Headstay Sag

[Ted]

Is there a general formula for maximum headstay sag. I know that headstay sag should be increased when you want to power up a given headsail and less sag helps pointing ability. Assume the subject boat is a masthead rig with an adjustable backstay and is used for club racing with kevlar sails. When you design a new headsail, do you design for a specific percentage of the luff length or other means? Thanks for your input.

 

[Bill Colombo]

Ted,The amount of headstay sag designed into a racing genoa depends on the wind range of the sail. Approximate numbers, for example would be 0.1% of luff length for a light #1 genoa, Med #1 would be 0.2%,0.4% for a #2, up to 0.5% for a #3 genoa. These numbers are based on catenary curves generated by applying increasing but even pressure to a tensioned stay. Different rigs will have different base tensions as a starting point. Given this design point it is then the trimmers job to manipulate the rig and sail in order to achieve optimum shape.Thanks,Bill C.Doyle Sails