Target Speed, Target Angle: How to Read a Diam 24 Polar
Walk past a serious Diam 24 campaign and you'll often find a small, laminated card taped right where the trimmer can glance at it mid-race — rows of numbers by wind speed and angle, worn soft at the corners from being checked a hundred times a regatta.
That card is the polar, reduced to exactly what a crew needs in the moment: what speed should we be doing right now, at this angle, in this breeze?
What a Polar Tells You
A polar is deceptively simple: for a given wind speed, it tells you the boat speed you should be able to hold at any given angle to the wind. Look at the Diam 24's numbers in 10 knots of true wind, from close-hauled out to a beam reach — 9.0 knots of boat speed at a tight 45 degrees, climbing to 13.0 knots by the time you open up to 70 or 80 degrees. Every one of those pairings is a target: a specific speed the boat should be making at that specific angle, in that specific breeze.
The point isn't to hit the highest number on the chart. It's to hit the right number for the angle you're trying to sail — because the fastest boat speed and the fastest way to your next mark are usually two different angles entirely.
Speed Isn't the Target; Progress to the Mark Is
The fastest angle and the fastest route to the mark are rarely the same. What matters is VMG, velocity made good: how fast you're actually closing on the mark. Upwind in 10 knots, the Diam 24 does 9 knots at 45° but 13 knots at 70°. Yet at 45° you're closing on the windward mark at about 6.4 knots, and at 70° at barely 4.4. The extra boat speed doesn't make up for sailing so far off the wind.
That's what a target angle is: the angle where VMG peaks for that wind speed, paired with the boat speed you should be doing there. Because apparent wind shifts as the breeze builds, the peak moves too, and a target angle from one wind band doesn't carry over to another.
Downwind: Faster Isn't Always Better
Downwind the same logic runs the other way. In 6 knots the boat is faster at 100° (7 knots) than at 155° (4.5 knots), but sailing deeper gets you to the leeward mark several times sooner. Heating up in light air builds apparent wind and speed, but only up to the point where the extra distance cancels the gain, and the polar's target angle tells you where that point is.
In 18 knots, boat speed barely changes between 100° and 145°, holding around 19 knots. That's exactly why angle matters so much there: when going deeper costs you almost no speed, it's nearly free progress toward the mark.
Using the Numbers on the Water
None of this matters if the numbers stay on a laminated card nobody looks at. The reason serious crews tape a polar where the trimmer can see it mid-race is simple: it turns "we feel slow" into something specific. If the wind is blowing 14 knots and you're sailing 60 degrees but the boat's only doing 14 knots instead of the 16 the polar says you should be hitting, that's not a vague feeling — it's a two-knot gap with a cause, whether that's trim, a sea state the polar doesn't account for, or dirty air from another boat.
Used well, a target isn't a scoreboard. It's a diagnostic tool — a number that tells you the moment something's off, well before you'd notice it any other way.
Ready to Sail to Your Own Numbers?
Reading a polar is one thing. Building the instinct to check your speed against a target without even glancing at the card — because you already know roughly where you should be — takes time on the water with someone confirming when you're on target and when you're not.