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Tanton Y_M

What about free standing rigs?

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This issue of adding righting moment by lifting with a foil or providing more form stability is fascinating. The wing in the water sort, no matter what design it is, has a lot of parasitic drag that an additional hull being moved further to leeward doesn't. However, in a fast boat it may pay off because moving that hull further to leeward has a mess of bad habits when sailing in heavy seas.

 

On my short list of things that might really radically improve the performance of boats, I left off my absolute favorite: the kite. I've watch some fun nutty guys over on Alameda Island in SF Bay who built a 20' cat with a BIG kite. The thing was astoundingly fast. It, obviously, needed no mast. There is no "heeling force" from a mast; although the thing does try to heel a bit as the center of lateral resistance is on the board below the water about 3' and the kite line is attached to the front cross member. It goes up wind just fine as the cat has boards. There is a massive amount of power that can be trivially reduced by flying the kite higher. Indeed, it can simply sit still in a 25k breeze and then shoot off at 20 to 25 knots over the water. It was truly amazing to watch. My favorite was when the skipper decided to turn the boat while going about 20 and one of the crewmen simply flew off! Hysterical!!!

 

So, were I to be building a long distance trade-wind sailing boat I would certainly consider trying a kite flying from the bow fitting. The guys in Alameda were also developing a completely computer controlled auto-fly system that would let them simply punch in some numbers and the kite would generate a specific amount of "power". They had uses for this other than sailing that I won't go into, but it worked and the computer could generate pull of X pounds at Z angle to the wind. Pretty cool!!

 

BV

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P. Ed,

 

Yup, I remember those days. The guys in Alameda had a much more controllable kite. I couldn't find their video on-line, but have a look at this one. Two things to note: one, at the end the guys just calmly walks up the beach with the kite flying from his waist, showing an amazing ability to de-power, two the waves and wind condition he's sailing in would be considered a "storm" by many on CA and this guy is just playing around. He can get airborne, but I'm sure that a "cruising boat" with all the SOTB would stay well stuck down even with a pretty big kite pulling on the bow.

 

Video

, and
, and here is a moderate one, finally a BIG one
.

 

BV

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DSS like stability systems have been in widespread use for years on motor vessels. I first saw it in the '60 on large car ferries where it helped by keeping the passengers from puking all over. The Costa Concordia has it - maybe that's what the captain tore off to get enough impact to overwhelm the bulkheads? http://i.dailymail.co.uk/i/pix/2012/01/14/article-2086527-0F75B20E00000578-975_964x494.jpg Some years ago we sailed in 25-30 kt and pretty big waves. I was with a friend on his Cal 30-3 and another friend was on his Westerly 29' Konsort DUO - it was impossible for us to go as fast or point as high as the Westerly, one keel was pointed straight down and the other showed it shoulder occasionally acting much like a stabilizer http://falmouth.boat...%20Boatshed.com Comparing the Konsort Duo with the Quant28 you will see that on the Westerly one keel is pretty much pointed straight down at normal heeling angles while the "upper" keel is more likely to be in the water than on a Quant28 http://www.boatdesig...50-port-aft.jpg - both are fighting the extra wetted surface. It would be great to see something more practical come from all of this. Maybe twin keels weighed with a heavy liquid (Mercury?) that could be pumped to the windward side when needed.

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

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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.

 

 

 

Van de Stadt shows some seperation between the sail and the mast in the section below (might be just schematic), and shape to the back of the mast section that is probably designed to reduce the seperation bubble on the sail. The hydraulic maintains the angle between the (faired) mast and the suction side of the sail which has most of the lift. Has anyone seen any performance figures for this design ..... or is there a good reason why this wouldn't be better than current practices on larger boats with unstayed masts? swing_rig21.gif

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The concept is covered by Sailing Theory and Practice by C.A. Marchaj-published by Dodd, Mead and Co - I do not have the book (yet). There is a posting here on the subject: http://www.boatdesign.net/forums/sailboats/rotating-wing-mast-theoretical-discussion-14714.html

 

I tried it on my Freedom 21 which you see in the picture I posted above. My first try was best because the sail would "fall out" in line with the backside of the mast. As I tried to rig better control lines the sail pulled more behind the mast and the benefits were reduced. This was disappointing but it is consistent with theory.

 

I think simplicity is essential for success so the Van der Stadt method is fine for expensive boats but overkill for affordable production boats - the benefits are real but I only think they are sufficiently important on a cat-rig or racing sloop ti build is as complicated as that.

 

I have been toying with a design for a triangular mast where the sail track and boom move from side to side so here it is: For the heck of it I included a public domain copyright statement - does that make me an anarchist? A sliding sail track would work on small boats - a forward hinged sail track would probably be necessary on big boats to manage the forces

 

post-59748-062508700 1329960743_thumb.jpg

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I found an article that show that metal wire stays are so passe that is would be embarrassing to be seen using them:

 

http://www.unols.org/publications/winch_wire_handbook__3rd_ed/03_synthetic_fiber_ropes.pdf from the University-National Oceanographic Laboratory System RI - they have other interesting papers.

 

I also saw some posts on a 4x4 bulletin board that mentioned that getting hit by a broken metal winch cable was pretty ugly, whereas the synthetic lines merely gave you a lashing (lashings and pain make you a better sailor, right?)

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would this thread kindly just fuck off and die.

 

 

After you.

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

Yeah, you could be wrong....how you gonna make that wire stand up straight? Rub it real hard?

 

Van de Stadt shows some seperation between the sail and the mast in the section below (might be just schematic), and shape to the back of the mast section that is probably designed to reduce the seperation bubble on the sail. The hydraulic maintains the angle between the (faired) mast and the suction side of the sail which has most of the lift. Has anyone seen any performance figures for this design ..... or is there a good reason why this wouldn't be better than current practices on larger boats with unstayed masts? swing_rig21.gif

The Bethwaites had done quite a bit of work in this area. Their conclusion is that it is too tweaky to be worth it: the mast shape has to be exactly right, and the trim perfect. The main advantage of getting it perfect is a higher max lift coefficient, which only matters before the rig is fully powered up. A little more sail area can overcome that. To go along with this small advantage on a cruising boat, there are several disadvantages. The main one being that you cannot stop the mast from lifting and it will cause the boat to sail at anchor, particularly if it is cat rigged. There are a few cruising boats that have had airfoil masts that have been converted back to round because these disadvantages were found to outweigh the advantages.

