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masthead v. fractional rig
Fractional vs. Masthead rigs
These terms both derive from the point at which the forestay hits the mast. On a masthead rig the forestay hits the mast at the masthead (top of the mast). Masthead rigs are far and away the more common of the two rigs. Until the 1950''s Masthead rigs were virtually unheard of. But with the advent of low stretch sail cloth and better winches, as well as, changes in the racing rules Masthead Rigs became the norm. This change came about as a rule beating method for racing sailboats. Under the CCA and IOR racing rating rules, jib size was under penalized. This promoted small mainsails and big jibs.
On a fractional rig, the forestay hits the mast somewhere below the masthead (or a fraction of the overall height of the mast. It is not unusual to see fractional rigs referred to as a 2/3 (Folkboats), 3/4 (J-24) or 7/8th''s (Triton) rig.
Each rig has its own advantages and disadvantages. There are some big advantages to a fractional rig for cruising and racing. For cruising, you are dealing with smaller and easier to handle headsails. Not only are the headsails smaller because of the shorter headsails but, because the headsails represent a smaller percentage of the overall sail area, you don''t need to have overlapping jibs. The sail area missing from the foresails is made up in a bigger mainsail. This makes sense since, using modern hardware and sail design, mainsails are easier to tack, depower and reef efficiently.
Fractional rigs often have purposely designed flexible masts and, when combined with a backstay adjuster permits quick, on the fly, simultaneous depowering of both jib and sails. Mainsails are easier to reef in a manner that results in an efficiently shaped sail for heavier conditions. Smaller jib area means that you don''t have to take on the expense, complication, maintenance and performance hit of a mainsail furler. Controlling mast bend you can often avoid reefing as the winds build. Roller furling genoas have notoriously poor shape when partially furled. The smaller jibs of a fractional rig rarely need reefing and when they do the fact that they are non-overlapping results in a better partially furled shape.
Masthead rigs have larger running sails and so can typically point closer to dead down wind. They are a little more forgiving. Because Fractional rigs permit such a large range of easy adjustment, they can be trimmed through a range of adjustments that results in a bigger range of speed both slower or faster than a masthead rig of similar sail area. The limited adjustment of a masthead rig means that you more or less live with what you have. Therefore a masthead rig has less of the opportunity for makind fine tuning adjustments that mean going really faster and with less heel, or going much slower either.
My biggest problem with Masthead rigs is that you really need to carry more headsails and make more headsail changes. This is partially a function of the responsibility of the jib for drive. If you take a Fractional Rig 100% jib on a 28-footer it might be 150 s.f. and its 150% Genoa would be 225 square feet. But on a masthead rig 28 footer the 100% jib might be as much as 225 to 250 square feet and its 150% Genoa would be 337 S.F. to 375 s.f. That is a really big sail to manhandle and the when you increase a sail by 125 S.F. vs. only 75 s.f. there is a much smaller wind range that the bigger sail can be carried in so you might end up also carrying a number 2 Genoa as well as a working jib and a 150% #1 Genoa. With roller furling you end up sailing more frequently with (much less efficient) partially rolled up sails.
I strongly favor Fractional rigs for coastal sailing because the are so much easier to tack and jibe, you are not carrying around the big winches and as many large sails, and subjecting the boat to the much higher loads of a masthead rig.