Gunfleet of Hamble was designed and built for the the 1973 Admiral's Cup competition. Unfortunately she was late to the starting line and missed the opportunity to race. In the mean time the design was utilized for the new Swan 41 so by the time 1974 competition came around the custom one-off Gunfleet found herself racing against a stock boat of similar proportions.
Here's an early article on this very subject. That's a stock Swan 41 in the photograph below.
Gunfleet of Hamble was constructed of aluminum by Joyce Marine of Southampton, England.
Here are the plans.
Displacement 17,675 lbs
Ballast 10,400 lbs
Sail Area 624 sq ft