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

 

Well, one option would be to not read it.

 

Look, I won't argue with your statement that nothing is as light and strong as wire. Why? Not because I'd be wrong (I could be but that has never been the death of me yet) but, because your statement, without context, can mean anything. That makes debate useless.

 

Sure, a carbon rig, with wire would be lighter than a free standing carbon mast -- on a scale.

 

It would be a lot lighter still if one of the many parts of the system fails, as the rig falls into the ocean, relieving the boat of the weight.

 

Not that free standing masts are without failure but, the simplicity and durability of the system is hard to argue against. For the most part, they keep standing up.

 

You may not enjoy this thread. Maybe a good idea is to not read it.

 

They like talking about unconventional rigs. It's *fun* to speculate on new ideas.

 

Wasn't making masts out of composites a new idea once?

 

How about the idea of spectra rigging? As Brion Toss put it, "we had rope once, then we went to wire, then rod and now it seems we are back to rope."

 

Other people are enjoying this thread.

 

Why piss in their Wheaties?

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What I heard from the Freedom sailor side is exactly what DDW mentions about complexity. The wishbone wraparound sails were great when you needed 100% but hard to reef and not well suited for the new more durable but also stiffer sail cloth.

 

The world does go around, even for those who wish to stop it ;-) maybe someone will invent flexible sailcloth that is dimensionally stable so we can try those things again.

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What I heard from the Freedom sailor side is exactly what DDW mentions about complexity. The wishbone wraparound sails were great when you needed 100% but hard to reef and not well suited for the new more durable but also stiffer sail cloth.

 

The world does go around, even for those who wish to stop it ;-) maybe someone will invent flexible sailcloth that is dimensionally stable so we can try those things again.

 

Garry Hoyt carried two sets of sails on his prototype F40, the "full" set (which in my opinion were too small) and a storm size. If I remember what he wrote about it, you simply dropped the mains and zipped on the storms above them. This was more than most owners wanted to deal with.

 

I think you're about the sailcloth, but additionally the complaints I heard about the sleeved sails was that replacement costs were too high since you essentially had to buy two sails instead of one for each mast.

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Ref: DSS. A little off the subject of free standing rig, but...Ancestry of the DSS. Palmquist patent Document 1982-1987. The WingMaran.post-32003-057913800 1330349444_thumb.jpgpost-32003-014027800 1330349474_thumb.jpg

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

 

Hey, you off your meds??

 

You may or may not be wrong, but you are most certainly irritating. You can't manage to avoid reading threads you don't like? Geeesh. Need help operating your computer?

 

BV

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Their conclusion is that it is too tweaky to be worth it: the mast shape has to be exactly right, and the trim perfect.

 

I think that Richard Woods felt the same way about rotating masts on catamarans: if it wasn't trimmed right, it wasn't better. They went to fixed masts on boats expected to be sailed by non-experts.

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As long as folks are expanding the discussion to DSS and other techniques, I would suggest that tipping the rig to windward is a vastly underrated technique. Not only does it start to lift the boat from the water and thereby make it "lighter" as far as the water is concerned, but it moves the center of effort to windward (provided you tip the top upwind vs sliding the base downwind) and helps relieve weather helm. Have folks had any experience with this other than wind-surfers and weird one-offs like the Rocket??

 

I have frequently thought that having a track for the base of the mast on a cat would be perfect, you can just slide the butt to leeward as the load increases and keep lifting the boat.

 

Again, just as with DSS, the complex tradeoff is between "lift" and the "drag" that the lift creates. While I'm certain that we don't fully understand this trade-off for DSS and foils working underwater at a wide range of speeds, I think we probably don't have a very complete understanding of the "lift" of the tilted sail. Hopefully, the aircraft designers will have spent more time on lift/drag ratios in air speeds of about this range that will help.

 

BV

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Hi Beau.... well I've been looking at that as well. The unstayed una rig is so much simpler to cant, as you say. No shrouds, and much less compression to worry about for the curved athwartships track for the heel. And with no jibs, all you need to do is adjust the mainsheet as you're canting the rig. Real engineering is needed however for the mast partners bearing, as it has to be a two-order spherical type (for a rotating spar).

 

Re efficiency, it's definitely going the right direction. The SailRocket guys have shown that nicely.

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post-906-098290500 1330489223_thumb.jpg

 

?

 

post-906-098290500 1330489223_thumb.jpg

 

As long as folks are expanding the discussion to DSS and other techniques, I would suggest that tipping the rig to windward is a vastly underrated technique. Not only does it start to lift the boat from the water and thereby make it "lighter" as far as the water is concerned, but it moves the center of effort to windward (provided you tip the top upwind vs sliding the base downwind) and helps relieve weather helm. Have folks had any experience with this other than wind-surfers and weird one-offs like the Rocket??

 

I have frequently thought that having a track for the base of the mast on a cat would be perfect, you can just slide the butt to leeward as the load increases and keep lifting the boat.

 

Again, just as with DSS, the complex tradeoff is between "lift" and the "drag" that the lift creates. While I'm certain that we don't fully understand this trade-off for DSS and foils working underwater at a wide range of speeds, I think we probably don't have a very complete understanding of the "lift" of the tilted sail. Hopefully, the aircraft designers will have spent more time on lift/drag ratios in air speeds of about this range that will help.

 

BV

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post-32003-042685400 1331488295_thumb.jpg

Aerodynamic shape around a free standing spar and a partial solution. Part 1.

Over the years, I have adopted many options.

The track on the mast and a sail without battens is the simplest but worst scenario. Next, the track on the mast with battens is an improvement, however, the track on the mast with full battens is the best normal set-up. I have also tried a "Thick" sail, with foam inserts, as well as a wing mast and full battens. This is certainly a valid system, but is complicated and expensive. On the original 40' Freedom Cat-Ketch, Gary Hoyt adopted a double ply sail going around the mast. The result was of too much friction, causing difficulties hoisting, lowering and reefing the sail.

I propose another solution; the "SockSail", and I am using the Ocean Going Volkswagen 37 to illustrate.

