Hi John, Right. And, because this sail is so small (a bit over 100 sq ft) it doesn't contribute as much windage as does the hull and superstructure - it merely adds a small amount. Nevertheless, the (included) angle the boat rolls through when heeled in a beam wind becomes less, the further heeled it is. I believe this is due to the ballast becoming more effective, as the wind force is only decreased by heeling and "spilling". Of course the reserve buoyancy is increasing on the leeward side the hull too. Thoughts? John In a message dated 1/27/2009 12:51:02 P.M. Eastern Standard Time, JohnPH@Comcast.net writes: I would suggest that the very good improvement in roll stability that you observe in a sail boat with sails set is not so much do to the weighted keel (which is important to keeping it upright) as it is to the large increase and decrease of force on the sail as the APPARENT velocity of the boat increases and decreases in phase with the roll in such a way as to maintain a perfectly phased stabilizing force on the roll of the vessel. Keep the sails full. John Harris **************A Good Credit Score is 700 or Above. See yours in just 2 easy steps! (http://pr.atwola.com/promoclk/100000075x1215855013x1201028747/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=62%26bcd=De cemailfooterNO62)