From 7b248dc5d055e4cac5e5ba7a6edb22e9493107d0 Mon Sep 17 00:00:00 2001
From: marinlauber <marinlauber@gmail.com>
Date: Sat, 17 Oct 2026 10:57:29 +0200
Subject: [PATCH] feat: package as python_vpp for PyPI

- move the code to src/python_vpp/ and the model coefficient data to
  src/python_vpp/dat/, loaded relative to the package (DATA_DIR) so the
  VPP runs from any working directory
- ship the YD-41 righting arm curve as the fallback when no GZ is given
  and there is no righting_moment.json in the working directory
- expose VPP, Yacht, appendages and sails at the package top level, with
  __version__ from the installed metadata
- relative imports inside the package; drop the sys.path hacks
- pyproject: wheel package path, project URLs, keywords, slim sdist
- README: pip install, usage example and release steps

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JN4y2NWa8kFMBZ5FV92jkj
---
 Procfile                                      |  2 +-
 README.md                                     | 38 ++++++++++++++++++-
 benchmark/benchmark.py                        |  8 ++--
 "demos/pages/1_VPP_\342\233\265.py"           |  7 ++--
 pyproject.toml                                | 15 +++++++-
 runVPP.py                                     |  6 +--
 scripts/Resistance.py                         |  4 +-
 sphinx/conf.py                                |  2 +-
 sphinx/index.rst                              |  2 +-
 src/__init__.py                               |  1 -
 src/{ => python_vpp}/AeroMod.py               |  2 +-
 src/{ => python_vpp}/HydroMod.py              |  4 +-
 src/{ => python_vpp}/SailMod.py               | 11 +++---
 src/{ => python_vpp}/UtilsMod.py              |  5 ++-
 src/{ => python_vpp}/VPPMod.py                |  8 ++--
 src/{ => python_vpp}/YachtMod.py              | 14 +++++--
 src/python_vpp/__init__.py                    | 14 +++++++
 src/{ => python_vpp}/api.py                   |  9 ++---
 .../python_vpp/dat}/ORCi_Drag_Surfaces.csv    |  0
 {dat => src/python_vpp/dat}/fcdmult.dat       |  0
 {dat => src/python_vpp/dat}/jib.dat           |  0
 {dat => src/python_vpp/dat}/kheff.dat         |  0
 {dat => src/python_vpp/dat}/kite.dat          |  0
 {dat => src/python_vpp/dat}/main.dat          |  0
 .../python_vpp/dat}/orc/asym_cl_kite.dat      |  0
 .../python_vpp/dat}/orc/asym_pole_kite.dat    |  0
 {dat => src/python_vpp/dat}/orc/jib.dat       |  0
 {dat => src/python_vpp/dat}/orc/jib_low.dat   |  0
 {dat => src/python_vpp/dat}/orc/kite.dat      |  0
 {dat => src/python_vpp/dat}/orc/main.dat      |  0
 {dat => src/python_vpp/dat}/orc/main_low.dat  |  0
 {dat => src/python_vpp/dat}/orc/sym_kite.dat  |  0
 src/python_vpp/dat/righting_moment.json       |  4 ++
 {dat => src/python_vpp/dat}/rrk.dat           |  0
 {dat => src/python_vpp/dat}/st.dat            |  0
 {dat => src/python_vpp/dat}/ut.dat            |  0
 {dat => src/python_vpp/dat}/wr.dat            |  0
 tests/test_aero.py                            | 14 +++----
 tests/test_api.py                             |  2 +-
 tests/test_hydro.py                           |  6 +--
 tests/test_resistance.py                      |  6 +--
 tests/test_utils.py                           |  6 +--
 tests/test_vpp.py                             | 14 +++----
 tests/test_yacht.py                           |  4 +-
 44 files changed, 140 insertions(+), 68 deletions(-)
 delete mode 100644 src/__init__.py
 rename src/{ => python_vpp}/AeroMod.py (99%)
 rename src/{ => python_vpp}/HydroMod.py (99%)
 rename src/{ => python_vpp}/SailMod.py (97%)
 rename src/{ => python_vpp}/UtilsMod.py (97%)
 rename src/{ => python_vpp}/VPPMod.py (98%)
 rename src/{ => python_vpp}/YachtMod.py (96%)
 create mode 100644 src/python_vpp/__init__.py
 rename src/{ => python_vpp}/api.py (95%)
 rename {dat => src/python_vpp/dat}/ORCi_Drag_Surfaces.csv (100%)
 rename {dat => src/python_vpp/dat}/fcdmult.dat (100%)
 rename {dat => src/python_vpp/dat}/jib.dat (100%)
 rename {dat => src/python_vpp/dat}/kheff.dat (100%)
