Metrics
Eight tiles above the panels summarize key results. Each has an ⓘ InfoTip in the app — this is the extended reference.
Take-off
Minimum speed where calm lift equals total weight.
- Below that the foil does not fly (take-off zone in panel D)
- When pumping, stay above it — otherwise touchdown
- More area or less mass lowers the value
Best glide
Speed with the best whole-rig lift-to-drag.
- Default for the analysis slider and panels C/D/E with goal Efficiency
- Often the most comfortable pump point: less thrust fighting drag
- Subline: L/D at that point
Vmax
Highest useful steady ride speed of the rig — the high-speed end of the curve, not the sweep grid’s edge.
Criterion
- Point still trimmable (
solve_trim) - L/D at least 40 % of peak L/D on the curve
- Adaptive speed sweep up to 25 m/s, so Vmax does not stick to the default grid (~14 m/s)
What it is not
- Not GPS / session top speed
- Not “pump forever at this power” — the subline only lists steady power (drag × speed) at the Vmax point
- Pump-sustainable top speed (power budget over time) is intentionally out of scope
Goal Efficiency | Speed
| Goal | Analysis marker | Trade-off default |
|---|---|---|
| Efficiency | Best glide | unchanged / all-round |
| Speed | Vmax | focus High speed |
Persisted locally as pumpfoil.intent.v1. Visible from skill Advanced / Pro (profile enum downwind counts). Beginners and intermediate keep take-off and best glide as before; intermediate can still pick High-speed focus in the trade-off.
Compare: Two setups with High-speed focus — higher Vmax ranks as the speed win; take-off regression stays visible in the bullets.
→ What changes? · Panel D
L/D max
Best lift-to-drag among all trimmable speed points — whole rig, not front wing alone (panel C).
- Higher → less pump thrust needed
- Subline: drag at the best-glide point
Pump power
| Column | Meaning |
|---|---|
| Mechanical | drag × path speed in the settled cycle |
| Metabolic | roughly what you feel (~ muscle efficiency) |
From the last cycles of the simulation. Panel A stops when the foil no longer sustains.
Distance per cycle
Distance per pump stroke at mean speed of the sustaining solution.
- Couples frequency and speed: ≈ mean speed ÷ frequency
- More distance at the same power = more efficient pumping
Reduced frequency
How “fast” the pump rhythm is relative to wing depth and speed.
- Typically 0.05–0.2
- Higher → stronger lag and damping of lift
- See also panel B (k in the header)
Reynolds (front wing)
Flow scale at the front wing: speed × wing depth ÷ viscosity.
- Affects friction and stall proximity
- Smaller wing depth or colder water → more drag
Reading comparisons correctly
Core message
Relative changes between two setups are more reliable than absolute km/h or watt values. Systematic model errors often cancel in comparisons.