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Old 21-07-2008, 10:17   #1
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jibhead vs masthead rigs

To me, the 2 rigs seem identical. Reading Bolger's 100 Small Boat Rigs, he's quite specific in using the terms "jibhead" and "masthead", and doesn't swap them. But, there's no glossary in the book either, so I cannot see what the technical deffinitions are.

Can anyone help clarify this?
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Old 21-07-2008, 11:18   #2
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Hi,

You are not alone in your confusion of boat lingo.

Jib head means the boat is fractionally rigged. The jib's head (top of the sail) is lower than the mast head, or top of the mast. The forestay runs to a point lower than the masthead. 3/4's, and 7/8th's are the common fractions.

Fractional rigs are designed to be a little more flexible than masthead rigs and some of them have an extra set of stays mounted up high above the forestay. These are called jumper stays, a triangular strut pokes out the front and 90 degrees to port and starboard. The jumper stays keep the otherwise unsupported section of mast (The 1/3rd, 1/4 or 1/8th...) from bending backwards. Most of the new fractional rigs don't have them, but old Tritons like mine do...

Mast head rigged boats, the heads of both sails are pulled all the way up. The forestay runs all the way to the top of the mast. They tend to be stiffer by design, but a little less adjustable at the top third. Part of the reason for fractional rigs is to move the center of effort aft, but the racing benefit is that with backstay tension one can power up or depower the main very easily...

In my opinion, if you aren't one to tinker with tensions and fine tuning as you sail... a mast head rig is a good move. Less complex system with fewer parts to break. Stronger mast extrusion... but higher compression loads so the parts have to be stronger. (Think about a fractional mast as being in pulled into a constant S-curve. In order to compress downward one it has to pull the upper third into a banana. The loads are shared, and absorbed by the mast as it tries to spring back.)

The comfort downsides to masthead rigs: More sail area up high, so for the same wind speed the boat heels more than an identical boat with a fractional rig. Because the sail area is more balanced between the main and headsails, the headsails are larger, and main is smaller. It takes more sails to comfortably cover varying wind speeds, as reefing the main doesn't have as drastic an effect as on a fractionally rig.

As you might have guessed, the lingo is from days gone by... head simply means the top. But the oldsalts of days gone by threw a wrench in the works. A masthead light... isn't! It's the 225 degree steaming light on the front of the mast. The anchor light (360 degree) is often placed at the masthead up on the tippy top of the mast. Go figure...
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Old 28-07-2008, 12:44   #3
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Quote:
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Hi,

You are not alone in your confusion of boat lingo.

Jib head means the boat is fractionally rigged. The jib's head (top of the sail) is lower than the mast head, or top of the mast. The forestay runs to a point lower than the masthead. 3/4's, and 7/8th's are the common fractions.
...snip...
Thanks. I wondered if maybe this was the case. But, in this book by Bolger, it is not. It appears that he mainly uses this term when referring to triangular mainsails of the Bermuda or Marconi type. (But, I'm nut sure of this, it's only a guess.) He uses it plenty when referring to cat boats and cat-yawl/ketch/schooner rigs. Cat's don't typically have jibs at all, let alone fractional rigging of jibs.

Which leads to another term that his usage confuses me a bit on. I was under the impression that cats had no jibs, period, except as an optional added-on "sometimes" sail, say a small jib onto a little catboat so you could get a bit more into the wind. Here, Bolger's use usually means no jib, but not always, and seems to have as much bearing in how close to the tip of the stem the lone (or forward) mast is placed.

Bolger's considered fairly knowledgeable. I would assume there are specific reasons for his usages, and I would lean towards believing they're correct.

Anyone?
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Old 28-07-2008, 13:15   #4
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From some reading that I've done, I believe the term "jibheaded mainsail" simply means a Marconi or Bermuda style mainsail (triangular in shape), as opposed to a gaff-rigged main or a spritsail. The jibheaded main has become so commonplace, that the adjective, "jibheaded", has been dropped.
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Old 28-07-2008, 14:03   #5
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Thanks!

Venture to comment on the cat designation?
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Old 28-07-2008, 14:08   #6
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Yup, you are not alone in your confusion.

Thanks for the lesson, Hud!
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Old 29-07-2008, 00:53   #7
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cat as a rig description

A cat rig, generically, has the forwardmost mast stepped "in the eyes" of the boat: quite far forward, and usually not setting any sails before it.

The north american catboat, for example, usually has it's mast stepped just aft of the stem, and usually has no options for any form of foresail.
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Old 29-07-2008, 01:38   #8
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A few, of the many, sailboat rig types:
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Old 29-07-2008, 12:19   #9
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Isn't Bolger the guy who designed those really weird boats with off center mizzen masts and open bows and off set cabins?

Hope I don't step on anyone's toes on that question but I really feel you need to be "special" to enjoy his designs. Is the term "fairly knowledgeable" the same as knowledgeable?

regards,

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Old 29-07-2008, 12:31   #10
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Bolger

Bolger *did* design the famous "box boat" designs, as well as the Gloucester Light Dory, redrew Albert Strange's Wenda, and some of the most beautifully curvaceous designs to come off the boards of architects in the past several decades.

Bolger can't be limited only to his minimum materials and experimental designs. He has written several definitive texts on rig designs. He's just one of those break-through geniuses: some of what he does is universally acclaimed, and some is ugly as sin.
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Old 29-07-2008, 12:48   #11
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Quote:
Originally Posted by Amgine View Post
A cat rig, generically, has the forwardmost mast stepped "in the eyes" of the boat: quite far forward, and usually not setting any sails before it.

The north american catboat, for example, usually has it's mast stepped just aft of the stem, and usually has no options for any form of foresail.
Ah, so "mast well forward"is part of the defining characteristic.

Thanks!
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Old 29-07-2008, 12:59   #12
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Yes, usually. With boats nothing is absolute, and for all I know there's a "cat" rig somewhere with the mast at the stern and nothing but a huge staysail...

One thing you should know, though, is that adding a small jib of some kind to a catboat actually does not let it point higher. The polar chart will show the boat cannot point as high, in fact, but it will have more power pointing slightly lower than before. This can help in light airs.
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Old 29-07-2008, 13:11   #13
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Bassman,
The Sabot, El Toro, Laser are samples of little cat boats and the Nonsuch and Freedoms are bigger examples. Only one sail to worry about and no jib sheet handling although the mainsail on some is quite a bit larger than would be on a sloop or cutter rig. With the Nonsuch and Freedom also they used unstayed masts so that there is no rigging as well. That is definitely not the case with all cat boats.
Sorry about the disparaging remarks concerning Bolger. Not enough coffee this AM.
Kind regards,
John
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