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Old 18-04-2012, 20:00   #61
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Re: Why is the Marconi rig so popular…?

It's simple and efficient.
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Old 19-04-2012, 05:25   #62
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Re: Why is the Marconi rig so popular…?

IMHO the argument about plane wings 'not being marconi' is not supported by facts. Gliders are the most efficient planes, are they not? Do they have gaff rigged wings?

I would also not agree with some claims about lack off efficiency of marconi. It is the most efficient upwind rig, and upwind is when efficiency counts most (because we cannot sail direct and we lose some amount of distance anyway). Downwind, the gaff main will blanket fore sails as much if not more than a marconi sail.

Etc, etc.. Long story. Just my two cents in the 'gaff is more efficient' part.

b.
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Old 19-04-2012, 06:48   #63
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Re: Why is the Marconi Rig so Popular?

Anyone familiar with the crab claw rig? C.A. Marchaj seem to think this may be one of the best overall rigs? He states in his monumental "Sail Performance" : the crab claw..... "casts doubt on the assumed superiority of the Bermuda type of sail".
Cool looking too!
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Old 19-04-2012, 06:56   #64
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Re: Why is the Marconi Rig so Popular?

You will find pictures as you google. But how do you rig it on a modern offshore boat?

Sail efficiency is one thing, rig setup is another. Marchaj only wrote about what seems to work and under what conditions. Then someone has to build it, handle it, etc.. He never mentioned such aspects.

So to say, efficient does not mean likely to be found on a typical cruising boat. Look at AC wingsails. Sure they are efficient. Probably even more so than the crab's claw.

b.
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Old 19-04-2012, 09:27   #65
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Re: Why is the Marconi rig so popular…?

Square top mains are adjusting the tip shape of the wing with minor changes in sail area and aspect ratio. A better comparison to a gaff would be to cut the top third of the sail off and sew it back onto the leech.

Marchaj's book has a diagram showing polars of 4 different aspect ratio sails. The gaff rig develops more lift than a high aspect sail, but it does it way down on a reach. Close to the wind the high aspect sail is much better. If you're going to motor upwind or don't care about windward performance under sail, then go gaff.

John

Quote:
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I'm not sure we've written the gaff off entirely. These new square-topped mains that the go-fast crowd are so enamored with may not have an independent gaff on its own hoist, but there's not that much difference otherwise. Same basic shape, although now it's achieved with a batten system rather than a gaff.
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Old 19-04-2012, 10:07   #66
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Re: Why is the Marconi Rig so Popular?

What the marconi enthusiasts are forgetting is that the same materials that make a modern Marconi so much better than an ancient one can also be applied to a gaff rig. I could not so easily, and especially so cheaply, pulled off a Marconi rig in my back yard. My pilot cutter is gaff-headed, and was simple enough for me to build and rig at home. I have a lightweight aluminum mast, a very light aluminum gaff, and synthetic rigging, all of which alleviate some heeling moment, and make her stand up better when on the wind. The light gaff and battened-leech sail don't sag off to leeward like a heavy wooden spar on a flax sail would. So my windward performance does not suck, especially since having a real full keel (not in any way cutaway or modified), leeway is reduced to a minimum. I doubt that shape of hull could point much higher than it does even if I had a tall, expensive, bowstring-taut rig. I have found it perfect for the type of cruising I do, very easy to maintain, and not as finicky about tune as a marconi. Less efficient? Maybe in a narrow range of situations, but I've found it a most wonderfully suitable, affordable, simple and easy option, and I love it.
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Old 19-04-2012, 16:37   #67
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Re: Why is the Marconi Rig so Popular?

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Originally Posted by Benz View Post
The light gaff and battened-leech sail don't sag off to leeward like a heavy wooden spar on a flax sail would. So my windward performance does not suck, especially since having a real full keel (not in any way cutaway or modified), leeway is reduced to a minimum. .
Well, Benz, I am happy that you are enjoying your rig and your boat. However, to say that your full keel design reduces leeway better than fins or other keel shapes is simply wrong. Any treatise on yacht design will point out this well known fact.

Full keels have some practical advantages for some applications, but improving windward abilities are not among them.

BTW, I applaud your experimental improvements in the gaff rig, and agree with your approach to a home built design. Just don't get carried away with your rhetoric!

Cheers,

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Old 19-04-2012, 16:37   #68
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Re: Why is the Marconi Rig so Popular?

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Originally Posted by Benz View Post
(...) especially since having a real full keel (not in any way cutaway or modified), leeway is reduced to a minimum. (...)
???

I always thought that the efficient (minimum leeway) keel is the deep, fine foil, not a real full keel.

As an extension of this idea, I assumed the cutaway keel was cut away to improve the performance vs. the real full keel.

Was I wrong or do I read your post wrongly?

barnie
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Old 19-04-2012, 16:44   #69
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Re: Why is the Marconi Rig so Popular?

Quote:
Originally Posted by Benz View Post
(...) especially since having a real full keel (not in any way cutaway or modified), leeway is reduced to a minimum. (...)
???

I always thought that the efficient (minimum leeway) keel is the deep, fine foil, not a real full keel.

