I too have a folding aluminum one that I raised (once!!) using the spinnaker halyard with the bottom tied to the bow rail. No idea how effective it actually was but it certainly gets in the way a lot. When tacking, it has to be dropped and then raised on the other side, and it is impossible to get the halyard tight enough to stop it swinging quite wildly.
I used it in poor visibility because of rain and rough weather, but it would be much less of a problem in calm fog.
David Pocock
Parker 235/52 Arawa
David Pocock
Parker 235/52 Arawa