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April 2nd

A few words on rigs

Posted by // April 2, 2014 // COMMENT (0 Comments)

Boats and Gear, ,

I wrote this for my buddies blog.
I have done several entries for him and he lets me use them here.
Rigs are always fun to discuss. Everyone is an expert. I think I am an expert too. Like any discussion of yacht design elements I engage in, my first piece of advice is not to generalize. There are good sloops and bad sloops. There are good cutters and bad cutters. You get the picture. We can discuss efficiency and we can discuss personal preferences. The two can be at odds and often are. We can talk about evolution of rigs and why they became popular in the first place, i.e. handicap rule influences. I’ll also try to talk about the advantages to each rig when I think there is an advantage. And, like many other aspects of yacht design, simply saying, “I like this rig because I just like the way it looks” is a good attitude. So long as you don’t endow your favorite rig with a bunch of bogus positive attributes. I did a schooner for a client and I tried very hard to convince him that a cutter would be the better rig for what he had in mind. In the end he said, “I like schooners because I like the way they look.” End of discussion.
Yoni is a custom 50′ cutter with all headsails carried
on roller furling. That’s a lot of windage forward when
you need to dock the boat in a blow.
It’s pretty obvious today that the most efficient rig is a single, wing sail with variable segments that allow camber and twist control. We saw this type of rig at work in the last America’s Cup. So that is one extreme end of the rig efficiency spectrum. I’m not sure what goes at the other, far end. Maybe it’s a loose-footed sprit sail catboat?  Sliding gunter? Not sure. There are so many inefficient rigs that I shouldn’t generalize. It’s probably safe to say that none of us own boats with wing sails. However, I know that Beneteau is playing around with some wing sail models, so who knows? Maybe in a year or two wing sails will be seen on Mom and Pop boats. But not yet.
The simplest rig is the catboat with one mast, one sail, one halyard (two if it’s gaff rigged, peak and throat) and one sheet. This simple rig was made famous by the Cape Cod catboats in the US. Some Cape Cod cats flew very small jibs from short bowsprits but I still think of them as catboats. I like catboats and I have sailed a few. I have spent a lot of time sailing a 12′ Beetle Cat. The downside to a cat rig is that as the boat gets larger the single sail on a long boom can become difficult to handle. Jibing a big catboat in a breeze can also be a challenge. Sometime you just have to bite the bullet and tack the boat rather than risk a flying jibe. The other quirky attribute of many catboats is that they can build up massive weather helm when pressed on a reach. We’ll talk a lot about helm balance in this entry. I always prefer a boat to have a delicate helm feel and have the ability to be driven hard without having to fight too much rudder angle. Weather helm on a traditional catboat is just part of the picture. Kind of like a bumpy ride in a Morgan sports car.
Mark Ellis designed the Nonsuch series as modern catboats marrying the convenience of a one-sail rig with a modern hull form. The Ellis catboat hulls have moderate beam as opposed to the exaggerated beam of the Cape Cod type catboat.  Extreme beam can be one cause of weather helm. I have sailed the big Nonsuch, a 36’er as I recall, and I thought it balanced beautifully and had a good turn of speed. Another feature of the Nonsuch rig is that the mast is free standing, i.e. no standing rigging. This allows the mast to bend off to leeward in a breeze “depowering” the sail to help keep the boat on its feet. But the real negative side of the cat rig is its lack of versatility. When you just have one sail, the only options you have are reefing the sail.  Downwind you will not be flying a spinnaker from a Nonsuch. Although I suppose with some fussing with hardware and a bowsprit it’s possible.  If you want a rig that is truly versatile, you need to look at the sloop rig.
The term “sloop rig”  includes a wide variety of types with a mainsail and a jib. The two basic sloop types would be gaff rigged and Marconi rigged. But today gaff rigs are pretty rare so let’s confine our study to the Marconi rigged sloop. I like gaff rigs but it’s hard to find a Mom and Pop production GRP boat that came with a gaff rig. I can’t think of any. So, confining our discussion to the Marconi rig the two basic sloop rigs would be masthead with the headstay going to the masthead, and fractional with the headstay going up some portion of the mast but stopping short of the masthead. The spot where the headstay hits the mast is called the “hounds”.
Amati is a modern fractional sloop with a large mainsail
and small fore triangle. This is a very easy boat to sail.
