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Old 18-05-2008, 15:06   #16
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Red face The absurdity of the Marconi rig

Hi, Fard - My point isn't that people should do what I am doing, but rather that that they should question their assumptions about what is necessary. If someone sat down to design a sailboat rig who had never seen one, but he started with a list of handling requirements and a good knowledge of aerodynamics, I don't think he would invent the marconi rig as we know it.

Look at what Gary Hoyt has done, for example-at Balanced Rig Data Sheet -You will notice that there is no track and no slides. Why would you want to invent an expensive and complicated system in order to put a sail immediately behind a post that disturbs the airflow and creates huge eddies at the leading edge of the sail? Imagine that on an airplane-how silly it would be!

My only complaint about Hoyt's rig is that the yard seems to permanently aloft. Not something I would want aloft in a hurricane.

If you look at the history of astronomy, you will see that astronomers assumed that planets moved in circles. Closer observations showed that that didn't work, and so they added 'epicycles', or circles on circles, rather like the way the moon moves around the earth, which moves around the sun. They kept adding more epicycles, until the whole thing became obviously absurd, and the idea of elliptical orbits was introduced by Kepler.

The Marconi rig is like that-more and more gadgets are being added to it to make up for its deficiencies, until you have a vast array of expensive and vulnerable gadgets designed to compensate for its deficiencies.

I think that a rig which requires all of these little gadgets is as absurd as epicycles orbiting around epicycles orbiting around still more epicycles. I don't call that 'cutting edge.' I call that absurd. It is time to rethink our assumptions, and invent the sailing rig equivalent to the ellipse.
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Old 18-05-2008, 15:37   #17
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Talking Making life easier?

Gee, we are seeing batt cars on shorter and shorter rigs. Is this a triumph of marketing over product? On cats with swept aft shrouds the main friction component is in the main rubbing on the shrouds when attempting to lower or raise. Gee'se even crappy sliders work ok head to wind on most midsized boats. Try rubbing a bar of dry soap on the first meter of sail track before hoisting, it works wonders.
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Old 18-05-2008, 17:00   #18
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Unfortunately, Catty, you can't always turn to windward when you want to reef. If the storm comes up in the middle of the night wayyy offshore, and the waves get big fast, and then you want to reef--well, you get the picture. Not a theoretical scenario for me-I've been there. Kanter says you can unload some luff tension from full batten mainsails if your mast rakes 5% aft-so, if you are designing a boat with the Rube Goldberg rig, you might want to do that.
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Old 19-05-2008, 00:03   #19
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Hi, Fard - My point isn't that people should do what I am doing, but rather that that they should question their assumptions about what is necessary. If someone sat down to design a sailboat rig who had never seen one, but he started with a list of handling requirements and a good knowledge of aerodynamics, I don't think he would invent the marconi rig as we know it.

Look at what Gary Hoyt has done, for example-at Balanced Rig Data Sheet -You will notice that there is no track and no slides. Why would you want to invent an expensive and complicated system in order to put a sail immediately behind a post that disturbs the airflow and creates huge eddies at the leading edge of the sail? Imagine that on an airplane-how silly it would be!

My only complaint about Hoyt's rig is that the yard seems to permanently aloft. Not something I would want aloft in a hurricane.

If you look at the history of astronomy, you will see that astronomers assumed that planets moved in circles. Closer observations showed that that didn't work, and so they added 'epicycles', or circles on circles, rather like the way the moon moves around the earth, which moves around the sun. They kept adding more epicycles, until the whole thing became obviously absurd, and the idea of elliptical orbits was introduced by Kepler.

The Marconi rig is like that-more and more gadgets are being added to it to make up for its deficiencies, until you have a vast array of expensive and vulnerable gadgets designed to compensate for its deficiencies.

I think that a rig which requires all of these little gadgets is as absurd as epicycles orbiting around epicycles orbiting around still more epicycles. I don't call that 'cutting edge.' I call that absurd. It is time to rethink our assumptions, and invent the sailing rig equivalent to the ellipse.
The drag coefficient for a sphere is given with a range of values because the drag on a sphere is highly dependent on Reynolds number (One of the reasons why rod rigging is chosen for racing yachts). Flow past a sphere, or cylinder, goes through a number of transitions with velocity. At very low velocity, a stable pair of vortices are formed on the downwind side. As velocity increases, the vortices become unstable and are alternately shed downstream. As velocity is increased even more, the boundary layer transitions to chaotic turbulent flow with vortices of many different scales being shed in a turbulent wake from the body (This would occur at speeds where air craft operate). Each of these flow regimes produce a different amount of drag on the sphere.

The amount of drag generated by an object depends the size of the object. Drag is an aerodynamic force and therefore depends on the pressure variation of the air around the body as it moves through the air. The total aerodynamic force is equal to the pressure times the surface area around the body. Drag is the component of this force along the direction of travel. Like the other aerodynamic force, lift. The drag is directly proportional to the area of the object. Doubling the area doubles the drag.
So if your foil has a frontal area greater that that of the wire itís self then the drag coefficient of the foil will increase dramatically over the wire.

