impulse 21
Description
The Impulse 21 is a lightweight, trailerable, high-performance sportboat designed by William E. Cook and built by Johnson Boat Works (White Bear Lake, Minnesota) from 1985 to 1990. Only approximately 130 hulls were produced before the factory closed, making it a relatively rare but cult-favorite boat among sailors who love fast, planning keelboats with minimal wetted surface. It was created as a modern, fixed-keel alternative to the heavier M-20 scow while offering similar speed and excitement in a more conventional-looking package
Construction Details
| Designer | Bill Cook |
|---|---|
| Builder | Johnson Boat Works |
| Length | 21.000 ft |
| LOA | 21.000 ft |
| LWL | 18.500 ft |
| Beam | 8.000 ft |
| Displacement | 1300 lb |
| Max Draft | 3.250 ft |
The standard boat dimensions
| i | 23.50 ft |
|---|---|
| j | 7 ft |
| p | 26 ft |
| e | 9.70 ft |
| p2 | - |
| e2 | - |
| i2 | - |
| j2 | - |
| I | J | P | E | P2 | E2 | I2 | J2 |
|---|---|---|---|---|---|---|---|
| 23.50 ft | 7 ft | 26 ft | 9.70 ft | - | - | - | - |
Sails
impulse 21 - MAINSAIL
| Luff | * 26 ft - (7925 mm) |
|---|---|
| Foot | * 9.7 ft - (2957 mm) |
| Leech | * 27.22 ft - (8297 mm) |
| Tack Angle | * 88 ° |
| Diagonal | * 27.43 ft - (8361 mm) |
| Head (inches) | * 4.5 in - (114 mm) |
| Area | * 130.26 ft² |
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impulse 21 - JIBSAIL
| Luff | 23.42 ft - (7138 mm) |
|---|---|
| Foot | 6.25 ft - (1905 mm) |
| Leech | 21.5 ft - (6553 mm) |
| Percentage LP | * 80.71 % |
| Length Perpendicular | * 5.65 ft - (1722 mm) |
| Deck Angle | * 8.76 ° |
| Area | * 66.14 ft² |
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impulse 21 - JIBSAIL
| Luff | 23.42 ft - (7138 mm) |
|---|---|
| Foot | 7.67 ft - (2338 mm) |
| Leech | 21.5 ft - (6553 mm) |
| Percentage LP | * 100.29 % |
| Length Perpendicular | * 7.02 ft - (2140 mm) |
| Deck Angle | * 7.23 ° |
| Area | * 82.17 ft² |
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impulse 21 - GENOA
| Luff | 23.42 ft - (7138 mm) |
|---|---|
| Foot | 8.75 ft - (2667 mm) |
| Leech | 21.875 ft - (6668 mm) |
| Percentage LP | * 116.71 % |
| Length Perpendicular | * 8.17 ft - (2490 mm) |
| Deck Angle | * 4.36 ° |
| Area | * 95.69 ft² |
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impulse 21 - GENOA
| Luff | * 23.29 ft - (7099 mm) |
|---|---|
| Foot | * 11.22 ft - (3420 mm) |
| Leech | * 22 ft - (6706 mm) |
| Percentage LP | * 150 % |
| Length Perpendicular | * 10.5 ft - (3200 mm) |
| Deck Angle | * 4.06 ° |
| Area | * 122.26 ft² |
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impulse 21 - GENOA
| Luff | 23 ft - (7010 mm) |
|---|---|
| Foot | 10.083 ft - (3073 mm) |
| Leech | 21.75 ft - (6629 mm) |
| Percentage LP | * 135.43 % |
| Length Perpendicular | * 9.48 ft - (2890 mm) |
| Deck Angle | * 3.28 ° |
| Area | * 109.06 ft² |
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impulse 21 - ASYMMETRICAL
| Luff | 24 ft - (7315 mm) |
|---|---|
| Foot | 14 ft - (4267 mm) |
| Leech | 22.25 ft - (6782 mm) |
| Perc LP | * 165 % |
| Area | * 252 ft² |
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impulse 21 - SPINNAKER
| Stays | 23.58 ft - (7187 mm) |
|---|---|
| MidGirth | 14.4 ft - (4389 mm) |
| Foot | 14.4 ft - (4389 mm) |
| Perc LP | * 180 % |
| Area | * 289 ft² |
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impulse 21 - SPINNAKER
| Stays | * 23.29 ft - (7099 mm) |
|---|---|
| MidGirth | * 12.6 ft - (3840 mm) |
| Foot | * 12.6 ft - (3840 mm) |
| Perc LP | * 180 % |
| Area | * 249 ft² |
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impulse 21 - STORMJIB
| Luff | * 13.49 ft - (4112 mm) |
|---|---|
| Foot | * 5.16 ft - (1573 mm) |
| Leech | * 11.3 ft - (3444 mm) |
| Perc LP | * 60 % |
| Length Perp | * 4.2 ft - (1280 mm) |
| Deck Angle | * 18.95 ° |
| Area | * 28.32 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.