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About This Tool
This tool calculates the catenary curve required for a tarp or tent seam to ensure it remains taut when pitched. A straight cut will sag under tension, but a catenary cut removes this excess material.
The tool also compares the true catenary to a simpler parabolic approximation. For shallow cuts, the difference is minimal, but for deeper cuts, the catenary is more accurate.
Input Parameters (use consistent units, e.g., meters or inches):
- Seam Length (Span): The final, straight-line length of the seam / ridgeline.
- Cut Depth (Sag): The maximum depth of the curve you want to cut. This determines how much "belly" is removed.
- Steps: The number of coordinate points to calculate (higher = smoother curve for plotting).
Example:A very general rule of thumb is 1/4 inch for every foot of length (~2cm per metre). Not much is required.
Download 1:1 Scale SVG Template
Generate a 1:1 scale SVG file of the catenary curve. Ensure the units below match the units you used for the inputs above. This file is ideal for printing or for use with a vinyl/laser cutter to create a physical template.
Coordinate Data
Use these coordinates to plot the curve on your fabric. The centre of the ridgeline corresponds to X=0, with the Y-value representing the sag.
