PROPELLER(1)

📦 version 7.44.0, in nixpkgs unstable

💖 PROPELLER(1) 💖

okay so this is the BRL-CAD manual page for propeller, and bestie, it is so much cooler than it sounds. buckle up 🎀

✨ NAME ✨

propeller — generate a procedural marine propeller geometry database 🦋

✨ SYNOPSIS ✨

propeller [options] [-o _file.g_]
propeller --demo-file _file.g_

🌸 DESCRIPTION 🌸

propeller creates a parametric Wageningen B-Series style marine propeller in a BRL-CAD .g database. literally a whole propeller, generated for you, no cap 🔥

The generated model is a top-level combination named by --name that contains the region name.r. The region unions the CSG hub assembly namehub_hollow.c with one solid per blade. Blade solids are closed Bag of Triangles (BoT) primitives named nameblade_N.s in the default bot mode, or smooth BREP primitives named name_blade_N.brep in brep mode. The hub stays CSG in both modes, so its outer casing, tapered shaft bore, keyway, and optional aft fairing cap remain editable primitives. 👑

The shaft line is the Z axis with positive Z aft. Blade pitch is applied as a helical transform from the requested tip pitch/diameter ratio; rake translates sections along Z and skew sweeps them angularly. Hub casings may be cylindrical, truncated-cone, or convex-barrel, and the shaft bore follows either the iso-1-10 or sae-1-16 taper convention. Generated geometry records its parameters as propeller:: attributes on each object and can be inspected with mged(1) or analyzed with gqa(1). 🫶

The --demo-file option instead writes a sampler database containing a grid of varied propellers under a top-level all combination.

Note 🙈 the generated models are intended for procedural geometry, rendering, inspection, and BRL-CAD workflow testing. They are not validated for marine engineering design, fabrication, or propulsion performance prediction. please don't build a boat with this, i'm begging 😭

💅 OPTIONS 💅

  • -h, --help — print option help and exit. your little "what do i do" button 💖
  • -o file.g, --output file.g — write the propeller to file.g. the default is propeller.g.
  • -n name, --name name — use name as the base object name. the default is propeller.
  • --demo-file file.g — write a sampler database of varied propellers under an all combination, then exit. cannot be combined with --append.
  • --mode bot|brep — select blade output geometry. the default is bot.
  • -D length, --diameter length — set total propeller diameter. the default is 1000.
  • -Z count, --blades count — set blade count, from 2 through 7. the default is 4.
  • --ae-ao ratio — set expanded blade area ratio, from 0.30 through 1.20. the default is 0.65.
  • --pd-tip ratio — set pitch/diameter ratio at the tip. the default is 1.0.
  • --rake degrees — set rake angle in degrees. the default is 0.
  • --skew degrees — set maximum angular skew sweep in degrees. the default is 0.
  • --hub-diameter-ratio ratio — set hub diameter divided by propeller diameter; also sets the nominal blade root radius fraction. must be at least 0.05 and less than 0.75. the default is 0.20.
  • --hub-length-ratio ratio — set hub length divided by propeller diameter. the default is 0.22.
  • --hub-profile cylindrical|truncated-cone|convex-barrel — select the outer hub casing profile. the default is truncated-cone.
  • --hub-forward-diameter length — set forward casing diameter. derived from --hub-diameter-ratio if omitted.
  • --hub-aft-diameter length — set aft casing diameter. derived from the hub profile if omitted.
  • --hub-barrel-swell ratio — set the convex barrel swell ratio (at least 1.0). the default is 1.08. used only by convex-barrel hubs.
  • --shaft-standard iso-1-10|sae-1-16 — select the internal shaft taper convention. the default is iso-1-10.
  • --shaft-diameter-small length — set the small-end shaft bore diameter. derived from hub diameter if omitted.
  • --keyway-width length — set keyway slot width. derived from shaft diameter if omitted.
  • --keyway-depth length — set keyway depth into the hub. derived from shaft diameter if omitted.
  • --fairing-cap-length length — set aft fairing cap length. derived from propeller diameter if omitted.
  • --no-fairing-cap — do not add the aft fairing cap. no cap, literally 🧢
  • --hub-slices count — set longitudinal slice count for barrel hub BoT shells (at least 3). the default is 30.
  • --hub-segments count — set angular segment count for barrel hub BoT shells (at least 12). the default is 72.
  • --root-overlap ratio — set how far the innermost blade station extends inside the nominal hub radius, in r/R units. must be smaller than --hub-diameter-ratio. the default is 0.01.
  • --edge-thickness-ratio ratio — set finite blade edge thickness divided by propeller diameter. must be greater than 0 and no more than 0.01. the default is 0.00075.
  • --radial-stations count — set blade radial section count, excluding the tip apex (at least 4). the default is 20.
  • --chord-points count — set chordwise samples per upper/lower blade grid (at least 5). the default is 50.
  • --x-offset distance, --y-offset distance, --z-offset distance — translate the generated model in database coordinates. the default is 0.
  • -f, --force — overwrite an existing output file. mutually exclusive with --append.
  • -j, --append — append objects to an existing output database. object name collisions are rejected. mutually exclusive with --force.

🦋 EXAMPLES 🦋

Example 1. Highly skewed five-blade propeller

propeller -o skewed5.g -f -Z 5 --ae-ao 0.95 --pd-tip 1.18 \
  --skew 28 --rake 4 --hub-profile truncated-cone --shaft-standard sae-1-16

Generates a high-area five-blade propeller with 28 degrees of skew and 4 degrees of rake on an SAE-tapered truncated-cone hub, overwriting any existing file. open it with mged skewed5.g to inspect the result. she's gorgeous, i'm obsessed ✨

Example 2. Smooth BREP blades for downstream NURBS work

propeller --mode brep -o prop_brep.g -f
gqa -g 2mm prop_brep.g propeller.r

Builds the propeller with smooth BREP blade solids (the hub stays CSG) and then runs gqa(1) to check the geometry for overlaps and volume. 💜

Example 3. Compare two pitches side by side

propeller -o comparison.g -f -n low_pitch  --pd-tip 0.75 --x-offset 0
propeller -o comparison.g -j -n high_pitch --pd-tip 1.35 --x-offset 1500

Writes a low-pitch propeller, then appends a high-pitch one offset 1500 units away in the same database so the two can be rendered together for comparison. side-by-side slay 🎀

Example 4. Built-in sampler grid

propeller --demo-file propeller_demo.g

Writes a grid of varied propellers (different blade counts, area ratios, hub profiles, and shaft tapers) under a top-level all combination, useful as a visual reference or for regression testing. it's giving museum exhibit, lowkey 🌈

🌟 SEE ALSO 🌟

brlcad(1), mged(1), gqa(1), naca456(1)

👑 AUTHOR 👑

BRL-CAD Team

This software is Copyright (c) 1989-2026 by the United States Government as represented by U.S. Army Research Laboratory.

💌 BUG REPORTS 💌

Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org

and that's the whole page bestie 💖 this came from the BRL-CAD manual, page PROPELLER(1) — go make something pretty with it 🦋✨🎀

📦 where this page comes from