# Masthead versus Fractional



## Cruisingdad (Jul 21, 2006)

The traditional frame of thought, as I had always been told, was that a fractional rig was always preferred over a masthead. It was interesting, because in teh last race I was in, there seemed to be a real preferenece to move away from fractionals and go to mastheads for the extra sail area. I also found many of teh boats running a asym versus symetrical for ease of use and more versatility. This especailly comes in to play when racing with a short crew.

I have to tell you, after seeing what I saw, it would be hard not to go with a masthead. I wonder if the fractional frame of thought is overblown or out of date (jeff will kill me). I am curious what others think... also what they think about a symetrical versus asym. Now, in medium-heavy airs, I think the argument could be made for a fractional and probably a symetrical. But for lighter airs, I wonder if the mast head and asym will win every time???

Thoughts??

Brian


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## JomsViking (Apr 28, 2007)

Sure it was a masthead? Many newer fractionals look almost like mastheads (eg 16/20 fraction). But that gives additional sail-area like you say.
We like the Asym for easy handling, and that might mean that we get there faster anyways - even if racing, because we're squirrely DDW so prefer to tack a few times instead. Our boat is a masthead, and we get a LOT of sailarea with the Asym, or even the genoa. But as has been stated also hard work getting it home.


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## sailingdog (Mar 19, 2006)

CD—

IIRC, a while back, Jeff_H wrote a good post about masthead vs. fractional rigs and how, if given a choice on a boat, getting the fractional rig was a better idea, since it gives you more control over sail shape and such, even if it is a 7/8's fractional rig or so.


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## JohnRPollard (Mar 26, 2007)

CD,

I think there's a bit more to it than simply masthead vs fractional or asym vs sym. Hull forms, rig geometry, sprits, poles, weight all factor in. It's difficult to be categorical about either one - so much depends on the many variables.

For instance, there was a time when most fractional boats also flew fractional spinnakers (whether asym or sym). Now, it's not uncommon to see a fractional rigged sloop, flying a mast-head spinnaker. Some designs even fly a masthead asym, and a fractional symmetric chute. Lots of variables.

In my experience, asym chutes work best for cruisers that aren't following a windward-leeward course, or for sport boats that can get up on a plane and so take advantage of better downwind vmg (i.e. they sail higher jibe angles, but at faster speeds so the extra distance doesn't hurt them). Asyms can also work well for non-planing race boats, but usually only for long reaching legs (rather than a dead run downwind).

But sometimes, especially in light air, running deep with a symmetric chute works better. That's why from one race to another, certain configurations may seem superior than others.

As Joms said, fractional rigs come in a lot of varieties. Some are SO fractional they need running backstays to support the rig. Others are only moderately fractional, and use more conventional rigs. Some fractional rigs have big overlapping genoas just like masthead rigs. Some masthead rigs are designed to sail well across a wide wind spectrum with a non-overlaping jib.

I think one of the trends in rig design that I like, is the effort to get away from large overlapping genoas. You tend to see this more on moderately fractional rigs, that put proportionally more sail area into the mainsail. Also, with the mast typically stepped a bit farther forward, in addition to easier headsail handling, you also often get the advantage of being able to sail reasonably well, and balanced, under mainsail alone. 

There are downsides, of course. One important one is that the fractional rig will likely be significantly taller than a comparable masthead rig - a concern for many with bridge clearance issues.


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## smackdaddy (Aug 13, 2008)

Good topic CD. I've been wondering the same thing. I'd like to get a kite for the Smacktanic this spring - so this helps understand things a bit better.

Personally, I like the simplicity of the masthead. Like I need anything more complicated like running backstays at this point!


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## COOL (Dec 1, 2009)

As evident in most modern GP race boats,
the ideal configuration is a Fractional rig with 
Masthead Spinnakers, and in some cases
Masthead Genoas.


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## GeorgeB (Dec 30, 2004)

Cool is right on. Fractional boats allow for jibs to be sheeted closer to the centerline giving the boat more pointing ability. These boats are also often rigged with runners allowing for “chicken head” tops and roached out leaches. Instead of shifting through the gears by making headsail changes, these boats to a lot of main trimming and reefing. All those extra head sails on a mast head boat become a problem when trying store them on board for longer races/voyages. Mrs B. only allows me to take two when we do our summer cruises.