The mizzenmast (Aft mast) is fitted with with a regular mainsail and battens. I kept it as such so that you can visualize the difference between the main and the mizzen.

The "SockSail" on the mainmast consists of a wrap around canvas over the freestanding spar. The "Sock" is zippered on one side to permit easy installation and removal. The "Sock" has section cut out giving access to the fittings on the mast, which are necessary to control the wishbone. The "Sock" has a permanently attached headboard to the masthead. The tack has a Cunningham to control the tension at its base. The fore and aft dimension of the ""SockSail" is sized to provide rotation around the mast without much friction. The chord is calculated to achieve that effect, respecting a reasonable span thickness ratio. A grooved luff, similar to the headfoil for a jib, is sewn on the backside of the "SockSail" and runs the full height of the sail. The groove receives the luff of the sail with its own halyard and tacking line. The sail is fitted with normal length battens. Full lengths battens cannot be fitted because of the obstruction given by the rigid foil.

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As long as folks are expanding the discussion to DSS and other techniques, I would suggest that tipping the rig to windward is a vastly underrated technique. Not only does it start to lift the boat from the water and thereby make it "lighter" as far as the water is concerned, but it moves the center of effort to windward (provided you tip the top upwind vs sliding the base downwind) and helps relieve weather helm. Have folks had any experience with this other than wind-surfers and weird one-offs like the Rocket??

 

I have frequently thought that having a track for the base of the mast on a cat would be perfect, you can just slide the butt to leeward as the load increases and keep lifting the boat.

 

Again, just as with DSS, the complex tradeoff is between "lift" and the "drag" that the lift creates. While I'm certain that we don't fully understand this trade-off for DSS and foils working underwater at a wide range of speeds, I think we probably don't have a very complete understanding of the "lift" of the tilted sail. Hopefully, the aircraft designers will have spent more time on lift/drag ratios in air speeds of about this range that will help.

 

BV

An easy, ultra-simplified-but-not-wrong way of looking at it as an approximation is simply from behavior of sins and cosins.

 

Going to an angle such as 10 degees, there's a neat effect where there's a large increase in the sin (in this example, it becomes over 17%), but very little decrease in the cosin (in this example, it remains still over 98.4%.)

 

So essentially, at modest angles such as these one is getting almost free vertical lift relative to loss of driving (horizontal plane) lift.

 

That's not to say that once considering operational factors and practical rigging aspects that it's a no-brainer, but it does illustrate why there's nice potential for efficiency, as has also been shown in practice.

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The sail is fitted with normal length battens. Full lengths battens cannot be fitted because of the obstruction given by the rigid foil.

The goal is to improve the L/D ratio of the rig, no? I think there is far more to be gained with full length battens and a square head planform than can possibly be gained from a sleeved luff. This was proven decades ago in hang gliders, where the L/D ratio is easily and directly measurable. If the sleeve luff precludes an efficient planform, this is the wrong tradeoff. And the square head sail has almost no sail handling problems if rigged properly.

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DDW. You are probably right about efficiency of Full battens and Square heads planform. I am looking at a simpler, less expensive method on cruising boats to go around a circular mast section.

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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.

 

It does make a difference. The sail on my Adventure Island rolls around the mast, so when I reef, the sail is on the lee side of the mast for one tack, the windward side for the other.

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That's Seapr (prounounced CPR), a Freedom 33 that has made the Bermuda trip a few years ago. those are Cuben fiber sails, fully battened, very light, very strong. Very expensive. In every other way, the rig is a stock Freedom 33 rig, except that when it was converted from wishbones to standard booms, they did a real hack-job on the back of those cf masts. The result was that when the boat took a pounding on its way back from bermuda, there was some cracking and other damage. Composite Solutions, in consultation with Eric Sponberg, did an amazing repair job on both masts. You can read the story here.

 

With all due respect to Mr. Tanton, I like the simplicity of the full-battened, large roach main (or square top) over a sleeved design of any kind. Besides the potential for wear on the mast, what happens at anchor or at a dock with a load of zipped on canvas up the pole, and the loss of the use of the masts' surface for items like radar or steaming/deck lights, I don't think Mr. Tanton's design addresses one of the fundamental sources of parasitic drag in the marconi rig, and that's the tip vortex. By extending the head of the sail (something phrf committees LOVE, btw :P ), the flow around the head of the sail is dramatically improved and so you not only get more sail area, you get more *usable* sail area. At least, I think this is so. I know on my small boat, we trimmed the pinhead main with the top telltale fluttering about half the time. With our square tops, everything flows - if it doesn't, you adjust shape, twist, traveller, vang, outhaul, whatever until it does. 5 telltales flowing back in harmony is the goal. I think it has added quite a bit to our top end speed - more so than if we just built an oversized pinhead with the same area - and higher speed means better pointing and vmg.

 

I'm actually considering a squaretop for my Freedom 45 when we build it. Especially for the areas where we typically sail, new england and long island sound, a moderate square top might be able to give us that extra *oomph* that the 'condo' is currently missing. The north sails that are on it were definitely designed around much more wind, more off shore work, and ease of handling. I'm still young, and I still want to go fast, even if that's "cruising fast."

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where we typically sail, new england and long island sound, a moderate square top might be able to give us that extra *oomph* that the 'condo' is currently missing.

In my experience, in Maine and Long Island Sound oomph is needed more than south of the cape and RI.

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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.

 

It does make a difference. The sail on my Adventure Island rolls around the mast, so when I reef, the sail is on the lee side of the mast for one tack, the windward side for the other.

How did you measure the difference? and what is the difference? Speed? Pointing angle? Does the mast rotate to accomplish the reef (so you could have the luff on the lee side any time you wanted)? Since you are reefed I assume fully powered, does the difference become greater or less as you begin to feather the rig? Enquiring minds want to know.....

 

By extending the head of the sail (something phrf committees LOVE, btw :P ), the flow around the head of the sail is dramatically improved and so you not only get more sail area, you get more *usable* sail area. At least, I think this is so. I know on my small boat, we trimmed the pinhead main with the top telltale fluttering about half the time. With our square tops, everything flows - if it doesn't, you adjust shape, twist, traveller, vang, outhaul, whatever until it does. 5 telltales flowing back in harmony is the goal. I think it has added quite a bit to our top end speed - more so than if we just built an oversized pinhead with the same area - and higher speed means better pointing and vmg.