 rename {dat => src/python_vpp/dat}/kite.dat (100%)
 rename {dat => src/python_vpp/dat}/main.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/asym_cl_kite.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/asym_pole_kite.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/jib.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/jib_low.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/kite.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/main.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/main_low.dat (100%)
 rename {dat => src/python_vpp/dat}/orc/sym_kite.dat (100%)
 create mode 100644 src/python_vpp/dat/righting_moment.json
 rename {dat => src/python_vpp/dat}/rrk.dat (100%)
 rename {dat => src/python_vpp/dat}/st.dat (100%)
 rename {dat => src/python_vpp/dat}/ut.dat (100%)
 rename {dat => src/python_vpp/dat}/wr.dat (100%)

diff --git a/Procfile b/Procfile
index c99e5a1..6adb339 100644
--- a/Procfile
+++ b/Procfile
@@ -1 +1 @@
-web: gunicorn src.api:app --log-file=-
\ No newline at end of file
+web: gunicorn --chdir src python_vpp.api:app --log-file=-
\ No newline at end of file
diff --git a/README.md b/README.md
index 592b128..4f973d0 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,38 @@
 
 Please see the demo hosted at [https://yacht-vpp.streamlit.app/](https://yacht-vpp.streamlit.app/) and go for a test sail!
 
+## Installation
+
+Python-VPP is on PyPI and needs Python 3.11 or newer:
+
+```bash
+pip install python-vpp
+```
+
+Then build a yacht and run the VPP:
+
+```python
+import numpy as np
+from python_vpp import VPP, Yacht, Keel, Rudder, Main, Jib, Kite
+
+yacht = Yacht(
+    Name="YD41", Lwl=11.90, Vol=6.05, Bwl=3.18, Tc=0.4, WSA=28.20, Tmax=2.30,
+    Amax=1.051, Mass=6500, Ff=1.5, Fa=1.5, Boa=4.2, Loa=12.5,
+    App=[Keel(Cu=1.00, Cl=0.78, Span=1.90), Rudder(Cu=0.48, Cl=0.22, Span=1.15)],
+    Sails=[
+        Main("MN1", P=16.60, E=5.60, Roach=0.1, BAD=1.0),
+        Jib("J1", I=16.20, J=5.10, LPG=5.40, HBI=1.8),
+        Kite("A2", area=150.0, vce=9.55),
+    ],
+)
+vpp = VPP(Yacht=yacht)
+vpp.set_analysis(tws_range=np.arange(4.0, 22.0, 2.0), twa_range=np.linspace(30.0, 180.0, 31))
+vpp.run()
+vpp.polar(n=3, save=True)  # Polars.pdf
+```
+
+The righting arm curve is passed with `Yacht(..., GZ={"Heel": [...], "GZ": [...]})`. Without it, `righting_moment.json` is read from the working directory, falling back to the YD-41 curve shipped with the package. The ORC sail and resistance coefficients are part of the package.
+
 ## Using the code
 
 The project is managed with [uv](https://docs.astral.sh/uv/). Install it once (see the [uv docs](https://docs.astral.sh/uv/getting-started/installation/) for other methods):
@@ -20,7 +52,7 @@ cd Python-VPP
 uv sync
 ```
 
-The main files that are used are `runVPP.py` and `righting_moment.json`. These have to be filled with the data of your boat. By default they are using the YD-41 (from Principle of Yacht Design).
+From a clone of the repository, the main files that are used are `runVPP.py` and `righting_moment.json`. These have to be filled with the data of your boat. By default they are using the YD-41 (from Principle of Yacht Design). The code lives in `src/python_vpp/`, with the model coefficient data in `src/python_vpp/dat/`; `uv sync` installs it in editable mode.
 
 The VPP is run from the root of the repository with
 
@@ -111,6 +143,10 @@ You can run tests with
 uv run pytest -vv
 ```
 
+### Release
+
+Bump `version` in `pyproject.toml`, then create a GitHub release with a matching tag (e.g. `v1.0.0`). The `python-publish.yml` workflow builds the package with `uv build` and uploads it to PyPI through trusted publishing. Check the build locally first with `uv build`.
+
 You can run a benchmark against the YD-41 results from WinVPP by running the `benchmark.py` script (`-g` saves the polars as one `Figure_<label>_<TWS>.pdf` per wind speed plus a `Figure_<label>_stats.pdf` error summary, `-s` saves the results).
