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Structure

Analysis > Structure checks the actual wing (its assigned section thickness and planform) against the laminate from the Plies tab. Presets are free; custom laminate and core detail is Pro.

The headline names the one check that governs, at the worst station. Everything else is context for that number.

What is modelled

Spanwise loading solved with a vortex-lattice method, skins carry bending, design allowables with heavy knockdowns. Modelled: bending, core shear along the whole span on peak-load and high-cycle bases, flex, torsion and tip twist, skin wrinkling into the core, and torsional divergence.

Not modelled: slam and impact loads, fatigue of the skins, bondlines and joints away from the bolt line, and any defect. Guidance, not certification: verify with a qualified engineer before anyone rides what you build. Full method, assumptions, and validation: how the numbers are computed.

Construction notes

First-order (get these right)

• Section thickness: for a solid section, strength goes with t² and stiffness with t³ (sandwich skins gain roughly linearly with depth). Either way, the single biggest lever.
• Root laminate: plies at the inner third of the span do the work (75% of the integrated bending moment lives there). Taper them off past about 70% span, where the moment is down to about 5% of root.
• Fiber direction: bending wants fibers along the span. UD tape spanwise under a woven skin beats extra woven everywhere.
• Core near the root: shear lives there. Dense foam (PVC 80+) or solid laminate inboard; EPS only works far outboard, if at all.
• Wet-out and voids: a starved or bubbled laminate erases every margin above. Weigh your resin. Under a vacuum bag, target about 40% resin by weight; unbagged hand layups land nearer 50%.

Second-order (nice, not decisive)

• Exact weave style, cloth brand, and resin brand within a class.
• Finish plies, fill coats, and paint: cosmetic mass, not structure.
• Core density outboard of mid-span; tip laminate beyond a couple of plies.

The bolt line

Builds fail at the joint and from slam loads more often than mid-span. The bolt check uses the real root section with the holes subtracted. Peak stress at the hole edge is several times the net stress: metals redistribute, composites are notch-sensitive. Reinforce locally (+6-8 layers is common practice) and pot the core around bolts on sandwich builds.

Materials

Cloth, UD tape, and epoxy: Fibre Glast, US Composites, Rock West. Structural foam core (Divinycell H80): Fiberglass Supply. G10 and aluminum plate: McMaster-Carr.

Next: Core