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      A Few Simple Rules   05/22/2017

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Tanton Y_M

What about free standing rigs?

341 posts in this topic

DDW's comment about out-pointing a Freedom reminds me of a possibly relevant point about cat rigs. In general, cat rigs can be made to point higher than sloops because you don't have the issue of the luffing jib. If you point too high, however, the speed starts to drop off dramatically. This can sometimes be helpful when docking.

 

For this reason, a lot of cats don't have the best pointing angle "designed in" the way it is in a sloop, and it has to be found through experience. My limited experience sailing a gaff cat let me know that the sloop sailor has a lot to learn when changing to a cat rig.

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Just a couple of questions, if I may :

 

The Gentry paper is over 30 years old (fuck ! it was only the 80's- feeling old :huh: ) Is it still the current thinking amongst the great and good ?

 

Imagine a course whose legs are all the same length,of say 1 mile,dead upwind followed by a beam reach, then 45* up and then 45* down wind and finally a dead run, basically covering all the points of sailing. The wind is a true 15 Kn and constant,enough to fully power most things. You have a hull of say 40 ft.

 

The only rule regarding the rig is it must be reefable, any size, number,or type of sails and masts are allowed .Canting keels, moveable ballast ,righting movement, hull form, aspect ratios,displacement, anything you need to optimize the boat is up to you so long as it fits into 40 ft. The only thing you can't do is reef the sails or add to the sail plan, so the sails you use to beat upwind are the same ones on the run.

 

What sail plan would get you round that course in the shortest possible time ?

 

Or to put it another way; what sail plan is the most efficient when all points of sailing are taken into consideration and you don't have the option of spinnakers etc ?

 

:) R

 

PS Didn't the Redwings ban the rotating mast (like a Carbospar ) because it won all the time ?

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Cool thing about this boat is that you can put the masts in 5 different places, biplane to schooner to sloop arrays. And change it it on the water to fit conditions, point of sail, etc.

 

.

http://www.adventuretrimaran.com/

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I've always been curious about what to do with the vang attachment on the mast with a free-standing rotating foil mast. Since you always over-rotate the foil spar for best airflow, the vang attachment low on the mast is rotated well beyond the boom angle, leading to all sorts of load, angle and trim problems.

 

Is is better to do a separate ring bearing in the deck outside the partners bearing for the vang attachment? Or just go with the low gooseneck and big twist like the O60 rigs?

 

Hmmmmm....

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I've always been curious about what to do with the vang attachment on the mast with a free-standing rotating foil mast. Since you always over-rotate the foil spar for best airflow, the vang attachment low on the mast is rotated well beyond the boom angle, leading to all sorts of load, angle and trim problems.

 

Is is better to do a separate ring bearing in the deck outside the partners bearing for the vang attachment? Or just go with the low gooseneck and big twist like the O60 rigs?

 

Hmmmmm....

 

Do a vang like a 49er. Solid bar that runs from the back of the mast above the gooseneck down to the boom. That also lets you get the boom a lot lower - best when it's just above the deck and everyone has to hide in the cockpit on a gybe ;)

 

Or, have a boat that is so amazingly fast that the AWA is always way forward and you don't need a vang :)

 

BV

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Speaking of freestanders, we saw this on the harbor on Thursday:

 

aerorig-lg.jpg

 

Yes, she could use a bath or two.

 

aerorig-2-lg.jpg

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Speaking of freestanders, we saw this on the harbor on Thursday:

 

aerorig-lg.jpg

 

Yes, she could use a bath or two.

 

aerorig-2-lg.jpg

 

Not the Aerorig again! :o

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I'm sure it's theoretically possible to make a good looking aerorig'ed boat, but that one doesn't look like they even tried.

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I would think an Areorig which has the boom thing sweeping the deck would look pretty good and be damned dangerous to the normal inebriated crew.

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I've always been curious about what to do with the vang attachment on the mast with a free-standing rotating foil mast. Since you always over-rotate the foil spar for best airflow, the vang attachment low on the mast is rotated well beyond the boom angle, leading to all sorts of load, angle and trim problems.

 

Is is better to do a separate ring bearing in the deck outside the partners bearing for the vang attachment? Or just go with the low gooseneck and big twist like the O60 rigs?

 

Hmmmmm....

 

Do a vang like a 49er. Solid bar that runs from the back of the mast above the gooseneck down to the boom. That also lets you get the boom a lot lower - best when it's just above the deck and everyone has to hide in the cockpit on a gybe ;)

 

Or, have a boat that is so amazingly fast that the AWA is always way forward and you don't need a vang :)

 

BV

Beau.... Good idea on the second, but the first one, the infamous gnav, or 'backwards' vang, may be a bit of a pain in bigger boats with the huge loads on a largely unsupported area of mast. Plus it still doesn't get past the rotation problem.

 

Hmmm....

 

J

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I've always been curious about what to do with the vang attachment on the mast with a free-standing rotating foil mast. Since you always over-rotate the foil spar for best airflow, the vang attachment low on the mast is rotated well beyond the boom angle, leading to all sorts of load, angle and trim problems.

 

Is is better to do a separate ring bearing in the deck outside the partners bearing for the vang attachment? Or just go with the low gooseneck and big twist like the O60 rigs?

 

Hmmmmm....

 

Do a vang like a 49er. Solid bar that runs from the back of the mast above the gooseneck down to the boom. That also lets you get the boom a lot lower - best when it's just above the deck and everyone has to hide in the cockpit on a gybe ;)

 

Or, have a boat that is so amazingly fast that the AWA is always way forward and you don't need a vang :)

 

BV

Beau.... Good idea on the second, but the first one, the infamous gnav, or 'backwards' vang, may be a bit of a pain in bigger boats with the huge loads on a largely unsupported area of mast. Plus it still doesn't get past the rotation problem.

 

Hmmm....

 

J

 

I don't see a problem with rotation, the gooseneck and the vang both rotate with the mast. What am I missing? As to the loads, that really isn't a problem anymore with carbon rigs, just make that bit of the mast stiff. It's low enough not to need to bend.

 

BV

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I don't see a problem with rotation, the gooseneck and the vang both rotate with the mast.

 

A solid vang attachment doesn't let you overrotate the mast. E.g., see here for references to over-roation in an article about designing the sails for Farfarer.

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post-2611-036499200 1326732400_thumb.jpg

Beau.... Good idea on the second, but the first one, the infamous gnav, or 'backwards' vang, may be a bit of a pain in bigger boats with the huge loads on a largely unsupported area of mast. Plus it still doesn't get past the rotation problem.

 

Hmmm....

 

J

 

I don't see a problem with rotation, the gooseneck and the vang both rotate with the mast. What am I missing? As to the loads, that really isn't a problem anymore with carbon rigs, just make that bit of the mast stiff. It's low enough not to need to bend.

 

BV

 

Here's a pic of Ocean Planet and the bottom half of the 49er style vang. Robust enough to make it around the world. The mast rotates.

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I don't see a problem with rotation, the gooseneck and the vang both rotate with the mast. What am I missing? As to the loads, that really isn't a problem anymore with carbon rigs, just make that bit of the mast stiff. It's low enough not to need to bend.

 

BV

Beau, you're right of course. Duh! The gooseneck and vang lug are in the same vertical plane, so it's not an issue after all. I was just over-thinking it.

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I don't see a problem with rotation, the gooseneck and the vang both rotate with the mast. What am I missing? As to the loads, that really isn't a problem anymore with carbon rigs, just make that bit of the mast stiff. It's low enough not to need to bend.

 

BV

Beau, you're right of course. Duh! The gooseneck and vang lug are in the same vertical plane, so it's not an issue after all. I was just over-thinking it.

 

Well, Presumed ED brings up an interesting point. Ed, I wasn't thinking that the top mount (attached to the back of the mast) was "fixed" except in the vertical direction. It will clearly need to swivel in the horizontal direction to allow the boom and the mast to move independently. It just won't have to swivel more than a few degrees - 20 maybe at most. It can't be locked to the mast - that won't work.

 

BV

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Getting back to the subject of free standing rigs, has the technology of designing and building free standing carbon fibre masts for bigger boats progressed much in the last decade? Farfarer is a good recent example - there must be many more. Looks like a lot of progress was made on bigger boats, twenty to thirty years ago but not much over the last decade when the greatest amount of change might have been expected. Is there any particular designer leading the charge now?

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Getting back to the subject of free standing rigs, has the technology of designing and building free standing carbon fibre masts for bigger boats progressed much in the last decade?

 

Quite a lot happening at the moment, AIUI. Thin film laminates, nano tube resins...

 

 

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That is true but with advances in materials, the disadvantage of a massive section at the base of the catilever and the windage issues higher up the mast may be reduced significantly with skinnier setions. Altough more complicated, I thought the Omer wing was interesting because it used the front section of the three part sail to overcome the windage issues. Instead of having disadvantages that have to be overcomeome, the free-standing mast becomes part of the foil. If the claims are true, a 10% improvement in performance warrants a closer look. I thinks free standing masts may have a lot more going for them than just simplicity.

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How about this one?

 

http://www.omerwingsail.com/Video/

 

 

I thought that free standing rig stood for simplicity. One halyard, one sheet, no standing rigging.

 

Nope, it just means freestanding.

