Safest Water Ballast Boat

[George H260]

This comes under the category of "Nothing to do on a Saturday Night in March"US Sailing has an on-line calculator that allows you to determine key design aspects of a boat. http://www.sailingusa.info/cal__avs.htmI'm most interested in the "Angle of Vanishing Stability" as they relate to water ballast boats. Using the following variablesH260Beam 8.9 ftDisplacement 5000 lbsWt of Ballast 2000 Draft 1.5Screening Stability: 30.88. Angle of Vanishing Stability: 129.16H250Beam 8.5Displacement 4550Ballast 1300Draft 1.5Screening stability: 40.69; Angle of Vanishing Stability 123.03MAC 26XBeam 7.8Displacement 4000Ballast 1450Draft 1.5Screening stability 28.19, Angle of Vanishing Stability 131.99According to the site, angle of vanishing stability is the angle to which the boat can heel and still right itself. A dingy will have a stability range of about 80 degrees; an inland water boat should have a stability range of 100 degrees, and an offshore boat of at least 120 degrees. Boats which have a stability angle of less than 140 degrees may be left floating upside down once capsized. Boats with a higher angle will usually right themselvesNot sure what all these numbers mean. Is there an engineer or naval architect out that that can shed some light here? Can you use these numbers to determine the safest of these three boats? Or should I just watch some TV and forget it?

 

[Don12364]

Wild Estimates

George,The formula shown on sailingusa website are VERY generalised. They take no account of:- differences in hull shape, coachroof height & width, actual centre of gravity, plus owner installed items such as:-in mast furling, roller reefing, height of radar scanner etc,etc.As the page says "these are for educational purposes only" ie. they don't relate to any particular boat and are also unusable for making comparisons between hulls.The only certain knowledge is that out there somewhere is a wave which can invert you. It is just a matter of luck whether you ever meet it. Many hulls are quite content upside down, particularly if they are flush decked racers. One then has to hope that another wave comes along quickly and rights the boat. It only needs to be a smaller wave than the one which caused to original capsize. I've never met anyone to whom this did not happen - but then I would not have!!!! ;DThe AVS is the angle of heel from which the boat will just carry on rolling until she is completely inverted. But even then this takes no account of "Downflooding" which is when water can penetrate below decks and begin the process of sinking.One just has to trust the designers and the RCD category for any particular boat.