I believe you will see an increase in speed on all points in light pressure due to added area, and a decrease in pointing angle due to a decrease in induced drag. Back in my past, I designed and tested hang gliders. These have (or I should say used to have) a single surface cloth sail, and operated at about the same Re, speeds, A.R., and loadings that sailboats do. Since the lift is essentially fixed (just has to hold you up!) and the glide ratio is numerically identical to the L/D ratio, drag is directly measurable: jump off a hill, see how far you go. If you go farther then you had less drag. When we went from pointy wing tips to squared off ones there was a dramatic improvement in L/D. Not subtle, I'm talking 50% and more. All other things the same. These all had sleeves around the leading edge tubes, however different size sleeves and foam inserts to shape the leading edge were tried without a dramatic effect. Mainly the effect was on stall characteristics and even that was not dramatic.

 

The only sail handling problem with square heads is the need to remove the top diagonal batten or unpin the headboard when furling - this is a problem I have solved as you can see here.

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DDW, for those of us with pointy mains because of our backstays, is there an argument for lopping off the top of the sail to make it flat? Is it possible that the area given up would be made up for by less drag?

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Probably not. A sloop is more complicated, the main operates in the disturbed air of the jib and they really form one airfoil. So it is hard to guess what the effect of changing one part of that airfoil would be. I know that a tapered planform with a square tip, even if significantly lower aspect ratio, will outperform a pointy tipped one of the same area. But induced drag is proportional to the square of the lift coefficient divided by the "effective" aspect ratio. If you decrease the area, to achieve the same lift you must increase the lift coefficient by increasing the angle of attack (if you can without stalling it), that results in a geometric increase in induced drag. The reason the squared tip may result in less induced drag is that pesky term "effective". A square head planform has a higher "effective" aspect ratio for the same span compared to triangular. A trapezoidal planform with a tip (head) about 1/2 of the root (foot) comes close to an ellipse, which is the theoretical ideal planform. A square head sail with a large roach is very close to elliptical. By comparison a triangular planform may have about twice the induced drag. All of which is further complicated by twisted flow, twist in the airfoil, span wise flow due to heel, etc. etc. A sailboat is really a pretty complex aerodynamic animal.

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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.

 

It does make a difference. The sail on my Adventure Island rolls around the mast, so when I reef, the sail is on the lee side of the mast for one tack, the windward side for the other.

How did you measure the difference? and what is the difference? Speed? Pointing angle? Does the mast rotate to accomplish the reef (so you could have the luff on the lee side any time you wanted)? Since you are reefed I assume fully powered, does the difference become greater or less as you begin to feather the rig? Enquiring minds want to know.....

 

 

I don't really measure it, just notice it. It is more angle than speed, though a bit of both. It is just less powerful and quicker to stall. The mast works just like a RF jib, so if reefed, there will always be a favored tack and a sucky tack. I don't really understand your last question. If you mean heading up a bit in gusts, that definitely works better on one tack than the other. Very prone to stall on the sucky side.

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DDW, I like that solution for the headboard, although it's nearly a third of the cost of my new main, I don't think it's going to happen. I've seen some other methods for dealing with it without removing the batten that would probably work well enough for a cruising boat.

 

That anomaly headboard is very elegant, though.

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Aerodynamic Shape Around a Free Standing Spar and a Partial Solution. Part 2.

The behavior of wind on a circular leading edge is well known. Viscosity, pressure, and friction prevent the air particles from staying attached to the mast. Therefore the objective of this set up is to limit drake in the wake of the mast, to streamline the air flow, and to maximize sail power.

The classic jiffy reefing is the preferred method for shortening the sail. After reefing, the forward part of the soft sail leaves the "Sock" full height. The mainsail is received between the arms of the wishbone into lazyjacks which, when cruising, are left in place.

A cruising boat, such as this Cat-Ketch, can benefit in performance with a "SockSail". To what extent, is hard to say, and experimentation is in order. Maybe this half-way solution ought to be interesting to follow in practice.post-32003-016344700 1331735033_thumb.jpg

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Could not another solution be to add a very minimalistic self-tacking jib with the sole or primary purpose of improving flow past/around the mast?

 

With a short or very short I and the sail designed to require only modest luff tension, potentially that could be very compatible with a free-standing rig and would add little difficulty. Might make the boat look better too, at least to those who are not fond of the appearance of free-standing cat rigs.

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I don't really measure it, just notice it. It is more angle than speed, though a bit of both. It is just less powerful and quicker to stall. The mast works just like a RF jib, so if reefed, there will always be a favored tack and a sucky tack. I don't really understand your last question. If you mean heading up a bit in gusts, that definitely works better on one tack than the other. Very prone to stall on the sucky side.

Yeah, the stall behavior is what is most affected. A large radius nose is not stall resistant, flow separates at the turbulent flow trip point, limiting lift. I have wondered about adding "turbulators" to the mast to try to improve it. These are very commonly used on sailplanes, and more commonly still on golf balls. The idea is to trip the laminar flow to turbulent before it separates. The turbulent flow stays attached much better. This is actually more of a problem on a round mast cat rig in very light wind, the flow detaches easily and takes a long time to reattach. On your mast furling rig it would be hard to do because the mast is rolled inside the sail. On sailplanes, they typically use sticky back mylar tape, about 0.015 thick, that has been cut lengthwise with pinking shears leaving a zig-zag edge. That edge goes forward, the little "V"s creating mini vortices that are effective at tripping the flow to turbulent. On a sailplane with a bad separation bubble, this can reduce the wing drag by 10%. On the tailplane of my ASH26E, it is FAA required for airworthiness, to prevent stall of the stabilizer. If I lived closer to my boat I would experiment with this.

 

DDW, I like that solution for the headboard, although it's nearly a third of the cost of my new main, I don't think it's going to happen.

Well, now that I have my Vertical Machining Center that cuts about 5x as fast as my older CNC mill, I might be able to slide you into one for less... :D

 

Could not another solution be to add a very minimalistic self-tacking jib with the sole or primary purpose of improving flow past/around the mast?