 

Long ago airplanes had wires and spreaders to keep the wings straight. Eventually, monoplanes arrived with unstated wings. Boats haven't changed because reefing and adding sail area downwind are problematic. Also, aircraft aren't concerned about weight in the wing, for lots of reasons. It's why they keep their fuel there. Boats are the exact opposite. Thus, we have shrouds and spreaders, even on the most expensive boats, if one wants the best performance at sea. Flat water and steady winds change this a bit.

 

BV

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That is true but with advances in materials, the disadvantage of a massive section at the base of the catilever and the windage issues higher up the mast may be reduced significantly with skinnier setions. Altough more complicated, I thought the Omer wing was interesting because it used the front section of the three part sail to overcome the windage issues. Instead of having disadvantages that have to be overcomeome, the free-standing mast becomes part of the foil. If the claims are true, a 10% improvement in performance warrants a closer look. I thinks free standing masts may have a lot more going for them than just simplicity.

 

A quick read through their web site has me doubting many of the claims made when comparing to traditional sails. If anyone trimmed my sails the way that they chose to display the sails in the comparison, they'd be canned.

 

The issue with wing sails is not wing efficiency, of course they are more efficient. The issues are: Weight aloft, Reefing, Increasing sail area for reaching and running, Cost, and Reliability. These don't seem to have been addressed.

 

BV

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A middle approach between round and a full wing that needs to be rotated

 

http://www.hit-masts.nl/?id=127

 

http://www.wilke.ch/fileadmin/Finmast_pricelist_EURO_neu.pdf

 

 

They are better than round, but restrained by rule. However, they do have

 

A mast track

Internal halyard

Fitting for the boom

 

$$$$$$ to adapt to big boats, but possible.

 

But the big question is, how much of the engineering and build problems are being overcome by the size and weight requirements dictated by Finn class rules?

 

Would masts like this sized up to say 60' be too heavy?

 

Paul

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How about this one?

 

http://www.omerwingsail.com/Video/

 

 

I thought that free standing rig stood for simplicity. One halyard, one sheet, no standing rigging.

 

Nope, it just means freestanding.

 

Long ago airplanes had wires and spreaders to keep the wings straight. Eventually, monoplanes arrived with unstated wings. Boats haven't changed because reefing and adding sail area downwind are problematic. Also, aircraft aren't concerned about weight in the wing, for lots of reasons. It's why they keep their fuel there. Boats are the exact opposite. Thus, we have shrouds and spreaders, even on the most expensive boats, if one wants the best performance at sea. Flat water and steady winds change this a bit.

 

BV

 

Actually Beau, aircraft are very concerned with weight, whether in the wings or not. Every pound requires lift to get in the air and thrust to counteract the drag that comes when you create that lift. That costs either payload or gross weight and economy. The biggest improvement that came from moving to an unstayed wing was reduced drag and higher top speeds for a given amount of power. Stays are draggy as hell.

 

Fuel tanks are generaly in the wings because the airfoil shape accomodates "empty" space and it's a good place to carry an inflight consummable that makes up a significant proportion of the aircraft gross weight. Placing fuel in the wing also limits the center of gravity shift as the fuel is burned. In a "modern" fighter, fuel makes up about 1/3 of gross takeoff weight. You want to carry it as close the the center of gravity as you can.

 

I don't understand your comment on reefing an unstayed rig but I'll agree with the challenge of adding DW or, to a lesser extent, light air sail area.

 

Stayed rigs today are very refined old technology and hard to improve further unless you abandon the basic approach and bring in a new technology. Carbon for Aluminum for Wood and hi modulus fiber for rod for wire for rope are all really marginal changes to a basic design that is thousands of years old.

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Would masts like this sized up to say 60' be too heavy?

Paul

 

Could be, using today's materials and production techniques but things seem to be changing fast (carbon nanotubes) potentially enabling better free-standing mast design http://www.zyvexmari...-nanomaterials/ .... which will in turn enable changes to sail design and performance. As for cost, demand for improved performance (if that can be proven in practice) may create sufficient volume to drive down today's cubic dollars. A new project for WLYDO?

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How about this one?

 

http://www.omerwingsail.com/Video/

 

 

I thought that free standing rig stood for simplicity. One halyard, one sheet, no standing rigging.

 

Nope, it just means freestanding.

 

Long ago airplanes had wires and spreaders to keep the wings straight. Eventually, monoplanes arrived with unstated wings. Boats haven't changed because reefing and adding sail area downwind are problematic. Also, aircraft aren't concerned about weight in the wing, for lots of reasons. It's why they keep their fuel there. Boats are the exact opposite. Thus, we have shrouds and spreaders, even on the most expensive boats, if one wants the best performance at sea. Flat water and steady winds change this a bit.

 

BV

 

Actually Beau, aircraft are very concerned with weight, whether in the wings or not. Every pound requires lift to get in the air and thrust to counteract the drag that comes when you create that lift. That costs either payload or gross weight and economy. The biggest improvement that came from moving to an unstayed wing was reduced drag and higher top speeds for a given amount of power. Stays are draggy as hell.

 

Fuel tanks are generaly in the wings because the airfoil shape accomodates "empty" space and it's a good place to carry an inflight consummable that makes up a significant proportion of the aircraft gross weight. Placing fuel in the wing also limits the center of gravity shift as the fuel is burned. In a "modern" fighter, fuel makes up about 1/3 of gross takeoff weight. You want to carry it as close the the center of gravity as you can.

 

I don't understand your comment on reefing an unstayed rig but I'll agree with the challenge of adding DW or, to a lesser extent, light air sail area.

 

Stayed rigs today are very refined old technology and hard to improve further unless you abandon the basic approach and bring in a new technology. Carbon for Aluminum for Wood and hi modulus fiber for rod for wire for rope are all really marginal changes to a basic design that is thousands of years old.

 

IB,

 

Let me clarify why I was using the fuel in the wing as an example of the difference between aircraft and boats. I couldn't agree more that aircraft don't want weight - over all. What I was saying is that they actually want the weight in the wing while a sailboat definitely does not want the weight in the rig. As you obviously know, the lift in an aircraft comes from the wings, and as you correctly point out the fuel is about the heaviest thing in a plane and it's great to put the weight where the lift is. Then the aircraft doesn't have to transfer the weight load of the fuel, where it carried in the cabin, to the wings through some extremely strong spar. Instead the weight of the fuel rides exactly where the lift is - perfect you can make the aircraft lighter.

 

In a sailboat you want the opposite. You do NOT want any more weight in the rig at all. There are two big reasons for this.

 

First, as a boat heels, and the rig moves over to leeward of the center of buoyancy, any weight in the rig starts to tip the boat over - a bad thing.

 

Second, and more importantly in my view, each time a boat pitches up and back down over a wave the mast swing fore and aft in a motion that no aircraft ever does much of; it would be like constantly yawing. However, a sailboat does this millions of times in its life. In this instance the weight in the rig inhibits the ability of the boat to climb up over a wave and once the boat starts to pitch down again the momentum of the rig keeps it pitching long after it should have stopped and started going the other direction. Having a heavy rig is bad for precisely the same reason as placing a couple of heavy anchors on the bow or hanging a heavy dingy full of COTB off the stern in davits are bad. The reason the rig is more important than a poor choice of anchor storage is that most of the rig is further from the center of rotation of the boat when it is pitching. I am probably going to get this wrong, the NAs here can correct me, but I believe that the resistance to rotation around the center of pitching for a given weight in the ends of the boat and up the rig increases as the square of the distance from that center of rotation. Because the weight of the rig is so much further from the center of pitching rotation than the bow and stern combined with this "Square of the distance" stuff make weight in the rig very painful.

 

The reason this all matters in a freestanding vs stayed rig is simply weight. All the freestanding rigs I'm aware of are much heavier than a stayed rig of the same strength - much heavier. As a result, a freestanding rigged boat will almost always sail less well in a sea or chop than a stayed rig of the same strength and lesser weight.

 

Everything else you say about the drag of shrouds etc... I completely agree with, but the drag caused by the shrouds is trivial compared to the drag caused by forcing the bow to dig into wave fronts and troughs in a sea.

 

BV

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How about this one?

 

http://www.omerwingsail.com/Video/

 

 

I thought that free standing rig stood for simplicity. One halyard, one sheet, no standing rigging.

 

Nope, it just means freestanding.

 

Long ago airplanes had wires and spreaders to keep the wings straight. Eventually, monoplanes arrived with unstated wings. Boats haven't changed because reefing and adding sail area downwind are problematic. Also, aircraft aren't concerned about weight in the wing, for lots of reasons. It's why they keep their fuel there. Boats are the exact opposite. Thus, we have shrouds and spreaders, even on the most expensive boats, if one wants the best performance at sea. Flat water and steady winds change this a bit.

 

BV

 

Actually Beau, aircraft are very concerned with weight, whether in the wings or not. Every pound requires lift to get in the air and thrust to counteract the drag that comes when you create that lift. That costs either payload or gross weight and economy. The biggest improvement that came from moving to an unstayed wing was reduced drag and higher top speeds for a given amount of power. Stays are draggy as hell.

 

Fuel tanks are generaly in the wings because the airfoil shape accomodates "empty" space and it's a good place to carry an inflight consummable that makes up a significant proportion of the aircraft gross weight. Placing fuel in the wing also limits the center of gravity shift as the fuel is burned. In a "modern" fighter, fuel makes up about 1/3 of gross takeoff weight. You want to carry it as close the the center of gravity as you can.

 

I don't understand your comment on reefing an unstayed rig but I'll agree with the challenge of adding DW or, to a lesser extent, light air sail area.

