Square top mainsails on cruising yachts

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Ric

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The latest aluminium cruising yacht from Alubat - the Mortain & Mavrikos designed Ovni 400 has a lot of unusual features, amongst them a square top mainsail. Just how practical is this going to be on an offshore cruising yacht?

The illustrations seem to suggest that it is a conventional rig, with at least one backstay, so presumably every tack and gybe will require dropping the main to get the head under the backstay?

https://www.alubat.com/ovni-400
 
Perhaps running backstays will be incorporated in the rig,

Sound science behind tip losses at the head but questionable for a cruising yacht.
 
Ric said:
The latest aluminium cruising yacht from Alubat - the Mortain & Mavrikos designed Ovni 400 has a lot of unusual features, amongst them a square top mainsail. Just how practical is this going to be on an offshore cruising yacht?

The illustrations seem to suggest that it is a conventional rig, with at least one backstay, so presumably every tack and gybe will require dropping the main to get the head under the backstay?

https://www.alubat.com/ovni-400
Click to expand...

Send Alubat an e-mail and ask them? Then tell us ;-)
 
Presumably you hoist the classic main if you anticipate tacking or gybing?
People have cruised the world with 'maxi roach' mains which need to be reefed to tack or gybe.

Perhaps you have toview the full main as something you'd only set on a long leg in fair weather?
Like a gaffer might view the tops'l?
Most of the time where you're going to tack or gybe more than once a day, you'd reef the main?
 
lw395 said:
Presumably you hoist the classic main if you anticipate tacking or gybing?
People have cruised the world with 'maxi roach' mains which need to be reefed to tack or gybe.

Perhaps you have toview the full main as something you'd only set on a long leg in fair weather?
Like a gaffer might view the tops'l?
Most of the time where you're going to tack or gybe more than once a day, you'd reef the main?
Click to expand...

A polite correction.. gaffer topsls are definitely used on short runs and in poor weather, they are what you might call 'white sails', not an exotic special add-on (such as an assymetric for example).
Back to the OP, square topsls used to be if not popular, then at least not unusual for tradewing cruising, more so in the States I think, but have mainly fallen out of favour, obviously because of the major faff factor, plus modern trends.
 
Ladybirdgaffcutter said:
A polite correction.. gaffer topsls are definitely used on short runs and in poor weather, they are what you might call 'white sails', not an exotic special add-on (such as an assymetric for example).
Back to the OP, square topsls used to be if not popular, then at least not unusual for tradewing cruising, more so in the States I think, but have mainly fallen out of favour, obviously because of the major faff factor, plus modern trends.
Click to expand...

The OP is referring to a mainsail with a flat top, i.e. a rhomboid shape,held open by a flexible springy device. You will see these on high tech racing yachts.
 
I wonder how much extra speed you get.

The winglets on aeroplanes save about 3% in fuel. Maybe a poor comparison, but that is about
an extra .15 of a knot travelling at 5k for a sailing boat. Is it worth it ? Yes................. :)
 
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Ric said:
The latest aluminium cruising yacht from Alubat - the Mortain & Mavrikos designed Ovni 400 has a lot of unusual features, amongst them a square top mainsail. Just how practical is this going to be on an offshore cruising yacht?

The illustrations seem to suggest that it is a conventional rig, with at least one backstay, so presumably every tack and gybe will require dropping the main to get the head under the backstay?

https://www.alubat.com/ovni-400
Click to expand...

Are you sure it has a backstay as if fitted with swept back spreaders, it may not need a backstay at all. A number of cruising yachts like the American Hunters do not have backstays.
 
I suspect that when close hauled upwind the sail does not need to pass outside the widely spaced twin backstays. If that is the case you would still need to lower the sail if gybing on a downwind course, or to set the boom well out for nicer points of sail than bashing upwind. To my eye the yacht looks ugly, and I much preferred the shape of older Ovnis, which are nice solid boats.
 
A flat topped main sail is not to be confused with winglets on aeroplane wings. Indeed a falt top sail will lose efficiency from wind flowing from one side to the other over the flat top. (compared to a triangle top)
The flat topped main sail is used to give more sail area at the top for more power. It does mean you cna have a shorter mast but it does mean the drive at the top has the greatest heeling moment.
The question of back stay is handled by not having a back stay or by having a long crane (extension of the top of the mast backwards coupled with a "flicker". This is a fibreglass bowed spring on the back stay which flicks the back stay outwards to clear the sail when back stay tension is taken off. So like runners you still have to adjust for a tack or gybe. Not pretty for a cruising boat. ol'will
 
A flat topped main will require a lot of attention to how the sail is set up wind. An understanding of sail twist would be essential.
It would require a good vang system along with a strong boom & properly set up traveler etc.
Just hauling the main sheet in & forgetting it would not get the best from the sail & personally I could not see it being of benefit to a cruising boat. The batten etc at the head would be a constant source of wear & the sail material would have to be a laminate to resist the stretching. Although laminates are improving I am not sure that they are the best for long term cruising although I accept that cruising laminates are becoming more of a norm.
I would expect that the weight of cloth, along with battens, cars etc aloft would be higher in this type of sail.
One advantage would be the tendency for the sail to twist off in a gust. However, the crew would have to react quickly, otherwise the advantage would be lost & that is not a cruising sort of reaction
Lowering a sail to perform a manouver is a strict no no, so I would expect to see a rig without a single backstay but possibly runners to support the mast. Swept back spreaders (like those used in backstay less rigs) are not really good for long term cruising due to sail wear from spreader ends.
Flick up masthead systems really only handle smallish roaches in sails further down the leech. They do not deal with a sail where there is a substantial area of sail in the head because ( as far as I am aware)they cannot reach out several feet.
So a flat head sail may be good for racing but as a cruising sail it would be strictly off the wish list
 
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Square top mainsails have undoutably a performance, long term shape holding and ease of sailing over a pin top but are more difficult in manoeuvres and storage.

A square top allows you to have a flatter sail at the top, thus meaning your flying shape stays better for longer.

When sailing it will produce more drive with less heel and will respond much better in gusts and be overall much much easier to trim.

The Ovni will have twin backstage which will be useful for forestay tension upwind but not critical to be on during manoeuvres. Jeanneau and others have been supplying boats without backstays and squaretops for a while now

The main drawback on the square top is that due to the gaff batten it does not show away flat without un-pinning the head.

If some one was planning on doing lots of short local sailing with a aim to get out on the water quickly then the pin top is great and simple but for long distance cruising the square top does provide a much better sail and a much more enjoyable performance.
 
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