Symmetric Spinnakers project a greater sail area per a given “J” than A-kites. To take advantage of an A-kit the boat must be an effective surfer or planer at those hotter wind angles. Our heavier Catalinas and other cruiser boats are better served with symmetrics. I’m planning on retiring our A-kite from racing next year as I am frustrated with it’s relatively poor performance and I’m experimenting with doublehanding the symmetric. I’m a bit surprised (and a little disapointed) that the new C354 is going A-kite and sprit. They take time off your PHRF number out here for a max girth larger than 180% * “J".


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## tdw (Oct 2, 2006)

One of if not the most difficult aspects of sailing a boat short handed is headsail sheeting. Larger, multi speed self tailing winches have certainly made things somewhat easier but anything that can reduce the size of headsails is OK with me. 

I figure that is as good a reason as any to support the fractional rig argument.


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## COOL (Dec 1, 2009)

JohnRPollard said:


> CD,
> 
> I think there's a bit more to it than simply masthead vs fractional or asym vs sym. Hull forms, rig geometry, sprits, poles, weight all factor in. It's difficult to be categorical about either one - so much depends on the many variables.


This is true, we are making some gross generalizations here, 
while in fact there are many variations on the theme.
Some Masthead rigs use runners, or check stays,
some Frac rigs do not have runners, some do not even
have backstays.
Not all Asymetric spinnakers are flown on a centerline sprit,
or tacked to the bow.
For a displacement boat offshore, the fastest set up is an
A kite, on a conventional pole.


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## Cruisingdad (Jul 21, 2006)

I can talk more about this tomorrow hopefully, but we had a Tiger and a Melges with a Asym that KICKED OUT BUTTS! Very light air, but shifty, which made the Asym awesome. It was a masthead. Manhy of teh racers were saying that fractional was a thing of the past. Me, I just lusted after the Melges...

But good food for thought and makes a good discussion.

B


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## Cruisingdad (Jul 21, 2006)

BTW, I know the Melges and Tigers are frac's... I was just bringing up that they are PHRF killers.


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## JohnRPollard (Mar 26, 2007)

Cruisingdad said:


> BTW, I know the Melges and Tigers are frac's... I was just bringing up that they are PHRF killers.


Brian,

Not sure which model Melges that was -- but the M24 is fractionally rigged with a masthead asym spinaker (flown from a sprit). So there's a good example of a fractional/masthead combo.

We had fun with ours - we never hit 20 knots like some folks have, but we came close several times. When the keel is humming like that, it's an awesome sound.


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## Faster (Sep 13, 2005)

JohnRPollard said:


> (on the Melges) We had fun with ours - we never hit 20 knots like some folks have, but we came close several times. *When the keel is humming like that, it's an awesome sound.*


Occasionally followed by the equally awesome wipeout?!?!?


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## JohnRPollard (Mar 26, 2007)

Faster said:


> Occasionally followed by the equally awesome wipeout?!?!?


In our case, more than just occasionally.


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## JomsViking (Apr 28, 2007)

smackdaddy said:


> Good topic CD. I've been wondering the same thing. I'd like to get a kite for the Smacktanic this spring - so this helps understand things a bit better.
> 
> Personally, I like the simplicity of the masthead. Like I need anything more complicated like running backstays at this point!


As COOL stated, many masthead rigs do have check stays - we do, but mainly use those when it's blowing 30+ knots. It's not really a great complication, but "just" something you need to remember.


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## puddinlegs (Jul 5, 2006)

Cruisingdad said:


> I can talk more about this tomorrow hopefully, but we had a Tiger and a Melges with a Asym that KICKED OUT BUTTS! Very light air, but shifty, which made the Asym awesome. It was a masthead. Manhy of teh racers were saying that fractional was a thing of the past. Me, I just lusted after the Melges...
> 
> But good food for thought and makes a good discussion.
> 
> B


What kind of boat are you sailing? It is similarly rated to the boats you mentioned? Sport boats... very low weight and wetted surface area. I'm a regular on a 39' boat that's absolutely runner dependent, tallish carbon rig _( I:50.20' J: 14.53' P: 51.90' E: 19.03' ISP:52.17' SPL:15.75' ) _10,500 lbs displacement), very fast, but is just out of the sport boat displacement numbers and without masthead assy kites. We owe them time, but sail boat for boat in the really light stuff. Give us any breeze over 4-5 kts though, and we're gone. The only exception is a very well sailed Melges 32 which are always just blazing fast and will crush any Flying Tiger/ Farr 30/Henderson 30 etc... any day of the week hung over and sick. There are just so many variables (displacement, wetted surface, design era, rule being raced under, etc...) that mast head vs. this or that is a hard one to work with exclusively. Indeed, newer GP boats are fractional w/ masthead spinnakers, sometimes assy only, and sometimes both depending on what the box rule or rating committee says, which leads to a whole different dimension of the argument; many of these rig 'optimizations' are rule driven.We're much much faster than a state of the art fractionally rigged (or masthead rigged for that matter) IOR design of equal length. Even GP boats like TP 52's, Open class boats, etc... have rules limiting to their sail inventories that drive rig and sail choice/design, but they are all fractional.... rumors of their obsolescence are little pre-mature.