 

With a short or very short I and the sail designed to require only modest luff tension, potentially that could be very compatible with a free-standing rig and would add little difficulty. Might make the boat look better too, at least to those who are not fond of the appearance of free-standing cat rigs.

Along with turbulators, I investigated this a bit and tried to design such a system. Basically a leading edge slat, a high lift device you can see on most modern airliners. It would have to be tacking, I was looking at rigid devices and it seemed overly complicated for the expected gain. Mainly you get an increase in lift. But you can get an increase in lift by just adding some sail area, cheaper and simpler, and more effective downwind too.

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Certainly a jib is also part of the solution to improve airflow around a free standing spar. I was concentrating on the main and mizzen sails. (Sorry, I could not resize the picture).post-32003-089159700 1332006294_thumb.jpg

 

Could not another solution be to add a very minimalistic self-tacking jib with the sole or primary purpose of improving flow past/around the mast?

 

With a short or very short I and the sail designed to require only modest luff tension, potentially that could be very compatible with a free-standing rig and would add little difficulty. Might make the boat look better too, at least to those who are not fond of the appearance of free-standing cat rigs.

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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">

 

Awesome. Where's a link?

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http://www.stadtdesi...g_rig/swing_rig

 

not mentioned any more is that the rig has an off axis pivot so when you let it out the whole rig tips to windward providing lift and when running keeps means the CE is closer to the boat (though I can't remember if it was supposed to be completely balanced when running or just more so).

EDIT: N/M looks like I mis-remembered the reasoning behind the canting mast.

http://web.archive.org/web/20070101232513/http://www.stadtdesign.com/products/SwingRigInfo.html

probably jumbled it up with some random theoretical post.

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http://www.stadtdesi...g_rig/swing_rig

 

not mentioned any more is that the rig has an off axis pivot so when you let it out the whole rig tips to windward providing lift and when running keeps means the CE is closer to the boat (though I can't remember if it was supposed to be completely balanced when running or just more so).

EDIT: N/M looks like I mis-remembered the reasoning behind the canting mast.

http://web.archive.org/web/20070101232513/http://www.stadtdesign.com/products/SwingRigInfo.html

probably jumbled it up with some random theoretical post.

 

Dear Magnus Opus,

 

to my view your first theory is correct - running downward to keep the center of effort closer to centerline for better balance. Here is the sketch of a bigger 80 ft version - I read that this caught fire shortly before commissioning. What a pity!

 

Another very nice example of a freestanding is Gray Wolf of Rodger Martin Design. This triggered my interest in freestanding rigs some years ago - I just had to share this pic with you.

 

Regards (pics are from Van de Stadt and nauticexpo websites)

post-11987-000650600 1334183796_thumb.jpg

post-11987-071532100 1334184273_thumb.jpg

post-11987-058354100 1334184317_thumb.jpg

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Dear Magnus Opus,

 

to my view your first theory is correct - running downward to keep the center of effort closer to centerline for better balance. Here is the sketch of a bigger 80 ft version - I read that this caught fire shortly before commissioning. What a pity!

 

Another very nice example of a freestanding is Gray Wolf of Rodger Martin Design. This triggered my interest in freestanding rigs some years ago - I just had to share this pic with you.

 

Regards (pics are from Van de Stadt and nauticexpo websites)

 

Well yeah in an absolute sense the CE will be closer to centerline but in my head the canting was more dramatic, but as drawn on Van deStadt's site it doesn't look like it would move it closer by more than a couple percent.

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Knut,

 

Very interesting design, thanks for posting.

 

 

 

Magnum,

 

One nice feature of this is that the boom goes up as it's eased and would tend to drag in the water a little less on a reach in strong winds.

 

BV

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Aerodynamic Shape Around a Free Standing Spar and a Partial Solution. Part 2.

The behavior of wind on a circular leading edge is well known. Viscosity, pressure, and friction prevent the air particles from staying attached to the mast. Therefore the objective of this set up is to limit drake in the wake of the mast, to streamline the air flow, and to maximize sail power.

The classic jiffy reefing is the preferred method for shortening the sail. After reefing, the forward part of the soft sail leaves the "Sock" full height. The mainsail is received between the arms of the wishbone into lazyjacks which, when cruising, are left in place.

A cruising boat, such as this Cat-Ketch, can benefit in performance with a "SockSail". To what extent, is hard to say, and experimentation is in order. Maybe this half-way solution ought to be interesting to follow in practice

James Wharram's Tiki catamarans have what he calls a 'soft wing' rig now; it's a stayed sloop rig with a short gaff, with the luff zipped around a round-section mast. Only three stays - no backstay, so the sock can run right up to the masthead. They sail very well indeed, and it's a beautifully low-tech way to achieve a number of aerodynamic improvements: the short gaff gives a square head, the luff pocket gives a smooth airflow around the lee side. It's boomless, with a mainsheet track running right across the boat, so the mainsheet is holding the leach down without a kicker on all points of sail. It eliminates lots of apparently essential elements - boom, kicker, backstay, spreaders - while seemingly increasing aerodynamic efficiency.

As it stands it only works for catamarans - you can have a big drift on the shrouds to hold the mast up without a backstay because they are sat so wide apart, with no spreaders needed. Reefing works ok - you unzip the mast sleeve as far as necessary and bundle it all up. There are reinforcement straps around the mast at the reef points, with buckles. I don't know how well they hold the foresail luff tight in strong winds. Possibly you might need runners.

Maybe a similarly low-tech solution would work for free-standing rigs? A short gaff might work wonders.

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http://www.stadtdesi...g_rig/swing_rig

 

not mentioned any more is that the rig has an off axis pivot so when you let it out the whole rig tips to windward providing lift and when running keeps means the CE is closer to the boat (though I can't remember if it was supposed to be completely balanced when running or just more so).

EDIT: N/M looks like I mis-remembered the reasoning behind the canting mast.

http://web.archive.o...ingRigInfo.html

probably jumbled it up with some random theoretical post.