 

Stayed rigs today are very refined old technology and hard to improve further unless you abandon the basic approach and bring in a new technology. Carbon for Aluminum for Wood and hi modulus fiber for rod for wire for rope are all really marginal changes to a basic design that is thousands of years old.

 

IB,

 

Let me clarify why I was using the fuel in the wing as an example of the difference between aircraft and boats. I couldn't agree more that aircraft don't want weight - over all. What I was saying is that they actually want the weight in the wing while a sailboat definitely does not want the weight in the rig. As you obviously know, the lift in an aircraft comes from the wings, and as you correctly point out the fuel is about the heaviest thing in a plane and it's great to put the weight where the lift is. Then the aircraft doesn't have to transfer the weight load of the fuel, where it carried in the cabin, to the wings through some extremely strong spar. Instead the weight of the fuel rides exactly where the lift is - perfect you can make the aircraft lighter.

 

In a sailboat you want the opposite. You do NOT want any more weight in the rig at all. There are two big reasons for this.

 

First, as a boat heels, and the rig moves over to leeward of the center of buoyancy, any weight in the rig starts to tip the boat over - a bad thing.

 

Second, and more importantly in my view, each time a boat pitches up and back down over a wave the mast swing fore and aft in a motion that no aircraft ever does much of; it would be like constantly yawing. However, a sailboat does this millions of times in its life. In this instance the weight in the rig inhibits the ability of the boat to climb up over a wave and once the boat starts to pitch down again the momentum of the rig keeps it pitching long after it should have stopped and started going the other direction. Having a heavy rig is bad for precisely the same reason as placing a couple of heavy anchors on the bow or hanging a heavy dingy full of COTB off the stern in davits are bad. The reason the rig is more important than a poor choice of anchor storage is that most of the rig is further from the center of rotation of the boat when it is pitching. I am probably going to get this wrong, the NAs here can correct me, but I believe that the resistance to rotation around the center of pitching for a given weight in the ends of the boat and up the rig increases as the square of the distance from that center of rotation. Because the weight of the rig is so much further from the center of pitching rotation than the bow and stern combined with this "Square of the distance" stuff make weight in the rig very painful.

 

The reason this all matters in a freestanding vs stayed rig is simply weight. All the freestanding rigs I'm aware of are much heavier than a stayed rig of the same strength - much heavier. As a result, a freestanding rigged boat will almost always sail less well in a sea or chop than a stayed rig of the same strength and lesser weight.

 

Everything else you say about the drag of shrouds etc... I completely agree with, but the drag caused by the shrouds is trivial compared to the drag caused by forcing the bow to dig into wave fronts and troughs in a sea.

 

BV

 

 

Beau,

 

I guess my response would be that freestanding rigs, to date, are examples of overengineering to account for unknown unknowns and not very sophisticated. A lot like early fiberglass hulls. They were heavy and resin rich because they were immature technology and the tools and processes were not available to know how much was "enough". The technology now exists to tailor a freestanding spar in both weight and stiffness and I would bet you could reduce that spar weight substantially. Stayed spars have literally thousands of years of development to get to the exquisite "buggy whips" that grace the latest and greatest designs today. Racing mores and a naturally conservative approach to cruising make investment risky but that's what it will take to move freestanding rigs forward.

 

Remember. Steamships will never catch on, man was never intended to fly, supersonic flight is impossible and God intended sailboats to have shrouds. :)

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Typically in the 70's, the most sophisticated free standing rig for up to a 45' boat., had the following characteristics. Base dia. 10"; top mast 4".; weight 240 lbs. without the fittings. They were individual epoxy impregnated filaments, woven over a mandrel. And cured in an hot oil bath. The company; Mclean Anderson, manufacturer of composite elements for the Military. Nothing has been bettered since.

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2009-05-16_093411_team_philips.jpg

 

The ill-fated Team Philips had two 135' unstayed rotating carbon wing spars. Each mast weighed about 5,500lbs. Despite being greatly over-engineered for the attempt on the Jules Verne round-the-world record, I believe they were not much heavier than a complete 1999-vintage maxi yacht rig, despite being 35% taller.

 

Things have only progressed since then.

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The main mast on Farfarer is reported 400mm dia. tapering to 100mm at the top which is at 82 feet. Farfarer is 56 feet LOA. There was no mention of the weight of the mast on the website but intuitively one could expect some improvement since the 70's. That is the heart of the issue - have there been sufficient improvements in materials and manufacturing technology to make freestanding rotating rigs more viable? Also, are there any efficiency improvements to be gained with a sail type more suited to a frrestanding rotating rig? For the people that think freestanding rigs look funny, it's hard to find something not to like in the aesthetics of Farfarer's rig.

 

 

5109341590_99a575cf001.jpg

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All,

 

I'm happy to accept that there may be freestanding rigs that are better than stayed ones, but not without actual data. We need weight data - real data. Yes, it is certainly the case that the rigs could be better than they were in the 70s. But, so far on this thread we don't have a single real comparison. I will say that Tom Wylie, who has done a ton of them, has told me that his opinion (again, not data) is that a freestanding rig is between 20 and 35 percent heavier for the same sail area.

 

I have no opinion on the aesthetics. I hate plumb bows and clipper bows and all sorts of things that go in and out of fashion. I love other things that go in and out of fashion as well, it's not relevant.

 

The only real issue is performance, for those of us who race, and there is a reason that the very highest performance boats all have shrouds.

 

BV

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The only real issue is performance, for those of us who race, and there is a reason that the very highest performance boats all have shrouds.

 

 

..... and that reason isn't necessarily because the performance is poorer. Remember this story .... Krazy K-Yote. I don't know anything more about it than I read on the www, but those better informed might have a view.

 

foto-krazy2.jpg

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I had an interesting talk with a very good and experienced sailor who has a large wylie cat. He said that the biggest issue with cat rigs and the most scary thing to go through is catching a wave in the huge wishbone. Which case he said the decision point for when you reduce sail also includes what sort of wave conditions your looking at. On the West Coast of CA especially north of Santa Barbara you'll find that experienced sailors with wishbone free standing type rigs are quite familiar with the force and risk that water can play when your catching the wishbone on some big waves.

 

As for reliability - rig failure almost always involves failure of a fairly cheap part in the rigging which case a free standing well built rig has far fewer potential failure points than your standard rigged mast.

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All,

 

I'm happy to accept that there may be freestanding rigs that are better than stayed ones, but not without actual data. We need weight data - real data. Yes, it is certainly the case that the rigs could be better than they were in the 70s. But, so far on this thread we don't have a single real comparison. I will say that Tom Wylie, who has done a ton of them, has told me that his opinion (again, not data) is that a freestanding rig is between 20 and 35 percent heavier for the same sail area.

 

I have no opinion on the aesthetics. I hate plumb bows and clipper bows and all sorts of things that go in and out of fashion. I love other things that go in and out of fashion as well, it's not relevant.

 

The only real issue is performance, for those of us who race, and there is a reason that the very highest performance boats all have shrouds.

 

BV

 

BV,

 

I guess I can't counter the "show me data." Of course, no technology advancement started with empirical data showing it was unquestionably better. It started with analysis and experimentation. I see stayed rigs at the end of the development cost/performance improvement curve where very marginal performance gains require significant investment. It's a stable technology. Stable technology doesn't intrigue me very much. It's just there. The last piston engined fighters were very good. The first jets were really awful and it took several generations before experimentation and development delivered on the analytical promise.

 

No question that today, for type formed W/L racing, a stayed marconi rig provides higher performance, particularly upwind. If that is your metric, a stayed rig and very deep fin is the only answer - today.

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The only real issue is performance, for those of us who race, and there is a reason that the very highest performance boats all have shrouds.

 

BV

 

Not quite all. The board people would beg to differ, but OK, maybe it's not a boat if you don't get in it.

 

Look Ma! No shrouds! :P

 

sailrocketlaunch.jpg

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The Sailrocket actually does have shrouds.

 

Edit: Or at least rigging, I don't know if they count a shrouds.

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the biggest issue with cat rigs and the most scary thing to go through is catching a wave in the huge wishbone.

 

.... maybe the next generation of freestanding rigs won't have wishbones. Here's Van de Stadt's "swing rig".

 

swing_rig41.jpg">

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This is an excerpt from an article in Ocean Navigator of 9 years ago. Does anyone have any additional information on the outcome of Hall's trials with "Blackwing"

 

 

"On a more down-to-earth scale, Eric Hall, co-owner of Hall Spars, has built three unstayed wing mast prototypes for a J/90 sportboat. This lively 30-footer has proven an excellent benchmark because several sisterships with standard rigs are actively raced in Hall's neighborhood. Unlike either the AeroRig or the Team Phillips spars, Hall's "Blackwings" have true airfoil mast sections, not a simple cylindrical or modified cylindrical masts. The first two versions were sloop-rigged with running backstays for better headstay control. However, the third is a so-called "uni-rig" - essentially a super-efficient cat rig with all upwind sail area concentrated in the mainsail but with provisions to set an asymmetrical chute for off-wind work. Experience with iceboats and high-performance catamarans has established that a wing-mast uni-rig is potentially more efficient than a sloop with equal sail area. Hall's 30-foot Blackwings have shown good speed against similar, conventionally rigged boats, and plans for similar commercial rigs are now in the works."

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the biggest issue with cat rigs and the most scary thing to go through is catching a wave in the huge wishbone.

 

.... maybe the next generation of freestanding rigs won't have wishbones. Here's Van de Stadt's "swing rig".