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## Jeff_H (Feb 26, 2000)

I would say that since almost every new leading edge racing design is fractionally rigged, and nearly all new production cruising designs are fractionally rigged, the rumors of the fractional rig's demise is premature. 

That said there are a lot of aberations that show up in race boats that are rule driven (such the current spate of flat top mainsails). 

But if you were designing a boat for speed, efficiency, and ease of handling across a broad range of windspeeds, it would still be a fractional rig with a minimally overlapping headsail and with a choice of using both masthead and fractional hoist chutes. Whether or not these chutes are asymmetrical or symmetrical is dependent on the sailing venue and the L/D of the boat, with lighter boats rarely needing a symmetrical chute while a heavier displacement boat really benefits from having a symmetrical chute. More later. 

Jeff


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## maxmunger (Dec 29, 2005)

if you can fly masthead spins and genoas from a fractional rig (?) then isn't it a masthead rig?
As one opinion indicated, its all a matter of boat design and purpose. To each his own.


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## blt2ski (May 5, 2005)

maxmunger said:


> if you can fly masthead spins and genoas from a fractional rig (?) then isn't it a masthead rig?
> ......


To me, the mast head vs fractional is NOT the spin portion of the rig, but the main and jib. If the jib is not pulled to the mast head, then it is a fractional. Some 15/16 fractionals have mast head kites as std. Others in the 3/4 range, can do either mast or fractional kites. A couple of local boats, have choose to take the rating hit with a mast head kit, do exceptionally well, along with having a cheater kite out of 1.5-2oz cloth for windier days. Advantages to both set ups as many mention.

marty


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## puddinlegs (Jul 5, 2006)

f


maxmunger said:


> if you can fly masthead spins and genoas from a fractional rig (?) then isn't it a masthead rig?


Fractional boats don't fly genoas from the masthead... they're typically not designed for the load going to weather. On the other hand, some can carry a masthead spinnaker and something like a Code O within certain wind ranges. But even that depends on the particulars of the rig design.


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## smackdaddy (Aug 13, 2008)

Cruisingdad said:


> I can talk more about this tomorrow hopefully, but we had a Tiger and a Melges with a Asym that KICKED OUT BUTTS! Very light air, but shifty, which made the Asym awesome. It was a masthead. Manhy of teh racers were saying that fractional was a thing of the past. Me, I just lusted after the Melges...
> 
> But good food for thought and makes a good discussion.
> 
> B


I had a run on a Melges a couple of months ago. Flew the kite (and trimmed for a bit) in 20+. HAD A BLAST! That was a damn fun boat.


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## COOL (Dec 1, 2009)

puddinlegs said:


> f
> 
> Fractional boats don't fly genoas from the masthead... they're typically not designed for the load going to weather. On the other hand, some can carry a masthead spinnaker and something like a Code O within certain wind ranges. But even that depends on the particulars of the rig design.


Actually, many modern Offshore race boats do fly masthead genoas
from frac rigs. They function very much in the manner of a upwind 
Code Zero, but with subtle differences. A Code Zero must measure
as a Spinnaker, therefore the midgirth must be at least 75% of the 
foot length. This makes it difficult to design an extremely efficient
close winded sail. While it will incur a rating penalty, a masthead 
genoa can be a very effective light air sail on a boat that 
otherwise carries non overlapping frac rigged headsails.


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## paulk (Jun 2, 2000)

I seem to remember reading somewhere (CA Markaj?) that fractional rigs create a better or more effective vortex for their size than masthead rigs. It seems their overall shape with the leading edges of the forestay and then mast more closely resembles the curve of the vortex you want to create in order to move the boat upwind. Downwind... it's another story. I keep toying with the idea of putting a masthead chute on our boat. Maybe I can borrow one from a Swan 48 and see if it works.