 

anybody in here?

happen to have read a lot of artikels about the vandestad swingrig.

the blue boat is 40 ft windshift and was built next to a same hull 40ft raceslooprig both 6500kg

they did a vvp comparing and found the swingrig faster even with spi(cause drag vs lift they say)

also flying a spi on a swingrig doesnt help besause you have to sheet your main in making it a drag sail instead of lift (tested)

the swingrig on the windshift was 320kg at 6m above dek. 100m^2 (6m^2 mast)

beeing pretty interested in this type i also contacted ian gonen for specs on the omerwing

he told me also 320 kg, cg4m above deck

 

they also did al open40 class, 50ft cruiser and an 8m trailersailor with the swingrig

 

if interest is there (presuming this threadisdead) i can post some pics,polar,specs once i findout how.

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... ....

James Wharram's Tiki catamarans have what he calls a 'soft wing' rig now; it's a stayed sloop rig with a short gaff, with the luff zipped around a round-section mast. Only three stays - no backstay, so the sock can run right up to the masthead. They sail very well indeed, and it's a beautifully low-tech way to achieve a number of aerodynamic improvements.

... ...

 

I kind of like gaff rigs, but I have a hard time seeing one as an aerodynamic improvement.

For one thing, if Wharram's rig works so very well indeed, how come nobody else uses it? As I recall, among the many things Wharram has said about his boats' best characteristics are that you can build them with little skill, cheap materials, and borrowed hand tools.

 

Boats of this nature are generally not 'cutting edge' in fluid dynamics, except of course the the true believers.

 

FB- Doug

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Here's another strategy at dealing with a round unstayed mast:

 

Check out this video on YouTube:

 

 

 

Sent from my iPad

 

Edit- and of course,

 

http://www.roxane-romilly.co.uk/

 

Now, a dipping lug would keep the mast on the side of the sail where it's mischief could be kept to a minimum. Like a 1-2% loss in drive.

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http://www.stadtdesi...g_rig/swing_rig

 

not mentioned any more is that the rig has an off axis pivot so when you let it out the whole rig tips to windward providing lift and when running keeps means the CE is closer to the boat (though I can't remember if it was supposed to be completely balanced when running or just more so).

EDIT: N/M looks like I mis-remembered the reasoning behind the canting mast.

http://web.archive.o...ingRigInfo.html

probably jumbled it up with some random theoretical post.

 

anybody in here?

happen to have read a lot of artikels about the vandestad swingrig.

the blue boat is 40 ft windshift and was built next to a same hull 40ft raceslooprig both 6500kg

they did a vvp comparing and found the swingrig faster even with spi(cause drag vs lift they say)

also flying a spi on a swingrig doesnt help besause you have to sheet your main in making it a drag sail instead of lift (tested)

the swingrig on the windshift was 320kg at 6m above dek. 100m^2 (6m^2 mast)

beeing pretty interested in this type i also contacted ian gonen for specs on the omerwing

he told me also 320 kg, cg4m above deck

 

they also did al open40 class, 50ft cruiser and an 8m trailersailor with the swingrig

 

if interest is there (presuming this threadisdead) i can post some pics,polar,specs once i findout how.

 

Hi loefbijter,

 

there surely is considerable interest. It would be great if you could share so more pics/data with us.

 

Keep well!

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All the above, about square top, full battens, Van de Stadt is interesting. But what it come down to for a cruising boat with a free standing rig is the ability to handle the size of the sails. For boats over 35' I recommend two masts for a start.

post-68955-0-06404300-1351348729_thumb.jpg

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Phil Bolger and Tad Roberts have both looked at adapting the Chinese rig to allow more control of big sail.

 

http://tadroberts.ca/services/new-design/sail/tilikum32

 

Bolger's idea was to use a gaff sail with battens and sheetlets in the Chinese style. He hoped to get more control and good sail shape. The only one that I know of that was built was not popular with the owner. He thew the non-gaff stuff overboard after a while.

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

 

What is wrong is how you treat people.

 

Peace

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post-32003-042685400 1331488295_thumb.jpg

Aerodynamic shape around a free standing spar and a partial solution. Part 1.

Over the years, I have adopted many options.

The track on the mast and a sail without battens is the simplest but worst scenario. Next, the track on the mast with battens is an improvement, however, the track on the mast with full battens is the best normal set-up. I have also tried a "Thick" sail, with foam inserts, as well as a wing mast and full battens. This is certainly a valid system, but is complicated and expensive. On the original 40' Freedom Cat-Ketch, Gary Hoyt adopted a double ply sail going around the mast. The result was of too much friction, causing difficulties hoisting, lowering and reefing the sail.

I propose another solution; the "SockSail", and I am using the Ocean Going Volkswagen 37 to illustrate.

The mizzenmast (Aft mast) is fitted with with a regular mainsail and battens. I kept it as such so that you can visualize the difference between the main and the mizzen.

The "SockSail" on the mainmast consists of a wrap around canvas over the freestanding spar. The "Sock" is zippered on one side to permit easy installation and removal. The "Sock" has section cut out giving access to the fittings on the mast, which are necessary to control the wishbone. The "Sock" has a permanently attached headboard to the masthead. The tack has a Cunningham to control the tension at its base. The fore and aft dimension of the ""SockSail" is sized to provide rotation around the mast without much friction. The chord is calculated to achieve that effect, respecting a reasonable span thickness ratio. A grooved luff, similar to the headfoil for a jib, is sewn on the backside of the "SockSail" and runs the full height of the sail. The groove receives the luff of the sail with its own halyard and tacking line. The sail is fitted with normal length battens. Full lengths battens cannot be fitted because of the obstruction given by the rigid foil.

Aerodynamic Shape Around a Free Standing Spar and a Partial Solution. Part 2.

The behavior of wind on a circular leading edge is well known. Viscosity, pressure, and friction prevent the air particles from staying attached to the mast. Therefore the objective of this set up is to limit drake in the wake of the mast, to streamline the air flow, and to maximize sail power.

The classic jiffy reefing is the preferred method for shortening the sail. After reefing, the forward part of the soft sail leaves the "Sock" full height. The mainsail is received between the arms of the wishbone into lazyjacks which, when cruising, are left in place.

A cruising boat, such as this Cat-Ketch, can benefit in performance with a "SockSail". To what extent, is hard to say, and experimentation is in order. Maybe this half-way solution ought to be interesting to follow in practice.post-32003-016344700 1331735033_thumb.jpg

 

http://wharram.com/s...wharramwingsail

 

I am still not sure why the Freedom double luff did not work out, but Wharram seems to have solved the problem.

