Masteheaded Vs Fractional rig

[mholguin]

Can somebody explain in plain english waht are the advatanges a fractional rig has over a mastheaded and viceversa?

Nothing too deep...

[Finlander]

Ok, nothin' too deep here, otherwise I'll drown rather quickly... :)

It is my understanding that the most efficient stayed-rig is one that has a jib without overlap. Instead, the sail area should be weighted toward a big mainsail. Large, overlapping Genoa's are used for certain types of racing, but that's because the overlap isn't counted toward total sail area; otherwise they're not especially efficient.

Hence, a fractional rig helps to satisfy the goal of having a small non- or only slightly- overlapping jib and large mainsail, because the mast can be placed further forward.

Someone please correct me if I'm wrong; this is only derived from something I've read. I'm not an expert in the theory of rig design.

Kristian

[jarhead]

sounds good,kristian. no jib at all is even better, in my view. on a boat up to about 7 metres, you can use a cat rig and forget about jibsheets and backwind. for bigger boats a small jib on a club will take you up to 9-10 metres.

[RHough]

sounds good,kristian. no jib at all is even better, in my view. on a boat up to about 7 metres, you can use a cat rig and forget about jibsheets and backwind. for bigger boats a small jib on a club will take you up to 9-10 metres.

A single element foil ala cat rig cannot develop as much lift for the same area as a split sail plan. In conditions where the boat can use the maximum lift for a given area a large main, small jib combination will produce more power. A single foil has a CL limit somewhere in the .9 - 1.1 range. A multi-element sail has a CL max of 1.6-2.0, the potential for almost twice the power for the same area.

If you look at classes that have a sail area limit, after some extreme experiments, they all end up with the fractional rig, large main, small jib configuration. In classes like 18 foot skiffs, even though there is no limit to sail area, they have chosen the large main, small jib combination also.

[gggGuest]

If you look at classes that have a sail area limit, after some extreme experiments, they all end up with the fractional rig, large main, small jib configuration. In classes like 18 foot skiffs, even though there is no limit to sail area, they have chosen the large main, small jib combination also.

Actually that's not quite true. There are several single handed dinghy classes where a single sail is preferred, notably the A Class Catamaran and the Moth.

But agreed, you never see big overlapping jibs or masthead jibs.

[Raggi_Thor]

For upwind work, tacking, it's convenient to have a small jib.
For downwind sailing maybe a large genoa or two, one on each side is easier to manage than a spinnaker.
So masthead rigs may be good for cruising while fractional rigs are better for racing, also because you can trim the main with a backstay (bend the mast top).

Just my impression :-)

[mholguin]

Good answers. I think I understood. But of course, a follow-up questioon:

In a boat rigged as masthead, using a smaller jib (say a No. 3 or 2) is not as efficcient as the No1 for winds around 15 KNots... this would be because a masthead rig places the head sail too forward? Or can any boat benefit from using a smaller jib?

Before somebody asks to test it myself, we are currently restoring our boat, a Tartan 30C. There are no plans to re-rig her, just curious to see what would be faster....

[Vega]

They say it better than I can, but I agree with those Guys:

“In my sailing experience I have learned to prefer a fractional rig to a masthead version, whether cruising, racing or daysailing.
.................
So why are so many cruising boat built today with masthead rigs? For one reason they are simple and cheap. The mast is usually just a straight un-tapered extrusion. For another reason, builders seem to be reluctant to change, a problem in our industry that has stifled growth and innovation. The masthead rig is largely an anachronism left over from days when the racing rules gave favored treatment to boats with masthead rigs. This is no longer the case, but cruising boat design was adversely influenced for years by handicap rules, even though most boats never see the starting line”.
................

http://www.rcryachts.com/fractional.htm


.... “The fractional rig was first used on race boats, as it gives more control in raking the mast with an adjustable backstay giving more control with mainsail shape.

These rigs are used mainly because they offer better performance. The larger mainsail increases performace downwind and in light airs. The downside is that the big mainsail can overpower the boat in heavy winds and you should reef sooner rather than later. However, because of the greater control you have with mainasail shape, by tightening the backstay, the draft of the sail moves farther forward, increasing stability to windward in heavy conditions. In light air, releasing the backstay puts more camber back into the main and it offers plenty of power.

The fractional rig makes for a very good racing rig and cruising rig. The headsail is smaller and there is no inner forestay, forward lowers or large overlap to slow down tacking the jib. The smaller headsail means faster tacking and less physical effort for the crew - good for racers and cruisers! Many fractional rig boats sail nicely under main alone which is another bonus for cruisers.”

http://marina42.net/cgi-bin/p/m42p-custom.cgi?d=passage-yachts-inc&id=615


“I like the simplicity and strength of the masthead rig but I like the versatility of the fractional rig. My own boat has a fractional rig. Fractional rigs are pretty”.

