edge D structure, carries all flight loads for +6 -3 g. 2.3 kilograms including the fiberglass on the web faces. Will go up to 2.5 or 2.7 kilos when I include the metal fittings, and there will be about 100-200 g of glue. But it's still pretty light. Notice in the spar, the balsa wood, which is 120 kg/m3, is replaced by 28 kg/m3 foam on the outer 110 cm of the wing.

Detailed Wing Structure

I'm working on the detailed wing structural model, starting with the front D-Section.
Ribs - 20 mm extruded polystyrene 28 kg/m3
Spar is 100 x 10 x 3000 mm dimension
Spar Caps - unidirectional carbon
Spar Web - Vertical Grain Light Balsa, 120 kg/m3
Spar Faces - 45 deg. fiberglass 0.2-0.5 mm thick to be determined
D-Section shell: 0.8 mm aicraft plywood
Strut attachment is not yet in place in these pictures (it will be at 50% span)

Wing Analysis

Here is the negative 3G case. The struts do not take any load. The required spar cap sections in unidirectional carbon fiber are:
Red - 60 mm2
Orange - 40mm2
Green - 30mm2
Light Blue - 15mm2
Dark Blue - 6mm2

We need to use for each spar cap, the larger of the two sections for the 6G positive or 3G negative case. This means, basically, tapering from 60mm2 at the wing root (required for the 3G neg case), down to about 35 mm2 at the strut attachments (required for the 6G pos case), and then tapering down to zero at the wingtip.

Analysis of the wing in 6G positive loading.
Principal flight loads are handled by unidirectional carbon fiber in the spar caps.
The color corresponds to the mm2 of unidirectional carbon that will be necessary (spar cap section):
Red - 40 mm2
Orange - 30 mm2
Yellow - 25 mm2
Green - 15 mm2
Light Blue - 10 mm2
Dark Blue - less than 5 mm2

The behaviour in negative G will be different because the struts do not have any compression capacity. Negative G is handled by the wing root and it will increase the forces in the center section between the struts.