Python Sailocus (Center-of-Effort)

paul.dicarlo@gmail.com

Blog: https://sailocus.blogspot.com/

The purpose of this project is to explore creation of REST APIs and Python. The intent is to provide APIs (and a web app) that allows for creation of sail geometries and calculation of the sail's Center of Effort (CoE).

"the approximate locus of net aerodynamic force on a craft with a single sail is the centre of effort (ce) at the geometric centre of the sail". https://en.wikipedia.org/wiki/Forces_on_sails

Background

Sailocus is an attempt to write code that will explore the aerodynamic forces on sails. It is meant to be a development exercise to build my proficiency in some new programming languages... as well as better understand forces on sails... and maybe even design my own sails someday.

The Name Sailocus

The name Sailocus comes from "sail" and "locus" (see quote above)

Simple Example

from sailocus.sail import sail
from sailocus.geometry import point
from sailocus.svg import svg

# we're making a 4-sided sail here so we need
# to have the peak, throat, take, and clew...
# Point(x,y) where x/y are millimeters and ints
peak = point.Point(213, 510)
throat = point.Point(10, 233)
tack = point.Point(0, 0) 
clew = point.Point(397, 29) 

# create a Sail with the points
xsail = sail.Sail(tack=tack, clew=clew, head=None, peak=peak, throat=throat, sail_name = "Four sided sail")
xsail.validateSail()
print(f"CoE={xsail.coe}")

# Create SVG file of sail and its CoE
xsvg = svg.SVG()
pathToFile = "./simpleSailFromClass.svg"
off_set = point.Point(25,25)
xsvg.createSailSVG(xsail, pathToFile, True, off_set)

Caveat

You should only use sails designed and made by a professional. This code is just for a learning excercise.

Project Todos

Future thigns ao add to this project

• Improve math/geometry code, handle edge conditions, etc
• JWT tokens for Rest APIs (just to have them)
• Hook up database, allow logins and ability to save/modify/delete sails in db
• Login/create login pages
• Group of premade dimensions for common sails (later in db)

Setting up environment

python3 -m venv .venv 
source .venv/bin/activate
pip3 install  -r requirements.txt

Saving the environment

 pip3 freeze > requirements.txt

Testing

python3 -m pytest
mypy .

Main modules:

• main.py - simple. Uses PyQt5 to display SVG of COE of simple sail.
• main_fastapi.py - Use a URL similar to http://127.0.0.1:8000/sailocus/api/v1/coe/
  • And to get the Swagger docs: http://127.0.0.1:8000/docs
  • sample script to invoke post_request_create_svg_fastapi.sh
  • for the FastAPI web app
    • If only HTTP enabled: http://127.0.0.1:8000/sailocus/api/v1/sailocus/
    • If HTTPS enabled: https://127.0.0.1:8000/sailocus/simple/
• main_flask.py - DEPRECATED. Use a URL similar to http://127.0.0.1:5000/sailocus to get a simple form that takes sail coordinates for a 4-sided sail, calculates the CoE, and then displays an SVG of the sail/CoE.
  • sample script to invoke post_request_create_svg_flask.sh
  • for the Flask web app: http://127.0.0.1:5000/sailocus

Sample HTML

Screen grab of first time getting simple code path to work for a web interface to generate the Center of Effort (CoE).

Notes

• If you are like me and use a debugger, you may want to set this in your VSCode launch configruations: "justMyCode": false