(Robert Perry)

Perhaps there is one case were I would prefer a Masthead Rig, and that’s if that rig is for a Cutter.

[RHough]

Actually that's not quite true. There are several single handed dinghy classes where a single sail is preferred, notably the A Class Catamaran and the Moth.

But agreed, you never see big overlapping jibs or masthead jibs.

You are right of course. I should have said ... Except for single handed boats ... :)

[mholguin]

Veda:

You made me realize that is not simply a matter of headsail size... the fractional rig has clear advantages over a masthead, when it comes to shaping the mainsail thru mast bend. That would be hard at best with our masthead as the mast is quite old and with an elipitical cross section.

Question still remains on on a mastheaded being able to perform better with a smaller jib...

Thanks guys, this is going great...

[Finlander]

Question still remains on on a mastheaded being able to perform better with a smaller jib...

I also wouldn't switch to a fractional rig if the boat wasn't originally designed for it. There's probably not much advantage unless the mast was placed far forward in the first place. Then again, consider this....

<begin slight digression> But first, my preference---and I plan my next boat using this concept---is to have a small, boomed, self-tending jib. Perhaps it will be extended by a bowsprit. However, a boomed jib and bowsprit might not easily work in your case. That's because you have to consider the geometric center of effort---it might mean changing the mainsail-traveller's position further aft, etc.... <pardon my digression>

Nevertheless, a moderately-sized working jib is still a good idea. I always prefer it over a Genny for upwind and close reach conditions---even in light winds. But for a broad reach in light conditions, I prefer a cruising spinnaker or blooper (I can't remember the correct terminology these days). Not a full spinnaker in any case.

And for dead-downwind sailing, consider that mainsails aren't great because the boom can't extend beyond the sidestays (generally, free-standing masts rule in this regard, but they appear to be very expensive). Hence, many stayed-rig sailors prefer to tack downwind to improve speed and comfort and also to avoid jybing.

So, to enable acceptable, dead-downwind performance, I'd want dual wing to wing headsails (as was mentioned in a previous post), but with no mainsail. For example, it could have a cruising spinnaker, plus the small working jib opposite. If the working jib jybes, then it's no big deal; just keep focused on the cruising spinnaker.

In any case, this is where I see a benefit to a fractional rig: The short jib would probably interfere less with the cruising spinnaker---assuming that the cruising spinnaker is pulled to the masthead.

No matter whether you ultimately choose fractional, masthead or a combination of both, you might consider dual-headstays, depending on the type of cruising spinnaker you choose (some attach to a headstay, some don't), and of course, dual-halyards. IMO, a good downwind rig will increase your sailing enjoyment more than anything else. Plan accordingly :cool:

[mholguin]

I think I was misleading in the way I formulated my questions.

we are currently restoring a Tartan 30C. We are not considering any modification onf the rig. I was wondering, if first fractional rigs had any advantage over mastheads, and -back to our boat- using smaller than 150% jibs and trimming the mainsail better would yield better performance.

Back in the days we used to race, we used the 150% as much as we could, by reflex if you will. I guess the question is now, considering that in a fractional, the small jib/big main works so well, if the same can be applied to a masthead, using a smaller jib to get better? performance.... I guess I'll have to wait to have the boat fully repaired....

[Finlander]

You're not planning on racing are you?

I know I'm not exactly answering your question, but here's how I dealt with a similar issue as you're facing....

First, I'm a cruiser; not a racer. One thing that I never liked about 150% Genoas is that the low foot tends to obscure viewing. Naturally, the clew can be raised, but then weatherhelm suddenly increases. Care must be taken to keep the rig balanced.

In my case, I trimmed both foot and leech to make the the whole thing smaller. Scary! And to counter weatherhelm and also to maintain adequate sail area, I added a boomed staysail to effectively transform the rig into a double-headsail ketch.

It was a relatively simple task, but before cutting and drilling, I first tested the rig by adding a temporary staysail and fastening the jib-sheet blocks further aft, etc. to simulate the intended balance.

Ultimately, the smaller jib and self-tending staysail made things easier to handle and improved visibility. Plus, the sail area actually increased. Since the smaller sails seemed to hold their shapes better, sailing characteristics improved under all conditions. There was probably some extra speed, too.