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## blt2ski (May 5, 2005)

Paul,

A couple of boats in my YC, a Farr 1020, and a hotfoot 32? might be a 30, anyway, they have gone to a mast head spin, gained lots of speed down wind, penalty was not enough to make them non competitive, along with they now use the smaller fractional kite in upper winds to there advantage too. 

Marty


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## JohnRPollard (Mar 26, 2007)

GeorgeB said:


> ...Fractional boats allow for jibs to be sheeted closer to the centerline giving the boat more pointing ability. ...


George,

That's one point that strikes me as not necessarily correct. In general, I'd say the opposite.

The truncated foretriangle of a fractional rig usually makes achieving tight sheeting angles trickier. Whereas, generally speaking a longer foretriangle shrinks the acute angle between the centerline of the boat and the imaginary line from the tack to the sheet leads.

There are ways to work around this, but in general I'd say the masthead rig has the advantage here -- simply due to the geometry of the foretriangle.


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## LeftCoast (Nov 12, 2010)

I've not heard an argument yet that really convinces me that a fractional is better than a mast head.

The two I hear most..

A) You can bend the mast to depower the sailplan. - The J35 is a masthead rig, and the mast bends wonderfully for depowering the sailplan.

B) Masthead rigs need large overlapping jibs to work. - Thats not because they are masthead rigs, that's just how they were designed. You could just as easily design the boat for small non-overlapping jibs and just run the forestay to the top of the mast.

As for chutes.. Seems no one wants them anywhere but at the top of the mast now.

-jim lee


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## Faster (Sep 13, 2005)

LeftCoast said:


> I've not heard an argument yet that really convinces me that a fractional is better than a mast head.
> 
> The two I hear most..
> 
> ...


What you've said is true, of course, though the masthead kite issue is primarily a racing one. And in the J35, the rig is not exactly the same section and the controls are more involved than the typical run-of-the mill masthead cruiser-racer.

What I like about the frac rig is that jibs, genoas and standard hoist kites are smaller, lighter loaded and easier to tack, gybe and winch in than a masthead for a given sized boat. Not an issue until you get up into the 30+ footers, I suppose, but while I do find our 3/4 rig a tad underpowered at times, I like that the boat handles like 30 and lives like 35....


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## RichH (Jul 10, 2000)

The simple answer (from the mind of a fluid dynamicist) is: fractional boats are more efficient aerodynamically when close hauled .... AND with a masthead spinnaker are ~equal to the SA of a downwind masthead rig. 

Large overlapping headsails are simply aero-inefficient ... as most of the 'suction peak' due to aerodynamic flow is near the luff of a headsail. Extreme overlapping headsails retard the 'dumping velocity' or 'reposition it' too far aft of the point of max. draft in the main and thus decrease the aero-efficiency (circulation flow) of the interaction of the 2 sails. 

The fract rigs. (with mast head spinns) for *windward-leeward racing* are simply 'more optimized'. 
If races were limited to *close reach or below* .... you'd all would be frantically selling/touting masthead boats. 
Long distance cruisers try to avoid 'beating' and thats why cruisers prefer non-frac. boats. - the benefit of larger SA when 'off the wind' and not having the *almost-requirement* of needing to use a spinn. when going 'down'. Nothing is worse than going 'down' on frac. boat with NO spinn flying.


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## LeftCoast (Nov 12, 2010)

Wait a sec..

RichH : "The simple answer (from the mind of a fluid dynamicist) is: fractional boats are more efficient aerodynamically when close hauled ."

Why? I don't understand why this is.

and..

"Large overlapping headsails"

What my question was that -if- the boat was designed to use non-overlapping sails, then why not just run the headstay to the top of the mast?

I don't see why running the headstay to the top of the mast could hurt anything.

Sorry, this fractional thing has been a pet peeve of mine for a long time. I went around and around with our designer on it and never got an answer that I was really happy with.

-jim lee


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## paulk (Jun 2, 2000)

*To get the full answer*

you may have to read C.A Marcaj's books on aero and hydrodyanmics. My understanding is that the fractional rig, going upwind, has a better balance of factors that create a spiralling vortex UP, off the mainsail, than a masthead rig does. This enables a fractional rig to have better (more?) airflow over the sails than a comparable masthead rig, would, so the fractional rig therefore goes faster. In a masthead rig, the flow in the vortex may get disturbed by the flow from the jib, slowing the overall airflow, and making the masthead rig less efficient. Everything is relative, of course. A 50' masthead rigged boat will probably sail faster upwind than a 20' fractionally rigged boat. Fractional rigs and masthead rigs both work; what's being discussed is their average efficiencies under certain conditions.


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