Bill angle can change simulated depth and action, but it does not give a universal depth rule. In our square-bill example at 0.6 m/s, 50°, 60° and 70° bills produced mean simulated depths of 0.698 m, 0.524 m and 0.338 m over the final four seconds. Those values apply to this setup, not every crankbait.
What does the angle mean?
In MakeMyLure, the angle is measured downward from the body’s forward axis, not from the water surface or a photograph of the lure at rest. Record that convention with your results. An apparent bill angle in a side photograph also depends on the body’s pitch.
Keep the comparison controlled
Copy one design rather than choosing three different presets. Keep the body, bill length and width, line-tie setting, ballast, hooks, materials, print settings and water conditions unchanged. Change only the bill-angle input. Reset each run and compare equal time windows under the same retrieve.
One edited input does not mean one isolated physical effect. The geometry and as-built mass are rebuilt after an angle change. In this example, finished-model mass changed from 11.695 g at 50° to 11.304 g at 70° because the lip and printed tab geometry changed. The experiment compares the resulting complete designs; it does not isolate hydrodynamic angle alone.
Read depth, wobble and roll together
Allow the start-up transient to pass before reading action metrics. We ran each design for 10 simulated seconds and analyzed seconds 6–10. Mean depth is the average over that window. Wobble and roll amplitudes are peak-to-peak angles; they are not the movement to one side of the centerline.
The 50° design ran deeper in this model, while wobble frequency stayed close to 3.64–3.66 Hz across all three designs. Wobble and roll amplitudes did not follow a simple increasing or decreasing order. A deeper curve therefore did not mean that every action measure improved.
Why tank depth is not cast diving depth
This experiment uses a 3 m tank towline and a constant 0.6 m/s tow speed. The line constrains the motion. It does not model a full cast with a changing retrieve distance, so its deepest point is not a claim about the maximum depth you will achieve when fishing. If the question is casting depth, run a separate cast scenario and state the line and retrieve conditions.
Reproduce the comparison
Open one of the public experiment models. You can inspect the model and run its swimming simulation without changing the shared original.
Sign in and copy the snapshot to your own design if you want to edit it. Keep an unchanged baseline and create separately named angle variants.
Keep the same scenario, speed and line settings, reset each run, and record the same duration and analysis window. Download the public input JSON and CSV to compare with the published setup.
If you print prototypes, record actual mass, materials, hardware and water-test results separately. Do not label numerical output as a physical measurement.
What this experiment cannot establish
The results are deterministic comparisons from a simplified numerical model. They do not validate a universal bill-angle formula, a real lure’s maximum diving depth, manufacturing accuracy, snag resistance or catch rate. No physical water test is reported here. Use a prototype and controlled measurements to test those claims.