Guidelines or formulas for how much water to dump in narrow or weakthermal racing?

On Saturday, May 16, 2020 at 10:59:37 AM UTC-7, Charles Ethridge wrote:
Thinking about Tim Taylor's comment: Yes, it feels like this is something that software would be good at solving. (I'm a 35 year software engineer, BTW...just not an aeronautical engineer :-) )

A few years ago I wrote a script that computes the climb rate of a glider based on the factors you mention plus air density (thermals widen significantly at altitude) and the glider's performance polar. The calculations for climb rate given thermal strength & width are actually much simpler than you might expect, the vast majority is just trigonometry.
Modeling thermals is a little more tricky and the lift distribution varies drastically depending on which model you believe.
The model I have is by no means perfect for several reasons, a big one being that glider polars are measured in straight flight and as such, they are not necessarily representative of performance during circling flight (this effect is amplified for gliders with significant di/polyhedral and/or winglets). At some point it might be worthwhile to actually measure circling performance to avoid misappropriating polar data for this. Plus, this model does not take into account individual gliders' handling characteristics at different wing loadings, which is a non-negligible issue in real life.
To be clear, I don't suggest blindly following the numbers provided below.

If you aren't a flight dynamics expert but have some fundamental understanding of aerodynamics, I highly suggest reading the following source if you wish to learn more.
https://booksite.elsevier.com/978012...SAILPLANES.pdf

The results for a few gliders we
Discus 2a:
For lift stronger than 5kn, max gross.
For lift [3kn, 5kn], half ballast.
For lift weaker than 3kn, no ballast.

Standard Cirrus:
For lift stronger than 3kn, max gross.
For lift [2kn, 3kn], half ballast.
For lift weaker than 2kn, no ballast.

ASW-22BL (750kg):
For lift stronger than 4kn, max gross.
For lift [2kn, 4kn], half ballast.
For lift weaker than 2kn, no ballast.

This is only useful for average climbrate throughout your entire flight. If you're hauling for most of your flight with strong conditions and fail to switch gears with changing conditions, get low and have to take a weak climb to get back up, you might as well throw this information out the window.

The non-binary decision-making involved in resolving situations like this one or (avoiding it altogether) is what separates the great pilots from the decent ones, and the results of such decisions are reflected in big differences in average speed.

I am open to discussion regarding sharing my code (written in MATLAB) but in its current state it may not be easily comprehensible to an average user.

Thomas