 
 ```bash
diff --git a/benchmark/benchmark.py b/benchmark/benchmark.py
index a44fcbe..9c5b07d 100644
--- a/benchmark/benchmark.py
+++ b/benchmark/benchmark.py
@@ -6,11 +6,9 @@
 import matplotlib.pyplot as plt
 from datetime import datetime
 
-sys.path.append(os.path.realpath("."))
-
-from src.YachtMod import Yacht, Keel, Rudder
-from src.SailMod import Main, Jib, Kite
-from src.VPPMod import VPP, KNOTS_TO_MPS
+from python_vpp.YachtMod import Yacht, Keel, Rudder
+from python_vpp.SailMod import Main, Jib, Kite
+from python_vpp.VPPMod import VPP, KNOTS_TO_MPS
 
 tws = np.array([3, 4, 5, 6, 7, 8, 10]) # TWS in m/s
 data_file = "dat/YD-41/YD41.dat"
diff --git "a/demos/pages/1_VPP_\342\233\265.py" "b/demos/pages/1_VPP_\342\233\265.py"
index b7629e3..27b18a0 100644
--- "a/demos/pages/1_VPP_\342\233\265.py"
+++ "b/demos/pages/1_VPP_\342\233\265.py"
@@ -9,9 +9,10 @@
 import streamlit as st
 from utils import footer, header
 
-sys.path.append(os.path.realpath("."))
-from src.api import app
-from src.UtilsMod import KNOTS_TO_MPS, _get_cross, _get_vmg, _polar, cols, stl
+# the demo may run without the package installed (e.g. Streamlit Cloud)
+sys.path.append(os.path.realpath("src"))
+from python_vpp.api import app
+from python_vpp.UtilsMod import KNOTS_TO_MPS, _get_cross, _get_vmg, _polar, cols, stl
 
 st.set_page_config(page_title="VPP", page_icon="⛵")
 
diff --git a/pyproject.toml b/pyproject.toml
index 76bee68..09bc5fa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,7 +1,7 @@
 [project]
 name = "python-vpp"
 version = "1.0.0"
-description = "OOP Velocity Prediction Program"
+description = "3-DOF sailing yacht Velocity Prediction Program based on the ORC models"
 readme = "README.md"
 license = "MIT"
 requires-python = ">=3.11"
@@ -10,8 +10,11 @@ authors = [
     { name = "Otto Villani" },
     { name = "Thomas Dickson" },
 ]
+keywords = ["VPP", "velocity prediction", "sailing", "yacht", "ORC", "naval architecture"]
 classifiers = [
     "Programming Language :: Python :: 3",
+    "Intended Audience :: Science/Research",
+    "Topic :: Scientific/Engineering",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
 ]
@@ -21,6 +24,11 @@ dependencies = [
     "scipy>=1.12",
 ]
 
+[project.urls]
+Homepage = "https://github.com/marinlauber/Python-VPP"
+Documentation = "https://marinlauber.github.io/Python-VPP/"
+Demo = "https://yacht-vpp.streamlit.app/"
+
 [project.optional-dependencies]
 api = ["flask", "gunicorn"]
 demo = ["streamlit>=1.37"]
@@ -35,7 +43,10 @@ requires = ["hatchling"]
 build-backend = "hatchling.build"
 
 [tool.hatch.build.targets.wheel]
-packages = ["src"]
+packages = ["src/python_vpp"]
+
+[tool.hatch.build.targets.sdist]
+include = ["src/python_vpp", "tests", "README.md", "LICENSE"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
diff --git a/runVPP.py b/runVPP.py
index 39559ec..2d7cda5 100755
--- a/runVPP.py
+++ b/runVPP.py
@@ -6,9 +6,9 @@
 
 logging.basicConfig(level=logging.INFO)
 
-from src.SailMod import Jib, Kite, Main
-from src.VPPMod import VPP
-from src.YachtMod import Keel, Rudder, Yacht
+from python_vpp.SailMod import Jib, Kite, Main
+from python_vpp.VPPMod import VPP
+from python_vpp.YachtMod import Keel, Rudder, Yacht
 
 YD41 = Yacht(
     Name="YD41",
diff --git a/scripts/Resistance.py b/scripts/Resistance.py
index 034b72c..6ed005d 100644
--- a/scripts/Resistance.py
+++ b/scripts/Resistance.py
@@ -8,8 +8,8 @@
 __email__ = "M.Lauber@soton.ac.uk"
 
 import numpy as np
-from src.HydroMod import HydroMod
-from src.YachtMod import Yacht, Keel, Rudder
+from python_vpp.HydroMod import HydroMod
+from python_vpp.YachtMod import Yacht, Keel, Rudder
 
 if __name__ == "__main__":
 
diff --git a/sphinx/conf.py b/sphinx/conf.py
index c7d2707..6b03392 100644
--- a/sphinx/conf.py
+++ b/sphinx/conf.py
@@ -13,7 +13,7 @@
 import os
 import sys
 
-sys.path.insert(0, os.path.abspath(".."))