Just put that on an unstayed rig, which cannot be used on a catamaran with douglas fir beams and a plywood tablernacle.

 

Such a rig could easily be put on a tall solid section unstayed mast, as found on the http://www.wyliecat.com/models/wylie_48.html#

 

What do you think?

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Let's see,,,2 posts and GT is telling other people who have posted here for years how to behave?

That's just wrong.

 

I have some advice for you GT,,,HTFU!

 

How much forum experience does one need to be polite?

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GT:

Polite doesn't really cut it here. If you want to be polite then good for you.

But if a poster with a long history of cogent posts wants to post in a less than polite way we accomodate him/her. We even welcome them.For For

 

If you have your panties all twisted up because someone is not "polite", you are in the wrong place. This is ANARCHY did you not read the heading?

For the most part we are polite when we respect the other guy. Not always. It's our way. But you have to earn that respect. It's kind of like real life.

 

I'd like you to stay here and share your views but first you need to HTFU and muck in and fight for your opinions. It's a pretty damn good place if you want to argue sailing issues. There is an amazing amount of knowledge and talent here.

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Hi Bob, my name is Greg.

 

Rude, is generally uncalled for, in most situations; paticularly when meeting someone new.

If I waited for every passerby on the street to 'earn' the respect of decency, I would be snarling at everyone I meet. Which, generally reminds me of being a teenager.

Golden rule stuff, is really very basic. The only thing that anyone must do to earn the respect of decency, is to show the respect of decent conduct to everyone they meet, else we would be antagonizing each other on sight.

Might be worth noting that I am not the only one to tell the troll off, just the only one who does not resort to 'you too buddy' as a retort.

 

It has always peplexed me, how forum count is equated with 'cred', regardless of the validity of any statement made.

As far as HTFU goes, check out http://forums.darkfallonline.com/ ; those guys really know hard, the flame on Sailing Anarchy could never compare.

In Darkfall, folks can shoot each other off each other's boats, capture the enemy boat, and then proceed to *sell it on the forums*, now that is my idea of hard, and I don't think that happens here.

 

The thing is, I am really facinated by the alternatives in sailing, much is known about jibs and stayed rigs, however cat rigs and unstayed masts are terra incognita for most sailors. ( Here be Dragons! ) ( save for dingys )

Unstayed masts allow the boom to be brought forward of the beam, thus enabling downwind lift, even on slower ballasted monohull boats.

Also, cat ketchs and cat yawls have the reputation of being docile to handle, especially on a down wind run.

Sadly, I have yet to experience this for my self, so I have to take these guys word for it: http://www.bandbyach...om/catketch.htm

A cat ketch or yawl may not point as high on the wind, but even that is still significantly a matter of draft, followed by hoist / aspect ratio, at least that is what I have read.

 

Perhaps the mistake I made, was using the King's English; I should have spoke in Pirate!

 

Avast!

 

A naysayer!

Prepare to walk the plank, ye scuvy dog!

Ye be polite upon me boat, or into the sea ye go!

Arrrrrrr!

 

As salty as the sea I ARRR!

As salty as the sea I be!

And when I spits, I spits epoxy!

 

Of sailboats, I may know little, of Pirate talk, I can speak like the salt o' the sea!

Savvy?

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Greg:

Too much information. Too much pomposity. Too much BS.

You are not going to like it here. We don't talk "pirate talk". We just talk like regular guys. Is that a problem for you?

We exchange ideas and we give each other shit when it seems right. We deal with it.

From what I can see so far from your posts, if you came and sat down with me and Cave in our corner of the tavern, Cave and I would get up and move. But you are entirely welcome to sit there by yourself and talk pirate talk.

It's a good tavern. We have a good time here. You have 4 posts. STFU and sit and learn a little bit. Earn your own credibility here.

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Jerezus Paps. I thought you had my back.

 

It's 9:24,pm the fire is slowly going out. The cat is still out. I'm waiting up for her. I'd kick her ass if I didn't love her. My college football team is hanging on by the skin of their teeth. And it's begining to look like a tooth.

Meanwhile:

I have this smarmy wanker pestering me and the rest of you are sitting in the opposite corner laughing and tipping pints.

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The cat is in. Finally. Lookinj quite sure of herself. She knows she is the Queen here. I'm out of pop corn and I'm going to bed. My team is still hanging on. Meet the Press at 6 am, I need my fill of liberal BS.

Boomer is coming up on Tuesday.

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I'm on a good behavior bond KD.

 

Pussy.

 

Hey Greg.

 

Its sorta like this, post bullshit you'll get bullshit, just don't make it personal.

 

This instruction video may help...

 

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

 

There's some evidence that you're right. It sure would be handy if this thing didn't need to drag all those wires through the air.

 

CC121010-690.jpg

 

Yikes. Could those hulls develop a consensus on which way is level?

 

We're supposed to have a nice breeze here today, strong enough to make it fun to go play with my kayak and its free-standing rig. 8 lb mast. Plug and play. B)

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would this thread kindly just fuck off and die.

 

There is nothing as light and strong as a wire.

 

At the Reynolds number that sails operate at, a free standing rig is ridiculous.

 

Just my opinion, I could be wrong....

 

There's some evidence that you're right. It sure would be handy if this thing didn't need to drag all those wires through the air water.

 

 

catamaran-capsize7_1920258i.jpg

 

 

Yikes. Could those hulls develop a consensus on which way is level?

 

We're supposed to have a nice breeze here today, strong enough to make it fun to go play with my kayak and its free-standing rig. 8 lb mast. Plug and play. B)

 

Fixed.

 

Have fun sailing. We might get off the dock today...

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Seems to me if getting the hulls out of the water with horizontal underwater foils is important this time around we've reached a new level of twitchy boats. True?

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CC121010-690.jpg

 

 

There is nothing quite like being on a cat flying a hull, but look at the flex in that pic.

 

Port bow out of the water, starboard stern out of the water, I guess due to foiling rudder, and they are 72 foot. :blink:

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Unstayed masts allow the boom to be brought forward of the beam, thus enabling downwind lift, even on slower ballasted monohull boats.

 

 

What the fuck does that mean?