So, to answer your question as specifically as I can: Yes, IMO, a small masthead jib is better than a Genny. But keep overall sail area in mind---think about adding a staysail if necessary and possible. I know you stated that you're against modifications, but this isn't a big one ;) And it only works if you're not confined by racing rules of course.


Kristian

[gggGuest]

.... “The fractional rig was first used on race boats, as it gives more control in raking the mast with an adjustable backstay giving more control with mainsail shape.”
Arguably any gaff or gunter rigged boat is effectively a fractional rig.

[sharpii2]

Can somebody explain in plain english waht are the advatanges a fractional rig has over a mastheaded and viceversa?

Nothing too deep...

The biggest advantage I see I a fractional rig is balance. In every one Iv've sailed on, the first step in reefing is dropping the jib. In every occasion I have done so, I have successfully shortened sail without creating a monster weather helm. The next step in reefing is taking a slab out of the main. But if merely dropping the jib will do, it's easy enough to hoist it again very quickly.

With a masthead rig, I don't think you can get away with that. Once the jib, which is usually larger than the main, is dropped, The Center of Area (CA) of the rig moves way aft which can create a wicked, maybe uncontrollable, weather helm. The cure is to hoist a smaller jib, or reef the original jib, then take a slab out of the main. Without roller reefing, this can be a lot of work. Especially when you are out alone.

The main advantages of the masthead rig are that:
1.) it can carry more sail on the same height of mast and
2.) it is enormously strong for its weight and level of materials technology. It is possible to make a masthead rig that is all but indestructable with relatively inexpensive materials. George Buehler claims that a masthead rig of his design was hit by a seaplane and was still standing afterward. (the seaplane didn't do as well). I have read accounts of vessels with such rigs being rolled completely over and having the rig still completely in place.

Also, the CA problem can be easily solved by going to cutter or ketch rig. Maybe thats why you occasionaly see very small, under 30ft, masthead cutters and ketches.

I hope this helps.

Bob

[Crag Cay]

A simple 'Masthead vrs Fractional' debate is really too simplistic without reference to all the other variables that are involved. If you constrain some of the these, such as for a given sail area, or mast height, or cost, or boat speed, or ease of use or structural strength, the 'best' rig advice might well vary.

For instance, if you were going to do a lot of trade wind sailing, then there are specific issues that may well influence what rig would be best: If you fancied twin poled out headsails, then a mast head rig might be preferred as you could set a larger running rig. Also, the common use of swept back spreaders with fractional rig can also lead to loads of wear and tear off the wind, but some people find running backs a pain, but the alternative diamond stays seem to have fallen from fashion of late. However the smaller spinnaker on fractional rigs can be easier to handle when short handed and fractional rig boats generally can manage a wider range of wind speeds (and angles) with fewer headsails, or cope better with a roller furling headsail.

Your Tartan 30 is very similar to our old S&S on which I have covered tens of thousand of offshore miles. They were both children of the seventies whose fine upstanding mothers were inseminated, (probably against their will) by the sperm of the IOR devil. The rig rated well but was never designed for ease of handling or outright speed. However it's not all bad news as in the 30ft size things are still manageable and the slippery hull moves well.

But they are headsail driven. Any dreams you may have of only using non over lapping headsails in winds much less than 20kts will be frustrating at best. The most versatile headsail will be a 135 percent, fairly high clewed genoa, similar to the No2's of old. On the wind, you will be able to carry this into the 20's but will lose power much below 10 kts. We carried a 155 light No1, but frequently augmented the 135 with a bit of engine, rather than do a headsail change, unless we were certain conditions would be light for some time.

Our next smaller headsail was a full hoist 100 percent solent jib, that would take us up wind in the trades, or to snug us down a bit at night with winds in the high teens. It had a set of reef points that would quickly allow us to shorten it by about 30 percent of area in squalls. After that it was a proper storm jib. Most sailing was with the 135, and today set on a roller, I still think it would be your most useful sail. But if heading for the trades, I may well still take a full hoist 100 that also fitted the roller. However, I think I would carry more diesel than the 155.

The other bad news about the 70's IOR boats is they need spinakers to move off the wind. The mainsail again is not really big enough to give much power, and the genoas twist off and do diddly. The original racing chutes were huge, driven by the boats long J measurement. However they were what we had and with a well rehearsed system were usable singlehanded by me and the girlfriend without any trouble. However if I was putting together the ideal system I would carry a .5oz conventional spinaker and a 1.5oz cruising chute for running in heavier airs with the tack on the stem and the clew poled out, or reaching set without the pole. The 135 with its higher cut clew also poles out well, and when the self steering struggled as the boat got skittish in about 25kts of wind, a reef in the main balanced her up, which defies all logic as the 135 was already significantly bigger than the main.