As an extension of this idea, I assumed the cutaway keel was cut away to improve the performance vs. the real full keel.

Was I wrong or do I read your post wrongly?

barnie
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Old 19-04-2012, 16:53   #70
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Re: Why is the Marconi Rig so Popular?

Quote:
Originally Posted by barnakiel View Post
???

I always thought that the efficient (minimum leeway) keel is the deep, fine foil, not a real full keel.

As an extension of this idea, I assumed the cutaway keel was cut away to improve the performance vs. the real full keel.

Was I wrong or do I read your post wrongly?

barnie


Yes, lift and hence efficiency to windward is definitely a function of depth and not length. Just like an airplane wing. High aspect ratios are more efficient than low. Length creates more wetted surface area and drag while only providing better tracking. Hence the compromises ie "modified" keels. You want good tracking but not a slow boat. A compromise must be reached unless you value one trait over the other.
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Old 19-04-2012, 16:58   #71
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Quote:
Originally Posted by minaret

Yes, lift and hence efficiency to windward is definitely a function of depth and not length. Just like an airplane wing. High aspect ratios are more efficient than low. Length creates more wetted surface area and drag while only providing better tracking. Hence the compromises ie "modified" keels. You want good tracking but not a slow boat. A compromise must be reached unless you value one trait over the other.
In order not to get confused on this thread it may be important to nail down proper terminology.

Length is tip to root on an airplane wing or hull to "bottom" on a keel
Chord is leading edge to trailing edge
Camber is curve of the foil

So fin keels have less chord compared to full keels.

Aspect ratio is length to chord ratio

Fin keels generally have a higher aspect ratio
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Old 19-04-2012, 18:51   #72
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Re: Why is the Marconi Rig so Popular?

All,

I did not suggest that a full keel offered the best windward performance (read post carefully), but that a high-end marconi rig on a full keel would be a waste, since that sort of hull cannot point as high as the fin-keel, spade rudder sort. In other words, my rig and hull match each other nicely. I have a hull that is not designed to squeeze up super-tight into the wind, and a rig likewise.
As to leeway, I can only say that my last boat, a cutaway sort with a spade rudder, made sick leeway--in comparison, my boat now really resists slipping sideways. I have great difficulty standing on a pier trying to push it straight sideways, much more than with most other boats I've had occasion to manhandle. Again, not having sailed much on racers I can't testify to their leeway or lack of it, but I find my boat's leeway small enough to rate it 'minimal'.
To summarize: the long, deep keel does not 'point' as well as other hull designs, but it sure has some resistance to slipping sideways, regardless of speed.
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Old 19-04-2012, 18:54   #73
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Re: Why is the Marconi Rig so Popular?

Barnie:

The cutaway hull was made to improve speed of turning, since a deep forefoot resists being turned--it wants to carry straight on, which makes full keelers a joy to steer downwind in heavy seas. But the cutaway forefoot does nothing toward mitigating leeway. In fact, leaving deep fins aside (most cruisers aren't this sort anyway), I'd say my keel makes less leeway than the racer/cruiser designs with a cutaway forefoot and aft end, with a spade or skeg-hung rudder. There is more to leeway than just wind pushing sideways; there are waves whacking the bows trying to push them off, there are gusts trying to make the boat round up, which will slow it down; all these things contribute to losing good way. But a heavy boat with good tracking ability that is easy to steer will carry on more steadily in these adverse conditions than a light-displacement, low-wetted-surface hull that requires endless helming to keep on a straight course.
Ben
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Old 20-04-2012, 05:39   #74
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Re: Why is the Marconi Rig so Popular?

I like it because it looks like macaroni. that is all one needs; a sailing craft marconi and cheese
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Old 20-04-2012, 06:56   #75
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Re: Why is the Marconi Rig so Popular?

Quote:
Originally Posted by barnakiel View Post
You will find pictures as you google. But how do you rig it on a modern offshore boat?

Sail efficiency is one thing, rig setup is another. Marchaj only wrote about what seems to work and under what conditions. Then someone has to build it, handle it, etc.. He never mentioned such aspects.

So to say, efficient does not mean likely to be found on a typical cruising boat. Look at AC wingsails. Sure they are efficient. Probably even more so than the crab's claw.

b.
Barnakiel: I assume you are responding above to my crab claw post. you ask how to rig it using modern materials,well I don't know ,but the pacific islanders were able to do so and navigate the worlds largest ocean using only stone age technology,so surely today's materials can make do.
In all this discussion regarding rigs it is a mistake to consider the rig as divorced from the hull form.A cat rig mandates a wider hull form than a sloop rigged analogous craft,since on different points of sail the forces generated by the various rigs transmit different turning moments on the hull ,so the naval architect must counter these forces with hull shape, ballast placement etc..
It is likewise a mistake to consider that the"modern" hull form as divorced from the rig placed on top.
FWIW: Marchaj claims that the various racing rules that have favored the sloop rig are not tweaked as much as those regarding hull form and thereby innovation regarding rigs is attenuated.
Have sailed sloops, gaffs and cats,and have never even seen a crab claw rig but if I do you can bet I'll wrangle a ride and report back.
Cheers.
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