# What do you call those square-topped main sails?



## hellosailor (Apr 11, 2006)

I've been noticing mainsails, mainly on racing boats, where the main sail no longer has the usual triangular shape, but the top has been cut off parallel to the foot, typically running what seems like 3-6 feet straight back from the mast.

What do you call that kind of cut?

And HTF does that work? I haven't seen them clearly enough to tell how or if that's supposed to clear a single backstay when the boat is tacking? Or? What goes on there?


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## pdqaltair (Nov 14, 2008)

hellosailor said:


> I've been noticing mainsails, mainly on racing boats, where the main sail no longer has the usual triangular shape, but the top has been cut off parallel to the foot, typically running what seems like 3-6 feet straight back from the mast.
> 
> What do you call that kind of cut?
> 
> And HTF does that work? I haven't seen them clearly enough to tell how or if that's supposed to clear a single backstay when the boat is tacking? Or? What goes on there?


Square top mainsails (yes, that is what they are called).

* Some boats (most multihulls) have no fixed backstay.
* Some use backswept spreaders (B&R rig) and running backstays.

It is also typical that 1-2 battens must be removed before fully lowering. since they run at a sharp upwards angle.

Advantages? Better aerodynamics, lower center of effort for a given area, and better control of heeling in gusty conditions. The down sides are higher fabric stress, cost, and assorted handling complexities. I've had both; if you can fit one and like going fast, you'll like it.

[BTW, classes that can run either refer to conventional mainsails as "pinheads."]


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## hellosailor (Apr 11, 2006)

Thanks, I suspected that, but figured there's always room for magic.
"complexities" Nah. I try to avoid those on boats.


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## Capt Len (Oct 9, 2011)

May be preferred by those with gaffer envy but can't handle the complexity of two halyards.


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## Jeff_H (Feb 26, 2000)

There seems to be two versions of the square top mainsail. The one version is what you see on multihulls and bigger race boats, where the flat top is pretty long, maybe 15-20% of foot. Those either use no backstay or have running backstays. Usually multihulls opt for no backstay and racing monohulls opt for runners. There is a less extreme version of a square head mainsail used on boats like J-70. In the case of this less aggressive square top a 'flicker' is used at the top of the mast to lift the backstay out of the way during a tack or jibe. 

These sails generally have an advantage when reaching since the can add 15-20% to the main sail area. There was a theory that they would help upwind because the upper quarter of the sail would have a more efficient shape with a square head. My sense is that the jury is still out on that. From some of the theoretical discussions that I have read, having a square head does not seem to hurt but it is not obvious that it actually helps. From sailing with them it is a little harder to control twist. 

Jeff


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## hellosailor (Apr 11, 2006)

And a flicker is...? A very slender garden gnome that sits atop the mast and play jump-rope with the backstay? Or some less elegant mechanism?


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## pdqaltair (Nov 14, 2008)

hellosailor said:


> And a flicker is...? A very slender garden gnome that sits atop the mast and play jump-rope with the backstay? Or some less elegant mechanism?


Only useful in marginal cases. Useless with large square top.


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## hellosailor (Apr 11, 2006)

So the flicker is no more active than a garden gnome, it basically is just a masthead crane and a piece of "spring" to hold the backstay away from the mast and sail?

Reminds me of Scheel keels. They were supposed to take over the world.


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## pdqaltair (Nov 14, 2008)

hellosailor said:


> So the flicker is no more active than a garden gnome, it basically is just a masthead crane and a piece of "spring" to hold the backstay away from the mast and sail?
> 
> Reminds me of Scheel keels. They were supposed to take over the world.


OK. I'll watch for you in my rear view mirror.:wink


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## Telesail (Dec 28, 2011)

In terms of sail handling, the diagonal battens can be handled automatically with the right mast track equipment. That has resolved the toughest problem. Square top mains have an advantage of spilling wind in a sudden gust (thank you for correcting my English) when compared to a conventional sail. 