Downward lift, Is like a turbo encabulator type thing?

 

Greg. Read my sig line the post some tities.

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"downwind lift"

 

I suppose he means the sail can be let out far enough to get the sail in aerodynamic lift mode rather than just barn door mode.

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CC121010-690.jpg

 

 

There is nothing quite like being on a cat flying a hull, but look at the flex in that pic.

 

Port bow out of the water, starboard stern out of the water, I guess due to foiling rudder, and they are 72 foot. :blink:

 

I think the issue is that the rule does not allow controllable foils so the what control there is comes from allowing the boat to flex.

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Google "Nigel Irens Farfarer" and you'll find it. Built to replace the Irens Schooner MAGGIE B which was lost in a fire at Covey Island.

 

http://www.na.norths...px?news_id=2367

 

Most North Sails don't look that good, that cut is flawless. I have seen too many baggy battened sails, many with the North logo on them, to care much for what battens usualy do to the sail. Clearly, a top quality sail can be made with battens, but this is not indicative of thier typical work.

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Unstayed masts allow the boom to be brought forward of the beam, thus enabling downwind lift, even on slower ballasted monohull boats.

 

 

What the fuck does that mean?

Downward lift, Is like a turbo encabulator type thing?

 

Greg. Read my sig line the post some tities.

 

Please, learn to read. It's called research, you did not even bother to read up on the whole thread, or you would have noticed this information.

While you are at it, learn to spell before you try to put someone in check.

 

And no, I will not post any pics of tities.

"downwind lift"

 

I suppose he means the sail can be let out far enough to get the sail in aerodynamic lift mode rather than just barn door mode.

 

From earlier in the thread: http://www.stadtdesign.com/swing_rig/swing_rig

and: http://www.omerwingsail.com/air-flow/

 

The claim is that such sails produce lift due to proper trim on a downwind run or broad reach.

Personally, I really want to sail on such a boat and see how it works.

I will find a way to build one if I can't get a ride from someone first.

 

For your further edification, the Goat Island Skiff: http://www.storerboatplans.com/wp/design/rig/sails/sailing-unstayed-cat-ketches-and-cat-yawls-safely-and-efficiently-downwind-in-strong-winds/

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What is with this new crop? Really difficult to get along with. No tits, no respect. Probably know shit about food, either. And they can't spell. Tities. Bah, bumfuck.

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Unstayed masts allow the boom to be brought forward of the beam, thus enabling downwind lift, even on slower ballasted monohull boats.

 

 

What the fuck does that mean?

Downward lift, Is like a turbo encabulator type thing?

 

Greg. Read my sig line the post some tities.

 

Please, learn to read. It's called research, you did not even bother to read up on the whole thread, or you would have noticed this information.

While you are at it, learn to spell before you try to put someone in check.

 

And no, I will not post any pics of tities.

"downwind lift"

 

I suppose he means the sail can be let out far enough to get the sail in aerodynamic lift mode rather than just barn door mode.

 

From earlier in the thread: http://www.stadtdesi...g_rig/swing_rig

and: http://www.omerwingsail.com/air-flow/

 

The claim is that such sails produce lift due to proper trim on a downwind run or broad reach.

Personally, I really want to sail on such a boat and see how it works.

I will find a way to build one if I can't get a ride from someone first.

 

For your further edification, the Goat Island Skiff: http://www.storerboa...n-strong-winds/

 

Right, now listen here ass wipe.

 

You appear to be the first person in this thread to use the term "Downward lift" So fucken excuse me if I don't understand what it means.

 

If you don't like my spelling then you can shove it up your ass. And what did I spell wrong anyway? fuck it I don't care.

 

I can fucken read, some times I skip over what looks like shit posted by idiots, Maybe I missed something. You called someone else out for being rude, Look how you are behaving now.

 

If you want me to start being civilised to you you had better post some Tit's.

 

And after all that I still don't know what the fuck downward lift is. Is the same as lift?

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Unstayed masts allow the boom to be brought forward of the beam, thus enabling downwind lift, even on slower ballasted monohull boats.

 

 

What the fuck does that mean?

Downward lift, Is like a turbo encabulator type thing?

 

Greg. Read my sig line the post some tities.

 

Please, learn to read. It's called research, you did not even bother to read up on the whole thread, or you would have noticed this information.

While you are at it, learn to spell before you try to put someone in check.

 

And no, I will not post any pics of tities.

"downwind lift"

 

I suppose he means the sail can be let out far enough to get the sail in aerodynamic lift mode rather than just barn door mode.

 

From earlier in the thread: http://www.stadtdesi...g_rig/swing_rig

and: http://www.omerwingsail.com/air-flow/

 

The claim is that such sails produce lift due to proper trim on a downwind run or broad reach.

Personally, I really want to sail on such a boat and see how it works.

I will find a way to build one if I can't get a ride from someone first.

 

For your further edification, the Goat Island Skiff: http://www.storerboa...n-strong-winds/

 

Actually Bob I've slept on it and changed my mind

 

Hello Greg, my name is Tony and I'm here to help. Now, you do realise(sic) that spurning an established custom when meeting a new tribe is extremely cloddish and rude. Many a missionary got sent to the bosses office for making this mistake.

 

Also if I read them correctly your first link describes the Van de Stat swing rig that sort of claims obliquely that it might generate lift down wind but we all know thats BS.

 

The second actually refers to a "wing" sail which is an entirely different animal. Technically, yes it can be argued that a wing generally speaking can still produce lift down wind trimmed as shown but its as slow as a dead dog. Please use your research skills to produce photos of the AC cats running down wind with their wings positioned thus, it never happens.

 

You present as a pompous arse (sic) with an over inflated sense of self worth who learned everything he knows about sailing from a fucking book.

 

Good day.

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Also if I read them correctly your first link describes the Van de Stat swing rig that sort of claims obliquely that it might generate lift down wind but we all know thats BS.

 

Yes, but the flag on the ground pointing one direction as the streamers on the vehicle fly in the opposite direction is a pretty cool effect. ;)

 

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... ...

You present as a pompous arse (sic) with an over inflated sense of self worth who learned everything he knows about sailing from a fucking book.

 

... ...

 

No only that, he learned everything he knows about fucking from a sailing book

 

FB- Doug

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