It's these sort of idiosyncrasies that you have to explore with boats. The simple models about weather helm aren't always that helpful. Our boat never carried any weather or lee helm despite radically different sail combinations. But her balanced waterlines, did mean she didn't have much stability in her 'stern quarters' and hull speed when deep running could be a bit rosy. But plenty of main boom vang to keep the leech bar tight stopped it getting out of hand (too often).

People may say that's a lot of sails and different combinations. But I'm afraid that's the legacy of that damn rule. Certainly a well sorted modern cruising specific rig, either fractional or masthead, would be easier, but go with what you've got rather than sit at home dreaming of the ideal.

But I actually thought at the time it was a very reserved wardrobe. We had been campaigning an IOR 2 tonner at the height of their 'development'. We wouldn't have left the dock without (if I remember) a Drifter, Heavy No1, Medium No1, Blast Reacher, No2, Solent No3, No4, Storm Jib, .5oz floater, .75oz radial head, 1.5oz cross cut, .2oz storm chute, blooper, heavy blooper, mainsail and trisail. I can't work out if I miss that lot more, or stainless steel wire halyards. Now they were a really good idea! Not.

[mholguin]

Cay:

Your explicit post answered my question. Thanks. Like many have said, is a whole package issue, not simply a matter of changing one factor. I never intended to modify athe rig,, anyway, and your explanations on the origins, make perfect sense...

Thanks a lot!!

[Ryerson]

[QUOTE=Finlander]

And for dead-downwind sailing, consider that mainsails aren't great because the boom can't extend beyond the sidestays (generally, free-standing masts rule in this regard, but they appear to be very expensive). Hence, many stayed-rig sailors prefer to tack downwind to improve speed and comfort and also to avoid jybing.

So, to enable acceptable, dead-downwind performance, I'd want dual wing to wing headsails (as was mentioned in a previous post), but with no mainsail. For example, it could have a cruising spinnaker, plus the small working jib opposite. If the working jib jybes, then it's no big deal; just keep focused on the cruising spinnaker.

QUOTE]

I've got a 170 Genoa on a 40 foot mast (masthead rig, 38 ft. Cross Tri) and when running downwind in moderate wind I pole it out and run dead downwind with a cruising chute on the other side, wing and wing, no main. very comfortable and balanced. The auto helm even likes it, and for downwind sailing with the main it doesn't hold course, overpowered easily. Easier to tack downwind but a lot more miles if the destination is directly down. I have roller furling but don't roller reef the sail. When going to weather and wind speeds get above 14 or 15 I roll it up and use my staysail. (cutter rig) to put the center of effort closer to the mast. I find I can definately point higher especially in rough seas.

[Ryerson]

Thanks for that one, the specifics are indeed very important in this discussion.

[brian eiland]

I've got a 170 Genoa on a 40 foot mast (masthead rig, 38 ft. Cross Tri) and when running downwind in moderate wind I pole it out and run dead downwind with a cruising chute on the other side, wing and wing, no main. very comfortable and balanced. The auto helm even likes it, and for downwind sailing with the main it doesn't hold course, overpowered easily. Easier to tack downwind but a lot more miles if the destination is directly down. I have roller furling but don't roller reef the sail. When going to weather and wind speeds get above 14 or 15 I roll it up and use my staysail. (cutter rig) to put the center of effort closer to the mast. I find I can definately point higher especially in rough seas.
Have you ever seen this 'cutter rig' combined with a mizzen, and no mainsail??
http://www.runningtideyachts.com/sail/ (http://www.runningtideyachts.com/sail/)

[Roly]

Fractional rig--Raggi Thor
also because you can trim the main with a backstay (bend the mast top).

Oh-boy,,,,does that ring some bells.

A little digression, but, it seems as thought using the back stay as a main flattener on a masthead rig is not ideal (more stress on the rig & hull, pumping, and or inversion) and you really need a flatter cut main to carry more mainsail in higher winds?
(ie more sails)

[yokebutt]

Roly,

What you do is to crank/jack/winch on the backstay until the mast overbends from the compression load, then you use the checkstays to pull the middle of the mast back to your desired amount of bend, that will give you really nice headstay tension.

Yoke.

[Roly]

Thanks for the explanation, yoke.
My boat has only fixed lowers;No checkstays.
And my mast is symetrically oval with no taper. Old.
My over exuberance on the backstay probably contributed to my current rebuild.

