Catalinas in Ratios

[Edward 14244]

I came across this site recently: it contains interesting information on things like capsize ratios and motion comfort for many yachts, based on their 'figures'. My gutfeeling -based on the few boats I know- is that it seems to be spot-on. I would be interested to hear from more mathematically/yacht design inclined sailors what their comments are on such ratios, and how useful they are when selecting a boat.I found it intriguing to see the wide disparity between the various Catalina models in terms of these capsize and motion comfort ratios. E.g. there seems to be a deterioration in these ratios from the Cat30 to the 309 and 310, whilst I thought the hulls, displacements and ballast were pretty much identical.

 

[Big Joe]

Capsize ratio

Looking at the C30 vs. the 309, the numbers are not that close. The C30 has a better capsize ratio because it is not as beamy at 10.8 vs 11.5. Narrower beams lower than Capsize ratio drastically.It has more ballast at 4200 lbs vs the 309's 4000 lbs. Add another 100lbs for the Cat 30's shoal draft keel. The 30 is 400 lbs heavier overall than its longer brother the 309. This extra weight helps produce better comfort numbers.I find the capsize ratio to be of limited use in that it does not take a lot of important things into consideration for example it looks at total displacement. Not ballast numbers. And it ignores things like the shoal keel version is heavier but carries it's weight higher than it's deep fin counterpart. Capsize ratio ignores the benefit of keel area in that full keel boats are not only typically heavier but the sheer area of their full underwater surfaces help them resist a capsize.If you look at a given boats beam the wider beam boat would be reasonably expected to have a harder time recovering once capsized but be harder to capsize in the first place.Just some amatuers thoughts.Regards, Big Joe.

 

[Bob B.]

Ratios?

I don't know anything about capsize ratios. I do know that when I had my C22 sails flat in the water, she was in no hurry to right herself. I had to swim around, reach up & pull down on the keel. I could just reach the keel as it is quite high when parallel to the water. The sails were still up so there seemed to be a lot of "suction?" to lift them from the water. Once they broke free from the water, it came up fast.