A wing with the same frontal area as a sphere.
The Cd of the sphere is .07 to .5
The Cd of the foil is .045
CD been (Drag coefficient) and this is the formula to work it out.
Cd = D / (.5 * r * V^2 * A)

I am not sure where Mr Hoyt gets his numbers.
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Old 19-05-2008, 13:20   #20
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Fard12, the mast is the drag to be looking at, as I indicated, and the issue is not just the drag, but its location at the leading edge of an important foil, the mainsail, where the turbulence is doing damage far out of proportion to its simple drag. I am also addressing issues that are not concerned with aerodynamics at all, but also economy, reliability, seaworthiness, and ease of handling. I think that we can do better than the marconi rig in each category- aerodynamics, reliability, economy, seaworthiness, and ease of handling.
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Old 19-05-2008, 16:31   #21
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Fard12, the mast is the drag to be looking at, as I indicated, and the issue is not just the drag, but its location at the leading edge of an important foil, the mainsail, where the turbulence is doing damage far out of proportion to its simple drag. I am also addressing issues that are not concerned with aerodynamics at all, but also economy, reliability, seaworthiness, and ease of handling. I think that we can do better than the marconi rig in each category- aerodynamics, reliability, economy, seaworthiness, and ease of handling.
Yes I agree totally. The ideal mast is a wing section (rotating) with a boltrope connection to the mast. However this is not practical on larger boats. The high and low-pressure areas affected by the use of a car system are not as great as you think.
However there are horses for courses. Not all designs suit all comers.
If you are looking for a fast racer / cruiser then hull form and weight a paramount to start with.
The standard double diamond and variations of it gives the best performance of all known designs today.
The use of carbon has address weight issues with mono and multi alike. The cost of carbon is still high when looking at other mediums used to build masts and boats.
To run stay less rigs on larger boats does impose a large cost and the weight saved buy not having shrouds, spreaders, batten car systems does not offset the size of the section required to achieve a safe acceptable result.
The use of carbon rigging and other fibers has gone a long way in reducing weight aloft. This and carbon sections has had a great impact in reducing the VCG of masts.
When looking at the modern multihull these days you see large roaches in the main with square tops. This is the reason that batten cars are used as the batten compressions is very high .To hold the leech up in these boats you also have to use exotic types of cloth. Dacron won’t achieve the result you are looking for nor the weight savings required on these boats.
Cheers Fard
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Old 19-05-2008, 17:07   #22
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Hi, Fard - The carbon fiber for two unstayed masts to support 1200 sq. ft. of sail each mast on a catamaran is about $30,000 for both. If you look at the cost of the very extensive list of items that you can do without when using this approach, I think you will be surprised. My own unusual design has big roaches with square tops, and no batten cars. I agree that this approach is not light, however-it totals about a pound a square foot of sail area-but the center of the weight is lower than with a marconi rig. My own interest is in full on cruising boats-not racing boats, which live in a different, labor and cost intensive environment. Racing boat owners care little about economy, reliability, seaworthiness, and ease of handling, except to whatever extent a racing governing body requires.
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Old 19-05-2008, 19:01   #23
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The cost of materials is around $30,000. You have to add the labour to build these masts. I have seen home built masts in the past and most I wouldn’t go to sea with.
I take it that the masts are strip plank then carbon (wet lay-up) over.
Does the cost include the added cost of the strengthening of the partners, collar etc?
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Old 19-05-2008, 19:23   #24
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Racing boat owners care little about economy, reliability, seaworthiness, and ease of handling, except to whatever extent a racing governing body requires.
BigCat, thats a fairly broad statement to make about racing boat owners, I beleive that most racers would hold these values in high esteem regardless of their budget, it may hold true for a few gung-ho sailers but most I've met seem to rate seaworthyness, safety & reliability with finishing & placing somewhere in the results. All the best in your endeavours from Jeff
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Old 22-05-2008, 21:43   #25
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Unstayed masts are easy

Hi, Fard

The masts will be resin infused in female half molds. The mold consists of a long skinny box filled with plaster of paris, bondo, or whatever, and scraped out to form a semicircular cavity. There will be part bulkheads every few feet inside with the correct semicircle removed for the taper, to give guidance for the "goop scooping" process.

There will be an overlapping joint where the halves join. The overlaps will be stuck together with epoxy adhesive. The overlaps and adhesive will add about 22% to the mast weight.

No racer would tolerate this extra 22% of weight, but it isn't important to me. Basically, it is just like making two little hulls and attaching them together with epoxy adhesive, hardly rocket science. No tows involved- just carbon unis with a little polypropylene scrim added to promote wetting out, and some plus/minus 45 glass to take wringing strains. The resin will be vinylester.

I'm not sure where people get this impression that it takes a huge, complicated structure to hold up an unstayed mast. On Batwing, I had a 43' long (34' above deck,) solid wood mast 8" thick, carrying 440 sq. ft. of sail area. This mast and the foremast were completely unstayed.

