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## Catboat Sail Trim 

## © Sailing Magazine, January 2007 

## How ‘deep throat’ can give better performance in a single-sail, gaff-rigged boat 

n many areas of the country, the traditional gaff-rigged catboat is seeing a comeback. They are stable, easy to sail and fun to race, with fleets sailing strong in Barnegat Bay, Cape Cod and in Florida. In a classic gaff-rig the sail controls are simple, but the essentials of sail shape remain the same as in contemporary three-sided racing sails. A properly managed four-sided gaff mainsail is very responsive to sail shape efforts, and the resulting increase in performance is astounding. I 

It is important to approach the problem of sail shape by focusing on the end result: The shape of the sail. All of the controls effect changes in the three components of shape: angle of attack, draft and twist. With a four-sided gaff rig, there are limited controls, so compromises have to be made. First we will discuss the three components of sail shape, then speak to specific trim suggestions for various points of sail and wind condition. 

## Angle of attack 

The mainsheet is the only sail control for bringing the mainsail to the proper angle of attack with the apparent wind. This is the familiar easing out or bringing in of the boom to attach airflow to the sail’s surface. With time in the boat you will develop a feel for when the boat is performing well, however, you will need telltales to actually see the wind on the sail. 

Telltales should be mounted on both sides of the main well back from the mast as well as on the leech. Usually four sets of telltales are sufficient; 

two above the throat and two below the throat, while only two are needed on the leech. Be sure to offset the starboard and port telltales from each other so you can tell them apart when the sun is behind the sail. Color-coding is also helpful. 

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The gaff-rigged catboat sail is very forgiving and generally has a wide groove upwind and down, making it very easy to sail. However, to get the best performance close-hauled, you need to sail on the edge of the groove closest to the wind. This is a very narrow part of the groove where the windward telltales should be lifting 50 to 80 percent of the time. It takes a lot of concentration and practice to stay in this narrow slot of performance through the constant changes in wind direction and strength. 

## Draft 

Draft is the curvature of the sail, described as both the position of maximal depth along the length of the sail and how deep the curve is relative to the length of the sail. 

