How to shred, mathematically.
You get better at what you can measure. Shred Score gives you something to chase: carving harder, carrying more speed through your turns, and linking them more consistently. Getting shreddier, with math!
A low score isn’t a verdict on your riding. If it misses a good run, help shape Shred.
Speed, lift, and the shape of a carve.
Pick up speed from a swell and bank across its face. Your foil’s lift tilts with you, and a sideways component of that force helps redirect your momentum through the arc.
That’s sideways acceleration: your velocity changes direction, even if your speed stays steady.
For speed v and turn radius r, the sideways acceleration a is:
Speed is squared. Double it around the same arc and the acceleration quadruples. A fast, open carve can produce substantial sideways acceleration; tighten the arc at that speed and it rises further.
What does G mean?
G expresses that sideways acceleration as a fraction of gravity. Standard gravity, written g₀, is about 9.81 m/s². Divide by it to get G.
0.5 G means sideways acceleration half as large as gravity, about 4.9 m/s².
For example
At 10 m/s (about 19.4 knots) around a 20 m radius, a = 10² ÷ 20 = 5 m/s². So G = 5 ÷ 9.81 ≈ 0.51.
Foil Run estimates G from GPS speed and curve shape. It does not measure actual board lean, rider force, or effort.
How far around did you go?
Rotation is the total change in direction through a bend.
The maths uses radians. One radian is the angle you turn while travelling an arc as long as the radius, about 57°. A full circle is 2π radians.
Our example turn through 90° covers π/2, or about 1.57 radians.
Turning intensity × turning angle.
The physics gives us lateral G. Our scoring choice is to accumulate it over angle turned. That’s a bend’s base points, before any linking bonus.
One base point means 1 G held through one radian. We write that as G·rad.
Our example, continued
Hold that 0.51 G through the 90° turn: 0.51 × 1.57 ≈ 0.80 base points.
Real turns tighten and open out. We weight the average G by how much direction changes in each part, so the parts where more turning happens count more.
The calculus view
Let θ be turning angle in radians and P be base points. For a bend that turns in one direction, the score approximates:
Foil Run uses a smoothed GPS path. If there are small reversals, it averages G over the rotation in the bend’s direction, then multiplies by the net angle after subtracting the reverse rotation.
There is no separate smoothness bonus. In the ideal maths, at equal speed, path length, and total rotation, concentrating the turning into tighter sections can score more than a constant-radius curve.
Same 0.50 G. More turn, more points.
90°
π/2 rad
0.79G·rad
180°
π rad
1.57G·rad
360°
2π rad
3.14G·rad
A gentler sweep can earn just as much.
At the same speed, the second turn below has twice the radius and half the G. It turns through twice the angle, so both earn the same base points.
| Average G | Rotation | Base points |
|---|---|---|
| 0.80 | 90° (π/2) | 1.26 |
| 0.40 | 180° (π) | 1.26 |
Both examples assume qualifying turns, before combo bonuses.
Points accumulate over angle, not time. Taking longer adds no separate bonus, and smoothness itself is not a score input.
Carves, shreds, and combo bonuses.
For a scored bend, base points determine its name:
- Weave
- Under 0.50 base points.
- Carve
- 0.50 or more. Can link into a combo.
- Shred
- A carve worth π/2 base points or more (about 1.57). That threshold equals 0.5 G through 180°.
Linked carves get a bonus. The first uses ×1.0, the second ×1.1, the third ×1.2, up to ×2.0.
Our 0.80-point example is a carve. As the second carve in a combo, it earns 0.80 × 1.1 ≈ 0.88 points.
A weave, unscored bend, or break ends the combo; you keep the points earned. A scored full rotation jumps to ×2.0 for itself and the rest of its combo.
Your Shred Score is those points per minute of riding. A long run doesn’t win just by lasting longer. A run needs a minute of riding to get a score. Course boards still rank total points, not points per minute.
Analyze also shows your Best minute: the most points in any 60 seconds of one continuous ride. Swell and terrain still matter, so compare similar conditions or attempts on the same Course.
Follow the turns and their points.
Choose a turn to see its G, rotation, and base points. Then show what the linking bonus adds.
Thatspec · Swell City to Hatchery Point
Illustrative scores from an earlier scoring version, on a public GPS path with estimated timing. Not a current analysis.
Carve
Turn 1 of 7
- Rotation
- 126.0°2.20 rad
- Lateral G
- 0.57G (est.)
- Base points
- 1.26G·rad
126° of rotation and 0.57 G put this bend comfortably over the 0.50-point carve threshold.
Linked turn 1: ×1.0
1.26 × 1.0 ≈ 1.26 points
The first carve starts the chain at its base value.
See the combo bonus.
Turns 1–6 form a combo: each carve earns a bigger bonus. Turn 7 is a weave. It earns its own base points and ends the combo.
Why might a turn or score look wrong?
For the full-rotation bonus, we accept 330° or more to allow for GPS noise. A shred badge alone does not trigger that bonus.
Small wobbles, slow turns, incomplete turns, and unreliable GPS evidence may earn no points. Scoring also depends on progress down the run. Tap a bend on a selected Run in Analyze to see its points or why it was unscored.
Analyze scores a detected Run; a Course scores between its gates and pauses scoring during detected redeploy recovery. They can include different turns and produce different totals.
Does it feel like your ride?
So far, most of the tuning has been on Gorge riding. Different swell, terrain, and riding styles may need a different approach. We’d love alpha testers outside the Gorge to help shape it.
“That felt amazing, but the score missed it” is exactly the feedback we need. Open your track in Analyze and use Feedback to tell us where to look, what you were doing, and what felt good.
This is experimental GPS-based scoring, not a measure of skill or effort. You can be shredding before we’ve figured out how to measure it. Scores may change as we develop it.