Join Date: Feb 2000
Location: Annapolis, Md
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Value of capsize ratios?
I think that your approach is worse than useless. The capsize ratio includes almost none of the critical determinants of the likelihood of a capsize (such as the vertical center of gravity, vertical and horizontal center of buoyancy, weight and bouyancy distribution, waterline beam and the depth of the canoe body, center of effort, roll moment of interia, etc) By the same token the Motion Comfort Index has almost none of the critical factors related to motoin comfort, (such as the vertical center of gravity, hull form stability, weight and bouyancy distribution, roll and pitch moments of interia,dampening, etc)Both of these formulas were developed when boats were very different than today and were all very similar in hull form and weight distribution. These surrogate formulas allow some comparison of very similar boats but in almost all cases provide no accurate or useful information. In fact the information is so misleading that I consider it dangerous to rely on these information derived from these formulas in any real way.
The example that I give is two identical sailboats, only one has a rig that has a 1000 lb weight at its masthead (and yes I know no one would actually put a 1000 lb weight at the mast head of a boat.) Under the capsize screen the additional 1000 lbs would make this boat seem more stable, but in reality the 1000 lb weight would raise the vertical center of gravity and make the boat with the weight more prone to capsize and more prone to a much wider pitching and rolling angle (albeit at a slower speed) and so less comfortable.
Similarly if that same 1000 lbs were a bulb at the bottom of the keel,the 1000 lb weight would lower the vertical center of gravity and make the boat with the weight more far less prone to capsize and more prone to a much narrower pitching and rolling angle still at a slower speed, and so far more comfortable.
As you can see nowhere in either formula are these factors taken into account but if you strickly followed the formulas the boat with the lead weight at the mast would look like the better boat in terms of seakindliness and stability.