I seem to recall a while back a post that the C-42 MII "empty" displacement was acknowledged by Catalina (Gerry?) to be closer to 22500# rather than the published spec of 20500#. I recently came across an article in Boat/US Magazine (July, 2005 by marine surveyer Jack Hornor) that confirmed the 22500# number.
[ www.boatus.com/jackhornor...lina42.htm ]
If that be the case. The changes in capsize ratio and motion comfort for the Mk II becomes significant for both fin and wing keel models:
C-42 Mk II - WING & VFIN keels:
Displacement to LWL: 186 becomes 204
Hull Speed (standard) : unchanged 8.11
Max Hull Speed (Dave Gerr): 9.6 to 9.3
[EWA www.catalina42.org/techsp...#hullspeed ]
Sail Area to Displacement: 17.02 to 16.0
LWL to Beam: unchanged at 2.65
Motion Comfort: 24.87 becomes 27.32 (ideal in low 30's)
Capsize Ratio: 2.02 (unfavorable) becomes 1.96 (favorable)
[From Carl's www.image-ination.com/sailcalc.html]
Screening stability: 27.62 becomes 27.21 (meaningless - does not account for vertical center of gravity of keel)
Angle of vanishing stability: 132.71 becomes 133.25
[From Sailing www.sailingusa.info/cal__sad_ratio.htm
using 2.4' as draft less keel for 20500#; 2.6' for 22500#)]
From the above, our Catalina-42's appear to be more stable and more seakindly than the previous numbers implied. Note that increased displacement markedly affect these parameters, but had only a minor affect on Gerr's Max. Hull Speed. But to us, it was always obvious.
Ernie April
WindCatcher (#618, Wing)
[ www.boatus.com/jackhornor...lina42.htm ]
If that be the case. The changes in capsize ratio and motion comfort for the Mk II becomes significant for both fin and wing keel models:
C-42 Mk II - WING & VFIN keels:
Displacement to LWL: 186 becomes 204
Hull Speed (standard) : unchanged 8.11
Max Hull Speed (Dave Gerr): 9.6 to 9.3
[EWA www.catalina42.org/techsp...#hullspeed ]
Sail Area to Displacement: 17.02 to 16.0
LWL to Beam: unchanged at 2.65
Motion Comfort: 24.87 becomes 27.32 (ideal in low 30's)
Capsize Ratio: 2.02 (unfavorable) becomes 1.96 (favorable)
[From Carl's www.image-ination.com/sailcalc.html]
Screening stability: 27.62 becomes 27.21 (meaningless - does not account for vertical center of gravity of keel)
Angle of vanishing stability: 132.71 becomes 133.25
[From Sailing www.sailingusa.info/cal__sad_ratio.htm
using 2.4' as draft less keel for 20500#; 2.6' for 22500#)]
From the above, our Catalina-42's appear to be more stable and more seakindly than the previous numbers implied. Note that increased displacement markedly affect these parameters, but had only a minor affect on Gerr's Max. Hull Speed. But to us, it was always obvious.
Ernie April
WindCatcher (#618, Wing)
Figuring out how fast your boat can go will help you determine just how far and fast you should be running her" by Dave Gerr, N.A., Offshore Magazine, Volume 28, Number 9, September, 2003. (The article may be continued into the following month.) In this article he clearly and convincingly explains the theory and his formula. It is easy enough to pop the equation into an Excel spreadsheet. That formula is spot-on for my Catalina-42. I've corresponded with Gerr on several occasions and he has conviningly answered my questions and acknowledged that the discussion in his book 8 years prior was incomplete. You can probably get a copy of the articles from Offshore Magazine or at least purchase the back issues. 
