Parametric Boat Propeller Generator

Print a custom boat propeller. Pick a style, set the size, export.

Parametric Boat Propeller Generator

A fully customizable boat propeller built in OpenSCAD. Pick a style, set the diameter and pitch, match it to your motor shaft, done. Three classical marine prop styles included, each with its own preset.

Three styles

• Conventional: 3-blade leaf-shape outboard prop. Best all-around thrust.
• Weedless:  2-blade scimitar shape with heavy backward sweep. Sheds aquatic weeds by deflecting them along the leading edge instead of catching them at the root.
• Cleaver:  3-blade racing prop with a straight radial trailing edge and forward-swept leading edge. Surface-piercing style, built for top-end speed.

All three are generated with proper boat-prop geometry — ogival airfoil cross-section (flat pressure face, curved suction back), constant geometric pitch held across the blade, leaf-shape planform rounded at both root and tip. No flat plates or toy-looking blades.

Fully customizable

Every parameter is exposed as an OpenSCAD Customizer slider or dropdown:

• Propeller diameter and pitch
• Blade count (per style)
• Hub diameter, length, and bore size
• Shaft engagement: set screw (self-tapping or captive M3 nut), D-shaft bore with filed flat, or both
• Blade planform proportions, section thickness, and print resolution

If your motor shaft isn't 5 mm, just set shaft_bore to match. If you want a 4-blade conventional, change conv_num_blades. The defaults are sensible; the knobs are there when you need them.

Shaft fitting

The hub has two independent locking features:

• Set screw — radial M3 hole through one side of the hub. Self-tapping by default (no extra hardware), or switch to a clearance fit with a captive M3 hex nut for stronger, re-tightenable grip. Auto-positioned in a blade-free gap.
• D-shaft bore — cuts a flat into one side of the bore that mates with a matching flat filed onto your motor shaft. The flat is aligned with the set screw direction so the screw tip bears on the shaft's flat for true positive (no-slip) engagement.

For the most secure connection, use both.

Printing

Orient hub-axis vertical (prop standing on its hub). The twisted blades need supports — tree supports work best.

Bump blade_slices from 24 to 40–60 before exporting the STL for the smoothest blade twist.

What it's for

• RC boat replacement props
• Bench testing motor thrust at controlled RPM
• Science-fair experiments on how diameter, pitch, and blade count affect thrust
• Anything else you'd bolt a boat prop onto

I built this originally to help my son make some propellers for his science fair project. Tested with a brushed 775 DC motor with a 5 mm shaft, but every dimension is a parameter — adjust to fit your hardware.

Made one? Post a print, I'd love to see what you build.