Masthead vs Fractional

Apex · Nov 7, 2016

you should see a noticeable difference in the mast position as well?
The main difference is what sail is providing the most driving force: masthead = jib/genoa and a fractional drives with the main. Mains are easier to tack.

markwbird · Nov 7, 2016

The fractional rig allows for more adjustable main sail shape. This can be significant. That is why performance boats pretty much always have fractional rigs. The offset between where the backstay attaches to the mast and where the head stay attaches means that when you add more tension to the backstay it will bow the mast and change the shape of the main as per design. Without going into the details of what exactly that does, it adds to the boats performance.

Jackdaw · Nov 8, 2016

Fun question. Both rig style have been around for many years. And while the fract is clearly the performance rig of choice now, it's had an interesting evolution.

First some tech background; fractional rigs are described by what percentage up the mast the forestay attaches. This started out at 3/4, went to 7/8, and now lots of boats at 9/10s. More on that later.

As other have noted, fract rigs came about as a way to bend the mast to create sail shape. While this is possible on masthead boats (think C&C babystays) it was much easier with a fractional boat, in particular ones with aft swept spreaders.

This was known in the 70 and 80, but why so long to take off?

In North America in particular, fractional rigs were penalized by handicap rating systems that measured rated sail area by a boats JIPE numbers. Doing so rewarded huge headsails and tiny mainsails. That's why use used to see masthead boats with 180% genoas and dinky mains. That era has passed but the effects linger in production design here.

In Europe where formula-based rating are more popular, fractional boats took over and most have been so for over 30 years.

Racing for sure; I'd have to guess that the last serious race boat designed with a masthead rig was about 20 years ago. Again its a C&C (99).

For cruisers the advantage can be sail handling; in the past fractional rigs promised smaller headsails and maybe just one on a furler. And that's true.

Nowadays the difference is even more clear for both racers and cruisers, with the advent of the non-overlapping rig.

Designed tall with enough sail area to power the boat in almost all conditions, it only flies a jib and a powerful main. De-powering is done by reefing alone; the jib flies in most sailable conditions.

What also has happened is that with the 9/10s rig and moving the mast aft, the jib is almost the size of the main, creating a very powerful and adjustable sailplan. As a plus and by design, tall high-aspect sails are more powerful on an area by area basis, making tall jib and main better for racers then a squatter genoa.

Its interesting to look at the Beneteau First 30 as it evolved, from a genoa driven masthead rig from the 70s, to a fractional but still genoa boat of the 90s to the very modern non-overlapper of today. Look at how far aft the mast is, creating a huge jib.

Barnacle Bill · Nov 8, 2016

It was the old IOR days (for racers) where the rigs were high aspect, the booms were short, the J area was large and much bigger headsails were in use. So, most of the horse power was coming off the larger genoas and not so much the mains (albeit important). With the advent of the fractional rigs, the boom length increased, the mains got much bigger and the headsails got much smaller. This allowed for tapered and bendier masts on many boats that allowed, as mentioned above, a mast to be adjusted to create more bend for various wind conditions. For the casual cruiser (or anyone for that matter), the smaller headsails made for easier headsail handling (much easier to tack) and required less crew. Of course the large genoas, especially when the wind piped up on larger boats that could carry the larger sails through higher wind velocities, were a bear to get around the mast and winch in. Not so much with the fractional rigged mast. Also, the larger mains often were designed where the boat would be balanced and one could sail on the main alone without the headsail at all, which is hardly the case with most masthead boats. So, apart from racing rules and ratings, there was a difference in rig design when it comes to performance. An example would be the J/29. It was offered in several configurations. There was a mast head rig with an outboard. A mast head rig with an inboard and a fractional rig with both either an outboard or inboard choice. Depending on where you sailed, the rig made a difference. There was no doubt in an area (perhaps more inland) where the winds were generally lighter (or certainly not high), the masthead rig was the choice as it was a faster boat than the fractional rig going to weather. In bigger water, where de wind blow harder, the fractional rig was desired. Today, J/Boats have such keen designs that all of their modern boats have non-overlapping headsails (large mains and blades for jibs) and they still outsail many other types of boats both racing and cruising. But, more goes into this than just the rig. Carbon helps, keels help, close construction methods and materials all go into the mix to make them sail outstanding. But, I know all are not interested in J/Boats. Even a Precision 23 has a big main and smaller jibs (fractional) to make it an easier boat to sail on a Sunday afternoon in a blow.
Mains play an important role regardless of the type of rig, but with the fractional, they really are more important for producing much of the horsepower of the vessel.

Jackdaw · Nov 9, 2016

dehler25 said:
Certainly well thought out replies and I thank you all! It is still a question though in the respect that I have a 2002 H 450 and my neighbor has a 2007 45CC. The masts appear identical except for maybe a foot difference in air draft, the booms identical. I carry on the furler a 135 and a 95 as a he has something around a 110 on his furler and both boats have furling mains. I have not looked specifically at where the mast sits in a side by side as there is a bit of difference in the cabin top and foredeck layout. If it is different it can't be but inches as it has gone unnoticed. I am now wondering if I have been doing something wrong for all this time as I have only sailed the boat once where I was not singlehanding and that was the sea trial and yet tacking is almost no effort. I throw most of the turns off the working sheet, take slack on the lazy sheet, tack and as the sail swings through haul in the slack, set the A/P, trim.

I'm not sure i got your question.

A 110 will be much easier to tack than a 135, and will not have to be rolled down in a blow. That would be enough reason for most. The extra main makes up a lot of the difference in lost headsail area.

Most american cruiser manufactures are moderizing their rigs. While the First series has been fract for 20+ years, all oceanis now have been for awhile. Hunter was 50:50 for a while before going almost all fract. Even stodgy Catalina is getting into the act, at least partially.

Butch23065 · Nov 10, 2016

It sounds like you are saying the 45 is faster than your 450. Is that why you are questioning the rig differences? You can check but I would bet the 45 is a Henderson hull design and his designs are faster. I have an h41 and it out sails its sister 410 and the 420.

splax · Nov 11, 2016

How the boat is balanced under sail determines the rudder countersteer needed when going to weather. Countersteer creates a large amount of drag. Is it better to go faster or maintain a course, many times that is a dilemma. From your question it seems that you have been on the same tack and lost distance to another. Sail trim, sail condition, and a balanced boat may be the things you should consider.

Franklin · Nov 17, 2016

The one advantage the masthead rigs have is they can let their main out more because they rarely have swept back spreaders...at least on the old cruisers. They can also pole out the genoa and go faster with just the headsail even though that is bad for the mast. It is also easier to do wing on wing due to them being able to get that main out farther.