On a lot of boats with a roller-furling foil, and particularly with no sail rolled on it, the headstay will start to pump once the wind gets up, sometimes to the point it gets quite alarming.
Not only that, all that pumping can do real damage to the rig if left long enough.
But there’s a hack that stops it every time, at least for a boat swinging to the wind on a mooring or anchor.
Set up a spinnaker halyard just forward of the headstay as shown in the shot above. That’s it? Yup.
I guess the halyard causes turbulence that breaks up the laminar flow on the headstay foil…or something.
Anyway, we have been doing this for years and it works.
Thanks to Deborah Shapiro and Rolf Bjelke, as I read the tip years ago in one of their excellent books.