 

 

Wishbones aren't really a generation thing, it's just that they kind of require a freestanding rig so they've kind of created a reverse associastion. And even then catching waves is kind of specific to cat (uni)rigs. You could stick a wishbone on a sloop/cutter and it wouldn't be nearly as much a problem, or a 50/50ish split rig (which is what Tanton does).

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All,

 

I'm happy to accept that there may be freestanding rigs that are better than stayed ones, but not without actual data. We need weight data - real data. Yes, it is certainly the case that the rigs could be better than they were in the 70s. But, so far on this thread we don't have a single real comparison. I will say that Tom Wylie, who has done a ton of them, has told me that his opinion (again, not data) is that a freestanding rig is between 20 and 35 percent heavier for the same sail area.

 

I have no opinion on the aesthetics. I hate plumb bows and clipper bows and all sorts of things that go in and out of fashion. I love other things that go in and out of fashion as well, it's not relevant.

 

The only real issue is performance, for those of us who race, and there is a reason that the very highest performance boats all have shrouds.

 

BV

 

"Better" is a pretty subjective term. I know what's better for me, glad you know what's better for you.

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This is an excerpt from an article in Ocean Navigator of 9 years ago. Does anyone have any additional information on the outcome of Hall's trials with "Blackwing"

 

 

"On a more down-to-earth scale, Eric Hall, co-owner of Hall Spars, has built three unstayed wing mast prototypes for a J/90 sportboat. This lively 30-footer has proven an excellent benchmark because several sisterships with standard rigs are actively raced in Hall's neighborhood. Unlike either the AeroRig or the Team Phillips spars, Hall's "Blackwings" have true airfoil mast sections, not a simple cylindrical or modified cylindrical masts. The first two versions were sloop-rigged with running backstays for better headstay control. However, the third is a so-called "uni-rig" - essentially a super-efficient cat rig with all upwind sail area concentrated in the mainsail but with provisions to set an asymmetrical chute for off-wind work. Experience with iceboats and high-performance catamarans has established that a wing-mast uni-rig is potentially more efficient than a sloop with equal sail area. Hall's 30-foot Blackwings have shown good speed against similar, conventionally rigged boats, and plans for similar commercial rigs are now in the works."

 

In the right conditions, Blackwing has shown itself to be competitive, and it's fast, but I don't think it's ever been truly able to sail to its rating. in 2001, at BIRW, they had pretty good success against Rodney's J90 despite having less upwind sail area, and they said that they certainly were winning the tacking duels. It is also very fast off the wind. Without the jib, they carry between 40 and 120sf less sail area than a stock J90. The boat wasn't designed for a free standing rig, and could be made lighter in the ends since it doesn't have head/backstay loads to deal with. I don't think the issue with this boat was ever pointing ability, just the ability to set more sail going upwind.

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but, but, but...if you don't have shrouds, where are you going to put the belaying pins?

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That's the best part with out shrouds you're free to place the belaying pins for maximum aesthetic saltiness instead of worrying about trifles like "function"

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Ryley.

 

Sounds like you may know some of the people involved. Would it be possible to find information on the relative weights of the stayed versus the unstayed rigs? (A shame to spoil a good story with facts.) On the issue of the boat not being optimised for the unstayed rig, the true relative performance of the rigs may be easier to evaluate by having all the other variables unchanged. Any boat improvements (and there are probably many) are gravy.

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This is an excerpt from an article in Ocean Navigator of 9 years ago. Does anyone have any additional information on the outcome of Hall's trials with "Blackwing"

....

 

Experience with iceboats and high-performance catamarans has established that a wing-mast uni-rig is potentially more efficient than a sloop with equal sail area. Hall's 30-foot Blackwings have shown good speed against similar, conventionally rigged boats, and plans for similar commercial rigs are now in the works."

 

9 years ago - so recent enough that the tech was pretty darn good (especially with Hall himself sailing it) but ti never set the world afire.

 

Iceboats and cats have a LOT less drag

 

Love how the writere couched that "shown good speed" and "plans now in the works" - nothing that could be called 'wrong' but no others were built.

 

Not to be the wet blanket - heck I dig these too, but conventional tech still holds court.

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My dear anarchists,

 

it is a real pleasure every evening for me to follow this basically technical/theoretical thread with some clever and jolly good jokes. In contrary to the cuise ship terror (google this song!) thread where it slowly drifts away from knowledge sharing into a crusade between...

 

Nevertheless - you all keep going strong - this is what the free standing - pardon thinking - of SA is all about. Live without SA would be less.

 

Enjoy the sea!

 

Knut

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This is an excerpt from an article in Ocean Navigator of 9 years ago. Does anyone have any additional information on the outcome of Hall's trials with "Blackwing"

 

 

"On a more down-to-earth scale, Eric Hall, co-owner of Hall Spars, has built three unstayed wing mast prototypes for a J/90 sportboat. This lively 30-footer has proven an excellent benchmark because several sisterships with standard rigs are actively raced in Hall's neighborhood. Unlike either the AeroRig or the Team Phillips spars, Hall's "Blackwings" have true airfoil mast sections, not a simple cylindrical or modified cylindrical masts. The first two versions were sloop-rigged with running backstays for better headstay control. However, the third is a so-called "uni-rig" - essentially a super-efficient cat rig with all upwind sail area concentrated in the mainsail but with provisions to set an asymmetrical chute for off-wind work. Experience with iceboats and high-performance catamarans has established that a wing-mast uni-rig is potentially more efficient than a sloop with equal sail area. Hall's 30-foot Blackwings have shown good speed against similar, conventionally rigged boats, and plans for similar commercial rigs are now in the works."

 

In the right conditions, Blackwing has shown itself to be competitive, and it's fast, but I don't think it's ever been truly able to sail to its rating. in 2001, at BIRW, they had pretty good success against Rodney's J90 despite having less upwind sail area, and they said that they certainly were winning the tacking duels. It is also very fast off the wind. Without the jib, they carry between 40 and 120sf less sail area than a stock J90. The boat wasn't designed for a free standing rig, and could be made lighter in the ends since it doesn't have head/backstay loads to deal with. I don't think the issue with this boat was ever pointing ability, just the ability to set more sail going upwind.

 

 

Since the impetus for the experiment was the A class cat, there was a pretty big surprise, in that the initial assumption was that a square head planform would be da bomb on the una rig, but no, a roachy pinhead did tha trick. can't remember if they went with more luff length, Steve Clark found empirically that 10-20% more made up for the lack of the jib on an una rig IC he did.

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Ryley.

 

Sounds like you may know some of the people involved. Would it be possible to find information on the relative weights of the stayed versus the unstayed rigs? (A shame to spoil a good story with facts.) On the issue of the boat not being optimised for the unstayed rig, the true relative performance of the rigs may be easier to evaluate by having all the other variables unchanged. Any boat improvements (and there are probably many) are gravy.

 

I'll see what I can find out. I looked at buying this boat when it came up for sale a few years ago, and it has recently been sold again.

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I think Nigel has the right idea: if you are going free standing, two (or many more) rigs are the way to go, rather than one. A uni rig (cat rig) is OK for close hauled only. Slots are very fast when cracked off. And DDW you can go wing and wing.

 

Here is what I am working on: about 6 little high aspect free standing rigs with wishbone booms. Its for cruising, so upwind unfurl the iron genny or just live with the performance. Crack off, and its all good. Low CE, so long and narrow hull works well. The low loads can open up a lot of possibilities...

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I think Nigel has the right idea: if you are going free standing, two (or many more) rigs are the way to go, rather than one. A uni rig (cat rig) is OK for close hauled only. Slots are very fast when cracked off. And DDW you can go wing and wing.

 

Here is what I am working on: about 6 little high aspect free standing rigs with wishbone booms. Its for cruising, so upwind unfurl the iron genny or just live with the performance. Crack off, and its all good. Low CE, so long and narrow hull works well. The low loads can open up a lot of possibilities...

Sort of like a tiny version of the great Thomas W Lawson, but without the rigging?

 

OK.

 

CL0375b%252B.jpg

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Airfoil vs. round:

 

An airfoil section in theory is better than a round section. But in practice, at least on a cruising boat, the difference vanishes. The round section allowed by carbon is quite a small percentage of chord: on my mainsail, about 3%. The best information I could find is that with a carefully arrived at section (must be developed either in extensive wind tunnel or two boat testing) and a dedicated mast trimmer, it could be marginally faster upwind. Otherwise, maybe slower. (This is from discussions with 5 boat owners with rotating masts, Bethwaite, others). On the Finot open 60s they think it is worth about 5% in upwind speed - don't know how that translates to a cruising boat. On the other hand, an airfoil section causes all kinds of trouble on a cruising boat with no easy solutions.

 

Wishbone vs. boom:

 

A wishbone works well with a conventional pointy sail. Not so good with a square head, and you need a square head. There is insufficient leech tension for a square head unless a vang is also used, as was done on Team Philips. On the other hand, there does not seem to be much disadvantage in the inverted vang, other than the parts currently have to be custom made. As far as dragging the wishbone goes, this isn't a consequence of an unstayed rig so much as a cat rig: the cat has to have a long foot in order to have enough area, and the longer the foot the more likely to drag it. A wishbone though, has no vang you can blow to get the boat back up, and you can be pinned.

