J/125
J/Boats · Rod Johnstone · 1997
Updated
The J/125 is a 12.53 m planing racing yacht designed by Rod Johnstone and built by J/Boats, first launched in 1997. It races in Class A.
Length
12.53 m
41′ 1″
Beam
3.21 m
Draft
2.48 m
Displacement
4.2 t
Sail area
97 m²
On the podium
Where a J/125 finishes when she goes racing.
0
Wins
0
Seconds
0
Thirds
1
Starts
Not enough races yet for a percentage — these are the counts so far. We keep collecting results, so this will fill in.
Read from 1 start by 1 boat between 2025, counting races with six boats or more.
Recent regattas
The latest events where a J/125 was on the start line, named as the organisers publish them.
Rolex Middle Sea Race2025
Raced one we are missing?
Report a regattaRound the buoys, or offshore
A short windward-leeward and a night at sea ask different things of a boat. Here is how this one does in each.
Round the buoys
—
Not enough data yet: no races of 10 NM or less carry a published distance.
Offshore & coastal
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Not enough data yet: 1 race over 10 NM carry a published distance.
Who she races against
The designs a J/125 actually lines up with, most often first. The bar shows how those meetings ended.
Met too few times for a figure:
Pac 52 (1 meeting), Sun Fast 3300 (Andrieu) (1 meeting), Sun Fast 3200 (1 meeting), JPK 10.30 (2 meetings), Irc 52 (1 meeting), TP 52 (Carkeek) (1 meeting), Comet 38 (Vallicelli) (1 meeting), Dufour 34 (1 meeting), Arcona 380 (1 meeting), First 40 (1 meeting), Botin 56 (1 meeting), Farr 30 (1 meeting), J/109 (1 meeting), Sun Fast 3600 (1 meeting), Elan 450 (1 meeting), IMX 40 (1 meeting), Cookson 50 (1 meeting), J/111 (1 meeting), First 45 (Briand) (1 meeting), TP 52 (Judel/Vrolijk) (1 meeting), X-41 (1 meeting), Mat 122 (1 meeting), Swan 42 (3 meetings), Xp 44 (2 meetings), Dufour 44 (1 meeting), J/121 (1 meeting), Dehler 41 (Judel/Vrolijk) (1 meeting), Mat 11.80 (1 meeting), DK 46 (1 meeting), First 45 (Farr) (1 meeting), Neo 400 (1 meeting), Swan 56 (1 meeting), HH 42 (1 meeting), Sydney 43 (1 meeting), Farr 45 (2 meetings), Pogo 36 (3 meetings), Neo 430 (2 meetings), X-482 (1 meeting), Ice 52 (1 meeting), Swan 651 (1 meeting)
Speed at every angle
The shape of this design's speed, drawn from the measured fleet. Pick a wind and watch it stretch.
Upwind VMG
6.10
37°
Beam reach
10.41
90°
Broad reach
13.33
135°
Downwind VMG
10.89
170°
Speed in knots at 20 knots of true wind. Green marks the angles that pay: the closest useful beat and the deepest run worth sailing.
Where it wins and where it pays
Every boat is judged against its own measurements — length, weight, sail area. The quicker those say it should be, the more it has to deliver just to break even. Going fast is not enough: it has to go faster than its own numbers promised.
The stronger it blows, the better this design looks. On a windy coastal course it is in its element; on a light-air windward-leeward it has to be sailed well to hold on.
Where it gains
Its best ground is running deep in a strong breeze, where it outruns what it looks like on paper, and by a margin worth having. It holds that advantage on a broad reach as well, so the gain is not down to one leg of the course.
Where it pays
There is no condition where it falls away badly, which is worth something over a season of mixed weather.
Above the line it delivers more than promised and gains on the fleet. Below, it falls short. Move the wind: plenty of boats sit on one side in the light and the other when it blows.
Full width is 1.8 kn either way.
At 10 knots this design makes back more than its rating asks on the broad reach.
How fast is a J/125
Boat speed in knots, by true wind angle and wind strength.
| Angle | 6 kn | 10 kn | 14 kn | 20 kn |
|---|---|---|---|---|
| Beat VMG | 4.29 | 5.64 | 5.94 | 6.10 |
| 52° | 6.55 | 8.02 | 8.32 | 8.55 |
| 60° | 6.91 | 8.26 | 8.63 | 8.93 |
| 75° | 7.14 | 8.52 | 9.11 | 9.64 |
| 90° | 6.98 | 8.55 | 9.45 | 10.41 |
| 110° | 6.75 | 8.67 | 9.68 | 11.23 |
| 120° | 6.62 | 8.80 | 10.09 | 11.90 |
| 135° | 5.92 | 8.45 | 10.29 | 13.33 |
| 150° | 4.95 | 7.47 | 9.17 | 12.57 |
| Run VMG | 4.29 | 6.47 | 7.95 | 10.89 |
How they are set up
The range each sail spans across the fleet.
Nearly all carry a folding propeller. A bowsprit is standard across the fleet. Crew weight is declared around 720 kg.
Rigging
J/125 rig and sail dimensions
A J/125 carries 14.17 m of mainsail hoist on a 5.46 m boom, a forestay 14.94 m above the deck and a 7.18 m bowsprit. Typical figures across the 7 boats measured under the current VPP, with the range each one spans.
Rig
Sails
The spinnaker spreads widest of all — 154 to 168 m² depending on bowsprit and set-up. Before ordering a sail, read the figure on your own measurement record rather than the typical one for the design.