Originally Posted by Brent Swain
A fractional rig makes no sense for a cruiser.
Brent, From earlier posts I understand that you are not a fan of fractional rigs for cruisers, but I suggest that you are mistaken when you flatly say that a fractionally rigged sloops makes no sense for a cruiser. At least for many cruisers, especially those interested in performance and ease of handling, a modern fractional rig does make sense. These days, most new cruising designs employ a fractional rig for a range of reasons.
Generally, fractionally rigged sloops are generally closer winded and easier to handle because their smaller jibs and larger mainsail sailplan are easier to power up and down. Without a jibstay to drag the Genoa across, sloops are generally easier to tack. With less hardware fractionally rigged sloops sloops are less expensive to build.
Their smaller jibs are easier to tack and in a building breeze, they are easier to depower and then they reef down to a snug masthead rig. Because virtually all boats develop some weather helm with heel angle, reefing the mainsail, while leaving the jib, makes sense in terms of balancing the helm. But also because the jib represents a smaller portion of the overall sail area, one jib can often function across an extremely wide range of windspeeds. Fractional rigs generally place a lower stress on their hulls and often get by with lighter rigging and hardware for an equal structural safety margin.
One of the major advantages of a fractional rig is the ability, especially when combined with a flexible mast, to use the backstay to control mast bend and sail shape. Increasing backstay tension does a lot of things on a fractional rig: it tensions the forestay which in turn flattens the jib. Increasing backstay tension induces controlled mast bend, which flattens the mainsail and opens the leech of the sail. This allows quick depowering as the wind increases and so allows a fractional rig to sail in a wider wind speed range without reefing, or making a headsail change than a masthead rig, although arguably requiring a bit more sail trimming skills.
In the past fractional rigs used to require running backstays. But today better spar materials and design approaches have pretty much eliminated the need for running backstays. That said, fractional rigs intended for offshore use, will often have running backstays that are only rigged in heavy weather once the mainsail has been reefed. The geometry of these running backstays typically allows the boat to be tacked without tacking the running backstays.
Originally Posted by Brent Swain
Overly asymmetrical looks like poor directional stability. A couple of dagger boards aft, at an outward angle may help.
I am not sure whether the 'overly assymmetrical' comment was directed towards the hull or rig. In terms of the rig, the fractional rigs allow the center of effort to be moved slightly further forward in the boat, and that allows the center of resistance of the keel to be located further forward so that there is a greater separation between the keel and the strut and rudder, improving diectional stability.
In terms of the hull being assymetrical, I have not run any detailed numbers, but I ran a quick calculation at 15 degrees of heel and the center of buoyancy did not move very far foreward, and therefore the boat is not likely to noticably change trim. The waterlines remain fairly symmetrical at that angle of heel as well. There would be some jacking of the rudder at that heel angle but the rudder is reasonably deep and has good surface area so I would not expect the design to be excessively prone to wiping out or broaching.
That said, I ready acknowldge that I am an amateur, and this was not drafted on software that allowed quick calculations at various heel angles. If I thought that I was actually going to build this boat, I would want to work with a professional yacht designer and would expect the lines to be tweaked accordingly.