BOSTROM 31
Specifications
Hull
| LOA | 30.64 ft |
| LWL | 25.98 ft |
| Beam | 9.06 ft |
| Draft | 5.91 ft |
| Displacement | 7,782 lb |
| Ballast | 3,747.8 lb |
| Hull speed1.34·√LWL | 6.8 kn |
Rig & Sails
| Iforetriangle height | 37.4 ft |
| Jforetriangle base | 11.98 ft |
| Pmainsail luff | 31.82 ft |
| Emainsail foot | 9.19 ft |
| FLforestay | 12 ft |
| Mainsail | 381.9 sq ft |
| Jib (100%) | 224 sq ft |
| Spinnaker | 380.8 sq ft |
About the BOSTROM 31
Also known as B-31, STAR BOAT 31.
The Bostrom 31 is a classic Swedish cruiser designed by Bruno Boström and Grandinsson, with production records indicating builds in 1973. As a masthead sloop with a displacement of 7782.0 lb and a comfort ratio of 23.32, it offers a balanced blend of performance and stability typical of its era.
- Best for:
- This boat suits coastal cruisers and weekend sailors who value a comfortable, stable platform, as evidenced by the high frequency of dodger and bimini installations for protected cockpit living. It is well-suited for owners willing to perform diligent maintenance on aging composite structures.
- Bluewater capability:
- With a capsize ratio of 1.83 and a D/L ratio of 198.12, the Bostrom 31 possesses the heavy displacement and low center of gravity necessary for offshore passages, though its age requires careful verification of structural integrity before extended voyaging.
- Comparables:
- Comparable boats include other 1970s Scandinavian designs like the Hallberg-Rassy 31 or Nauticat 31, which share similar displacement, fin keel configurations, and a focus on seaworthiness over pure speed. These vessels appeal to buyers seeking robust, traditional cruising platforms from the same period.
Performance
ORC Performance Data(1 certificate)
Measured performance data from ORC (Offshore Racing Congress) certificates.
Polar Diagram
Boat speed (kn) vs. true wind angle. Source: ORC
Racing Ratings
Triple Number
ORC Measured
Sail Areas (ORC)
Speed Table (kn)
| TWA \ TWS | 6 | 8 | 10 | 12 | 14 | 16 | 20 |
|---|---|---|---|---|---|---|---|
| 52° | 4.2 | 4.9 | 5.6 | 5.9 | 6.2 | 6.3 | 6.3 |
| 60° | 4.4 | 5.3 | 5.8 | 6.2 | 6.3 | 6.5 | 6.6 |
| 75° | 4.7 | 5.5 | 6.1 | 6.3 | 6.5 | 6.7 | 7.0 |
| 90° | 4.7 | 5.5 | 6.1 | 6.3 | 6.6 | 6.8 | 7.2 |
| 110° | 4.2 | 5.1 | 5.8 | 6.2 | 6.5 | 6.7 | 7.2 |
| 120° | 3.9 | 4.8 | 5.6 | 6.1 | 6.4 | 6.6 | 7.1 |
| 135° | 3.5 | 4.3 | 5.1 | 5.7 | 6.1 | 6.4 | 6.9 |
| 150° | 3.0 | 3.8 | 4.6 | 5.2 | 5.8 | 6.2 | 6.6 |
| Beat VMG | 2.7 | 3.2 | 3.6 | 4.0 | 4.2 | 4.3 | 4.4 |
| Run VMG | 2.6 | 3.4 | 4.1 | 4.8 | 5.4 | 5.9 | 6.4 |
Market Price
Estimated Cost of Ownership
Based on 30.64ft LOA. Actual costs vary by condition, usage, and local rates.
Known Issues & Pre-Purchase Inspection
10 reported issues across 7 systems for the BOSTROM 31, compiled from owner reports in sailing forums and owner-association material.
Unlock the full inspection report
Thinking of buying a BOSTROM 31? This is an in-depth report on the faults this model is known for — so you know exactly what to check when you walk the boat. For the price of a coffee.
- ✓ All 10 specific issues — severity, symptoms & fixes
- ✓ Model-specific pre-purchase inspection checklist
- ✓ Downloadable PDF to take to your surveyor — yours to keep
One-time $2.99 · secure checkout by Stripe · instant access · 30 days online, PDF yours to keep
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Which engine powers your BOSTROM 31?
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Used sails that fit the BOSTROM 31
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