My extra structure on Batwing, a well built conventional fiberglass boat with a standard balsa cored deck, consisted of a foam cored frame 4" high by 1" thick, a "cup" on deck to hold the mast wedges made of solid fiberglass, (about 1/2" thick by 4" high that lapped under and over the hole in the deck for the mast,) and a mast step that was similar. The foremast was pretty much the same. That's it.

I sailed this boat through, literally, hurricanes with an unstayed junk rig in a Pacific crossing. No problem. It then sailed around the world under new ownership, and is now in central America, having been sailed there from near Seattle by the 3rd owners.

On BigCat, the extra stiffening consists of a ringframe of fiberglass, and a couple of extra deck stiffeners of foam core fiberglass.

There is a full watertight bulkhead about 2' forward of the masts, and another ringframe about 2' aft of the masts. Running fore and aft next to the masts is a bulkhead that forms part of a shower stall, and I'll beef that up a bit. The mast will step on the cabin sole, and the deck cup will be like my former boat's, described above.

The total extra framing, besides the interior that would be there anyway, is one perfectly ordinary fiberglass ring frame, and a couple of short foam cored deck stiffeners. Oh, and the balsa deck core will be replaced with something denser, either very high density foam or marine grade plywood, for a 2-1/2' wide strip from hull to hull where the mast penetrates the deck.

I'd say this is no more stiffening than most hulls get where the chainplates attach for a stayed rig, and it may well total less weight and complexity than that.
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Old 22-05-2008, 22:10   #26
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Carbon fiber heads, and those who love them

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BigCat, thats a fairly broad statement to make about racing boat owners, I beleive that most racers would hold these values in high esteem regardless of their budget, it may hold true for a few gung-ho sailers but most I've met seem to rate seaworthyness, safety & reliability with finishing & placing somewhere in the results. All the best in your endeavours from Jeff
Hi, Jeff, I guess I should have said "highly dedicated" racers. I remember how I laughed when I read about Cherokee Monkee installing a carbon fiber head. Remember the guy who said, "If it doesn't break, it's too heavy?" Dennis Connor maybe?
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Old 22-05-2008, 22:46   #27
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You’re still a fair way off the mark. “highly dedicated” racers are in my view the most responsible of the lot. Apart form the few dills out there. However there are dills in the cruising fraternity as well. No smart race boat owner multi or mono wants to place crew or boat in danger due to short cuts or poor design.
PS what's wrong with a carbon head?
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Old 22-05-2008, 23:55   #28
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Carbon fiber head? The cost to weight benefit ratio makes it something only a very rich person or a complete fanatic could possibly want, IMHO. Our frames of reference are probably too different to reconcile-To me, a boat that comes apart or turns over while being used as intended is a sign of incompetence, but it is commonplace in the racing world.
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Old 23-05-2008, 04:02   #29
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BigCat, I think it may have been Lindsay Cunningham? but cant really be sure on the if it dont break its too heavy thing, All the best from Jeff.
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Old 23-05-2008, 09:41   #30
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The standard double diamond and variations of it gives the best performance of all known designs today.
The use of carbon has address weight issues with mono and multi alike. The cost of carbon is still high when looking at other mediums used to build masts and boats.
To run stay less rigs on larger boats does impose a large cost and the weight saved buy not having shrouds, spreaders, batten car systems does not offset the size of the section required to achieve a safe acceptable result.
Cheers Fard
G'day,

I totally disagree with you on the superiority of double diamond rig particularly for cruising boats. We discussed this on the unstayed mast thread and I showed that an unstayed pro built carbon mast ( ) is cheaper than your pro built alloy stayed one, at least for at least for the 40' cat you and I compared.

An unstayed carbon mast has less drag, less weight and lower centre of gravity than the standard double diamond rig, It is also far easier to use (the first reef is automatic as the mast flexes) and has virtually no maintenance.

Anyone using a double diamond rig on a cruiser with sufficient bury for an unstayed rig must like hard work, spending money, sailing dramas and nervous stress.

As for crappy home built masts, they exist, but there are also crappy alloy extrusions and no shortage of horror stories about stayed masts falling down through bad workmanship by "professionals". Anybody who can use a vacuum bag can build themselves a high quality carbon mast (stayed or unstayed) cheaper than they can buy an alloy rig.

How much does the bare anodised mast tube cost for the Wilderness 12.3 that we used for the comparison in the other thread? How much does it weigh? The mast in the video weighs 120 kgs, painted. This is $33.33 per kg.

The materials for the mast in the video cost $4,000, incl 10% tax and is 60' long. The bare anodised tube may be less than this, but by the time it is fitted out and all the rigging bought and installed it is 4-5 times the price. Then add on all the beefing up of the boat and unnecessary deck gear and you are up for even more money and weight. For an inferior rig.

To address the original question, a mast where the sail is _always_ hoisted and lowered with the sail luffing does not need fancy cars and tracks, even for highly roached sails.

Big cat, if you re paying $15,000 per mast for materials, you might want to drop me a line and see if we can save you some money.

regards,

Rob
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