The masthead sloop rig can be very simple and strong. On older boats you will probably have single spreaders, fore and aft lowers, inline cap shrouds and a standing backstay. If your boat is newer and more performance oriented, you may have two sets of spreaders with inline single lower shrouds. You may even have a forward “baby stay” to help stabilize the middle section of the mast fore and aft. The more spreaders you have the lighter the mast extrusion or “section” can be. But as you reduce the mast section and add spreaders you increase the complexity of tuning the rig and at the same time you increase the scrutiny required to keep the bendier, light section in column. The mast can see a compressive load equal to the displacement of the boat so the mast must be kept “in column”.
The benefits of the masthead sloop are its simplicity and strength. The drawback is that the fore triangle will most probably be large. If your boat came out of the IOR era you will have a large fore triangle and a small, perhaps even IOR minimum, main. We called these IOR mains “blades”. Not to be confused with “blade” jibs. Blade just means a tall and skinny, high aspect ratio sail. With a big fore triangle your options for reducing sail are reefing the main or changing to a smaller jib.
The masthead sloops of the last 30+ years generally carried genoa jibs with overlap as high as 160% of the “J” dimension, front side of mast to headstay tack location. Overlap is measured as LP or luff perpendicular and is expressed as a percentage of the “J” dimension. So, a 153% genoa on a boat with a 16′ “J” will have an LP of 24.48′. Overlapping sails can add a lot of useful sail area but they can be a nuisance to handle and tack. There is also quite a bit of controversy over just how effective overlap is once you get beyond about 124% LP. For a full and versatile headsail inventory, your typical production masthead sloop would need to carry at least three headsails to be ready for a range of conditions. That does not include a spinnaker or a storm jib. I would guess a 150% genny, a 120% genny and a 95% jib would be a reasonable headsail inventory. But today with almost everyone using roller furling I see a lot of sailors trying to get by on one all-purpose jib. It works, sort of. But in many conditions you are going to be compromised if you try and make one headsail fit all conditions. I grew up changing headsails to fit the conditions. Modern, matrix type sail fabric can help a lot if you are after a multi-purpose genoa.
As part of the trickledown effect from racing classes, cruisers soon realized that the fractional sloop rig with its small fore triangle and large mainsail was a far easier rig to use than the old masthead rig. For one thing, the big sail, the mainsail, is on the boom so that alone makes it easier to handle. With a small fore triangle, jib size is no longer so critical. Now you can get by very comfortably with two jibs. With the mast moved forward for the fractional rig and the headstay hounds dropped, the fore triangle is reduced in size so jib overlap is no longer so  important. Your main is now the important sail. Now jib LP’s can be reduced to 120% of “J” or even less. The less overlap the easier it is to tack the jib. On my own boat with a fractional rig, I used a 100% jib for heavy air and a 120% jib the rest of the time. If you fly an asymmetrical spinnaker (i.e. cruising chute) from the masthead, the gap between the hounds and the masthead makes it easier to fly the chute as it gets it away from the headstay.
Another benefit of the fractional rig is that now the mast has been moved forward. The “frac” rigged boat will sail much better under mainsail alone than will most masthead rigged sloops with their masts further aft. The frac rigged boat will also have a better helm feel under main alone. You still need your jib up to get the most out of the boat but sometimes we feel lazy and we may not feel like reefing or changing jibs.
Free Range Chicken is a modern frac rigged sloop for long distance cruising
Regarding this “fraction”; you will hear a “7/8th‘s rig” or an “80% rig” This is the percentage of “I”, mast height, up the mast to where the hounds are located. But it’s not important. I never calculate it. I just use target sail areas and distribution of sail area to determine the height of the headstay.
I don’t think I’ll talk about styles of standing rigging this time. Needless to say almost every new Mom and Pop production boat has swept spreaders. This means one set of chainplates so it’s a cheaper boat to build than the old fore, cap and aft shroud, inline rig. It’s a better rig as it is cleaner and easier to tack the jib around.
The Baba 30 is a typical bowsprit cutter. She was always well balanced.
