How to compromise junk to trimaran?

[stozi]

I've been looking around for a cruiser design. Both the junk rig and trimaran seem to have many advantages, but are hard to integrate. Nonetheless the Junk rig association says it can be done. People often say that the good thing about trimarans is their width for stays. To me, beachability, shallow draft, speed potential, positive buoyancy, deck space, and stability are more important than width for stays. The junk seems to be much easier and safer to reef, generally easier to handle and with less crew, resistant to accidental jybe, better downwind, quieter, cheaper, and home-buildable.

It seems that the initial cost will be high, probably mitigated by the financial crisis, but maintenence costs, beaching to repaint and building one's own sails, will cut long term costs.

The lack of existing designs is not encouraging. The closest things I've found are Chris White's Juniper and Dragon Wings, design which seems to have been replicated once or twice.

If you can stick an unstayed mast in each cat hull with pleasing effect, I think you should be able to do it in a tri.

If it really is just not worth it, how best to compromise? Copy that catamaran design? Use some kind of semi-stayed rig? is there one that allows the junk sail to operate as meant to? Are there any other options?

Thanks!

[oldsailor7]

IMHO junk sails are just that-------JUNK.

Bin there, Done that. (Ask James Wharram).

[stozi]

Thanks for your opinion. However I wonder how thoroughly Wharram experimented, given the diversity of junk layouts, and his tendancy towards cats rather than tris.

[Tad]

There are few cruising trimaran designs for a number of reasons, high cost relative to interior volume and load carrying ability is one. Also minimal accommodation in relation to all the parts and surface area you must build. and awkward or impossible marina mooring is another negative. The major plus of a tri is high stability with minimal weight. Cruising is rarely about minimal weight. In my experience the majority of cruisers seem to want to take it all along, including the dishwasher and trash compactor.

To get reasonable accommodation the tri needs to be large, as Juniper is, a 50+ foot boat that has the accommodation of a 36-38' monohull.

So the main reason for building a trimaran is high performance.

The major pluses of the junk (chinese lug) rig are, ease of handling and simplicity of construction. High performance is not the intention or aim of this rig. Mediocre to reasonable performance is possible. Some of the problems are lack of sail area for light air, and high weight vs sail area. Obviously less than optimum shape on many (most?) points of sail is also a problem.

The trimaran form certainly lends itself to installation of unstayed or partially stayed masts on centerline.

BC is an area of very light air in summer, so then your tri becomes a powerboat, which is fine.

To me the two concepts (lug plus tri) do not really mesh well into a unified whole. Great boats are conceived as a complete system, all parts must seamlessly integrate with the rest. It takes considerable vision to successfully meld the disparate parts. With clients I discourage this type of undertaking as the potential for failure/major financial loss is very high. White elephants are a glut on the market....

Good luck with it.

[oldsailor7]

Thanks TAD for a very concise revue of the subject.

Having been intimately involved in the development of multihulls for the past forty six years I have never heard a better or more clearly put evaluation of the pros and cons of Cat vs Tri as a unified system.

Cheers. Paddy.

[FAST FRED]

However I wonder how thoroughly Wharram experimented, given the diversity of junk layouts,

Interesting that with dozens of Wharram owners experimenting never got it right either.

How many rigs can you afford to build to compare results?

Dozens? More? Years you have to refine a 5000year old rig?

Some folks just prefer to cruise , with out catching the "Bestitis" disease.

FF

[Ilan Voyager]

Thanks Tad for the very clear exposition about trimarans. Tris are very interesting boats but not well suited for cruising as Tad has explained so clearly. Tris must be kept light and are ecpensive to build. A catamaran would be more efficient and cheaper for a cruising boat.

Junk sails have been invented for slow boats going downwind, and are not suitable on "fast" multihulls. And why to go in complications? Fully battened main sails are very well mannered, easy to tune and efficient, and very easy to reef. The technology involved is well known today. Free standing masts are almost impossible to design for multihulls because of the big righting moments of these boats.

A long time ago, my associate and I designed -for a naval architect- a schooner rig for a cruising cat skipped by a lone guy. The rig was composed of 2 "short" identical rotating masts, fully battened mainsails with wishbones, not any jib, except a flying reacher for very light weather.

So the mast were very light (with very wide spreaders to minimize the compression), the center of sail was adjusted "playing" with the 2 main sails.

The owner aged of 67 years told us that the journey from Panama to Tahiti was the most boring of his life, as he had nothing to do except sleeping and reading while making 250 miles a day with his 45 feet catamaran, a part a few tacks...

[Tad]

Originally Posted by Ilan Voyager

Free standing masts are almost impossible to design for multihulls because of the big righting moments of these boats.

Almost.....but not quite impossible.

See the Dick Newick designs Cheers (40' proa), White Wings (37' tri), and Pat's (51' tri)

Also a number of cat's with un-stayed biplane rigs, including the Schionning designed Radical Bay...

