Kong2 - NOR1332
Sailing performance analysis for a J-70 ONE DESIGN (series year 2012), built by and designed by JOHNSTONE.
Data provided by the Offshore Racing Congress (ORC) · Certificate issued 11/06/2026
A performance sailboat with a light build for its length, the J-70 can reach 7.1 knots on a reach in 10 knots of wind. It shows planing potential, hitting 12.4 knots in strong winds. The asymmetric spinnaker complements its speed downwind, although the jib is compact compared to the mainsail, optimizing its upwind performance.
Sailing performance as a polar diagram
A polar diagram shows boat speed at different wind angles and wind speeds. The distance from center represents boat speed in knots, and the angle represents the boats angle to the wind. The wind speed is shown as true wind speed (TWS), not apparent wind speed. Likewise, the wind angle is shown as true wind angle (TWA), not apparent wind angle.
Beat: Sailing upwind (toward the wind)
Beam Reach: Sailing across the wind
Run: Sailing downwind (away from the wind)
VMG Performance
Wind Speed (columns): True wind speed (TWS) in knots - the actual wind speed, not the apparent wind you feel on deck.
VMG (Velocity Made Good) is your effective speed toward your destination, not your actual boat speed.
Beat VMG (top bars): Speed made good when sailing upwind. Higher is better - it means you're reaching the windward mark faster.
Run VMG (bottom bars): Speed made good when sailing downwind. Higher is better - it means you're reaching the leeward mark faster.
Measured sails
Measurements
Identity
Dimensions
Sail Areas
ORC Rating
Rated boat speeds
| Wind Speed (TWS) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 4 kt | 6 kt | 8 kt | 10 kt | 12 kt | 14 kt | 16 kt | 20 kt | 24 kt | |
| Beat VMG | 2.11 | 3.03 | 3.72 | 4.20 | 4.50 | 4.58 | 4.61 | 4.57 | 4.46 |
| 52° | 3.30 | 4.64 | 5.55 | 6.03 | 6.32 | 6.46 | 6.54 | 6.59 | 6.56 |
| 60° | 3.54 | 4.90 | 5.76 | 6.20 | 6.54 | 6.75 | 6.85 | 6.96 | 6.94 |
| 75° | 3.71 | 5.06 | 5.88 | 6.35 | 6.78 | 7.16 | 7.40 | 7.68 | 7.80 |
| 90° | 3.88 | 5.42 | 6.25 | 6.69 | 6.98 | 7.29 | 7.82 | 8.54 | 8.93 |
| 110° | 3.97 | 5.53 | 6.41 | 7.13 | 7.75 | 8.22 | 8.69 | 9.59 | 10.45 |
| 120° | 3.85 | 5.39 | 6.30 | 7.03 | 7.87 | 8.71 | 9.37 | 10.60 | 11.99 |
| 135° | 3.41 | 4.86 | 5.90 | 6.58 | 7.28 | 8.18 | 9.31 | 12.36 | 14.33 |
| 150° | 2.83 | 4.11 | 5.18 | 5.98 | 6.57 | 7.15 | 7.93 | 10.78 | 14.35 |
| Run VMG | 2.45 | 3.56 | 4.49 | 5.19 | 5.70 | 6.19 | 6.87 | 9.34 | 12.43 |
Boat speed (knots) at wind angle / wind speed