I apologize that this was written for another venue but it might still prove useful. Of the two rigs, masthead rigs are far and away the more common of the two rigs. It 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 7/8thís (Triton) rig.
Each rig has it 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 donít need to have overlapping jibs. The sail area is made up in the mainsail
The best fractional rigs often have purposely designed flexible masts and, when combined with a backstay adjuster
permits quick, on the fly, depowering of both sails
. Mainsails are easier than jibs to reef in a manner that results in an efficiently shaped sail for heavier conditions. It means that you donít have to take 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 often smaller or eveb 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 for a new sailor. 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 neither has the opportunity for 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 when you increase the size of 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. The lower rig loads can also mean a longer standing rigging
lifespan and lower stresses on the boat. Fractional rigs generally lack the redundancy of masthead rigs in that a properly designed fractional rig only has a single
set of lower shrouds.