February 28, 2012
Although they're called "vertical battens," these long tapered battens in roller furling blade jibs aren't really vertical. They're parallel to the luff so that the jib can roll smoothly without removing the battens. But why use battens at all? What's the advantage? Improved performance and versatility mostly. A surprising number of our cruising customers choose roller furling jibs over larger overlapping genoas, sacrificing light air boat speed for all around versatility and convenience. For a short-handed crew, a non-overlapping headsail is a cinch to tack. Designing the jib with a straight leech can add up to 10% sail area depending on the aspect ratio of the sail and improves twist, both features that can improve the bottom range of the sail. Battens are necessary to support a straighter leech and prevent it from flapping. Additionally, the narrow head angle of a jib can cause the top of the sail to become very tubular with a hooked leech. Battens prevent the leech from hooking and allow us to design a fuller jib with greater low end "punch" than we can without battens. The result is a sail that simply makes it easier to get out and go sailing.
February 15, 2012
I really like square-top mainsails. There's more to a square-top main than increased sail area . . . improved light air performance and improved heavy weather boat handling all in one package. What's not to like?
In light wind there can be a pronounced wind gradient from the deck to the top of the mast. Wind speeds increase with distance off the water, but the boat speed is the same from the water line to the tip of the mast. The result is that the top of the mainsail is in a constant velocity lift relative to the foot. In order to trim a mainsail to a multitude of different wind angles (the velocity lift increases with distance from the deck), you need twist . . . the top of the sail should be eased relative to the bottom of the sail. A square-top mainsail twists much more easily than a conventional pin-head mainsail when the mainsheet is eased. Imagine twisting a sheet of notebook paper. Now imagine twisting a triangle. Not so easy to twist the triangle is it?
A square-top mainsail has the advantage in heavy winds for much the same reason. When a puff hits, the top of the main deflects and quickly opens the leech and unloads the sail. The sail reacts faster than the crew can ease the mainsheet. Watch the mainsail react to a puff starting at the 32 second mark in this YouTube video of Hydroptere:
Square-top mainsails aren't for everyone, however. Racing handicaps limit mainsail head width and a backstay is certainly incompatible with a square-top. The angle of the top batten also complicates things by making it necessary to detach the head to fully douse the sail, but this can be mitigated with quick release pins and the like.
Although limited to multihulls and certain other specialty boats (all favorites of MSP), the technology and outside-of-the-box thinking behind square-top mains can lead to improvements in even our more traditional mainsail designs.
February 09, 2012
The first steps in creating a sail here at Maine Sailing Partners take place in the virtual world - the world of sail design software. Here is a quick visual overview of the design process, in this case for the mainsail of a 36' racer cruiser:
Step one: develop the basic outline of the sail.
February 02, 2012
Interest in code zero sails has grown steadily since they first appeared in the 1997/98 Whitbread as light air, close reaching sails. Their relatively flat cross-sections and large overlap make them especially effective from about 45 to 75-degrees apparent wind angle. No longer considered just a light air sail, a code zero can be used anytime the addition of more horse power can make the boat go faster. This is a narrow niche for some boats, but there are many boats that can benefit from additional sail area when close reaching.
To prevent sailmakers from building oversized genoas, PHRF considers a code zero a spinnaker so the mid-girth must be at least 75% of the foot. PHRF also penalizes boats that carry code zero sails - 6 seconds per mile for boats that carry genoas with LPs of less than 130% of J and 3 seconds per mile for 130% or greater. This pretty much limits the usefulness of code zero sails to long reaching races where the improvement in performance overcomes the penalty.
It's a different story with cruising boats where there are no such restrictions or penalties. Here we can take advantage of innovations in code zero laminates, continuous line furlers, and anti-torque luff ropes to make sails that don't comply with the racing rules and can't be penalized but are as easy to use as roller furling genoas and very effective windward reachers.
Finally, there is a loop hole if you race a classic yacht in CRF regattas like the Eggemoggin Reach Regatta. Provided your boat is already rated for a spinnaker, these kinds of sails are treated as a spinnakers no matter what the cut and without penalty provided they aren't set on a permanent stay. Such a sail could be devastatingly effective anytime it's too tight for a spinnaker but you need more power than you can get from the genoa.