Bostrom 31 MK II
Description
The Bostrom 31 MK II (also known as Boström 31 MK II or B 31 Mark II) is a classic Scandinavian cruiser sailboat, popular in Northern Europe, especially in Sweden, Denmark, and the UK. Designed by Swedish naval architect Bruno Boström (with input from Jens Grandinsson) in the late 1970s, it was produced from around 1978 to 1988 by the Danish yard Star Boat in Stenløse. About 198 units of the MK II were built, making it a sought-after but relatively rare classic today. It's an evolution of the earlier Bostrom 31 (B-31 or Star Boat 31), sharing the same hull but featuring increased freeboard for better interior volume and dryness, plus a redesigned deck and superstructure for improved comfort and aesthetics. Owners praise it as a safe, seaworthy coastal cruiser — very stable, stiff, and capable of handling longer passages (like North Sea crossings or Channel hops) while being fun to sail in varied conditions.
Construction Details
| Designer | Bruno Boström |
|---|---|
| Builder | Star Boat in Stenløse (Denmark) |
| Length | 31.000 ft |
| LOA | 30.610 ft |
| LWL | 25.980 ft |
| Beam | 9.060 ft |
| Displacement | 7275 lb |
| Ballast | 3638 lb |
| Max Draft | 5.910 ft |
| Year Built | 178 |
The standard boat dimensions
| i | 37.40 ft |
|---|---|
| j | 11.98 ft |
| p | 31.82 ft |
| e | 9.19 ft |
| p2 | - |
| e2 | - |
| i2 | - |
| j2 | - |
| I | J | P | E | P2 | E2 | I2 | J2 |
|---|---|---|---|---|---|---|---|
| 37.40 ft | 11.98 ft | 31.82 ft | 9.19 ft | - | - | - | - |
Sails
Bostrom 31 MK II - MAINSAIL
| Luff | * 31.82 ft - (9699 mm) |
|---|---|
| Foot | * 9.19 ft - (2801 mm) |
| Leech | * 32.63 ft - (9946 mm) |
| Tack Angle | * 88 ° |
| Diagonal | * 32.81 ft - (10000 mm) |
| Head (inches) | * 4 in - (102 mm) |
| Area | * 150.71 ft² |
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Bostrom 31 MK II - JIBSAIL
| Luff | * 31.42 ft - (9577 mm) |
|---|---|
| Foot | * 15.87 ft - (4837 mm) |
| Leech | * 27.28 ft - (8315 mm) |
| Percentage LP | * 115.03 % |
| Length Perpendicular | * 13.78 ft - (4200 mm) |
| Deck Angle | * 11.99 ° |
| Area | * 216.46 ft² |
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Bostrom 31 MK II - GENOA
| Luff | * 37.31 ft - (11372 mm) |
|---|---|
| Foot | * 19.35 ft - (5898 mm) |
| Leech | * 35.08 ft - (10692 mm) |
| Percentage LP | * 150 % |
| Length Perpendicular | * 17.97 ft - (5477 mm) |
| Deck Angle | * 4.02 ° |
| Area | * 335.2 ft² |
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Bostrom 31 MK II - GENOA
| Luff | 36.5 ft - (11125 mm) |
|---|---|
| Foot | 16.75 ft - (5105 mm) |
| Leech | 34 ft - (10363 mm) |
| Percentage LP | * 129.72 % |
| Length Perpendicular | * 15.54 ft - (4737 mm) |
| Deck Angle | * 4.18 ° |
| Area | * 283.55 ft² |
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Bostrom 31 MK II - ASYMMETRICAL
| Luff | * 37.31 ft - (11372 mm) |
|---|---|
| Foot | * 19.77 ft - (6026 mm) |
| Leech | * 34.33 ft - (10464 mm) |
| Perc LP | * 165 % |
| Area | * 553 ft² |
| Edit in Calculator | |
Disclaimer. Boats are not all the same -- even when produced in the same factory of the same model. Sailrite does its best to publish accurate dimensions, but we often find it worthwhile to have our customers measure their boats carefully before we produce kits for them. You should take the same precautions, especially when the data is not from Sailrite. The information on this site is not guaranteed to be accurate. Sailrite offers this content as a service to our community, but takes no responsibility for the reliability of the data provided.