The Spar Moment of Inertia Calculator helps you design wing spars by calculating the structural properties of different spar cross-sections positioned within an airfoil. The calculator supports hollow rectangular tubes, I-beams, and C-channels. It determines the spar height based on the airfoil thickness at the selected chord location (minus skin thickness), then computes the moment of inertia (Ix) using the appropriate formula for each cross-section type.
The moment of inertia is a critical parameter for structural analysis, determining how the spar resists bending loads. Higher moment of inertia values indicate greater resistance to bending, which is essential for wing structural design.
Cross-Section Types:
- Hollow Rectangle: Ix = (BH³ - bh³) / 12
- I-Beam: Parallel axis theorem applied to flanges and web
- C-Channel: Open channel section with centroidal axis calculation
Key Assumptions:
- Spar height is constrained by airfoil thickness minus skin thickness
- Skin thickness is uniform and creates inner boundary for spar
- Wall/flange thickness is uniform throughout the cross-section
- All dimensions are in millimeters