The complexity of running back-stays can be limited since upwind, the boom does not shift enough to require immediate adjustment to the runners and with the wind abaft the beam, it is only one additional step to Gabe - while centering the boom to pull the runners hand tight and release the working stay,

With the proper design of the square top main, the runners do not need to come into play when you have your first reef and for many conditions, the drive comes from the head sails and the main is mostly used for controlling heel to maximize performance. However, unless there is a specific reason to go fast, the KISS principle seems best and it would be hard to justify a square top main - The extra cost is certainly not negligible!


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## pdqaltair (Nov 14, 2008)

For most boats, it's a matter of what they were designed for. 

The advantages are in aerodynamics and gust (not squall) control. In fact, the first place they were used was wind surfer sails, where automatic gust control in waves is critical. Thus, they make sense in a lot of performance boats. Multihulls are natural, since backstays are not needed. They make a lot of sense on racing multis since they are pressed hard and heel control is vital. 

That said, I think they are often a fashion accessory on cruising boats. Cruising multis are better served by a foot or two more mast and large roach (I've had both on the same boat). The sail holds up better and is easier to hoist. But a square top looks cooler and so they sell. it is often said that a square top adds sail area, but compared to a very full roach, there is often no difference.

Time will tell.


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## jblumhorst (Apr 14, 2002)

Jeff_H said:


> There seems to be two versions of the square top mainsail. The one version is what you see on multihulls and bigger race boats, where the flat top is pretty long, maybe 15-20% of foot. Those either use no backstay or have running backstays. Usually multihulls opt for no backstay and racing monohulls opt for runners. There is a less extreme version of a square head mainsail used on boats like J-70. In the case of this less aggressive square top a 'flicker' is used at the top of the mast to lift the backstay out of the way during a tack or jibe.
> 
> These sails generally have an advantage when reaching since the can add 15-20% to the main sail area. There was a theory that they would help upwind because the upper quarter of the sail would have a more efficient shape with a square head. My sense is that the jury is still out on that. From some of the theoretical discussions that I have read, having a square head does not seem to hurt but it is not obvious that it actually helps. From sailing with them it is a little harder to control twist.
> 
> Jeff


On most newer trimarans and catamarans, it's pretty common to have the head width about 45% of the foot, E. Many of the newer racing multihull designers are building heads as big as 60% of E. These boats don't have backstays.

If we're retrofitting the square top to an older design, we usually keep the Sailarea the same . The foot gets shorter and the head gets wider.

I notice that, all things being equal, l need to reef earlier when I put a square head mainsail on a boat that previously had a pinhead mainsail. That's not surprising, because the area is up higher.

The diagonal battens are a lot of bother for a cruiser because you can't lower the main all the way ithout removing either the batten or the top luff slide. A more convenient design for a cruiser would be a fat, elliptical shaped head with all the top battens parallel to the foot.

But there are fancy ways to rig the head to a head car to allow the sail to drop. For example the Lagoon catamarans.

http://www.cruisersforum.com/forums/attachment.php?attachmentid=136233&d=1479230873

Judy


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## pdqaltair (Nov 14, 2008)

jblumhorst said:


> On fast trimarans and catamarans, it's pretty common to have the head width about 45% of the foot, E. The area stays the same . The foot gets shorter and the head gets wider. A few newer racing multihull designers are building them as big as 60% of E.
> 
> I notice that, all things being equal, l need to reef earlier when I put a square head mainsail on a boat that previously had a pinhead mainsail. That's not surprising, because the area is up higher.
> 
> ...


The other thing I have noticed is that twist control can be weird in some lighter conditions; a puff twists it off a little, and then it springs shut, hooking back too far. Not generally a problem and a reasonable tradeoff, all things considered.


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## Telesail (Dec 28, 2011)

pdqaltair said:


> For most boats, it's a matter of what they were designed for.
> 
> ..... They make a lot of sense on racing multis since they are pressed hard and heel control is vital.
> 
> ...


Assume you mean racing monos  ... However, I agree with the point about square tops being a fashion accessory on cruising monos. The development of systems to automatically handle the head battens may neutralize the argument in favor of a large roach but the latter will almost always make more sense when short handing.


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## maw (Nov 29, 2018)

Telesail said:


> Assume you mean racing monos  ... However, I agree with the point about square tops being a fashion accessory on cruising monos. The development of systems to automatically handle the head battens may neutralize the argument in favor of a large roach but the latter will almost always make more sense when short handing.


