PROPELLER(1)

NAME

propeller - generate a procedural marine propeller geometry database

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SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

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

propeller creates a parametric Wageningen B-Series style marine propeller in a BRL-CAD .g database. The generated model is a top-level combination named by --name that contains the region name`.r`. The region unions the CSG hub assembly name`hub_hollow.c` with one solid per blade. Blade solids are closed Bag of Triangles (BoT) primitives named _name`blade_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.

OPTIONS

-h, --help: Print option help and exit.
-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.
--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.

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.

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.