I am fairly new to sailing and I''m trying to learn more about boat designs as it pertains to performance. I have been researching lots of different racer / cruisers in the 34-36'' size.
What is the relationship between things like LOA, LWL, Displacement, Sa-D, and hull speed relate to performance (as measured by PHRF ratings).
For example, according to Sail Calculator Pro (http://www.image-ination.com/sailcalc.html), a catalina 36 has these numbers:
LOA - 36.3, LWL - 30.25, displacement - 13500, sail area - 555, SA-D - 15.66, hull speed - 7.37, and PHRF rating of 138.
A C+C 36 (late 70''s to early 80''s) has these numbers:
LOA - 35.7, LWL - 27.7, displacement - 12000, sail area - 600, SA-D - 18.32, hull speed - 7.05, and a PHRF of 129.
Why is the C+C rating faster? Is it because the SA-D is higher?
Comparing a catalina 34 and C+C 34 (again, early 80s) is similar. The Catalina has a greater LWL, greater hull speed, 2000 lb greater displacement, a little more sail area (530 vx 517), a slightly worse SA-D ratio (17.3 vs 17.7) and a slower PHRF rating (150 vs 144).
So is the SA-D ratio the most important thing to measure performance of a boat?
If you were looking for a cruising boat, but valued performance, would you draw a line
at SA-D or something like that?
All comments welcome.