# type of mainsail



## TSOJOURNER (Dec 16, 1999)

americas cup boats have their mainsails cut off at the top of the mast.
can someone please explain?


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## Gary M (May 9, 2006)

*Adds to the roach.*

They are not cut off they are done like that to get more sail area. A lot of racing catamarans do that as well.

Instead of basically coming to a point at teh head like a standard main they have this extended area that is supported by some form of wire/rod, what ever. It not only gives you more area at the top but additional area in the main's roach all the way down. If the rules allow it and you can afford it, it should give you more power.

Gary


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## TrueBlue (Oct 11, 2004)

Gary M said:


> . . . they have this extended area that is supported by some form of wire/rod, what ever.


Isn't this "wire/rod" called a roach clip?


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## sailortjk1 (Dec 20, 2005)

TrueBlue said:


> Isn't this "wire/rod" called a roach clip?


Whats a roach clip? I never heard of one.
Just kidding, I grew up in the seventies.


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## Sabre66 (Feb 3, 2007)

Every time the mast breaks they cut a little more off


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## nolatom (Jun 29, 2005)

Kinda like a high-tech gaff rig...


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## paulk (Jun 2, 2000)

Aerodynamic studies have shown that the squared off top of the main not only increases sail area, but also improves the airflow vortices coming off the top of the mast so as to provide more force to move the boat forwards. Airplane wings don't end in points, the way standard sails do, because of this. It can create instability in the airflow and cause the plane to stall out. (Trailing points on wings are there for other reasons.) On a boat, a pointed top is easier and cheaper to make, but it is not the optimal shape - thus the squaring off on AC boats.


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## sailingdog (Mar 19, 2006)

A lot of multihulls have a square top main like the AC boats do. Generally, they're only found on faster boats...


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## maestro (May 3, 2002)

*the term is called*

"Fat Head" or sometimes "Flat Head" Mainsails.


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