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  #1  
Old 02-11-2011
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The gaff Rig

The lift to drag ratio of a rig as it relates to aspect ratio is highly dependent on the angle of incidence to the apparent wind. So when going to windward, the higher aspect ratio foil can point higher (and for racers, that is what counts). However off the wind lower aspect ratio foils really start to kick butt as they can give more sail area at a lower center of effort.
Which brings us to the good old Gaff Rig-
This little bit of news has support as noted in Marchaj's Aero-hydrodynamics of Sailing- actually it's second only to the crab-claw in L/D off the wind without the tacking issues that having a boom that crosses the mast entails.
Large SA + low CE= good off wind performance. E.G. the Jolie Briese. So if some of the new technology (carbon spars, stable sailcloth etc.) were applied to a Gaff rig we may see improved performace in cruising boats as well as any but all out 'round the buoys racers.

Sooo. whadda 'ya think about that?

Here's a link: http://www.kastenmarine.com/gaff_rig.htm
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Old 02-11-2011
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About the good old gaff rig.....

I have been sailing the same 33 foot bald-headed schooner for 49 years. I like the simplicity and never missed having topsails. The masts are stiff enough without spreaders, and don't require backstays. With the short rig you avoid high forces in the shrouds. In an older wooden boat like mine high shroud forces are a common cause of hogging, but the sheer line is almost unchanged after 60 years of sailing.

As for going to weather...Sure, an old gaff-rigged schooner does't point very well. My windward performance improved a great deal when I put on the largest possible jib. The original setup was two headsails of about equal size. I fly the large jib even when double-reefed on the main and fore. For the kind of sailing I do... casual coastwise cruising between between Norfolk and Maine, I don't mind using using the engine at times. Sheet the jib in hard, give her a little engine power and she points right up there.

In Massachusetts Bay where I do most of my sailing these days I don't much care where I go. I just want to reach. It's glorious, for off the wind a gaff rig schooner goes like a freight train. It's jolly fun to go driving right on by larger modern boats.

Downwind the gaff rig is very forgiving in the sense you can sail a good way by the lee without jibing. Get her wing and wing, or reading both pages, as some say, and she almost steers herself. I don't bother with a spinnaker. I will admit that night sailing in heavy conditions straight downwind is pretty stressful unless you reef the main way down.

One maintenance issue... I have been through a couple gaff jaws and broken a couple gaffs over the years. That's about the worst of it as far as rigging failures go.

The photo in my avatar shows the sail arrangement I use most of the time.
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Last edited by FishSticks; 02-15-2011 at 08:29 AM.
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Old 02-11-2011
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I have seen Tony's presentation on this and it is very interesting, although except for the crab claw rig which stunned everyone, there was no new news here. There are a number of issues with the gaff rig which Marchaj's experiments did not explore. For example, since the 'sails' which were tested were rigid rather than fabric, they were not able to achieve a flying shape. The general problem with obtaining decent performance with gaff sails is the inability to control twist and also the turbulence of having the additional spar (gaff).

In any event, reaching the gaff rig does generate a lot of drive relative to heeling. This worked well when combined with the relatively inefficient keels and hulls which were popular during the period when Gaff rigs were popular.

Tony's research was not ignored by modern designs. Modern distance racing boats now have square head mainsails. These square head mainsails take advantage or modern materials so that the gaff has been pared down to a very stiff carbon fiber batten that cantilevers over a band of low stretch fibers which when combined with modern sail handing gear allows reasonably good control over twist.

Now then, I would like to caution you against citing Jolie Brise as an example of a boat with good offwind performance. She needs to be understood in context. Jolie Brise existed in a time when almost all of her comptetion were gaff-rigged. Her wins were on corrected time rather than pure speed and they were of the 'in the land of the blind, the man with one eye is king' variety. She had a huge sail plan, of which very little area was actually her gaff rig mainsail. In her famous series of Fastnet wins, the 1929 victory was over Halloween which had the actual fastest time around the course, setting a course record which stood for 50 years before being broken by Ted Turner during the disasterous Fastnet of 1979. Halloween was Bermuda Rigged. When additional Bermuda rigged race boats like Dorade hit the race course in 1931, gaffers never won the Fastnet again.

Old style Gaff rigs still make sense on burdensome hulls with a lot of drag relative to their stability and on boats whose keels are so inefficient that they cannot point very high no matter what rig they have.

