Hull Speed
The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.
5.6 kts
A displacement hull pushes a bow wave whose speed is limited by the waterline length.
With a waterline of 17.5′, the Rk 20 tops out around 5.6 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √17.5′ LWL = 5.6 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
PHRF Rating
264s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
Ballast / Displacement
28.2%
Light ballast — tends to be tender; reef earlier than the numbers suggest.
Displacement / Length
162
Moderate — a good balance of speed and load-carrying ability.
Hull Speed
5.6kts
Pounds/Inch Immersion
3lbs
Weight needed to sink the hull one inch — loading sensitivity.
PHRF Fleet Position
Where the Rk 20 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Rk 20
Heavy or slow cruiser — all about the journey, not the elapsed time.