Join Date: Feb 2000
Location: Annapolis, Md
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I assume that you indeed mean wing *mast* and not the wing sails that proved so devastating in the last America's Cup.
Wing Masts are like many ideas which really well work in narrow applications. Wing masts offer very small gains in performance but with a high degree of complexity. Wing masts work very well on high efficiency, low drag applications. In that mode they offer an efficiency that can actually be used by the vessel. They are great on high speed vessels like ice boats and racing multi-hulls, because these crafr have apparent wind that is almost always from forward of abeam.
But that small gain in efficiency comes at a price; a very big price in terms of practicality when applied to more normal vessels.
For example, wing masts need to be free to rotate, but with their angle of attack controllable, so that they can offer the proper angle of attack for the wind direction. That means that the crew needs to be able to adjust not just the mainsheet, but the mast angle of attack. Around here there are folks who argue against the advantages of a fractional rig by suggesting that it is too hard for the average sailor to learn to use a backstay adjuster. Visualize the average sailor learning to properly adjust the angle of attack of the mast (remembering that a wing mast is only more efficient when the angle of attack is correct, but greatly increases drag when it is improperly adjusted).
Allowing free rotation requires a single axis of attachment for the shrouds or else a cantilevered connection. If a vessel is very beamy then the vertical staying of the mast can be isolated from the bending sideloads on the spar itself, which is part of the reason that wing masts work really well on multihulls or iceboats. But on a monohull this makes staying very tricky without something like the side struts seen on open class boats. If the choice is to use a cantilevered connection, there needs to be adequate fore and aft as well as side to side bracing of the bearing points for the embeded portion of the mast, and either an above deck set of bearings or else a set of bearings at the heel or the mast and at the deck, with the deck bearings being water tight. Proper support of the deck mounted bearing would in all probability require fore and aft as well as lateral bulkheads or knees occupying much of the interior in the area of the mast.
Wing masts have a lot of 'sail area' in the mast alone, at times more sail area than the boat can safely use and so for a cruising boat, which encounters winds of a variety of forces and directions, this inability to 'reef' the sail area of the mast can be a dangerous liability. This can be a significant problem at anchor or tied up at a dock. In the past, vessels with wing masts were generally daysailors and boats which are small enough that the mast could be unstepped at night. There have been experiemental boats with wing masts which have allowed their masts to feather, but that can mean a lot of noise and a lot of vibration.
Then there is the weight versus cost issue. While a wing mast can be lighter than a conventional stayed spar, for the most part, they tend to be a heavier rig, due to the isolation of the side support from the structure resisting the bending of the spar. This can be worked around by using exotic materials but of course this has serious monetary consequences.
And even if these complications could be effectively addressed, the offshore sailing community tends to be pretty conservative. Here we are nearly fifty years after aluminum spars with modern engineering became the norm, and yet the cruising community still argues that deck stepped masts are somehow less safe. So if you can visualize that, now try visualize trying to convince them that a mast supported on a ball-joint with a single shroud lead to a strut on either side makes sense. I don't see that happening any time soon.
In terms of retrofitting a wing mast to a conventional monohull, there would be little to no real gains in performance, but even if there were measurable gains in performance, the costs and complication would be prohibitive, especially since there are a wide range of less expensive alternatives which would be more effective in improving performance.
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Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay
Last edited by Jeff_H; 12-28-2010 at 08:57 AM.