Respectfully,
Jeff
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Last edited by Jeff_H; 02-11-2011 at 01:15 PM.
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Old 02-11-2011
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Quote:
In any event, reaching the gaff rig does generate a lot of drive relative to heeling. This worked well when combined with the relatively inefficient keels and hulls which were popular during the period when Gaff rigs were popular.
I think you're missing the point- or you've made one you didn't think you did. Drive is independent of hull form. so for argument's sake, let's attach a "modern gaff rig " to a more efficient underwater planform. What do you get? Better speed probably. the real rise of the burbudan rig was, and is it's windward ability. Dorade's Fastnet win was more driven by her hull form than by her rig. (she can do 1.66 x sqrt LWL.IIRC) So let's not mix apples (rig efficiency) and oranges (hull efficiency)

Quote:
The general problem with obtaining decent performance with gaff sails is the inability to control twist and also the turbulence of having the additional spar (gaff).
This is as much a material problem as anything else. An aerodynamic shape for the spar should be fairly easy to accomplish nowadays. As can reducing twist (a common problem in the old days) Off th top of my head, maybe a small spreader at the top of the mast with a couple of lines to the middle of the gaff to position it? Just thinking out loud. What I am saying is that this may be should more actively looked into.

Quote:
Now then, I would like to caution you against citing Jolie Brise as an example of a boat with good offwind performance. She needs to be understood in context. Jolie Brise existed in a time when almost all of her comptetion were gaff-rigged. Her wins were on corrected time rather than pure speed and they were of the 'in the land of the blind, the man with one eye is king' variety. She had a huge sail plan, of which very little area was actually her gaff rig mainsail. In her famous series of Fastnet wins, the 1929 victory was over Halloween which had the actual fastest time around the course, setting a course record which stood for 50 years before being broken by Ted Turner during the disasterous Fastnet of 1979. Halloween was Bermuda Rigged. When additional Bermuda rigged race boats like Dorade hit the race course in 1931, gaffers never won the Fastnet again
As I said, you really can't compare apples to oranges by mixing hull forms with rig efficiencies. You need to remember that both the newer Rules, which heavily taxed sail area as well as stability and as the burmudan's somewhat better windward ability (no argument there) killed the gaff rig in racing. Not necessarily some "great new thing" with burmudan mains.

Quote:
For example, since the 'sails' which were tested were rigid rather than fabric, they were not able to achieve a flying shape.
Some tests were fixed planforms others with with fabric IIRC. The numbers are good.

Quote:
Old style Gaff rigs still make sense on burdensome hulls with a lot of drag relative to their stability and on boats whose keels are so inefficient that they cannot point very high no matter what rig they have
Thanks for making my point. If the rig is so good that it made up for hull inefficiencies, shouldn't it be looked at again with more efficient hull shapes? What about a New Style Gaff Rig?
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Last edited by cormeum; 02-11-2011 at 02:38 PM.
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Old 02-11-2011
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Corm:
I don't think that you understood a thing that I said Talk about a guy who won't take yes for an answer. I was mostly agreeing with you...

Quote-Cormeum says,"Thanks for making my point. If the rig is so good that it made up for hull inefficiencies, shouldn't it be looked at again with more efficient hull shapes?"

Seriously, starting from the back and working forward, I did not and would never say that the traditional gaff rig is so good that it made up for hull inefficiencies. Paraphrasing what I actually said, was that the traditional hull forms were so poor, that they were ideally suited to a mediocre rig like the gaff rig. In other words they would not benefit from a higher efficiency rig like a Bermuda rig. In terms of where the historic style gaff rig worked best. it was on hulls that took a lot of force to push, but which could not stand up to their rigs and whose pointing and running ability was limited by their hull and keel configuration so a righ that could not point well or run well was not as much of a liability as it would be on a more efficient hullform.

But I was basically agreeing with you that Marchaj's findings are correct, but also saying that they were nothing new even when he made them some 15 or so years ago. With the exception of the crab claw rig, his research basically quantified what was previously known empirically.

Quote-Cormeum says,"As I said, you really can't compare apples to oranges by mixing hull forms with rig efficiencies. You need to remember that both the newer Rules, which heavily taxed sail area as well as stability and as the burmudan's somewhat better windward ability (no argument there) killed the gaff rig in racing. Not necessarily some "great new thing" with burmudan mains."

You actually have the change in the rule partially wrong, and the chicken and egg backwards. The newer rules reduced the tax on stability with the intent of encouraging safer boats. Because of this plank on edge cutters were replaced with the later compromise cutters and as these boats gained stability they could have more efficient underbodies leading to the need for more effiencient rigs.

While you are right that hull forms evolved dramatically during the period when the gaff rig was dying out, it was a something of a chicken and egg situation. I once had a conversation with Olin Stevens at a Chesapeake Sailing Yacht Symposium. Olin was one of the authors on developing efficiency coefficients for the IMS rule using the schooner Brilliant as a test bed to validate their numbers. Olin was asked why the schooner rig died out and Olin anwered that as lead external ballast was popularized boats became more stablle and did not require as much internal volume to carry the ballast. With that hulls and keels could be made more efficient, meaning less drag for the amount of resistance to leeway and stability generated. At that point rigs needed to get more efficient to keep pace. As cruising boats began adapting more efficient hull forms as well, there was little place where a traditional gaff rig made sense.

