Glider Polar Visualiser

What it’s for

Shows how a glider’s polar curve shifts with ballast and MacCready setting, and what that means for speed to fly, across 200+ glider types.

How to use it

Open polars.neale.dev and pick a glider. Set a thermal strength and a ballast load, and the curve and the derived speeds update with it. Add a second glider to compare the two.

Features

• Over 200 glider types, with polar data taken directly from XCSoar’s codebase
• Hover any point on the curve to read the sink rate and glide ratio at that speed
• MacCready speed-to-fly: for a given thermal strength it gives the optimum inter-thermal cruise speed and the effective cross-country speed, and marks the tangent point on the polar
• Ballast adjustment by wing loading, which shifts the whole curve right and down
• Two gliders overlaid on the same axes for a direct performance comparison
• Multiple unit systems

How it works

Polar data is fetched from the XCSoar source, parsing the struct definitions with regex. A quadratic is fitted through the three measured points using a Cramer’s rule regression, and MacCready theory is applied to the fitted curve.