+sys.path.insert(0, os.path.abspath("../src"))
 
 
 # -- Project information -----------------------------------------------------
diff --git a/sphinx/index.rst b/sphinx/index.rst
index 39b1d34..7b748d7 100644
--- a/sphinx/index.rst
+++ b/sphinx/index.rst
@@ -1,7 +1,7 @@
 Welcome to Python-VPP's documentation!
 ======================================
 
-.. automodule:: src.VPPMod
+.. automodule:: python_vpp.VPPMod
     :members:
 
 .. toctree::
diff --git a/src/__init__.py b/src/__init__.py
deleted file mode 100644
index 8c43447..0000000
--- a/src/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-# empty __init__.py file
diff --git a/src/AeroMod.py b/src/python_vpp/AeroMod.py
similarity index 99%
rename from src/AeroMod.py
rename to src/python_vpp/AeroMod.py
index 5127f18..611dde2 100644
--- a/src/AeroMod.py
+++ b/src/python_vpp/AeroMod.py
@@ -6,7 +6,7 @@
 import matplotlib.pyplot as plt
 import numpy as np
 
-from src.UtilsMod import build_interp_func
+from .UtilsMod import build_interp_func
 
 
 Z_REF = 10.0  # m, height the true wind speed is given at (ORC 7.1)
diff --git a/src/HydroMod.py b/src/python_vpp/HydroMod.py
similarity index 99%
rename from src/HydroMod.py
rename to src/python_vpp/HydroMod.py
index a91962c..3476fb6 100644
--- a/src/HydroMod.py
+++ b/src/python_vpp/HydroMod.py
@@ -7,6 +7,8 @@
 import numpy as np
 from scipy.interpolate import RegularGridInterpolator
 
+from .UtilsMod import DATA_DIR
+
 
 class HydroMod(object):
     def __init__(self, Yacht, rho=1025.0, mu=0.00119, g=9.81):
@@ -61,7 +63,7 @@ def __load_data(self):
         """
         Loads ORC resistance surfaces from file and build interpolation function
         """
-        surf = np.genfromtxt("dat/ORCi_Drag_Surfaces.csv", delimiter=",", skip_header=1)
+        surf = np.genfromtxt(DATA_DIR / "ORCi_Drag_Surfaces.csv", delimiter=",", skip_header=1)
         surf = surf.reshape((24, 43, 42))
         # x is Fn := [0.,0.7], y is btr := [2.5,9], z is lvr := [3,9]
         # we add zero Fn resistance (0.)
diff --git a/src/SailMod.py b/src/python_vpp/SailMod.py
similarity index 97%
rename from src/SailMod.py
rename to src/python_vpp/SailMod.py
index 1612750..bbc0398 100644
--- a/src/SailMod.py
+++ b/src/python_vpp/SailMod.py
@@ -5,6 +5,8 @@
 import numpy as np
 from scipy import interpolate
 
+from .UtilsMod import DATA_DIR
+
 
 SAIL_TYPES = {
     "main": "main",
@@ -68,12 +70,11 @@ def _build_interp_func(self, fname, data_source="orc"):
         """Build cubic B-spline interpolation functions for CL and CD.
 
         Falls back to linear (k=1) if fewer than 4 data points are available.
-        Tries ``dat/{data_source}/{fname}.dat`` first, then ``dat/{fname}.dat``.
+        Tries ``DATA_DIR/{data_source}/{fname}.dat`` first, then ``DATA_DIR/{fname}.dat``.