 

Rig weight:

 

There is an assumption that an unstayed rig "must be" heavier than a marconi. That might be true in a pure racing rig. In the estimates we did or my cruising boat the unstayed rig is lighter. My main sail carries 960 sq ft, the mast weighs about 630 lbs. That is total weight, there are no shrouds, stays, or other hardware to add. Because of the taper of both diameter and wall thickness, the CG of the mast is only about 21 ft above the DWL (truck is 64 ft). In righting moment, I believe my unstayed rig is at a substantial advantage to a conventional one. Because is it stepped near the bow though, it does contribute to the longitudinal moment of inertia - a consequence of the cat rig, not the fact that it is unstayed.

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DDW,that is an excellent summary. Anecdotally, I am aware of one boat that was raced with a cat rig and with a sloop rig, by the same crew – that eliminates alot of variables in the comparison. The sloop rig could point 5° higher and sail shape was easier to control. As you point out, these are rig issues rather than whether the mast is stayed or not. Consistent with your comments, the weight issue appeared not to be a major factor.

 

 

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Anecdotally, I am aware of one boat that was raced with a cat rig and with a sloop rig, by the same crew – that eliminates alot of variables in the comparison. The sloop rig could point 5° higher and sail shape was easier to control.

What was the planform of the cat rig? I believe a square head is more of an advantage on a una rig than on a sloop. The sloop has a complicated span wise loading due to the slotted airfoil, but a triangular una rig has just a plain bad span wise loading. It isn't hard to get a 50% reduction in induced drag on a una rig with a square head vs. Bermuda.

 

I should have mentioned above, that I have dipped my boomed mainsail only briefly and rarely, it is only 24 ft long on a 45 foot boat. On my previous 30 ft wishbone boat (24 ft on the foot as well) you could dip it deeply and easily. The two big reasons to split the at rig as the boat gets bigger are to keep the sails within human manageable size, and to keep the boom out of the water.

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Not sure exactly, but probably looked like this ....... BTW, I was anchored in Todd Inlet last summer next to a boat (~50'LOA) with home port of Nanaimo, that had three free-standing masts with wishbones - visually quite appealing.

 

44i1.jpg

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...snip...

 

Rig weight:

 

There is an assumption that an unstayed rig "must be" heavier than a marconi. That might be true in a pure racing rig. In the estimates we did or my cruising boat the unstayed rig is lighter. My main sail carries 960 sq ft, the mast weighs about 630 lbs. That is total weight, there are no shrouds, stays, or other hardware to add. Because of the taper of both diameter and wall thickness, the CG of the mast is only about 21 ft above the DWL (truck is 64 ft). In righting moment, I believe my unstayed rig is at a substantial advantage to a conventional one. Because is it stepped near the bow though, it does contribute to the longitudinal moment of inertia - a consequence of the cat rig, not the fact that it is unstayed.

 

As a single data point, the rig on S'agapo weighs just about 530 pounds and holds up 970 sq/ft going upwind. That yields a 1.83:1 ratio of square feet per pound. DDW, your unstayed rig yields a 1.5:1 ratio, square feet to pounds. The difference, as I calculate it, is about 17%. This would be a REALLY big deal in a racing boat and only a moderate issue with a cruising boat. BTW, my rig isn't a "racing" rig. A sister ship accomplishes the same sail area for 425 pounds, yielding a 2.28:1 ratio and a 35% difference in pounds per square foot of sail area, which is a big deal for both racers and cruisers.

 

The weight numbers above for the Spirit-46s were done with a scale as part of the IRC measurement process and are not calculations. Sail area is only up-wind sails and doesn't address the downwind sail area which is much much larger for no increase in weight. The carbon rigs in both Spirit-46s are tapered walls with low CG.

 

BV

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I'm sure it's theoretically possible to make a good looking aerorig'ed boat, but that one doesn't look like they even tried.

 

 

Jet Services wasn't bad......

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post-32003-004545300 1328399688_thumb.jpg

Anatomy of a free standing rigged boat going upwind. Showing the wishbone boom set up.

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This is a post-race picture of the 2000 Bermuda race fleet. Centered in the picture is a cat-ketch. I asked a crew member who designed it, and, IIRC, she said Farr.

 

post-5724-026691900 1328471575_thumb.jpg

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I believe she is Acadia, a German Frers Design.

 

This is a post-race picture of the 2000 Bermuda race fleet. Centered in the picture is a cat-ketch. I asked a crew member who designed it, and, IIRC, she said Farr.

 

post-5724-026691900 1328471575_thumb.jpg

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So, what would you get if you crossed a free standing rig with a B&R rig? From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast. As the weight and diameter seems to be a major impediment to the freestanding rig, would a tripod like B&R compensate sufficiently for the extra weight of the freestanding rig? Furthermore, would the B&R rigging setup facilitate control of upper part of the mast?

 

3604561_20110509110206_2_LARGE2.jpg

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So, what would you get if you crossed a free standing rig with a B&R rig? From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast. As the weight and diameter seems to be a major impediment to the freestanding rig, would a tripod like B&R compensate sufficiently for the extra weight of the freestanding rig? Furthermore, would the B&R rigging setup facilitate control of upper part of the mast?

 

3604561_20110509110206_2_LARGE2.jpg

 

You'd get a fucking awful deck to move around on, for starters. I can't help feeling that would look better upside down.

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So, what would you get if you crossed a free standing rig with a B&R rig? From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast. As the weight and diameter seems to be a major impediment to the freestanding rig, would a tripod like B&R compensate sufficiently for the extra weight of the freestanding rig? Furthermore, would the B&R rigging setup facilitate control of upper part of the mast?

 

3604561_20110509110206_2_LARGE2.jpg

 

You'd get a fucking awful deck to move around on, for starters. I can't help feeling that would look better upside down.

 

You mean like a keel stepped mast?

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From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast.

 

Maybe you could have a forward-positioned pilot house and use the house-top for support instead of the tripod.

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Agreed, the tripod is not attractive and would make moving around the deck difficult ...... but the prize of a fast, light and simple rig is appealing - always a compromise in design. The owners of Route 66 (that also had a Bergstrom tripod) have commented that 200 miles "was a really bad day" - not all rig-related to be sure. YTM, as someone that has designed boats with freestanding rigs what do you think of SemiSalt's idea of incorporating the house top into the "tripod" for a freestanding rig?

 

 

Y661.jpg

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...snip...

 

Rig weight:

 

There is an assumption that an unstayed rig "must be" heavier than a marconi. That might be true in a pure racing rig. In the estimates we did or my cruising boat the unstayed rig is lighter. My main sail carries 960 sq ft, the mast weighs about 630 lbs. That is total weight, there are no shrouds, stays, or other hardware to add. Because of the taper of both diameter and wall thickness, the CG of the mast is only about 21 ft above the DWL (truck is 64 ft). In righting moment, I believe my unstayed rig is at a substantial advantage to a conventional one. Because is it stepped near the bow though, it does contribute to the longitudinal moment of inertia - a consequence of the cat rig, not the fact that it is unstayed.

 

As a single data point, the rig on S'agapo weighs just about 530 pounds and holds up 970 sq/ft going upwind. That yields a 1.83:1 ratio of square feet per pound. DDW, your unstayed rig yields a 1.5:1 ratio, square feet to pounds. The difference, as I calculate it, is about 17%. This would be a REALLY big deal in a racing boat and only a moderate issue with a cruising boat. BTW, my rig isn't a "racing" rig. A sister ship accomplishes the same sail area for 425 pounds, yielding a 2.28:1 ratio and a 35% difference in pounds per square foot of sail area, which is a big deal for both racers and cruisers.

 

The weight numbers above for the Spirit-46s were done with a scale as part of the IRC measurement process and are not calculations. Sail area is only up-wind sails and doesn't address the downwind sail area which is much much larger for no increase in weight. The carbon rigs in both Spirit-46s are tapered walls with low CG.

 

BV

We need to know the righting moment of both boats to have a basis for comparison. Or at least the displacement. Do you know what the max righting moment of S'agapo is? On Anomaly, about 100,000 ft lbs according to MSURF (13.5 ft beam, 29,000 lbs displacement). This is important because the rig only has to be strong enough to capsize the boat (plus whatever safety factor is thought appropriate). A lighter boat will have a lighter rig even with the same sail area. According to their own published data, a Spirit 46 is 9.25 ft beam and 9000 lbs displacement (and also a sail area of just 684 sq ft), so my guess is that the righting moment is substantially less, perhaps less than 1/2. Downwind on Anomaly we can more than double the sail area with no increase in weight other that the sails set. The designed safety factor is approximately 4x.

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From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast.

 

Maybe you could have a forward-positioned pilot house and use the house-top for support instead of the tripod.

 

 

like this?

 

post-906-038448500 1329030126_thumb.jpg

 

Paul Bieker's 'Rocket Science'

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The best thread on unstayed masts I have seen. Every time I think I have a comment to make, someone else makes it first. Well done to all concerned.

 

A couple more data points. The mast on the boat at

weighs 120 kgs/264 lbs, is 17m/56' long with main luff of 14.2m/47'. The boat has rm of 18000kgm. The cost, 10 years ago, was $12,000. Cost and weight were near enough the same as an alloy mast with ss rigging at the time. The cog of the unstayed mast was appreciably lower than the alloy one.

 

We have just quoted for a 20m/66' mast for a 20% higher rm at $17,000.

 

At the moment, we are building 6 unstayed carbon masts for 3 biplane rigged 40' catamarans. All are foldable for getting under bridges. Cost per mast is $11,500, plus $4,500 for the stub masts and folding arrangement. The wing mast version is 50% more.