[Ilan Voyager]

Yes I know these designs and some more as those by Philippe Harlé, Chris White, even Shutlleworth and others, plus in France a few shipyards had in catalogue multis with free standing masts and at my knowledge they were;

A-Or not very efficient as the mast was too bendy.
B-Or very, very expensive all carbon and so on.
C-Many times very expensive and bendy.

And I do not speak about weight, materials and reefing issues.

It has been a fashion of these masts in 80-85, and every designer was purposing them. Within the following years, these designs disappeared and many of those which were built were refitted with "classic" masts. I know at least five, the first being Juniper by White.

Unstayed masts work very well on monohulls and it's a rational solution.
On tris it's possible, but if you want a rigging able to give the power that a modern tri is able to withstand the task becomes difficult.
On a catamaran it's almost impossible because of mechanical problems, unless using a twin rig, which has its own little problems (and look closely at the pic of the catamaran...what do you think of the bending of the masts, and the shape of the sails in a very moderate wind?)

Furthermore, I was answering to a question about junk sails, something thought as cheap and simple, for someone who has not a big wallet. Good unstayed masts are not cheap, and far from simple on multihulls, a part some small ones.

A rotating aluminium extrusion with wide spreaders, 4 stays and a fully battened mainsail is a solution that has an excellent ratio simplicity/price/efficiency on a cruising boat. Engineering is easy and well documented, and the job can be done by an amateur. If you had a well designed fishbone, you save a lot of expensive hardware, and if you forget the jibs more money is saved.

2 "short" masts, 2 mainsails, an optional reacher. No tracks, no chariots, no winches, no furlers, no expensive hardware except one all purpose winch. Simple, effective, cheap for a cruising boat boat without search of speed.

Behind any picture we see, we should ask; was it successful? efficient? what was the cost? how long has taken the tuning? what happened in the following five years?

[boat fan]

Yes I know these designs and some more as those by Philippe Harlé, Chris White, even Shutlleworth and others, plus in France a few shipyards had in catalogue multis with free standing masts and at my knowledge they were;

A-Or not very efficient as the mast was too bendy.
B-Or very, very expensive all carbon and so on.
C-Many times very expensive and bendy.

Yes , the historic data seems to support your statement.

This approach seems to show some promise , without being excessively
expensive ;


http://www.harryproa.com/Builders/Ba...e/P1010055.jpg

http://www.harryproa.com/Builders/Ba...e/P1010054.jpg

http://www.harryproa.com/Builders/Ba.../Large/026.jpg

The rig is a ballestron so there is no deck gear. No tracks, winches or muscle required. Multipart block and tackles tension the halyards and the outhauls. For racing, a separate tackle is used for mainsail leech tension. The jib is sheeted to a track just forward of the mast. There are just as many strings to pull to achieve optimum performance as on normal boats, but none of them are highly loaded.

Seems to be home buildable , with some care and effort.

[boat fan]

Interesting Gunter rig from B.Kohler at K Designs :

The idea for the Gunter rig is to have a cheap and powerful rig.
The mast is a Al. tube, diameter 80/75mm. The gaff is made from spruce
with some UD carbon. Shape +/-
the gaff of the Vrijheid, but lighter and of course flexible.
The difference to other Gunter rigs is in the hoist. The halyard is
direct fastened to the upper slider on the gaff.
Both gaff sliders are running in a rail. The upper gaff slider is
detachable from the gaff. In this way setting and striking the sails is
easy done. The reefing points are just under the lower gaff part. So to
reef the sail is also an easy operation.
The mast rotates free. This means a low load on the gaff sliders.
Together with the sleeved upper part (on the gaff) the sail will be
aerodynamic clean and very powerful. The round tube is an compromise, a
more aerodynamic shaped leading edge would be better, but a round tube
costs less.

Sliding Gunter Schooner ?
Low cost , low tech.

[Ilan Voyager]

Very interesting...

The balestron has been tried several times. I have tried it on a 18 feet sport monodromic proa in comparison trials with a wing mast. On this particular case the wing mast was more efficient and lighter.

I has been also a big fan of RC class M boats (1.27m monohulls with radio command) where the balestron is the best solution. The purpose is to get a high Cz by ventilation of the mainsail extrados.

After squeezing my old brain, I remember of one made around 1920 by a German guy with fully battened main sail. I have read that in a -I'm not sure- sailing aerodynamics book.

I know very well the balestron made for Elf Aquitaine II. This balestron has been designed by top cream guys, after a costly wind tunnel campaign and built regardless of cost with the best of the better materials. I remember that the price of the custom conical rollers bearings was superior to the price of a new good car...Brief, it was beautiful, high tech, very expensive and a total, absolute failure.

In the French Flying Circus of racing multihulls (and everybody agrees that the French have the fastest multihulls of the world), the word balestron gives eczema to the designers, engineers, skippers and sailors. After 30 years of intense racing, where hundreds of millions dollars have been invested in the search of the ultimate sailing multihull, I think that the best solutions have been found and balestron is not among them.

