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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Fractional vs. Masthead Rig
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Topic Review (Newest First)
06-14-2004 02:37 PM
thorJ30
Fractional vs. Masthead Rig

I really like my J 30 frac rig.
Usually with only the wife on the boat, I can very easily slow the boat down, with a simple pull on the backstay. When the wind changes ( and it changes a lot on our inland lake ) I can step on the gas wihout lifting my butt from the seat.

I do not have roller furling, and usually too lasy to change headsails, therefore getting caught with too much sail a lot. The simple pull on the backstay makes life much easier.

Thorsten
05-25-2004 03:38 PM
max-on
Fractional vs. Masthead Rig

Thank you for your indepth responses to my inquiry, and you have confirmed my opinion and experience, and your responses are much more organized and thorough, which adds to my understanding of the topic. Thank you again.

Most, if not all, of my sailing experience has been on fractional rig boats, so I do not have much first hand experience with a masthead rig. I do enjoy the flexability that the fractional rig offers in powering-up or powering-down. Your comments confirm that the fractional rig is the way to go.



05-25-2004 10:28 AM
Silmaril
Fractional vs. Masthead Rig

Ahh, see the difference an archetect makes in a discussion! I developed my "feelings" based on years of imperical experience, and Jeff is able to put it into nice technical terms.

Either way, 6 of one, half a dozen the other, I think we are saying basically the same thing.

Jeff has picked up on my more "racing" spin on a topic.

From a rating standpoint, the masthead rig gets the advantage of the unrated sail area. That is where my "faster on all points of sail" comment comes from. If you limit actual sail area, you will see that the fractional rig comes out on top. Once again, an example of designs being influenced by rule formulae.

I can assure you of a good deal of "pucker facter" involved when dealing with the masthead rigs outsized down wind sails when the wind pipes up! The fractional rigged boats greater reliance in mainsail power makes it a much more controlable rig in a blow. They also respond very nicely to tacking down wind as their speed potential off dead down wind is greater, along with the greater ease of gybing the smaller chute.

Also my thoughts regarding running backs/check stays is geared towards the ultra high performance realm. I use runners to stop the pumping of my bendy masthead rig when sea conditions require it. A well designed fractional rig gets by nicely with just a backstay, but you still have to handle the tension properly to effect mainsail shape.

Now that I think more on it, the baby-stay, vang, backstay, outhaul, cunningham dance I do on my boat every time the wind changes 2kts is a little more complex than just a simple backstay adustment. Maybe I sould go out and play more on other boats...
05-25-2004 05:47 AM
Jeff_H
Fractional vs. Masthead Rig

I think that Silmaril hit the nail on the head, if you are looking for a rig that is simple and requires the least amount of ''fussing'' then a masthead rig makes sense because there is less that can be done to alter its sailing characteristics (without reefing or changing sails). This simplicity comes at the price that for any particular sail combination there is a vey narrow range of windspeed that works for that sail combo at least as compared to a fractional rig.

For any given actual sail area, properly sailed a fractional rig will offer better performance and be easier on the crew on all points of sail. The key phrase there is "actual sail area". When you look at race boats, many racing rules result in masthead rigs getting an advantage in ''unrated sail area''. Masthead rigs are a little faster in races sailed in a narrow range of conditions under rating rules that under penalize unrated area.

This means that in real life, if you are buying a boat mostly to go racing and want to race under a rule that underpenalizes overlapping jibs and spinnakers, then a masthead rig makes sense as long as you can afford to sail with a larger crew and maintain a more expensive sail inventory. (The C&C 99 has a masthead rig as a racing rule beating ploy more than any other reason.)

If you want to go cruising, or choose to race under a rule like the IMS rule (or to a lesser extent PHRF) that treats all sail area more fairly, then a fractional rig would makes more sense.

I did want to comment on Silmaril''s points:

Silmaril says that "a masthead rig is faster on all points of sail", all of the wind tunnel and actual in the field testing literature disagrees with that when taken on an absolute sail area basis. For a given actual sail area, fractional rigs with non-overlapping headsails, are actually the most efficient sailing rig meaning offering the best performance per square foot of sail area. So I think when Silmaril says that the masthead rig is faster on all points of sail, it is not that a masthead rig offers better performance for a given sail area, but as mentioned above it has a rating advantage under some racing rules. That advantage really goes away quickly in the case of rating rules that permit fractional rigs that use masthead spinnakers but then the smaller crew and easier handling advantage of a fractional rig goes away as well.

I also disagree that fractional rigs by their very nature need to be more complex. Racing masthead rigs are argueably more complex if they are to match and the performance of a fractional rig. While it is true that fractional rigs benefit more than masthead rigs from having a wide range of backstay adjustment. Backstay adjustment on a fractional rig quickly powers up and down both the jib and mainsail with one adjustment. Once you get used to having that tool it is very easy to use (Too much helm pull it in, too little speed, let it out) It is actually easier to use and far simpler than the combination of a babystays and adjustable backstays which is the masthead rig''s equivilent of a fractional rigs mastbend control systems.

With regards to running backstays, most traditional and modern fractional rigs do not use running backstays, any more than masthead rigs continue to use checkstays. It is only on boats that are designed with very bendy rigs that runners are still employed to fine tune forestay tension but then again, masthead rig boats with very bendy rigs end up with checkstays which in effect are less forgiving running backstays. (Most bendy rig frac''s can live without their runners but few bendy rig masthead righs can live without their checkstays being handled.)

That said cruising fractional rigs will sometimes rig running backstays in heavy weather in much the same way that cutters and sloops with a storm jib mounted on its own stay will rig runners in heavy going.