 

I am building a wing mast for my 25' test bed harryproa. It is a wing section and will sit on the stub mast from one of the old cut down rigs. The wing is 7.2m/24' high and will be used to test some novel sail ideas. When the sails are sorted out, it will become the lower part of a telescoping mast 13.7m/45' high. If/when that works, it will be scaled up for a 15m weekender/short handed racer currently being built.

 

rob

3 telescoping rig.pdf

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So, what would you get if you crossed a free standing rig with a B&R rig? From what research I can find, the B&R tripod moved the maximum bending moment further up the mast, distributed the load at the deck level and facilitated a lighter and narrower mast. As the weight and diameter seems to be a major impediment to the freestanding rig, would a tripod like B&R compensate sufficiently for the extra weight of the freestanding rig? Furthermore, would the B&R rigging setup facilitate control of upper part of the mast?

 

3604561_20110509110206_2_LARGE2.jpg

 

A lot of rig load comes in from the boom. In effect that removes those loads from the mast. Good idea? You decide.

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....... according to MSURF (13.5 ft beam, 29,000 lbs displacement)......

 

DDW, as I am trying to learn on the fly so I can keep up with the discussion, would you have a URL for MSURF? Also,is it correct that the narrow beam of the Spirit 46, reduces the potential maximum righting moment because of the lower displacement and the shorter moment arm (GZ) - a limitng factor in comparing righting moments for S'agapo and Anomoly maybe?

 

Considering the standalone mast design itself, it is basically a cantilever of reducing stiffness along its length (height). Stepped at the keel with the top of the house as lateral support, moving that support higher up the mast should facilitate a lighter mast which would lower the G and improve the righting moment, for the same M ?

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....... according to MSURF (13.5 ft beam, 29,000 lbs displacement)......

 

DDW, as I am trying to learn on the fly so I can keep up with the discussion, would you have a URL for MSURF? Also,is it correct that the narrow beam of the Spirit 46, reduces the potential maximum righting moment because of the lower displacement and the shorter moment arm (GZ) - a limitng factor in comparing righting moments for S'agapo and Anomoly maybe?

 

You can find info on Maxsurf here. In any boat, the stability comes from a lateral displacement of the center of buoyancy compared to the center of mass. Very rough guess is that the center of buoyancy will shift laterally about 1/4 of the beam (normal monohulls here) so the max righting moment can very roughly be estimated as 1/4 beam * displacement. On Anomaly, this gives us an estimate of 98,000 ft lbs, pretty close to the Maxsurf number which we can count on. On S'agapo, the estimate gives us 20,800 ft lbs., only about 1/5 of Anomaly. So her rig need only resist 1/5 the righting moment. Given the stated weight figures, I think - at least in this case - that Anomaly's freestanding rig is considerably lighter for the job it does.

 

Considering the standalone mast design itself, it is basically a cantilever of reducing stiffness along its length (height). Stepped at the keel with the top of the house as lateral support, moving that support higher up the mast should facilitate a lighter mast which would lower the G and improve the righting moment, for the same M ?

This is true - however the loads are not much different than a Marconi rig if the partners are at deck level (as they are on Anomaly). Nearly all the righting moment on a Marconi rig is reacted between the mast step and the windward shroud chainplate, at most 1/2 the beam. If you need 100,000 lbs resolved on a boat with 13.5 ft beam, there will be an upward force of about 15,000 lbs on the chain plate and an equal downward force on the mast step (more if the chainplate is set inboard of the rail). On a cantilevered mast, the moment is resisted by lateral forces on the mast step and partners. On Anomaly, the distance between them is about 5.5 ft, so the lateral force is about 18,000 lbs on each (ignoring shear, which adds a small about at the partners). If you somehow moved the partners twice as high, you would reduce these forces by half, but the maximum moment in the mast would be reduced far less, only about 20%.

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Many thanks for the Maxsurf link DDW - I did not know that existed. Armed with some analytic tools, it's time to play amateur NA :) Looking at the pictures of the rig modifications on Anomaly, your earlier comment re boom in the water is very clear - a beautiful boat.....

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...snip...

 

Rig weight:

 

There is an assumption that an unstayed rig "must be" heavier than a marconi. That might be true in a pure racing rig. In the estimates we did or my cruising boat the unstayed rig is lighter. My main sail carries 960 sq ft, the mast weighs about 630 lbs. That is total weight, there are no shrouds, stays, or other hardware to add. Because of the taper of both diameter and wall thickness, the CG of the mast is only about 21 ft above the DWL (truck is 64 ft). In righting moment, I believe my unstayed rig is at a substantial advantage to a conventional one. Because is it stepped near the bow though, it does contribute to the longitudinal moment of inertia - a consequence of the cat rig, not the fact that it is unstayed.

 

As a single data point, the rig on S'agapo weighs just about 530 pounds and holds up 970 sq/ft going upwind. That yields a 1.83:1 ratio of square feet per pound. DDW, your unstayed rig yields a 1.5:1 ratio, square feet to pounds. The difference, as I calculate it, is about 17%. This would be a REALLY big deal in a racing boat and only a moderate issue with a cruising boat. BTW, my rig isn't a "racing" rig. A sister ship accomplishes the same sail area for 425 pounds, yielding a 2.28:1 ratio and a 35% difference in pounds per square foot of sail area, which is a big deal for both racers and cruisers.

 

The weight numbers above for the Spirit-46s were done with a scale as part of the IRC measurement process and are not calculations. Sail area is only up-wind sails and doesn't address the downwind sail area which is much much larger for no increase in weight. The carbon rigs in both Spirit-46s are tapered walls with low CG.

 

BV

We need to know the righting moment of both boats to have a basis for comparison. Or at least the displacement. Do you know what the max righting moment of S'agapo is? On Anomaly, about 100,000 ft lbs according to MSURF (13.5 ft beam, 29,000 lbs displacement). This is important because the rig only has to be strong enough to capsize the boat (plus whatever safety factor is thought appropriate). A lighter boat will have a lighter rig even with the same sail area. According to their own published data, a Spirit 46 is 9.25 ft beam and 9000 lbs displacement (and also a sail area of just 684 sq ft), so my guess is that the righting moment is substantially less, perhaps less than 1/2. Downwind on Anomaly we can more than double the sail area with no increase in weight other that the sails set. The designed safety factor is approximately 4x.

 

DDW,

 

The actual measured weight of my Spirit-46, S'agapo, is 11,250 pounds and the lead is about 5,000 (also weighted on a scale) and is in the bulb with an apx center of gravity of 6' below the waterline. (I think you may have been using the wrong sort of "ton" when referencing their web site. Or, their web site is just wrong.) The Sail area upwind is right at about 787 sq. ft. without overlapping sails. (I just had new sails made and my earlier post was mistaken when I said 970, wrong assumption about overlapping jib.) Downwind, the sail area is increased to around 1,160 sq ft. I'm certain that the beamier boat has more righting moment from form stability, and depending upon where the 29,000 pounds of displacement is located, it may have more from the keel as well.

 

I am not acquainted with MSRUF. Is that a piece of software? A quick Google didn't turn anything up. I am not at all sure what you mean by 100,000 ft. lbs. of max righting moment. I know what foot pounds of torque are. Are you saying that at the center of effort of the rig, perhaps 10' up, there is 10,000 pound of pressure maximum to heel the boat? I'd be really curious what angle you think Anamaly generates the max righting moment.

 

Finally, my understanding from chatting with some rig folks is that the shock loads on a rig are much much higher than any static righting moment loading. Back in the '60s we used to loose rigs a lot before some of these guys figured out that the shock loads of falling 10' off a wave and landing while heeled over completely dwarfed anything the wind could do to the rig. As a result, they started paying a LOT of attention to getting the weight out of the rig and stop thinking as much about static wind-created loads.

 

BV

 

Edit: sorry, i found the link you posted to MSRUF. Next time I'll read more carefully.

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Beau,

Yeah, the Spirit literature may have been in long tons, they do not say. Even at that, your righting moment is very likely small compared to mine. S'agapo weighs 11,250. Anomaly's keel lead weighs 10,500 :P . The CG of the lead bulb is about 5.5 ft below DWL.

 

Upwind we carry 960 sq ft in the mainsail alone, 1180 with the small mizzen. Downwind, as much as 2500 with spinnaker and mizzen staysail. The righting figures come from the hydrostatic calculations which, if the lines represent the actual hull, are accurate. Maxsurf output and programs like it can be taken as fact (provided no garbage in....). The rig was designed to be able to withstand a knockdown from mainsail pressure (distributed across the span) and also from the spinnaker block alone. If we take the center of effort of the main to be its center of area, that is about 33 ft above the water. Max moment on the mast tube at the partners is the same in either case, shear load changes a little depending. The design safety factor above the forces required to do this is about 4x in the mast tube, and about 8x in the step and partners. The mast rotates, so these are bearings supporting it.

 

post-4075-023879400 1329326925_thumb.jpg

 

Note that the righting moment is in inch-lbs. Max righting moment occurs at 68 degrees heel (from the righting moment table, calculated for every degree of heel). Updating my righting moment guestimate for S'apago with 11,250 displacement, max righting moment is probably 26,000 ft lbs. On Anomaly, we exceed that at 9 degrees of heel and are back down to that at about 116 degrees heel - maybe a little more, the Maxsurf model was run on the hull without the house which usually adds a little bit of righting at extreme angles of heel.