         """
-        import os
-        path = os.path.join("dat", data_source, fname + ".dat")
-        if not os.path.exists(path):
-            path = os.path.join("dat", fname + ".dat")
+        path = DATA_DIR / data_source / (fname + ".dat")
+        if not path.exists():
+            path = DATA_DIR / (fname + ".dat")
         a = np.genfromtxt(path, delimiter=",", skip_header=1)
         self.kp = a[0, 0]
         # Filter NaN values (trailing commas in CSV create NaNs)
diff --git a/src/UtilsMod.py b/src/python_vpp/UtilsMod.py
similarity index 97%
rename from src/UtilsMod.py
rename to src/python_vpp/UtilsMod.py
index 3b33893..b0b84b9 100644
--- a/src/UtilsMod.py
+++ b/src/python_vpp/UtilsMod.py
@@ -2,6 +2,7 @@
 # -*- coding: utf-8 -*-
 
 import json
+from pathlib import Path
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -10,6 +11,8 @@
 from scipy.interpolate import RegularGridInterpolator
 
 KNOTS_TO_MPS = 0.5144
+# model coefficient data shipped with the package
+DATA_DIR = Path(__file__).parent / "dat"
 stl = [
     (0, ()),
     (0, (1.1, 1.1)),
@@ -43,7 +46,7 @@ def build_interp_func(fname, i=1, kind="linear"):
     """
     build interpolation function and returns it in a list
     """
-    a = np.genfromtxt("dat/" + fname + ".dat", delimiter=",", skip_header=1)
+    a = np.genfromtxt(DATA_DIR / (fname + ".dat"), delimiter=",", skip_header=1)
     # Filter out NaN values for make_interp_spline compatibility
     mask = ~(np.isnan(a[0, :]) | np.isnan(a[i, :]))
     x = a[0, mask]
diff --git a/src/VPPMod.py b/src/python_vpp/VPPMod.py
similarity index 98%
rename from src/VPPMod.py
rename to src/python_vpp/VPPMod.py
index 73a265e..dec9e72 100644
--- a/src/VPPMod.py
+++ b/src/python_vpp/VPPMod.py
@@ -7,10 +7,10 @@
 import numpy as np
 from scipy.optimize import minimize
 
-from src.AeroMod import AeroMod
-from src.HydroMod import HydroMod
-from src.UtilsMod import KNOTS_TO_MPS, json_write, polar_plot, sail_chart
-from src.YachtMod import Yacht as YachtClass
+from .AeroMod import AeroMod
+from .HydroMod import HydroMod
+from .UtilsMod import KNOTS_TO_MPS, json_write, polar_plot, sail_chart
+from .YachtMod import Yacht as YachtClass
 
 logger = logging.getLogger(__name__)
 
diff --git a/src/YachtMod.py b/src/python_vpp/YachtMod.py
similarity index 96%
rename from src/YachtMod.py
rename to src/python_vpp/YachtMod.py
index 0628263..108159e 100644
--- a/src/YachtMod.py
+++ b/src/python_vpp/YachtMod.py
@@ -1,10 +1,12 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
+import os
+
 import numpy as np
 from scipy import interpolate
 
-from src.UtilsMod import build_interp_func, json_read, json_write
+from .UtilsMod import DATA_DIR, build_interp_func, json_read, json_write
 
 
 def _zero_cr(fn):
@@ -248,8 +250,9 @@ def __init__(self, Name, Lwl, Vol, Bwl, Tc, WSA, Tmax,
             Sail inventory. Default is [].
         GZ : dict, optional
             Righting arm curve as ``{"Heel": [...], "GZ": [...]}``.
-            Heel in degrees, GZ in metres. If *None*, loads from
-            ``righting_moment.json`` (backward compatible).
+            Heel in degrees, GZ in metres. If *None*, loads
+            ``righting_moment.json`` from the working directory, or the
+            packaged YD-41 curve if there is none.
         crew_weight : float, optional
             Total crew weight (kg). If *None*, uses empirical formula
             ``25.8 * Lwl ** 1.4262``.
@@ -316,7 +319,10 @@ def _build_rm_interp(self):
         if self._gz_data is not None:
             a = self._gz_data
         else:
-            a = json_read('righting_moment')
+            fname = 'righting_moment'
+            if not os.path.exists(fname + '.json'):
+                fname = str(DATA_DIR / fname)
+            a = json_read(fname)
         return interpolate.interp1d(np.array(a["Heel"]), np.array(a["GZ"]),
                                     kind="linear", fill_value="extrapolate")
 
diff --git a/src/python_vpp/__init__.py b/src/python_vpp/__init__.py
new file mode 100644
index 0000000..31239dd
--- /dev/null
+++ b/src/python_vpp/__init__.py
@@ -0,0 +1,14 @@
+"""Python-VPP: a 3-DOF velocity prediction program based on the ORC models."""
+
+from importlib.metadata import PackageNotFoundError, version
+
+from .SailMod import Jib, Kite, Main
+from .VPPMod import VPP
+from .YachtMod import Bulb, Keel, Rudder, ShortKeel, Yacht
+
+try:
+    __version__ = version("python-vpp")
+except PackageNotFoundError:  # running from a source checkout
+    __version__ = "unknown"
+
+__all__ = ["VPP", "Yacht", "Keel", "ShortKeel", "Rudder", "Bulb", "Main", "Jib", "Kite"]
diff --git a/src/api.py b/src/python_vpp/api.py
similarity index 95%
rename from src/api.py
rename to src/python_vpp/api.py
index 006ec15..fe1d7fa 100644
--- a/src/api.py
+++ b/src/python_vpp/api.py
@@ -3,17 +3,14 @@
 
 """
 import logging
-import os
-import sys
 from typing import Any, Dict
 
 import numpy as np
 from flask import Flask, jsonify, request
 
-sys.path.append(os.path.realpath("."))
