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Old 31-07-2013, 22:24   #1
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Fractional Rigs

I'm in the market to buy my first boat ($30k - $40k range coastal cruiser) and I've been searching all over, from Portland up into Canada. I've seen several fractional rig configurations and I have to wonder why a manufactuer would design a boat that way. The headsail is obviously an important, driving sail. Would the mast on these boats have to be more forward so that the CE isn't too far aft? Is a fractional rig ever a positive thing?

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Old 31-07-2013, 22:37   #2
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Re: Fractional Rigs

Fractional rigs are handy for racing boats to help control the shape of the mainsail. If you are over powered going up wind and the boat is healing too much you bring on the backstay inducing mast bend and that flattens the top third of the main reducing heeling and also may put extra tension on the jib halyard bringing the jib draught forward and gives the jib a sharper/straighter entry along the leading edge. This helps the boat go faster and point higher. Not 100% sure about the affect on the jib maybe someone else will clarify.

More usefull as winds get stronger. Backstay is more eased in light conditions.

Downwind and reaching you let the backstay off a bit.

Basically gives you more control for sail shape.

Handy for racing but not really much reason for it on your average cruiser.

Just from my experience, I am no expert.

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Old 01-08-2013, 11:06   #3
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Re: Fractional Rigs

I agree with "gaint"
However it can get quite confusing when speaking on how frac ribs are controlled.
When compared to Masthead boats you have a proportionally larger main and yes your J measurement (foretriangle) is less. On both designs the headsail is important, it is just on the frac with your main being larger you have a wider wind range in which you can operate with the given sail area because of the control you have with the main. Theoretically you would need less of a sail inventory on a race boat because of this added flexibility. This would be true on a cruising boat too however when one adds roller furling then not so much.
Also a frac boat usually sails very well with just a main and this would be helpful in over powered conditions. Some masthead boats do not sail very well with just a main.
By adding backstay tension you are also twisting off your upper leech on your main which will give you a wider range in the higher winds.
As far as controlling your headsail goes it becomes more complex when you speak of headstay sag which can also sometimes be controlled by how tight your lowers are. And to make it even more complicated by adding runners you can specifically control headstay sag independently of the backstay. Most cruisers stay away from runners although there are a few out there.
Last but not least a Masthead boat usually can sail deeper downwind than a frac where your VMG is tied to sailing the right angles.
Well....hopefully this did not make you more unsure of what to buy.
I have owned both types of boats and love them both. I would definitely not avoid a frac boat for cruising providing all the other elements were there.
You should sail both and see for yourself.
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Old 01-08-2013, 11:34   #4
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Re: Fractional Rigs

makes a difference if whether it is a fractional rig to get around a rule for sail area, or if it is a fractional rig because it is designed with a big main sail with a ceneter of effort further aft

on my boat I find the frctional rig much easier to sail and control than my last boat's "standard" rig
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Old 01-08-2013, 14:51   #5
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Re: Fractional Rigs

Fractional is the more efficient rig. It is also the easier rig when fewer crew are sailing.

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Old 01-08-2013, 14:59   #6
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Re: Fractional Rigs

G'Day Steve,

Well, we've been cruising with a fractional rig (with swept back spreaders) for 10 years and ~42,000 miles now. In many ways I like it, but honestly the requirement for running backs in anything but mild wx is a PITA for a short handed crew.

Good things (IMO): sails well on main alone, uses smaller headsails, gives high performance.

Bad things (IMO): runners as mentioned above, can't get the main out far enough when sailing deep angles, mainsail is very expensive, because of large size, mainsail can be intimidating.

Bottom line for me is that I wouldn't deliberately design a boat with this rig for short handed cruising, but appreciate the advantages that it offers now that I own it!


Jim and Ann s/v Insatiable II , lying Twofold Bay, Eden,NSW after our 32d crossing of Bass Strait!
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Old 01-08-2013, 15:11   #7
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Re: Fractional Rigs

As the jib is the sail that is very hard to reduce in area without ruining the shape, while the main usually actually improves in shape when reefed, that makes the fractional rig easier to adjust to variable conditions.

Even with plenty of hands, a change of jib on a furler in worsening weather would be intimidating.

The jib on my masthead rig can be a real handful when the wind gets up. What you end up doing is sizing it for the strongest winds you think you'll see. I'm down to an 83% for summer in SF Bay.

A fractional rig would be able to use a 100% or bigger in the same weather - no different upwind, but your downwind / light wind performance will be better.
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Old 01-08-2013, 15:39   #8
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My Tartan 33 is my first "big" boat and it a fractional. FWIW I am still on the learning curve.

The T-33 does not have running backstays. She will sail fairly well under main alone. Or sometimes I roll up the 135 into a 90-100. No the shape is not perfect, but it does balance the rig nicely.

The boat is a solid first boat. Not sure if the masthead would be as easy to single hand
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Old 01-08-2013, 18:28   #9
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New designs do not require runners. Sure is a lot easer to tack a fractional boat. Most newer fractional rigs also only have a 100% - 130% jibs. All this makes sailing a larger a boat a whole lot easier.
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Old 01-08-2013, 18:40   #10
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pirate Re: Fractional Rigs

Fractional sails are pluses all the way.. better performers... and cheaper headsails than a masthead..

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