 

Didn't set the staysail for this picture, big space wanting to be filled, eh? Don't complain about the trim, we are trimmed for the picture. About 3 knots TWS.

 

[AnomalySmall-1.jpg

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I like The spinnaker! How'd you do he graphics? Nice to see almost maxed out sail separation. If you could incline the aft mast (ala the red French rocket) towards the wind whilst going upwind, do you think that would help?

 

Paul

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Graphics are inlaid and sewn by Doyle. A very nice job they did.

 

The mizzen does not seem to suffer too badly from the main. First of all, it is only 220 sq ft. Second, the main is not carried close to center line like it would be on a sloop. It's the first sail to meet the wind, not the second, so we trim it more like a genoa than a sloop's mainsail. Upwind the mizzen adds a few tenths of a knot to speed, and is carried a bit to leeward of centerline.

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DDW,

 

Perhaps I'm being dense here, but I'm trying to get my head around it taking 100,000 pounds to pull your boat over. I'm assuming that it takes that amount if one were to pull from a place one foot above the center of rotation. Is that correct? So, if you pulled from 10 feet above the center of rotation one would only pull with 10,000 pounds of force and if one pulled from 50 feet above the center of rotation one would pull with a force of 2,000 pounds.

 

What I'm trying to get to is resolving your numbers with my personal experience pulling boats over to horizontal at the dock so I can work on them. I've hauled a Santa Cruz 50 over 50 degrees with her spinnaker halyard and the genoa winch and while it was a lot of work, it doesn't seem to match your rule of thumb. SC-50 specs are 16,000 lb of displacement and 12' of beam. So, given your working rule of thumb: one quarter of the beam is 4 and that times the displacement is 64,000 ft. lbs of righting moment. The mast head is about 65' up so I take 64,000 and divide it by 65 which yields 1,000 lbs. The difficulty I'm having is that we heeled the SC-50 over by tying a halyard to a cleat on the dock a couple of slips away and we didn't lift the dock much at all. I know the docks are heavy, but they don't weight thousands of pounds.

 

What I'm I not understanding about your formula?

 

BV

 

Edit: BTW, I agree, very cool spinnaker! Reminds me of Escher.

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100,000 ft lbs is just as you say. I can't speak for the Santa Cruz, 50 deg is probably less than the max righting moment. If the floating dock was concrete like many in our area are, 1000 lbs is not really very much, you can get that with a reasonable pull on a #40 winch.

 

Quick reality check: take the center of effort to be the center of area as a rough approximation. I have 960 sq ft in the main, max coefficient of lift is maybe 1.2, center of area about 33 ft about DWL which we will also guess is the lever arm. So 100,000 / 33 is about 3000 lbs. Lift is 1/2 * rho * V^2 * Cl * A, so backing out V I get about 28 knots of wind for a knockdown close hauled under full sail. That is pretty close to reality.

 

The lever arm is actually the difference between the CLE and CLR. At least, that's the way the spar makers see it.

 

By the way, 1/4 of 12 is 3, not 4, so the righting estimate for the SC 50 would be 48,000 ft lbs. :D

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LOL - yup, I inverted the arithmetic on the 12/4! Ah well.

 

Pulling a ton on a Santa Cruz dock would destroy it. We have old tsunami twisted wooden docks that are all being rebuilt. I'm going to see if I can find a BIG fish scale and pull on S'agapo to measure this, I'm fascinated.

 

Thanks for the data. I've also asked a AC sailor for a little data from his programs of old where they had load cells on the stays. I'm curious about the static wind induced loads vs the dynamic loads created by the boats going over waves. I know that the keel designers for the canting keels have stated publicly that the dynamic loads caused by dropping off off waves are over 5 times the loads of heeling the boat over.

 

BV

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LOL - yup, I inverted the arithmetic on the 12/4! Ah well.

 

Pulling a ton on a Santa Cruz dock would destroy it. We have old tsunami twisted wooden docks that are all being rebuilt. I'm going to see if I can find a BIG fish scale and pull on S'agapo to measure this, I'm fascinated.

 

Thanks for the data. I've also asked a AC sailor for a little data from his programs of old where they had load cells on the stays. I'm curious about the static wind induced loads vs the dynamic loads created by the boats going over waves. I know that the keel designers for the canting keels have stated publicly that the dynamic loads caused by dropping off off waves are over 5 times the loads of heeling the boat over.

 

BV

 

This is why I like having Beau as a friend, he does all of the research..........

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Kimb, you get what you pay for! Just kidding. But I'm sure that BobP can give you whatever answer you want far more accurately than my homebrew science projects. I got a note back on shock loads and the AC guy said that there were lots of 2X and some 2.5X loads when the boats hit waves, these are old AC monohulls. He also said that these boats didn't sail in anything most of us would call "real waves". So I should expect much bigger shock loads from dropping into holes in a "real wave". He did not, however, give me any exact numbers... Grrrrr.

 

BV

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post-59748-057616600 1329718043_thumb.jpg If this is still about unstayed rigs let me add a few diversions, in no particular order.

 

The disadvantage of the unstayed rig is NOT weight - it is excess bending - which when compensated for with a large diameter tube equals weigh.

The corresponding disadvantage of a stayed rig is windage from mast AND wires, the power of which you hear in any marina when the wind pipes up.

 

The advantage of unstayed rigs is that you can give the sail the shape you want, including a big powerful roach AND the right twist on both points of sail.

The corresponding disadvantage of a stayed rig is that you end up with most of the sailarea on the deck and little pointy pieces at the top (researchers says the crab claw is the most efficient).

 

Another advantage of the unstayed rig is that you can turn turn the sail in the direction you want and use lift on a almost all points of sail.

This is impossible on a stayed rig which is why they invented beer can races that mostly go upwind so no one will notice this.

 

The (first) disadvantage of the cat-rig on an unstayed mast is not lack of weatherliness, it is that the mast is in the way of the front edge of the sail. You need a clean edge to get upwind not necessarily a backstay .

The stayed rig can carry a headsail on a wire that helps guide the wind around a less efficient mailsail hiding behind a "not quite so big" mast (that still sucks).

 

The second (rig independent) disadvantage of the cat-rig is that the center of effort changes with trim - this means you have to have the courage to give it a decent rudder - if you don't it will round up (Duh!)

This does not have anything to do with stays and a lot to do with where you place the sticks (as Tanton has demonstrated and explained).

However with stays you have to put the stick in the middle of the boat in order to be able to hold it up (middle of the boats, pointy inefficient upside down sails, whistling at night ....... )

 

These factors make unstayed rigs impractical and unsuitable for people who are not comfortable with anything outside the norm - and this particularly applies to people who are uncomfortable experiment with new and old technologies - or beer can racers who have to live by "The Mans" rules.

 

There are fortunately many cool things the rest of us can play with:

 

An old trick previously known as Gaf-Rings move the sail back from the mast and opens a slot that research has demonstrated increases sail efficiency - this help improve the efficiency of the sail behind the mast. Gaf-Rings slide real nice on unstayed masts - even all the way to the top! Others have used different spacer of modern materials. It works.

 

The Van der Stadt boom is an example of how you can move the sail curve to the lee of the mast - doing so improves sail efficiency significantly. This can be done with or w/o stays. It works.

 

A proper sail with full battens can provide a huge roach which can be nicely twisted in or out at will with the properly rigged boom or wishbone. It works.

 

Unstayed masts can be flexible which means they wont break when you fall off the waves - and they bend in gusts although I am not convinced it spills as much air as it keeps them from breaking. It works.

 

Mast shape, bend and curve is totally free-style with unstayed masts as long as it holds up and stays up. I really want to try this.

 

Solen,

 

I confess, I sailed a quick little freestanding mast cat rigged boat for 20+ years, and whenever I made an update, she rewarded me instantly.

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Solen,

 

I sailed a laser for years and years, and tried a finn for awhile until I found out I didn't weigh enough. I think a lot of what you're saying makes some sense, but don't try to attach a personality type to those who choose different rigs - you'll fine you're incorrect in such generalizations about trying new things.

 

I've no idea why you think beer can races "mostly go upwind", indeed we usually end where we started so going downwind is the same distance as up.... have you found a worm hole or something we've never heard of that gets beer can racers from the windward mark down to leeward so they can go up wind some more?? I'm confused!

 

Finally, without doubt there are better ways to build sails (air foils) than bits of cloth hanging from a wire or a mast. Those trixy America's Cup boys are doing it as we speak. But, and this actually matters, in a race for a lot of money and where they could build whatever rig they want - they use stays. Why is that??

 

Glad you had fun with your unstayed mast cat rigged boat - I keep having fun with mine. My first laser was #2021 and my most recent one has hull number 183,534 (I think). I guess there's probably a real market for freestanding mast cat rigged boats. That said, they are mostly pretty small.

 

BV

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As a guess his meaning was that more time is spent going upwind than downwind, and that sausage races are an unbalanced test of performance.

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The (first) disadvantage of the cat-rig on an unstayed mast is not lack of weatherliness, it is that the mast is in the way of the front edge of the sail. You need a clean edge to get upwind not necessarily a backstay .

The stayed rig can carry a headsail on a wire that helps guide the wind around a less efficient mailsail hiding behind a "not quite so big" mast (that still sucks).

 

 

The Van der Stadt boom is an example of how you can move the sail curve to the lee of the mast - doing so improves sail efficiency significantly. This can be done with or w/o stays. It works.