-from src.SailMod import Jib, Kite, Main
-from src.VPPMod import VPP
-from src.YachtMod import Keel, Rudder, ShortKeel, Yacht
+from .SailMod import Jib, Kite, Main
+from .VPPMod import VPP
+from .YachtMod import Keel, Rudder, ShortKeel, Yacht
 
 app = Flask(__name__)
 
diff --git a/dat/ORCi_Drag_Surfaces.csv b/src/python_vpp/dat/ORCi_Drag_Surfaces.csv
similarity index 100%
rename from dat/ORCi_Drag_Surfaces.csv
rename to src/python_vpp/dat/ORCi_Drag_Surfaces.csv
diff --git a/dat/fcdmult.dat b/src/python_vpp/dat/fcdmult.dat
similarity index 100%
rename from dat/fcdmult.dat
rename to src/python_vpp/dat/fcdmult.dat
diff --git a/dat/jib.dat b/src/python_vpp/dat/jib.dat
similarity index 100%
rename from dat/jib.dat
rename to src/python_vpp/dat/jib.dat
diff --git a/dat/kheff.dat b/src/python_vpp/dat/kheff.dat
similarity index 100%
rename from dat/kheff.dat
rename to src/python_vpp/dat/kheff.dat
diff --git a/dat/kite.dat b/src/python_vpp/dat/kite.dat
similarity index 100%
rename from dat/kite.dat
rename to src/python_vpp/dat/kite.dat
diff --git a/dat/main.dat b/src/python_vpp/dat/main.dat
similarity index 100%
rename from dat/main.dat
rename to src/python_vpp/dat/main.dat
diff --git a/dat/orc/asym_cl_kite.dat b/src/python_vpp/dat/orc/asym_cl_kite.dat
similarity index 100%
rename from dat/orc/asym_cl_kite.dat
rename to src/python_vpp/dat/orc/asym_cl_kite.dat
diff --git a/dat/orc/asym_pole_kite.dat b/src/python_vpp/dat/orc/asym_pole_kite.dat
similarity index 100%
rename from dat/orc/asym_pole_kite.dat
rename to src/python_vpp/dat/orc/asym_pole_kite.dat
diff --git a/dat/orc/jib.dat b/src/python_vpp/dat/orc/jib.dat
similarity index 100%
rename from dat/orc/jib.dat
rename to src/python_vpp/dat/orc/jib.dat
diff --git a/dat/orc/jib_low.dat b/src/python_vpp/dat/orc/jib_low.dat
similarity index 100%
rename from dat/orc/jib_low.dat
rename to src/python_vpp/dat/orc/jib_low.dat
diff --git a/dat/orc/kite.dat b/src/python_vpp/dat/orc/kite.dat
similarity index 100%
rename from dat/orc/kite.dat
rename to src/python_vpp/dat/orc/kite.dat
diff --git a/dat/orc/main.dat b/src/python_vpp/dat/orc/main.dat
similarity index 100%
rename from dat/orc/main.dat
rename to src/python_vpp/dat/orc/main.dat
diff --git a/dat/orc/main_low.dat b/src/python_vpp/dat/orc/main_low.dat
similarity index 100%
rename from dat/orc/main_low.dat
rename to src/python_vpp/dat/orc/main_low.dat
diff --git a/dat/orc/sym_kite.dat b/src/python_vpp/dat/orc/sym_kite.dat
similarity index 100%
rename from dat/orc/sym_kite.dat
rename to src/python_vpp/dat/orc/sym_kite.dat
diff --git a/src/python_vpp/dat/righting_moment.json b/src/python_vpp/dat/righting_moment.json
new file mode 100644
index 0000000..d331dff
--- /dev/null
+++ b/src/python_vpp/dat/righting_moment.json
@@ -0,0 +1,4 @@
+{
+  "Heel": [0.00,10.0,20.0,30.0,40.0],
+  "GZ": [0.00,0.400,0.730,0.960,1.100]
+}
\ No newline at end of file
diff --git a/dat/rrk.dat b/src/python_vpp/dat/rrk.dat
similarity index 100%
rename from dat/rrk.dat
rename to src/python_vpp/dat/rrk.dat
diff --git a/dat/st.dat b/src/python_vpp/dat/st.dat
similarity index 100%
rename from dat/st.dat
rename to src/python_vpp/dat/st.dat
diff --git a/dat/ut.dat b/src/python_vpp/dat/ut.dat
similarity index 100%
rename from dat/ut.dat
rename to src/python_vpp/dat/ut.dat
diff --git a/dat/wr.dat b/src/python_vpp/dat/wr.dat
similarity index 100%
rename from dat/wr.dat
rename to src/python_vpp/dat/wr.dat
diff --git a/tests/test_aero.py b/tests/test_aero.py
index 7e4718c..cf218fd 100644
--- a/tests/test_aero.py
+++ b/tests/test_aero.py
@@ -8,7 +8,7 @@ class TestWindTriangleCache:
     """Verify that wind_triangle uses lru_cache."""
