BTF · Downwind Performance
Pooled telemetry across every logged race says the boat is usually sailed shallower than its own best downwind angle. This isolates one lever, sailing 145–155° TWA as the default instead of the current ~132° habit — wind-axis VMG only, no course or finish-line tactics — and asks what that alone is worth.
Every downwind point in polar_coords_race at 8kt+ TWS, binned every 5° of true wind angle. VMG = Bsp × cos(TWA), averaged per point.
421.6 hours of pooled downwind sailing (TWS ≥ 8kt, all logged races), actual vs. holding 145–155°.
The gain holds across the whole range sailed, tapering only at the top end where the 24kt+ bin is a coarse catch-all.
| TWS band | Hours logged | Actual VMG | 145–155° VMG | Gain |
|---|---|---|---|---|
| 8kt | 39.8 | 4.75kt | 6.08kt | +28% |
| 10kt | 48.8 | 5.87kt | 7.30kt | +24% |
| 12kt | 56.9 | 6.59kt | 8.16kt | +24% |
| 14kt | 56.7 | 7.50kt | 9.28kt | +24% |
| 16kt | 65.3 | 8.58kt | 10.61kt | +24% |
| 18kt | 70.9 | 9.53kt | 12.01kt | +26% |
| 20kt | 49.8 | 10.61kt | 13.36kt | +26% |
| 22kt | 21.3 | 12.16kt | 14.59kt | +20% |
| 24kt+ | 11.9 | 13.42kt | 15.30kt | +14% |
The pooled number is dominated by one race — TransPac ’15 alone supplies about 41% of the pooled downwind dataset, thanks to its long, steady trade-wind runs. Worth checking whether the same logic, run against individual races in isolation, gives the same answer.
Single-race check
106.4 hours of downwind sailing (TWS ≥ 8kt) at a weighted-average 133.7° TWA — almost identical to the pooled 132.1° habit, which is exactly what you'd expect given how much of the pooled dataset this one race supplies.
| TWS band | Hours logged | Actual VMG | 145–155° VMG | Gain |
|---|---|---|---|---|
| 8kt | 11.2 | 5.99kt | 6.89kt | +15% |
| 10kt | 18.6 | 6.72kt | 7.49kt | +11% |
| 12kt | 20.7 | 7.20kt | 8.49kt | +18% |
| 14kt | 19.0 | 8.11kt | 10.29kt | +27% |
| 16kt | 17.1 | 9.41kt | 12.09kt | +29% |
| 18kt | 13.4 | 10.67kt | 13.20kt | +24% |
| 20kt | 4.7 | 12.15kt | 14.52kt | +20% |
| 22kt | 1.4 | 13.78kt | 16.15kt | +17% |
| 24kt | 0.3 | 14.71kt | 16.94kt | +15% |
Same direction, slightly smaller effect on this one race: +21.3% here vs. +24.1% pooled — close enough to say the pooled number isn't an artifact of averaging across dissimilar races. The top two bands are thin for a single race (22kt n=200, 24kt n=33 — that last one is only ~2.75 minutes of steady-state 145–155° sailing) and shouldn't be leaned on individually, though they don't move the overall number much given how few hours they represent.
Single-race check
67.8 hours of downwind sailing (TWS ≥ 8kt) at a weighted-average 133.5° TWA — again close to the pooled 132.1° habit, but a shorter, more coastal point-to-point course than TransPac's sustained trade-wind runs.
| TWS band | Hours logged | Actual VMG | 145–155° VMG | Gain |
|---|---|---|---|---|
| 8kt | 7.7 | 4.76kt | 6.07kt | +27% |
| 10kt | 8.5 | 5.92kt | 7.36kt | +24% |
| 12kt | 7.5 | 6.60kt | 8.28kt | +25% |
| 14kt | 5.2 | 7.49kt | 9.53kt | +27% |
| 16kt | 6.5 | 8.81kt | 10.44kt | +18% |
| 18kt | 8.9 | 10.04kt | 11.59kt | +15% |
| 20kt | 9.4 | 11.17kt | 12.56kt | +12% |
| 22kt | 7.5 | 12.59kt | 13.79kt | +10% |
| 24kt+ | 6.8 | 14.44kt | 15.47kt | +7% |
Positive, but the smallest of the three checks: +16.0% here vs. +24.1% pooled and +21.3% on TransPac ’15 — still a real gap in the same direction, just shallower. Gain runs highest at the lower wind bands (+24–27% at 8–14kt) and tapers as breeze builds (+7% at 24kt+), the reverse of the pooled table's own top-end taper — and the low-wind bands here are thin for a single race (n=30–52 per band under 145–155°/8–14kt), so that low-end number is suggestive rather than solid. Consistent with a shorter coastal course spending less time in the kind of sustained, steady-state deep running that let TransPac and the pooled fleet push the angle harder.
Pulled every downwind point (TWA 90–165°, TWS ≥ 8kt) from polar_coords_race, pooled across every race group currently logged. "Actual" is the real historical VMG per 2kt TWS band, weighted by real elapsed time and including maneuver time — it's what actually happened. "145–155°" is the steady-state VMG the boat has already demonstrated in that same wind band, with gybes/tacks excluded via the isTransition flag, so it's measured capability, not aspiration.
Each TWS band's actual hours were then re-priced at that band's 145–155° rate and summed, giving the total hypothetical distance for the identical time already logged. Every number on this page traces back to a live query against production telemetry, not a model.