I just read Don Casey's article on how to keep things quiet on board. Does he have any thoughts regarding the howling mast of a roller furling main?
Don Casey responds:
I have not heard many complaints about "howling" masts in recent years. My guess is that is because a few years back spar manufacturers began adding a chafing strip to the edges of the sail slot in roller-furling masts. This was good for the sail, made furling easier, and—perhaps unexpectedly—it seems to have stopped these masts from howling.
Reckmann—the German sparmaker—sells an aluminum extrusion with a plastic cap that can be retrofitted to the sides of the slot. Ruefully called the Windbreaker, this add-on should work on virtually any roller-furling mast that doesn't already have chafe guards. The cost, I think, is under $10.00 per foot of luff length.
If that seems too expensive, you can shut up a howling mast by hoisting a "flute stopper" in the slot when the sail is furled. This is essentially two equal lengths of stiff fabric tape or webbing stitched together longitudinally on their centerlines. The stopper should be as long as the open slot. It is hoisted with one tape inside the slot, the other outside.
This is obviously not a passive device like the Windbreaker, but if you think of it as similar to putting on a sailcover, it offers the least expensive fix. A flute stopper is quite easy to fabricate. Good luck in keeping things quiet on board.