[Mark 42]

...or stainless steel wire halyards. Now they were a really good idea! Not.As with much of engineering, it was a materials problem.
Stainless steel doesn't stretch much. These days we have very hi-tech synthetic lines, but back in the mid 1970's and 1980's the lines were more stretchy.
Most of the ones I dealt with had a line spliced to the SS wire so that you
handled the line most of the time.

As far as huge overlapping genoas: my understanding was that they were there to
create an aerodynamic slot and increase efficiency (as mentioned above;
like a multi segmented airfoil).

I sail (well, own anyway) a San Juan 24, and am used to the wire halyards.
Here on Puget Sound, the 170 Genoa is great for going to weather in light air.
The boat's biggest weakness is downwind in heavy air (death roll).

I crewed on a Synergy 1000 for awhile, and it's a very different type of sailing.

And somewhere between the two lies the Santa Cruz 27, which will be my next boat
if I ever find time to go sailing.

Or an Olsen 30 if I can get my accountant to approve it :p

Ultimately, they are all fun in different ways. If speed were the only factor
I would go to a multi hull with a rigid wing.

[Crag Cay]

Yes they were stainless steel halyards with rope tails, but the wire over the sheave, work hardened under load. Although we had four genoa halyards rigged we broke them all in one 650 mile off shore race. After that they were replaced with galvanised and we never had any trouble again.

[yokebutt]

Roly,

I wouldn't want to be without an adjustable backstay, since that is what you use to adjust the overall the overall power to suit conditions. Most importantly, restrict how much you can ease the backstay and not break it with the lowers, assuming the lowers are set a bit aft of the mast. At some point, additional tension will bend the boat but not straighten the forestay anymore, that is your max tension, don't exceed it.

A sailboat is designed to handle its rigging loads, provided its decently built, I wouldn't worry about maxing the backstay when conditions warrants it.

For your type of rig you want to set backstay, (headstay, really) depth, twist and halyard in the jib and match the main settings to the median wind and then shed the puffs by feathering and/or easing the mainsheet enough to keep the boat feeling good and fast. If the wind is trending up or down, you adjust the other controls to suit. When the wind is steady or you have plenty of people-power, playing the backstay together with the mainsheet is fast.

This might seem excessive to some, but for me, sailing on a poorly trimmed boat is a dreadful experience.

Yoke.

[FAST FRED]

"Yes they were stainless steel halyards with rope tails, but the wire over the sheave, work hardened under load."

With a bit of work perhaps you could rig halyard locks as used (usually) on much smaller boats.

A ball is siezed onto the wire and the sail is hoisted till it locks, and luff tension is put on at the foot.

To lower the sail its simply hoisted an extra 2 inches where it frees from the lock.

This effort will reduce mast compression by 1/2 , perhaps worthwhile to the "edge of the envelope" racers.

Even better for the window shaderoller jib folks as they almost never can hoise a straight luff.
A downhaul to a sheet winch is fast & EZ.

Actually built a forestay toggle with the halyard lock built in , bit couldnt find a market.



FAST FRED

[Mark 42]

On mast bending in masthead forestayed (forestaid?) rigs...
On some boats (Santa Cruz 27, San Juan 24, et. al.)
they use a babystay to either fix the position of the middle of
the mast so that bending is in the upper portion, or on some
they can adjust the tension in the babystay to pull the middle
of the mast forward (dependent upon class rules).

[kimper]

Hello,
Can anyone explain me why the mast is not as the same position for a masthead configuration and a fractionnal one? ( as written in http://www.rcryachts.com/fractional.htm). Is it only a problem of center of effort position or is there any other issue?


"The frac rig spar is farther forward in the boat, meaning that its' position relative to the logical location of the forward main cabin bulkhead is better, with the result that it is less intrusive in the cabin"

kimper

[sharpii2]

Hello,
Can anyone explain me why the mast is not as the same position for a masthead configuration and a fractionnal one? ( as written in http://www.rcryachts.com/fractional.htm). Is it only a problem of center of effort position or is there any other issue?



kimper

You're right the first time. It's mostly a matter of center of effort. The keel, because it also serves as ballast, has to be under the middle of the boat, or under the boats center of boyancy. Because the jib on a fractional rig is smaller than the main, the Center of Area ends up further aft.

So, to make the rig ballance with the boat, you have to move the whole thing forward. And, if you don't want to mess with a bow sprit, this has to be done at the expense of the jib sail area, making it even smaller in proportion to the main.

Bob

[kimper]

That's interesting... Does it mean that you actually take in account the asymetric spi when you define the lead?
kimper

[kimper]

just a test for profile setting issue -Not a post-

[brian eiland]

Just saw an ad for this vessel and thought "what a powerful looking mastheaded sailing rig"