The principal stress magnitudes (σ11, σ22, σ33) are shown for the use of eight measured directions for stress calculation for (a), (c), (e) the strut and (b), (d), (f) the knot positions. The missing direction on the x axis refers to the direction number in Fig. 1(d). The red data points represent the calculation with all nine measured components. The green band represents the error bar for the calculation with nine strain measurements.