But the speed disadvantages of the gaff rig went beyond being hitched to inefficient hulls. Back in the late 1970's I researched Halloween for a white paper that I was asked to write. Halloween had three rigs in her life and each represented a notable period in her then 50 year lifespan. The paper was intended to make a case for which rig she should be restored with. Halloween had originally been built as a Bermuda sloop and was built in total disregard for any rule of that era. After her record breaking race in the Fastnet she was converted to a gaff sloop with the goal of allowing her to race in the 15 meter class. She was later converted to a yawl rig in order to race under the CCA rule under the name of Cotton Blossom.

When she was a Bermuda rig sloop she was in races that included 15 meter class boats with their gaff rigs. The sailing master on Halloween described having an easy time beating them boat for boat on all points of sail and that matches the historical record and mark rounding times. After her first year the Bermuda rig was removed and a gaff rig installed. The gaff rig had substantially larger sail area than the bermuda rig it replaced, yet Halloween could not keep up with on a boat for boat basis with the boats she had previously bested easily. In frustration she was sold several times before being laid up and before being restored and receiving the yawl rig under which she eventually became famous as Cotton Blossom (The predecessor to Dennis Connors' Cotton Blossom). In the VPP analysis done in the early 1980's, she was still clearly faster on all points of sail with the original Bermuda rigged sloop.

But what the metal sails on the Marchaj windtunnel boats showed was that the plan form of a gaff sail has certain efficiencies if twist can be controlled and if the turbulence from the gaff can be eliminated. That cannot be done with a traditional gaff rig. The shape of the mast needs to be round so that the jaws of the gaff will work properly and can be lowered and the spreader positions need to be above the gaff jaws.

But here is where we are in agreement (as I said in my post above). I think we agree that the plan form of a gaff rig has advantages wen reaching if we can address the twist issue and gaff turbulance issue. And I think we agree that there would be an advantage to that more efficient version of a gaff rig. If we can couple that modern gaff rig with a modern hull form, we will end up with a faster boat on the reaching legs. And since modern race boats almost never go dead down downwind, reaching speed is more crucial than ever, and so there would be a real advantage to developing a 'modern gaff rig'.

And in fact that is what has happened. Modern race boats have what they call a "square head mainsail" and which by any other name is in fact modern gaff rig. As stated above, the gaff has been been replaced by a very stiff carbon fiber batten which cantilevers over a swatch of high modulus fiber embedded in the sail. These are wildly expensive, short-lived sails to build, they require running backstays, very high rigging loads, and sharp crews to handle them, but they offer a real speed breakthrough in certain types of racing. Then again, this rig lacks the virtues normally associated with a traditional gaff rig.

Jeff
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Last edited by Jeff_H; 02-11-2011 at 08:05 PM.
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Old 02-12-2011
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good info here
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Old 02-12-2011
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Here's a link to a modern schooner, with a fin keel and spade rudder. It's Bob Perry's Jakatan. Carbon fibre spars as well.

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Old 02-13-2011
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That Jakatan is a lovely boat and on his website the owner makes good points about schooners. I'm glad she's on the left coast where she can't threaten us in the Great Chespeake Bay Schooner Race.

As for "burdensome keels"... they do have their advantages at times. I have had some good doses of the lower Chesapeake during hard NW blows where the sea condition is like a washing machine. On a reach, the old boat, designed before 1939, drives right on through, straight and level, at hull speed, just under 8 kt. And dry to boot. The WL is about 28 ft, beam 9-1/2 ft, draft 5-1/2 ft and displacement 19,000 lb. And I sail in Maine where the lobster buoys are very dense. I don't bother them and they don't bother me, even at night. Try that with a fin keel and spade rudder.

So I say gaff schooners with full keels have been given a bum rap. Not by the posters here, but they seem to have been passed over. People are missing out on a good thing. It is true that many of us are not competitive with nongaffers on the weather legs that are the main feature in most races. So our preference is to flock together, but schooners are so scarce now it's difficult to assemble a race among our own kind. When we do we have a better time than anyone, and many seem to think our boats make a fine sight.

And another thing.... kids love to sail gaff schooners.

I'd like to see this discussion continue. Bring in the new! But don't throw out the old!

Edit added 2/15

Saw the post below by SD and his comment on a leadmine. After I figured out what the word meant I was reminded of another advantage... although in my case it's a big long ironmine. Now, if you sail around long enough in Maine you're going to carom off a ledge once in awhile. If not you are being overly cautious and missing some of the best places. Although some ledges are cushioned with a nice soft layer of weed I would hate to think of whacking one with a deep skinny spade, which, of course could select from a much larger inventory of granite pinnacles. And around the western end of Buzzards Bay I sure wouldn't want to have a fin and spade sticking down into all those hen and chickens or sow and pigs reefs.
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Last edited by FishSticks; 02-15-2011 at 02:28 PM.
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Old 02-13-2011
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Another little gaff gem from Bob Perry. We discussed this over at SA a year or so back when BP was working on this boat. Both boats are what the client wanted. Simple as that.
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Old 02-13-2011
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What a cute little leadmine.
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