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ROCK 20
Built by Birka Marine (FIN)
• Designed by Heinz-Jurgen Sass
Market Value
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General Information
Hull Type:
Fin with rudder on skeg
Rigging Type:
Masthead Sloop
Construction:
FG
First Built:
1968
Last Built:
1975
Number Built:
200
Dimensions
Length Overall (LOA):
7.17 m
Length Waterline (LWL):
5.95 m
Beam:
2.25 m
Draft (Max):
1.20 m
Weight & Ballast
Displacement:
1,750 kg
Ballast:
600 kg
Ballast Type:
Iron
Sail Plan
Foresail Area:
10.73 m²
Mainsail Area:
9.42 m²
Total Sail Area (calculated):
20.15 m²
Sail Area (reported):
20.16 m²
I (Fore Triangle Height):
7.80 m
J (Fore Triangle Base):
2.75 m
P (Mainsail Hoist):
7.08 m
E (Boom Length):
2.66 m
Engine & Systems
Performance Ratios
Hull Speed:
5.92 knots
SA/Displacement (Calculated):
13.88
SA/Displacement (Reported):
14.15
Ballast/Disp Ratio:
34.29%
Displacement/Length:
231.57
Comfort Ratio:
20.07
Capsize Screening:
1.88
S-Number:
2.04
Notes
Another version called the ROCK 24 is probably based on the same hull but with a different sail plan.