Hi Telesail,
I gently disagree, a square roach on a cruising boat works well. There isn't any issue with the battens on mine, let go of the halyard and the main drops into the boom bag. The head board moves away from the mast as you drop, the end result it lays neatly on the boom when you zip up the bag.
I wouldn't convert every pin head boat though unless it was really begging for it or the performance guarantee was there. Most pin head boats have a taller rig in comparison to gain the m2 required, so a conversion would need some thought. Standard? Works beautifully.


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## Samw90 (Mar 29, 2019)

I know that on historical ships they're called "top gallant" or "royal gallant" sails, but not sure if that applies to modern racing boats.


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## Jeff_H (Feb 26, 2000)

Samw90 said:


> I know that on historical ships they're called "top gallant" or "royal gallant" sails, but not sure if that applies to modern racing boats.


Historically that sail would not have been called a top gallant. The top gallants were square sails and the sail in question is a square top fore and aft Bermuda rigged sail with a flat top. In concept historically the closest thing I can think of in profile might be to a Dutch gaff sail and even those are not all that close. In any event they are called square head mainsails. The normal Bermuda mainsails that we all grew up with are now called 'pin heads'


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## colemj (Jul 10, 2003)

There is a third type on a lot of catamarans between a pinhead and square top - elliptical top. This type has a short horizontal or slightly angled batten to hold additional roach vs. a pinhead, but not a completely square top with an angled batten. The headboard doesn't need to be released to stow it. I don't know if "elliptical" is the exact term for it, but I think I heard Bob Patterson from Neil Pryde use that term once.


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## Samw90 (Mar 29, 2019)

Jeff_H said:


> Historically that sail would not have been called a top gallant. The top gallants were square sails and the sail in question is a square top fore and aft Bermuda rigged sail with a flat top. In concept historically the closest thing I can think of in profile might be to a Dutch gaff sail and even those are not all that close. In any event they are called square head mainsails. The normal Bermuda mainsails that we all grew up with are now called 'pin heads'


Oh cool. yeah i had my fore-and-aft mixed up with square-rigged.


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## outbound (Dec 3, 2012)

Is there any advantage compared with a short gaff? Have seen gaffers where two halyards were not employed. Of course it means full hoist isn’t to the mast top.


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## Jeff_H (Feb 26, 2000)

Rigs with battens and very full roach sails have been around for a very long time, as have rigs with short comparatively short gaffs and yards. These rigs have generally been very effective reaching rigs but not so great upwind. Typically they have been comparatively low aspect ratio sails intended to propel heavily laden working watercraft.

With the advent of comparatively light and strong battens, low stretch sail cloth, better sail shape control, stiffer stronger boats, and the very high stability of these modern designs, square head rigs could be produced which had the reaching advantages of a gaff rig, combined with the higher aspect ratios and efficient sail shaping of a modern Bermuda rig. 

The use of cantilevered battens at the head of these sails make gaffs (even short ones) unnecessary. Gaffs offer no real advantages over using battens to create a square top plan form. But since the cantilevered battens behave integrally with the sail, twist is more controllable, and they are much lighter than a gaff. 

Jeff


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## SanderO (Jul 12, 2007)

So when the designer of the boat designs the rig and sail plan... the boat has to sail in all wind conditions and sea conditions. What wind speed range is the basic unreefed sail designed for in a cruiser, a racer... and so on. How is the lift computed? This obviously determines heel and keel design. My hull is offered either a masthead rig or a 7/8 fractional. I assume each sail plan develops the same forces???? What are the advantages of these two approaches?

Have the fractional and find reefing the main is easier works better than "reefing" the RF headsail. The boat seems to almost sail on main alone.


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## hellosailor (Apr 11, 2006)

Pinheads, really?
What a curious malapropism, all considered.

The number of angels that can dance on the head of a pin (a classic math puzzle) is not necessarily the same as the number of angels that can dance on a pinhead.

I think I'll just refer to the classic traditional triangular mainsail as a "Brooks Brothers sail" instead.


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