The mast on a carbon unstayed rig is really quite a small percentage of chord (3 - 4%). Compared to a wire luff, there is a small reduction in maximum lift and nearly no increase in profile drag, so a performance difference is only apparent at low wind pressure - which can be made up for with a bit more area. While moving the sail to the lee side seems to test well in the wind tunnel with large section masts (7 - 10% chord), I know of no real boat that demonstrates any advantage, and it is mechanically complex. Most the double luffed early Freedoms have been converted to mast track single luffs.

 

Those trixy America's Cup boys are doing it as we speak. But, and this actually matters, in a race for a lot of money and where they could build whatever rig they want - they use stays. Why is that??

Using stays on a catamaran with a wing mast is a whole different thing: very few stays, no structure available to anchor a cantilever, Code Zeros allowed for light wind, etc.

 

In more normal racing, an unstayed mast una rig is virtually outlawed by the prevailing rules. With a large jib you need running backs and have significant mast compression, so now you have many of the disadvantages of both stayed and unstayed, without all of the advantages of either.

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BV you are right I know little about racing, I usually sail alone. In the Apostle Islands on Lake Superior where I sail now the racers actually hold "drifting contests" every year by scheduling their race-week during July when the wind is feeble, that hasn't help me understand any better.  On a positive note here's an example of a more "modern" suit for a Freedom 33 cat ketch. <a href='http://xa.yimg.com/kq/groups/14259440/sn/798809228/name/n_a' class='bbc_url' title='External link' rel='nofollow external'>http://xa.yimg.com/k...809228/name/n_a</a>  here's another (earlier) more radical English built Freedom 35 cat ketch - I seem to remember it was implemented by a Dutch sailmaker/rigger. <a href='http://f1.grp.yahoofs.com/v1/EHxCT4ecEOpLf9E7femTRPSqkUo7IaM1wgQQLV5vqL0mZyihrZ6EN1J8iJeig1ktAOScqQQFDbQodJjm-iUY5yznqFkTz0gSQg/Sail%20plan%20F35%20G10%20type%20Rev%2001.ppt' class='bbc_url' title='External link' rel='nofollow external'>http://f1.grp.yahoof...%20Rev%2001.ppt</a>  I hope the links work......

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My take on the advantages of the unstayed rotating una rig, in no particular order. FYI, my focus is on a big, light displacement, high speed ocean-crossing cruiser/racer.

 

  • Simplified (lighter) hull structure which no longer needs to counter massive bending loads from headstay and backstay
  • Much less mast heel compression - again a structural advantage in a light boat
  • No jibs, jibstays, jib tracks, jibsheets, turning blocks, winches
  • Fewer halyards, and therefore jammers/winches
  • No sail storage needed below
  • No roller furling at all (BV will appreciate this one!)
  • No running backs (everyone will appreciate this one)
  • Just one sail for crew to concentrate on trimming
  • Simple to depower by taking in reefs - the oceanic single-handers have given us the tools
  • With a light, fast hullform, no offwind sails at all, as apparent breeze is always forward
  • Much more capable of being short-handeded, especially a bigger boat

 

And some disadvantages...

  • Nowhere to hang courtesy flags
  • Ditto antennas
  • Can be troublesome 'sailing around' at anchor
  • Major engineering needed at mast partners and rotating bearings
  • Calibrating masthead instruments on a rotating rig - again our single-handing friends have worked this out
  • Finding a sailmaker that 'gets it'
  • Errr...
  • That's it

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Well also,

 

  1. Bigger mainsail for any given total sail area and number of masts
  2. More forward weight of mast, potentially yielding more pitching
  3. More disturbed airflow

And also I am really not sure of this claim of apparent wind always being forward?

 

For what unirig ocean-going and let's say non-canter monohull is this true?

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Well also,

 

  1. Bigger mainsail for any given total sail area and number of masts
  2. More forward weight of mast, potentially yielding more pitching
  3. More disturbed airflow

And also I am really not sure of this claim of apparent wind always being forward?

 

For what unirig ocean-going and let's say non-canter monohull is this true?

So I'm looking at the approximate size, general shape and displacement as Speedboat. But without the canting keel (such a nightmare), and with a DSS foil instead. This is a bit of a thought experiment.

 

In nearly all 'normal' wind strengths, i.e. 5-20 knots, boatspeed will be more than windspeed, propelling the apparent wind well forward on almost any course except near DDW. Of course, once you're up to near-gale or gale-force, this changes somewhat, but by then you're well-reefed, steering for minimal wave impact, and/or routing yourself away from problems.

 

Really looking at the mile-gobbling attributes of a VOR70, but without the handling issues. And before anyone starts, yes, I know the motion can be vile and violent - prepared to put up with that.

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DSS, out for years, performance claims unproven.

 

Digging into their documents (it's within a Powerpoint-type presentation, and written in a way to kind of disguise the fact), the big claims were based on computer modeling not actual sailing results or even test-tank results. So I would have some caution in assuming too much.

 

Yes, there's one lake racer that has won races, but not by margins proving any leap ahead, and the owner is pleased with the boat, so congratulations are rightly due there. But, there are very many designs made each year that win races and please their owners, so in and of itself this one thing doesn't prove a breakthrough or even anything really, beyond that in at least one application a boat doesn't have to be a failure if using it.

 

Is it that builders around the world just don't see the point of such great improvement in speed and handling -- "Naah, our customers don't want faster, better-handling boats!" -- or maybe is it that things are not quite as with the claimed huge benefits and no real drawbacks. Could the real picture perhaps be more complex?

 

Even if DSS would work well in your application, it seems speculation that a DSS ocean-going, no-A-sail, unirig racer/cruiser would have apparent wind always forward.

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I understand your position. No problem.

 

Actually I've been working quietly with Hugh on this concept off-and-on since 1987, and in more depth (especially re DSS) since 1999. As I said, it's still a thought experiment, but it's lots of fun.

 

I'll let you know how it works after we've built it. After all, you have to build things to know if they will work. All this computer modeling and simulation is just such nonsense, isn't it?

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Not nonsense, or at least not in all cases, but when years go by without real-world results showing accuracy to the predictions, then highly-remarkable claims can justifiably be called unproven.

 

That said, I do absolutely wish you the best success in building it and if your results are excellent, I will be quite happy that we have a new advance that does work well in practice! And happy for you as well for your personal good results.

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Just being tongue-in-cheek, of course, about the computer modeling.

 

As regards DSS, yes, as you say, there are not yet enough boats built with this system to get real-world comparison data. Attribute that to the very conservative nature of our activity. How long, for example, did it take aluminium to replace wood in masts after the initial work was done and proven to be vastly better in the 30's?

 

DSS, just like rotating carbon free-standing bendy masts supporting large una rigs on cruising boats - well, it's just a matter of time. And some brave and committed experimenters.

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P_Wop,

 

Not all "brave and committed experimenters" end up finding a successful improvement. Many, indeed some think most, end up failing utterly. We here in SiValley have this crazy view that inverts this and folks like you and I work on things all the time that "normal" people would consider crazy. But, as the results from Venture Capitalists will verify, only about 1 out of 15 "new" ideas have worked out in the last two decades. A number that is far below the 1 in 10 that VCs usually talk about.

 

In sailing technology, I fear that the number of really "big new innovations" is pretty darned small. Fiber reinforce resin construction, be it glass/polyester or carbon/epoxy, was clearly a big one. We're still figuring out the limits of that improvement over wood and metal. Metal and then fiber reinforced resin masts was another. Multi-hulls are clearly a big win in some conditions. But, there aren't many others.

 

In some ways the curved daggerboards of the high performance French Tris may be early evidence that some form of lifting foil actually contributes more to righting moment than it costs in drag. But the difference, as I understand it, is no where near as dramatic as some have proposed. It appears that in almost all cases just making a muli-hull wider is a bigger win than putting foils under it.

 

But, what do I know, I sail a wooden boat.

 

BV

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It would be somewhat interesting -- but probably won't happen anytime soon if ever in our lifetimes -- to know the story of why Wally had great enthusiasm for DSS at one point and then, it would surely seem, decided not to bother with it further.

 

This could have resulted from either or a combination of:

 

A) They did due diligence in evaluating how it would work in their yachts, and decided no based on this evaluation.

 

B) The royalties demanded weren't remotely within the realm of rationality, and so whether or not they were convinced it would have been a good improvement, they chose to have nothing further to do with it. Or otherwise there were business problems created that just weren't worth dealing with.

 

I think it would not have been:

 

C) They found it would perform as claimed with no real disadvantages but decided they couldn't sell even a single boat and so therefore didn't do it.

 

I know that some others have misinterpreted where I am coming from with DSS. In fact, the more success it has the more pleased I'll be. I'm glad for the owner of Quant28 for his success, and if P_Wop has fine success, I'll be much happier to have learned of that than to have learned of the opposite. Both for the reason of liking seeing people enjoy the rewards of risking new ideas, and because when advances prove out, this is good for all of us.

 

That said though, these things have to be viewed through the lens that BV describes. Most ideas that fail after being given plenty of R&D money and man-hours of time, did look good on paper. It's fun playing with new ideas but most times in sailing, huge advances (claims of 40% more speed, 10 knots more speed, while getting better handling at the same time and with only minimal extra cost and no real disadvantages) don't pan out. Instead, things like that are spaced perhaps decades apart, if they even occur at all. Actually I couldn't think of a single at-all recent advance in sailing that fits that bill. Personally I wouldn't give DSS a chance in a hundred of doing as claimed, but being some improvement? Perhaps!

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