I think I have designed more cutter rigs than any other living designer. I won’t count them for you but trust me. I know the cutter rig. I have sailed many different cutters. The cutter has been around forever. I think the current popularity of the cutter rig comes from the early 70’s when the Westsail was introduced.  Prior to that, the knee jerk rig choice for an offshore cruising boat was the ketch rig. I followed the Westsail 32 with the Valiant 40 and the Tayana 37 and in no time the cutter rig was the automatic choice for the cruiser. Why? Having three working sails gave you more options than having two. Instead of reefing the main you could drop the outer jib, sometimes a Yankee jib, and fly a staysail and mainsail. Often this loaded up the boat with weather helm as the center of pressure moved aft. A better way to reduce sail would be to reef the main first. Then drop the Yankee. Obviously this sail reduction sequence will vary with the boat’s handling characteristics and your personal sailing style. But in general, getting the main reefed moves the center of pressure of the rig forward and in so doing, reefing the main first will reduce weather helm. A bad way to reduce sail on a cutter is to drop the staysail first. This leaves you under full main and Yankee with a big hole between those two sails. It is not efficient. Your headsail and your main want to function basically like one big foil. Most Yankees have high clews so their center of pressure is high and this adds to heeling moment. I’m not a huge fan of high clewed Yankees.  My rule of thumb is that the clew of the Yankee should be no higher than I can reach when the boat is heeled over.
If I were going to rig a cutter for myself to use in the PNW I would have the outer jib cut more like a 135% genoa with the clew maybe just a bit above the top lifeline. It would be more of a genoa than a Yankee. I would not use the staysail for beating. I’d only use the staysail for reaching in conjunction with the genny or alone in heavy air. In most cutters your best performance to weather, i.e. your best VMG (velocity made good) will be achieved without the staysail. Trying to get three sails lined up and drawing well hard on the wind is only possible on a fat, non weatherly hull where your AWA (apparent wind angle) would be 40 degrees or more. The staysail can work. But if you are looking for an AWA closer to 34 to 32 degrees, as I would on a Valiant 40, then the staysail is not going to help. It will just suffocate the mainsail.
A trick I do with the staysail when running downwind is to pole out the genoa or Yankee to weather. Then drop the staysail and unhank it from the inner forestay. Next I move the tack of the staysail forward to where the tack of the genoa or Yankee is. I hoist the staysail “flying” – not attached to any headstay or inner forestay. I trim to leeward. Doing this gets the staysail out from the bad air of the mainsail. I’m not sure this would be good for your staysail if you were running downwind for three days, but cruising around the Sound I can’t imagine it does any harm. Downwind the loads on the luff are relatively light.
I’ve mucked around racing cutters for years and this is what my own experiments in sail choice and trim have taught me. In last year’s Race Your House race, for liveaboards, I raced my pal Donn’s Baba 35, pilot house model. This is hardly a race boat and is about as cruisy as it can get. We had good sails and I had Donn, his wife, Kerry and an Australian buddy of mine for crew.  We were racing against a diverse class of boats and many were newer fin keel types. We placed second in class and beat a lot of boats boat-for-boat that should have beaten us. We had a good breeze for most of the race and we drove the boat very hard. We made that traditional cutter go. We did not use the staysail except off the wind.
White Eagle (now Wild Horses) is another modern version of the cutter rig
I’ll tell you what annoys me a wee bit. I hate those cute names like “slutter” and “cutter rigged sloop” or the worst one, “cutter rigged ketch”. We already have all the terms we need to describe rigs that have been around for 200 years.  A sloop is a sloop. If someone chooses to add a staysail it’s still a sloop. If someone has a staysail on their ketch the boat is still just a ketch. I’m not in favor of adding a staysail to a sloop. Generally the mast of a sloop is further forward than that of a cutter so there is little room in the fore triangle to jam another jib. But I understand the appeal of the staysail for heavy air. It’s very convenient. I also like to see the sail area forward for a blow. When the boat is on its ear it will build up weather helm. Keeping sail area forward will help. If I owned a sloop and I wanted to carry a staysail for heavy air I would locate the tack of the staysail as far forward as possible, right on the stem fitting if there was room for it (There usually isn’t). I’d locate the hounds for the staysail at the upper spreader if I had two spreaders. This would be what I call a “Solent rig”. It’s pretty much changing the rig from masthead geometry to fractional geometry and it keeps the center of pressure forward.
I said “don’t generalize” then I spent 2,300 words generalizing. But I think there are some nuggets of rig wisdom here. I’ll take a look at “split rigs”, i.e. ketches, yawls and schooners in another follow-up blog entry. -BP
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This article was syndicated from YACHT DESIGN

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