Mary, Thom, John and Mark - thanks for the feedback.

I fully agree that rig proportions (as well as crew weight) factor into the equation, and that how forgiving a cat is depends on much more than boat weight, but it seems that weight is still a valid simplified way to look at overall stability since manufacturers tend to size the rig roughly proportionately to weight unless the boat is targeted at some extreme group (ie, Jav 2 may have a slightly bigger rig than the boat weight would oridinarily merit but this boat is targeted to the most highly performance oriented group). Also, it does seem to be some peoples experience that heavier boats are easier to handle in rough conditions.

John, I found your comments on heeling moment vs righting moment useful but I wonder if things aren't actually more complex than this depending on conditions. I would expect these to apply best when one looked at boat characteristics in steadier winds with flatter water; but in higly gusty conditions with big waves it's easy to imagine proportionately powered lighter boats becoming more difficult to handle, particularly for a non-expert sailor. I'm thinking that heeling and righting moments behave differently in steady state vs non steady state conditions.

Let's compare, for example, singlehanding an N17R or F18 (cat rigged) vs a F16. Aside: why do I want to compare N17R and F18 cat rigged? 1) see the recent thread about sailing TheMightyHobie18 solo and catrigged, 2)when I compared specs on the N17R vs the Nacra F18 I was surprised at how close they are:

Cat Length Beam Weight Mast Main Jib Spi
N 17R 17'5" 8'2.5" 335 lbs 30'4" 170 sf 37 sf 17 sm
N F18 18'1" 8'6" 385 lbs 29'9" 183 sf 37 sf 19 sm
Difference 8" 3.5" 50 lbs (7") 13 sf 0 sf 2 sm

(note: using smaller jib/spi option for F18 and subtracting about 10 lbs from ISAF I17N but not adding anything for jib or spi).

For example, taking F16 and F18: The F16 boat is lighter and has a smaller rig to give it similar overall performance. I would think that in gusty 20 kt winds and large waves the lower mass of the F16 would be effected more than the F18 by non steady state forces (gusts/waves): during gusts it would accelerate faster if well skippered or heel more if poorly skippered; when exposed to large waves it would be deviated or stopped more easily if poorly skippered than a heavier boat. I am NOT suggesting that F16 doesn't handle rough conditions as well as an F18 or that one boat is BETTER than the other!! Only that it may take a little more skill to handle the F16 in these conditions than a heavier F18. Note that if this is true, while this would make heavier boats easier for less experienced skippers/crew, it might also make them less fun and less a test of skill for experienced skippers/crew.

So, in summary, I'm asking if in demanding wind/wave conditions heavier cats such as N17R or F18 are easier to control and more forgiving than lighter cats such as F16. I'm also asking if a singlehanded F18 cat rigged would be roughly similar to an N17R as far as being stable and forgiving in rough conditions given their surprising similar specs (ie, is a F18 cat rigged as easy to sail as an TheMightyHobie18 cat rigged).

Experience and comments?

Jerry