 
     def test_wind_triangle_is_cached(self):
-        from src.AeroMod import wind_triangle
+        from python_vpp.AeroMod import wind_triangle
 
         # lru_cache-decorated functions have cache_info()
         assert hasattr(wind_triangle, "cache_info"), "wind_triangle should be lru_cache-decorated"
@@ -20,7 +20,7 @@ def test_wind_triangle_is_cached(self):
         assert info.misses == 1
 
     def test_cache_returns_same_result(self):
-        from src.AeroMod import wind_triangle
+        from python_vpp.AeroMod import wind_triangle
 
         wind_triangle.cache_clear()
         r1 = wind_triangle(10.0, 45.0, 6.0)
@@ -34,7 +34,7 @@ class TestSailCoefficientCalls:
     def test_get_coeffs_calls_cl_once_per_sail(self):
         """Each sail's cl(awa) should be called at most once per _get_coeffs()."""
         from unittest.mock import MagicMock, patch
-        from src.AeroMod import AeroMod
+        from python_vpp.AeroMod import AeroMod
 
         # Create a mock yacht with minimal structure
         mock_sail = MagicMock()
@@ -109,7 +109,7 @@ class TestWindTriangle:
     )
     def test_wind_triangle_analytical(self, tws, twa, vb, expected_aws, expected_awa):
         """AWA and AWS must match law-of-cosines closed-form solution."""
-        from src.AeroMod import wind_triangle
+        from python_vpp.AeroMod import wind_triangle
 
         awa, aws = wind_triangle(tws, twa, vb)
         assert aws == pytest.approx(expected_aws, abs=1e-10)
@@ -117,7 +117,7 @@ def test_wind_triangle_analytical(self, tws, twa, vb, expected_aws, expected_awa
 
     def test_no_fsolve_import_used(self):
         """The analytical path must not import or call fsolve."""
-        from src.AeroMod import wind_triangle
+        from python_vpp.AeroMod import wind_triangle
         import inspect
 
         source = inspect.getsource(wind_triangle)
@@ -128,7 +128,7 @@ class TestHeeledWindTriangle:
     """ORC 7.1: heel and the log wind gradient in the wind triangle."""
 
     def test_gradient_reference_height(self):
-        from src.AeroMod import Z_REF, wind_gradient
+        from python_vpp.AeroMod import Z_REF, wind_gradient
 
         assert wind_gradient(Z_REF) == pytest.approx(1.0)
         assert wind_gradient(5.0) < 1.0 < wind_gradient(20.0)
@@ -136,7 +136,7 @@ def test_gradient_reference_height(self):
         assert wind_gradient(5.0) == pytest.approx(np.log(1000.0) / np.log(2000.0))
 
     def test_heel_reduces_cross_wind(self):
-        from src.AeroMod import wind_triangle
+        from python_vpp.AeroMod import wind_triangle
 
         awa0, aws0 = wind_triangle(10.0, 45.0, 3.0)
         awa, aws = wind_triangle(10.0, 45.0, 3.0, 30.0)
diff --git a/tests/test_api.py b/tests/test_api.py
index 87d2fc7..7a4fdcd 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -2,7 +2,7 @@
 
 import numpy as np
 
-from src.api import app
+from python_vpp.api import app
 
 HEADERS = {"content-type": "application/json", "Accept-Charset": "UTF-8"}
 
diff --git a/tests/test_hydro.py b/tests/test_hydro.py
index 2de97b2..4bce1ce 100644
--- a/tests/test_hydro.py
+++ b/tests/test_hydro.py
@@ -2,9 +2,9 @@
 
 import numpy as np
 
-from src.HydroMod import HydroMod
-from src.SailMod import Jib, Kite, Main
-from src.YachtMod import Keel, Rudder, Yacht
+from python_vpp.HydroMod import HydroMod
+from python_vpp.SailMod import Jib, Kite, Main
+from python_vpp.YachtMod import Keel, Rudder, Yacht
 
 
 def _make_yacht(**kwargs):
diff --git a/tests/test_resistance.py b/tests/test_resistance.py
index f395ff4..8dadc3a 100644
--- a/tests/test_resistance.py
+++ b/tests/test_resistance.py
@@ -1,7 +1,7 @@
 import numpy.testing as np_testing
 
-from src.HydroMod import HydroMod
-from src.YachtMod import Keel, Rudder, Yacht
+from python_vpp.HydroMod import HydroMod
+from python_vpp.YachtMod import Keel, Rudder, Yacht
 
 
 def generate_YD41():
@@ -49,7 +49,7 @@ def test_build_interp_func_no_deprecation():
     """Verify build_interp_func doesn't use deprecated interp1d."""
