Can equal thickness-to-chord ratios describe different blade thicknesses?

The short answer

Yes. Thickness-to-chord ratio is dimensionless. Two blade sections can share that ratio while having different physical thicknesses because their chords differ. For a wind-blade interface or packaging review, obtain the local chord and the definition of thickness before turning a percentage into a clearance dimension.

Use the local section dimensions

An explicitly hypothetical ratio of 18% with a 250 mm chord gives a maximum section thickness of 45 mm. With a 400 mm chord, the same ratio gives 72 mm. These numbers illustrate t = (t/c)c only. They do not identify laminate thickness, internal spar dimensions or a structural load capacity, and they do not describe any MARSTON blade.

Identify what the thickness describes

Aerodynamic section thickness normally concerns the separation of the external profile surfaces under a defined section convention. Composite skin thickness concerns the material through one wall. A thick airfoil can contain thin skins and internal structure; a skin drawing therefore cannot be interpreted using airfoil thickness ratio. Also identify whether maximum thickness is measured normal to a reference chord or through another geometric construction before comparing two sources.

Choose the correct evidence for the decision

For external fit, request the dimensional section envelope at the relevant station and orientation. For structural review, request the actual section construction and validated material/design evidence instead of using the ratio as a strength indicator. NASA geometry references explain dimensionless section descriptors; the manufacturing drawing determines the supplied shape. When comparing blade offers, retain both chord and ratio so an apparently identical percentage does not conceal a different physical envelope or rotor design. When a fixture needs clearance around the blade, use the full oriented outline. Maximum thickness alone does not identify where that maximum occurs, so it cannot describe every local support or clamp contact.