Join Date: Feb 2000
Location: Annapolis, Md
Thanked 149 Times in 122 Posts
Rep Power: 10
I am not sure that I understand where you are going with this. I have sailed on traditional boats that had the sails laced on and have had brails rigged to be able to reef the sail to the mast rather than the boom. The problem with both is that your are dealing with pulling in a lot of line in order to alter the shape of the sail. Even the equivilent of a flattening reef could easily be yards of line that needs to be overhauled between the tension that you would want on a higher wind beat vs the shape you would want cracked off in the same conditions. With the high frictions involved, hauling that much line in and distributing the loads sufficiently evenly between the area of the differing loads on each cringle that result from the different tributary areas of the sail, becomes a very difficult if not imposible problem.
Beyond this you would be gather a turbulence producing bundle of sail right at the leading edge where clean air flow is most critical.
While there is a tendancy to think of a mast as a simple compression member, the reality is that masts have almost always been bending members as well. The ability and propensity of a wooden mast to bend has been an safety component of traditional boat design for centuries. Mast flexibility as a safety valve was well understood on an intuitive basis as early as the mid-19th century and is reflected in sharpie an skiff rigs by the early 1800''s.
Herreshoff''s understanding of role of mast bend was so acute that S-Boat designed in the first decade of the 20th century had a mast that was actually precurved for that purpose.
The first academic study of the role of mast bend on sailing that I know of occurs in Manfred Curry''s treatice on the Aerodynamics of sailing in the 1930''s.
In other words, mast bend has played a key role in sailing rig design for a very long time. It is only in the late 1950''s, that you find rig design changing to masts so stiff that fore and aft flexing is reduced to an absolute minimum. This is partially in response to the artificial shift to masthead rigs that resulted from boats trying to beat the CCA racing rule. Masthead rigs require much higher rig loads and so also develop much higher compression loads on the mast. Buckling in aluminum spars became a very real concern.
With the change in the racing rules, there has been a shift back to the greater efficiency of a fractional rig and to ''bendy'' rigs that can allow rapid, subtly adjustable, on-the-fly shifts in sail power. There is now quite a long track record on these bendy rigs as they first began to become popular in the mid-1970''s. While the more extreme cases have not proven to be extremely long lived, the more conservative bendy rigs, such as the J36 which also incorporated raked back spreaders and lowers to minimize pumping,have stood up very well indeed. Using an example of a boat that I know particularly well, the Farr 11.6 (Farr 38) The Farr 11.6 was designed around 1981 and has a very early very bendy rig. It depends on swept back spreaders and lowers to prevent over bending and pumping. Farr 11.6''s began racing in the South Atlantic out of South Africa in the early 1980''s. To this day they still race as a semi-one design class in the Capetown/Rio (comes in somewhere else these days) and some of these boats have been doing this race almost every running. This is a race known for its heavy air conditions. In talking to a fellow who was active in this venue, some of these early boats are just now replacing thier spars after 20 years. Given the very hard useage, pretty primitive design and workmanship on some of these spars, and the move to penalty chutes that these spars were never intended to live with, that is not unreasonable. When we had my spar down last year, (Mine has had 20 years of hard use) we found no signs of fatigue and franlkly the spar looks very good. Which is a very long way of saying that I really don''t think that mast bend offers any real problem in terms of spar durability or safety as long as the spar design is not taken to an extreme.
In other words, you are not behind the time, but are operating on a theory that was only popular for a very short period in the history of sailing rigs.