For most RC wing cores, lower-density EPS around 20–30 kg/m³ is the common choice: light, easy to cut, and stiff enough once sheeted with veneer, fibreglass or tape. For smaller or higher-load wings, denser EPS or XPS (~30–45 kg/m³) gives a stronger, smoother core that handles better and finishes cleaner, at a small weight penalty.
Match density to the job: big, light gliders favour light EPS; aerobatic or fast wings favour denser XPS. Whatever you choose, the core is almost always skinned afterward for strength, so the foam's job is shape and lightness, not load-bearing. Cut a test piece — the right density cuts cleanly and feels rigid for its weight.
Match density to the job: big, light gliders favour light EPS; aerobatic or fast wings favour denser XPS. Whatever you choose, the core is almost always skinned afterward for strength, so the foam's job is shape and lightness, not load-bearing. Cut a test piece — the right density cuts cleanly and feels rigid for its weight.