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Oddly enough I asked a similar question just yesterday. Logically, there should be no innate advantage in having a smaller shorter foresail, which suggests that all of the "logic" in favor of fractional rigs is based on bubbameisers. (Nonsense tales perpetuated by grandmas.)

So let's look at physics and ignore all the bilge myths.

What is different about the interaction of the sails (main and fore) when you have a fractional rig? Well, there's a vortex coming off the end of every wing and that turbulence creates drag. With a masthead rig, and the main and foresail both having their top ends in the same place, wouldn't those two vortexes reinforce and create extra drag, and a loss of lift on the top of the main?

Aha. Maybe, maybe not, but has anyone ever bought time in a wind tunnel and actually examined that? I don't know, I've never heard mention of it but I'm not into heavy reading of aerodynamic testing.

Now take the same two sails, and stagger them so the two tip vortexes do NOT intermingle and reinforce each other. What do you have? A fractional rig!

Maybe it could be that simple. Simple physics, which no one has bothered to document or examine in detail because "everyone knows" the fractional rig with less sail area magically is faster. Magically. Hmmm, maybe that way the vortex coming off the tip on the foresail actually increases the flow below the tip of the main, actually boosting the performance of the main as well?!

Or can anyone point us to some objective wind tunnel work on this?

" Argh, yes, cod be faster than whales, so that must be the right way to shape a hull."
Ahuh. And rotting meat generates flies. Nothing new under the sun.
 

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bob, if you won the race in a crippled boat, that doesn't reflect anything on the rig type. It just means someone designed and built a fast boat. Or, it was "take your kids to the races" day on the other boats. Or, if she also won on corrected time, Francis isn't rated correctly.(G)

So far I've seen no one post anything objective. An AC boat might have the wing (a real wing, not a sail) end two meters down from the masthead simply because more sail that high would only help it capsize faster--a real issue for them. Or, it might have been too tall to transport at that point. Just looking at it, without knowing the facts, is meaningless speculation.

Similarly, all the comparison of masthead to fractional rigged vessels ignore the larger questions of whether the "faster" rig is being compared apples-to-apples to the entire boat design having the same balance (fore and aft) and same sail area (main and fore and aloft) and without those things being apples-to-apples, all we have is what a dog knows about elevators.

Huh?

Yeah, I get up in the morning, and my master puts us in a box, and then he opens the door, and the whole universe is changed! And then we get back in, and he opens the door again, and the whole universe is changed back! I don't know how he does it, he's obviously God.

Well...that's how the dog sees it. Motors, cables, switches, Otis brakes...the dog knows nothing about those, he only thinks his master is remaking the universe.

From what I've seen, the question of rig type comes down to "This is what the boat comes with. This is what the grumpy old man, ergh, distinguished marine architect (G), says makes this boat work, and I'm not gonna argue with him."

Funny thing is, there's someone designing both kinds of rigs, somewhere, sometimes, isn't there?

Argue with the designer, and he'll give you a yawl like the Pearson 424. You know, where the yawl boom keeps trying to take off the helmsmen's head?
 
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