Drive form from stations and parameters

This is a geometry study, not flight hardware. Learn how one profile becomes a controllable form, then reuse that form around a hub.

A station is a contract {#stations}

A station is one cross-section plus its position and orientation. The wing needs a root station, a tip station, span, taper, and twist. Name those decisions once; do not hand-draw a second almost-identical profile whenever the wing changes.

Loft the first wing {#wing-worked-stations}

Read the three stages in the source: root profile, tip profile, then loft. root_chord controls the first section. tip_chord controls the second. twist rotates only the tip before the loft joins both profiles across span.

Render the supplied model. Change span from 90 to 120, render again, and identify the only dimension that should lengthen. Then restore it before continuing.

Derive the tip station {#wing-tip}

The starter has a hard-coded tip: 26, 2.6, 9, and -1.2. Replace those literals with two names: derived tip chord and derived tip thickness. The chord must come from root_chord * taper_ratio; thickness comes from that derived chord. Keep the existing rotation, because twist is a transform of the finished tip profile, not a number baked into its points.

Render after each small edit. Check Solution compares the lowered Ecky IR, so equivalent geometry passes even if variable names or whitespace differ.

Reveal taper and twist {#wing-solution}

The solution adds taper_ratio to the parameter block and derives both tip dimensions in let*. Compare it with your source. tip_chord remains a useful measurement, but the actual profile now follows one relation. Change taper from 0.6 to 0.45 and see the tip shrink without redrawing anything.

Repeat one blade from controls {#propeller-worked}

The propeller uses one lofted blade and repeat-union. blade_count selects copies by rotating the same blade through 360 / blade_count. diameter and hub_radius define usable blade length; pitch and twist alter the two station profiles.

Render once. Change blade_count from 3 to 4, render, and verify there are four evenly spaced copies rather than four separate blade definitions.

Finish the hub variant {#hub-variant}

The starter already builds blades and a press-fit hub. Add a second named hub for split_bolt: a named split gap, named bolt-bore radius, clamp ears, bore, and slot. Then use if to select split_bolt_hub only when hub_type is "split_bolt".

Do not change blade geometry. This task is one interface choice around a fixed repeated assembly. The bore clearance remains named because it is fit-critical.

Reveal the repeated propeller study {#propeller-solution}

The solution keeps one blade definition and adds two hub choices. It is a printable geometry study only. It does not prove balance, fatigue life, thrust, RPM limit, motor compatibility, or airworthiness. Treat it as an exercise in loft, repeat, named fit, and conditional composition.