     import warnings
 
-    from src.UtilsMod import build_interp_func
+    from python_vpp.UtilsMod import build_interp_func
     with warnings.catch_warnings():
         warnings.simplefilter("error", DeprecationWarning)
         func = build_interp_func("main", i=1)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 2edba8e..33b0f47 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,8 +1,8 @@
 import numpy as np
 
-from src.SailMod import Jib, Kite, Main
-from src.UtilsMod import _get_cross
-from src.YachtMod import Keel, Rudder, Yacht
+from python_vpp.SailMod import Jib, Kite, Main
+from python_vpp.UtilsMod import _get_cross
+from python_vpp.YachtMod import Keel, Rudder, Yacht
 
 
 def return_YD41_particulars():
diff --git a/tests/test_vpp.py b/tests/test_vpp.py
index 8e85037..bc81fe2 100644
--- a/tests/test_vpp.py
+++ b/tests/test_vpp.py
@@ -3,8 +3,8 @@
 import numpy as np
 import pytest
 
-from src.SailMod import Jib, Kite, Main
-from src.VPPMod import VPP
+from python_vpp.SailMod import Jib, Kite, Main
+from python_vpp.VPPMod import VPP
 from tests.test_utils import return_YD41_particulars
 
 
@@ -162,8 +162,8 @@ def test_speed_increases_with_tws_when_depowered():
 
 def test_stored_points_are_in_equilibrium():
     """Every stored point satisfies force and moment equilibrium."""
-    from src.UtilsMod import KNOTS_TO_MPS
-    from src.VPPMod import RESID_TOL
+    from python_vpp.UtilsMod import KNOTS_TO_MPS
+    from python_vpp.VPPMod import RESID_TOL
 
     vpp = _upwind_vpp(np.array([6.0, 20.0]), np.linspace(30.0, 120.0, 4))
     vpp.aero.sails[1] = vpp.yacht.sails[1]
@@ -191,8 +191,8 @@ def test_kite_heel_capped():
 
 def test_infeasible_kite_left_unsolved():
     """A kite that cannot be held at the heel limit is stored as 0, not a fake point."""
-    from src.UtilsMod import KNOTS_TO_MPS
-    from src.VPPMod import RESID_TOL
+    from python_vpp.UtilsMod import KNOTS_TO_MPS
+    from python_vpp.VPPMod import RESID_TOL
 
     yacht = return_YD41_particulars()
     yacht.sails = [Main("MN1", P=16.60, E=5.60, Roach=0.1, BAD=1.0),
@@ -297,7 +297,7 @@ def test_parallel_method_accepted():
 
 def test_sym_kite_vpp_runs():
     """VPP runs with symmetric spinnaker coefficients."""
-    from src.YachtMod import Keel, Rudder, Yacht
+    from python_vpp.YachtMod import Keel, Rudder, Yacht
     yacht = Yacht(
         Name="YD41", Lwl=11.90, Vol=6.05, Bwl=3.18, Tc=0.4, WSA=28.20,
         Tmax=2.30, Amax=1.051, Mass=6500, Ff=1.5, Fa=1.5, Boa=4.2, Loa=12.5,
diff --git a/tests/test_yacht.py b/tests/test_yacht.py
index 7f1a1b9..cc6e61d 100644
--- a/tests/test_yacht.py
+++ b/tests/test_yacht.py
@@ -1,7 +1,7 @@
 import numpy as np
 import pytest
-from src.YachtMod import Yacht, Keel, Rudder, ShortKeel
-from src.SailMod import Main, Jib
+from python_vpp.YachtMod import Yacht, Keel, Rudder, ShortKeel
+from python_vpp.SailMod import Main, Jib
 
 
 def _minimal_yacht(**overrides):