Anyway, here is my reply to an earlier discussion on this topic. Much of it is similar to Silmaril''s points and it was aimed at a person who was not clear on the definition of the two rigs.:

"These terms both derive from the point at which the forestay hits the mast. On a masthead rig the forestay hits the mast at the masthead (top of the mast). 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 7/8th’s (Triton) rig, 90% (Farr 40).

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 don’t need to have overlapping jibs. The sail area is made up in the mainsail.

Fractional rigs often have purposely designed flexible masts and, when combined with a backstay adjuster permits quick, on the fly, depowering of both sails. On either rig, mainsails are easier to slab reef in a manner that results in an efficiently shaped sail for heavier conditions. On a fractional rig that means that you don’t have to take the expense, complication, maintenance and performance hit of a mainsail furler. Controlling mast bend you can often avoid reefing the mainsail or furling the genoa 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 minimally or non-overlapping results in a better partially furled shape.

Masthead rigs typically have larger running sails and so can typically point closer to dead down wind. They are a little more forgiving. 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 all that much slower either (although jib sheet lead angles are way more critical on a masthead rig and require more skill from a performance standpoint than any other adjustment on either rig) as a result if sail trim is not your thing, then the masthead rig''s lack of adjustability would perhaps make more sense.

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 the when you increase 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 heavy weight rigging, and as many large sails, and lastly are not subjecting the boat to the much higher rigging loads of a masthead rig."

I was a little disappointed in the ''Sail'' magazine article. It seemed a little dated and seemed to be light on discussion.

Respectfully,
Jeff




05-24-2004 03:03 PM
Silmaril
Fractional vs. Masthead Rig

I''ve sailed a good deal on both (and more) types of rigs. There are advantages to both.

First, from a performance standpoint, a masthead rig is faster in almost all points of sail. Suprising? Not really. But it''s superiority comes at a price. It has a VERY narrow performance envelope for a given sail combination. As such, it requires a great deal of "gear shifts" as the wind changes. As an example, how about the optimum racing inventory for my 37'' IOR masthead sloop: Main, Storm Tri-sail, Drifter, Light #1, Heavy #1, #2, #3(reefable to #4), Storm Jib, 1/2oz Radial, 3/4oz Tri-Radial, 1.5oz Tri-Radial, 1.5oz Starcut, Staysail. Whew... where is the crew to sleep? Plus it takes a bunch of crew to make all these "gear shifts" happen. To give you an idea of the size of these sails, my 3/4oz Tri-Radial is over 1,400sf!

This is in a racing scenario. But when cruising, you could get by with a Main, 150%rf genoa, 110% rf genoa, and an asymetric spinn. In general terms, you can "reef" a roller furler genny by about 20%. After that the shape is pretty much worthless. I actually feel that you can''t roller furl a genny at all and maintain anything resembling a decent shape.

The masthead rig also works well for the set-and-forget-it crowd in that the mast doesnt respond too much in the way of rig tension beyond headstay sag. (My bendy rig uses an adjustable baby-stay to help control mainsail shape, but that is one more thing to worry about when racing, it has to be struck when flying the chute)

The fractional rig benefits from the metioned smaller headsails, and a smaller inventory to cover the anticipated wind range. Smaller chutes are easier to handle. My masthead rig does dip-pole gybes, while a similar sized frac-rigged boat can do end-for-end. The fractional rigged mainsail responds to tuning very well, and is very easy to de-power. But it also needs more sophisticated controls and knowledge. Things like running back stays need to be tacked, and the backstay tension is critical for mainsail shape. The fractional rigged boat just requires a more knowlegable crew to maximize it''s potential.

In one-design racing, almost every one is a fractional rig, as the limitation of a fixed sailplan requires one that can handle all wind conditions.

I raced on Atlantic Class sloops (31'' mini "J" boats) out of Cedar Point Yacht Club. These lovely old designs were able to sail at remarkable speeds in light air, and the same sailplan would be re-tuned to handle 30+ kts. I don''t know of any masthead rigs that can handle that kind of wind range with only two sails.

There are pluses and minuses everywhere in sailing. Just like the search for the "Perfect Cruiser/Racer/Circumnavigator/Shorthanded/Livabord" will require compromises, so will a skipper''s choice in rig.
05-24-2004 02:19 PM
max-on
Fractional vs. Masthead Rig

Mike, thanks for the reference to the article. This may be an interesting conversation.

As a further comment/question, do the considerations vary depending on the use - i.e. club racing, coastal crusing, or offshore crusing/racing? For my purposes, most sailing is/will be singlehand or short crew.
05-24-2004 01:53 PM
maestro
Fractional vs. Masthead Rig

not to throw fuel on any potential fire but, I''ve read Jeff''s comments on the ease of a fractional rig compared to a masthead rig. Smaller headsail, easier to singlehand, but has anyone read the recent article in SAIL magazine about rigs??? Because now I read a different point of view. "A masthead rig is simpler. It could be loosely be called a fixed rig, since the mast''s attitude is mostly present and is not likely to be changed at sea. Masthead rigs primarily generate their power from a large overlapping genoa and consequently have a smaller , easier to control mainsail. This rig is ideal for shorthanded bluewater sailors: The boat is easily depowered initially by simply furling the genoa a few turns, and, if conditions continue to wqorsen, the mainsail is small enough to reef without drama..." (SAIL, June 2004, p.61)

Comments???
05-24-2004 11:54 AM
max-on
Fractional vs. Masthead Rig

On many of the discussions commenting on the desireable qualities of a new boat, the writers recommend a fractional rig for the stated advantages.

However, boat builders, for example Tartan/C&C, are producing masthead rigs. What are the advantages of a masthead rig vs. a fractional rig? What are the disadvantages?

 
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