About the catamaran pics. I'm a hard believer in Occam's razor principle (in plain english MISS principle, Make It Simple and Stupid), and I do not see any advantage on the use of a gaff compared to a classic mast. I won't make any calculation but I have a doubt about the 80/75 mm aluminium tube, heavy for a 6.5m cat (It weights 3.3 to 3.5 kg/meter). The spruce/carbon gaff has to be made (money and work) with tracks, haulyards and so on. Plus a very custom sail, not easy to cut for the sail maker. What's the advantage compared to a "classic" rotating mast and a wishbone?

03/Jan/09 The german guy was Manfred Curry -a spicy name- in the 30's.
About balestron: the aerorig (the original internet site has disappeared) but an interesting link.

http://www.john-shuttleworth.com/Art...eroDesign.html

With pros and cons -to read between the lines- results heavy and very high tech. The rig cost surely 3 times the price of a "ordinary" rig. Very complicated to install on a catamaran. Gives a lot of aero infos.

Another link of a aerorig on a monohull

http://yachtlanovia.com/aerorig-unst...ing-yacht.html

Very good results.

I stay convinced that a schooner rigging (when the boat is long enough) of 2 identical masts (13 meters high on the 14m catamaran) with fully battened mainsails and wishbone, and a flying reacher is a good solution on a cruising cat, kept light. The mast are light (little compression), the height center of sail is low, the longitudinal center of sail easily adjustable and hardware kept to the minimum. Ok aerodynamics are not the best, but efficiency is largely enough for a cruising cat. The cost is rather low.

For the very heavy cats, the lone solution is diesel and big tanks of fuel, and/or a lot of patience.

[BigCat]

Originally Posted by oldsailor7

IMHO junk sails are just that-------JUNK.

Bin there, Done that. (Ask James Wharram).

If you've been there, done that, and thought it was junk, you didn't know what you were doing. I've been there, done that, and love it. See Batwing in Hasler's Practical Junk Rig - My boat, that I sailed across the Pacific.

[BigCat]

Originally Posted by Tad

There are few cruising trimaran designs for a number of reasons, high cost relative to interior volume and load carrying ability is one. Also minimal accommodation in relation to all the parts and surface area you must build. and awkward or impossible marina mooring is another negative. The major plus of a tri is high stability with minimal weight. Cruising is rarely about minimal weight. In my experience the majority of cruisers seem to want to take it all along, including the dishwasher and trash compactor.

To get reasonable accommodation the tri needs to be large, as Juniper is, a 50+ foot boat that has the accommodation of a 36-38' monohull.

So the main reason for building a trimaran is high performance.

The major pluses of the junk (chinese lug) rig are, ease of handling and simplicity of construction. High performance is not the intention or aim of this rig. Mediocre to reasonable performance is possible. Some of the problems are lack of sail area for light air, and high weight vs sail area. Obviously less than optimum shape on many (most?) points of sail is also a problem.

The trimaran form certainly lends itself to installation of unstayed or partially stayed masts on centerline.

BC is an area of very light air in summer, so then your tri becomes a powerboat, which is fine.

To me the two concepts (lug plus tri) do not really mesh well into a unified whole. Great boats are conceived as a complete system, all parts must seamlessly integrate with the rest. It takes considerable vision to successfully meld the disparate parts. With clients I discourage this type of undertaking as the potential for failure/major financial loss is very high. White elephants are a glut on the market....

Good luck with it.

An other uninformed opinion, worth every nickel it cost you. Junk rigs are weatherly, now, due to the advent of the cambered junk rig. Read about it at: http://groups.yahoo.com/group/junkrig/

[BigCat]

Originally Posted by Ilan Voyager

Thanks Tad for the very clear exposition about trimarans. Tris are very interesting boats but not well suited for cruising as Tad has explained so clearly. Tris must be kept light and are ecpensive to build. A catamaran would be more efficient and cheaper for a cruising boat.

Junk sails have been invented for slow boats going downwind, and are not suitable on "fast" multihulls. And why to go in complications? Fully battened main sails are very well mannered, easy to tune and efficient, and very easy to reef. The technology involved is well known today. Free standing masts are almost impossible to design for multihulls because of the big righting moments of these boats.

A long time ago, my associate and I designed -for a naval architect- a schooner rig for a cruising cat skipped by a lone guy. The rig was composed of 2 "short" identical rotating masts, fully battened mainsails with wishbones, not any jib, except a flying reacher for very light weather.

So the mast were very light (with very wide spreaders to minimize the compression), the center of sail was adjusted "playing" with the 2 main sails.

The owner aged of 67 years told us that the journey from Panama to Tahiti was the most boring of his life, as he had nothing to do except sleeping and reading while making 250 miles a day with his 45 feet catamaran, a part a few tacks...

A third uninformed opinion worth every nickel it cost. I designed a catamaran with 600,000 foot pounds of righting moment, and the USCG naval architects approved my unstayed biplane rig design. The rig cost is a lot less than a conventional rig. About 1/3, maybe less. See http://bigcatcatamarans.com .