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Old 01-28-2004
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Sloop vs. Fractional Sloop vs. Cutter

I had written this for another venue but might prove somewhat helpful.


Today these terms are used quite loosely as compared to their more traditional definitions. Traditionally the sloop rig was a rig with a single mast located forward of 50% of the length of the sailplan. In this traditional definition a sloop could have multiple jibs. Cutters had a rig with a single mast located 50% of the length of the sailplan or further aft, multiple headsails and reefing bowsprit. Somewhere in the 1950ís or 1960ís there was a shift in these definitions such that a sloop only flew one headsail and a cutter had multiple headsails and mast position became irrelevant. For the sake of this discussion I assume we are discussing the modern definition of a sloop and a cutter.

Historically, when sail handling hardware was primitive and sails were far more stretchy than they are today, the smaller headsails and mainsail of a traditional cutter were easier to handle and with less sail stretch, allowed earlier cutters to be more weatherly (sail closer to the wind) than the sloops of the day. With the invention of lower stretch sailcloth and geared winches, cutters quickly lost their earlier advantage.

Today sloops are generally closer winded and easier to handle. 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 sloops are less expensive to build.

As you note sloops come in a couple varieties, masthead and fractional. In a masthead rig the forestay and jib originates at the masthead. In a fractional rig, the forestay originated some fraction of the mast height down from the masthead. Historically, sloops were traditionally fractionally rigged. Fractional rigs tend to give the most drive per square foot of sail area. Their smaller jibs are easier to tack and they reef down to a snug masthead rig. Today they are often proportioned so that they do not need overlapping headsails, making them even easier to sail. One of the major advantages of a fractional rigs is the ability when combined with a flexible mast, is the ability to use the backstay to control mast bend. Increasing backstay tension does a lot of things on a fractional rig: it tensions the forestay flattening the jib, and induces mast bend, which flattens the mainsail and opens the leech of the sail. This allows quick depowering as the wind increases and allows a fractional rig to sail in a wider wind speed range than masthead rig without reefing, although arguably requiring a bit more sail trimming skills.

While fractional rigs used to require running backstays, better 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 allow the boat to be tacked without tacking the running backstays.

Masthead rigs came into popularity in the 1950ís primarily in response to racing rating rules that under-penalized jibs and spinnakers and so promoted bigger headsails. Masthead sloops tend to be simpler rigs to build and adjust. They tend to be more dependent on large headsails and so are a little harder to tack and so require a larger headsail inventory if performance is important. Mast bend is harder to control and so bigger masthead rigs will often have a babystay that can be tensioned to induce mast bend in the same way as a fractional rig does. Dragging a Genoa over the babystay makes tacking a bit more difficult and slower. While roller furling allows a wider wind range for a given Genoa, there is a real limit (typically cited 10% to 15%) to how much a Genoa can be roller furled and still maintain a safely flat shape.

Cutters, which had pretty much dropped out of popularity during a period from the end of WWII until the early 1970ís, came back into popularity with a vengeance in the early 1970ís as an offshore cruising rig. In theory, the multiple jibs allow the forestaysail to be dropped or completely furled, and when combined with a reefed mainsail and the full staysail, results in a very compact heavy weather rig (similar to the proportions of a fractional rigged sloop with a reef in the mainsail). As a result the cutter rig is often cited as the ideal offshore rig. Like fractional rigs, cutter rigs intended for offshore use, will often have running backstays that are only rigged in heavy weather once the mainsail has been reefed. Unlike the fractional rig, the geometry of these running backstays typically requires that the running backstays be tacked whenever the boat is tacked.

Cutters make a less successful rig for coastal sailing. Generally cutters tend to have snug rigs that depend on larger Genoas for light air performance. Tacking these large Genoas through the narrow slot between the Jibstay and Forestay is a much harder operation than tacking a sloop. As a result many of todayís cutters have a removable jibstay that can be rigged in heavier winds. This somewhat reduces the advantage of a cutter rig (i.e. having a permanently rigged and ready to fly small, heavy weather jib).

Cutters these days generally do not point as close to the wind as similar sized sloops. Because of the need to keep the slots of two headsails open enough to permit good airflow, headsails cannot be pulled in as far as on a sloop without choking off the airflow in the slot. Since cutters are generally associated with the less efficient underbodies that are typical of offshore boats this is less of a problem that it might sound. Cutters also give away some performance on deep broad reaches and when heading downwind because the Genoa acts in the bad air of the staysail.

There are a couple issues that are rarely talked about. You always hear about the greater flexibility of a cutter rig because the jib can be doused and still use the staysail as a storm sail. While a staysail is generally roughly the size of a stormsail it is generally a more powerful sail made from a lighter cloth than a proper storm sail. If properly cut as a storm sail, the staysail is of little use as a staysail in combination with a jib as it is cut way too flat. Also most boats develop greater weather helm in heavier air. The staysail is generally too far aft to balance the mainsail without a pretty deep reef in the mainsail. In that regard the smaller headsail on a fractionally rigged sloop when combined with a bladed out and reefed mainsail will often have a better balance. Lastly with a cutter there is often conditions where the jib is too large for the wind conditions but simply sailing under the staysail does not provide enough drive. Here the ability of a fractional rig to ''shift gears'' on the fly really comes into its own.

Jeff
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