SailEdge™ makes CE visible — computed for every sail, every wind condition, every configuration. In three dimensions. In real time.
Explore Your Edge See the Edge Map →Force Balance Diagram
Most references to Center of Effort treat it as a point on a sail plan drawing. SailrScience computes it as a three-dimensional position that moves with every change in wind, sail selection, reef state, and heel angle.
How far forward or aft CE sits along the deck. This is the axis that drives weather helm. Move CE forward and the boat wants to bear away. Move it aft and you get helm pressure.
How high CE sits above the waterline. Higher CE means more heeling moment for the same force. Reefing lowers CE. A staysail keeps CE low. This is the axis that governs comfort and control.
How far CE moves to leeward under heel. As the boat heels, CE shifts laterally — increasing the moment arm and changing the balance. This is the axis most sailors never think about.
Most models place CE from generic rig ratios. SailrScience uses centroid geometry — the measured planform of each sail defines where force actually acts. Tack, head, clew, plus roach profile when available.
A high-roach main puts CE higher and further aft. A deep-LP genoa moves it forward. These aren’t assumptions — they’re geometry, traced back to sailmaker cut-sheet measurements. When you change sails in the model, CE moves for the right reasons.
CE is one piece of the force balance. See how drive, side force, heel, and depower all connect. The Physics →
SailrScience computes CE individually for each sail — main, headsail, code sail — and then calculates the force-weighted combined CEeff that represents where the total aerodynamic force acts on your boat. The combined CE marker points straight down to the deck, showing you exactly where the resultant force meets the hull. This is the number that matters for balance.
Sitella (Cape 31) broad reaching at TWA 134°, 12 kt — Main (Mn-25), Headsail (J1-25), Asymmetric (A1.5-25)
More area moves CE forward and higher. Your digital twin shows exactly where CE lands with the new sail at every wind angle — before you spend the money.
CE is too far aft, too high, or both. See CE position at 16 kt with your current plan — and what happens when you switch to the jib, add a reef, or both.
Reefing reduces area but lowers CE height, cutting heel moment. At some wind speed, reduced heel gives back more than the lost area costs. CE shows you where that crossover is.
For sailmakers iterating on a design, CE tracks how planform changes shift the force application point. Different roach, different LP, different CE trajectory — visible across every regime.
Center of Effort above the water. Center of Lateral Resistance below it. The relationship between them determines whether your boat has weather helm, lee helm, or neutral balance. SailrScience computes both — and shows you how every sail change, reef, or furl shifts that balance.
When the mainsail blankets the headsail at deep angles, occlusion reduces headsail lift and shifts the combined CE. The balance you see reflects sail interaction, not just individual sail positions.
This is what experienced sailors feel. When they say "the boat feels heavy" or "she's balanced beautifully," they're describing the CE—CLR relationship. SailrScience makes that feel visible — the offset in meters, the resulting rudder angle, and how it changes with every puff and header. What took decades to develop as instinct, your crew can now see on screen before leaving the dock.
The force-weighted center of all aerodynamic forces. Moves forward with bigger headsails, moves up with more sail area, drops with reefs. The variable you control through sail selection and trim.
The center of all hydrodynamic resistance — keel, rudder, hull. Relatively fixed by the boat’s design but shifts dynamically with boat speed and heel angle. The anchor point that CE pushes against.
CLR (Center of Lateral Resistance) — the underwater pivot point where hydrodynamic side forces act on the hull and keel.
The horizontal distance between CE and CLR — the offset that creates helm. CE ahead of CLR means lee helm. CE aft of CLR means weather helm. In sign convention terms, positive Lead is forward (lee helm), negative is aft (weather helm). A few tenths of a meter is the difference between a balanced boat and one that fights you.
The vertical distance from CE down to CLR — the lever that turns side force into heeling moment. Higher CE, longer arm, more heel. Reef the main and the arm shortens before the force drops. That’s why a first reef often feels like free speed.