J/124
J/Boats · Rod Johnstone · 2005
Updated
The J/124 is a 12.38 m semi-displacement racing yacht designed by Rod Johnstone and built by J/Boats, first launched in 2005. It races in Class B.
Length
12.38 m
40′ 7″
Beam
3.47 m
Draft
2.11 m
Displacement
5.7 t
Sail area
80 m²
On the podium
Where a J/124 finishes when she goes racing.
0
Wins
0
Seconds
2
Thirds
3
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 3 starts by 1 boat between 2025, counting races with six boats or more.
Recent regattas
The latest events where a J/124 was on the start line, named as the organisers publish them.
GBCA ORC Championship2025
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: 2 races of 10 NM or less carry a published distance.
Offshore & coastal
—
Not enough data yet: 1 race over 10 NM carry a published distance.
Who she races against
The designs a J/124 actually lines up with, most often first. The bar shows how those meetings ended.
Met too few times for a figure:
Melges 24 (3 meetings), J/121 (3 meetings), J/109 (3 meetings), First 36.7 (3 meetings), J/105 (3 meetings)
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
5.84
37°
Beam reach
9.43
90°
Broad reach
11.89
135°
Downwind VMG
9.10
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.
It needs pressure to show what it can do. Give it a fresh day and long legs and it delivers more than it promised; in a drifter it is working uphill.
Where it gains
Its best ground is on a broad reach once it pipes up, where it outruns what it looks like on paper, and by a margin worth having. It holds that advantage running deep 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 1.4 kn either way.
At 10 knots this design makes back more than its rating asks on the broad reach.
How fast is a J/124
Boat speed in knots, by true wind angle and wind strength.
| Angle | 6 kn | 10 kn | 14 kn | 20 kn |
|---|---|---|---|---|
| Beat VMG | 3.66 | 5.17 | 5.66 | 5.84 |
| 52° | 5.76 | 7.48 | 7.92 | 8.14 |
| 60° | 6.24 | 7.70 | 8.15 | 8.42 |
| 75° | 6.56 | 8.00 | 8.49 | 8.92 |
| 90° | 6.41 | 8.01 | 8.71 | 9.43 |
| 110° | 6.46 | 8.30 | 9.11 | 10.15 |
| 120° | 6.32 | 8.32 | 9.41 | 10.80 |
| 135° | 5.63 | 7.95 | 9.24 | 11.89 |
| 150° | 4.71 | 7.08 | 8.44 | 10.50 |
| Run VMG | 4.08 | 6.13 | 7.34 | 9.10 |
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 750 kg.
Rigging
J/124 rig and sail dimensions
A J/124 carries 14.76 m of mainsail hoist on a 5.18 m boom, a forestay 14.78 m above the deck and a 5.84 m bowsprit. Typical figures across the 3 boats measured under the current VPP, with the range each one spans.
Rig
Sails
The spinnaker spreads widest of all — 131 to 157 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.