Seam 31
Tsuboi Yacht · Ichiro Yokoyama · 1999
Updated
The Seam 31 is a 9.50 m displacement racing yacht designed by Ichiro Yokoyama and built by Tsuboi Yacht, first launched in 1999. It races in Class C.
Length
9.50 m
31′ 2″
Beam
3.24 m
Draft
2.01 m
Displacement
3.2 t
Sail area
62 m²
On the podium
Where a Seam 31 finishes when she goes racing.
Not enough data yet to show how this design finishes. It has not been found in the race results we have collected so far.
Recent regattas
The latest events where a Seam 31 was on the start line, named as the organisers publish them.
No regattas found yet.
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
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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: no races over 10 NM carry a published distance.
Who she races against
The designs a Seam 31 actually lines up with, most often first. The bar shows how those meetings ended.
Not enough data yet to say who this design races against. No result we have collected puts it on the water beside another design we track.
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
5.25
36°
Beam reach
8.21
90°
Broad reach
9.43
135°
Downwind VMG
7.86
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.
This design is even-tempered. It rewards preparation and crew work more than it rewards picking the right day.
Where it gains
Its best ground is cracked off in a strong breeze, where it goes better than its measurements say it should, and by a margin worth having. It holds that advantage on the beat as well, so the gain is not down to one leg of the course.
Where it pays
It falls short cracked off once the breeze fills, giving away time it never gets back.
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 0.4 kn either way.
At 10 knots this design makes back more than its rating asks on the upwind.
How fast is a Seam 31
Boat speed in knots, by true wind angle and wind strength.
| Angle | 6 kn | 10 kn | 14 kn | 20 kn |
|---|---|---|---|---|
| Beat VMG | 3.73 | 4.90 | 5.17 | 5.25 |
| 52° | 5.61 | 6.79 | 7.03 | 7.16 |
| 60° | 5.86 | 6.92 | 7.21 | 7.37 |
| 75° | 6.01 | 7.04 | 7.47 | 7.76 |
| 90° | 5.89 | 7.10 | 7.62 | 8.21 |
| 110° | 5.77 | 7.21 | 7.96 | 8.80 |
| 120° | 5.58 | 7.12 | 7.98 | 9.42 |
| 135° | 4.99 | 6.79 | 7.69 | 9.43 |
| 150° | 4.19 | 6.24 | 7.27 | 8.67 |
| Run VMG | 3.63 | 5.44 | 6.66 | 7.86 |
How they are set up
The range each sail spans across the fleet.
Nearly all carry a folding propeller. Crew weight is declared around 540 kg.
Rigging
Seam 31 rig and sail dimensions
A Seam 31 carries 12.45 m of mainsail hoist on a 4.53 m boom, a forestay 12.32 m above the deck. Typical figures across the 2 boats measured under the current VPP, with the range each one spans.
Rig
Sails
The spinnaker spreads widest of all — 62 to 71 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.