Sail Measuring


You will notice, as you read the sail listings, that many sails have no boat class shown. This is simply because we just do not know. If all three edge dimensions are appropriate, the sail will fit. A sail does not have had to be made for your class boat to fit and work well. For nearly 40 years, we have gone by this principle and it has worked very well.
Measuring Your Boat Remember, every boat has maximum sail dimensions that cannot be exceeded. Establish the I, J, P & E for your boat, also the Py and Ey, if yawl or ketch rigged. It is a good idea to measure, to confirm your boat is rigged to specifications, as many boats are re-rigged or the specifications have been changed by the manufacturer. CAUTION: When measuring, ease up against mast top sheave; do not cause “jam.”

The P and E ( or B) refer to the mainsail luff and foot respectively. You will want to check if you have a tack setback; if so, note this dimension. E = setback and actual foot of sail. Also, check to see how much the luff and foot can vary; note the travel of the outhaul car and the gooseneck fitting if it slides. Now that you have found the minimum and maximum luff and foot dimensions, check the leach dimension. Hoist your tape measure on the main halyard and measure to the outhaul fitting. Remember, too long a leach will cause a droopy boom. Confirm the boom will clear any special fittings you have, such as boom gallows, dodger, etc. Do note the minimum and maximum dimensions acceptable to you.

Jibs and Genoas
The I and J are the controlling dimensions for headsails. The luff of the working jib is usually 80% to 90% of the I. The foot usually overlaps the mast by one to two feet. The leach is determined by the location of the jib lead block. See the paragraph below for “trying on sails.” In many cases, the best way to find the leach and foot dimensions is this trial method. 150% and larger genoas are usually full luff sails. The I on many boats equals the maximum luff, but it’s best to measure to insure a proper fit. Hoist your tape measure on your regular genoa halyard and measure to your regular tack fitting. If you want a 150% genoa, measure 1.5 x J from the tack fitting to the rail. Working from this position establish the minimum and maximum leach and foot dimensions. Again, the trial method works best. Keep in mind your sheet lead block positions.

If you are racing, we urge you to check your class rules on the allowable spinnaker size. Some racing classes, such as Lightnings, Solings, etc. have very strict rules. Most cruiser-racer classes use the I.O.R. rule. This rule allows the spinnaker luffs (leaches) to be a maximum of 95% of the square root of (I 2 + J 2 ). The sail width may not exceed 1.8 x J. The spinnaker pole length should equal J. Larger sails can be used, but expect a rating increase. Many boats that do not race like to use spinnakers. The rule of thumb for the spinnaker size is the luffs = I. The foot should be between 1.6 x J and 2 x J. Many cruising boats are now using “Poleless Spinnakers.” The luff on poleless spinnakers should not exceed the I or the full size genoa luff. The foot should be between 1.6 and 1.8 x J. The leach is usually 90% of the luff. No spinnaker pole is used with these “Poleless Spinnakers.”

To “TRY ON” any sail on the list, tie three ropes together to the exact three edge dimensions of the sail. Hoist the “sail” outlined by the ropes. If a jib or genoa, this will include putting a sheet rope on the ”clew.” If the “pretend sail” can be sheeted in so that ropes representing the leach and foot can be pulled taut at the same time from your lead block, the ACTUAL SAIL should fit OK.

Remember all dimensions shown on the list are fully stretched, as would be the sail when sailing.

NOTE: There is a maximum dimension for any sail that you can use on your boat. The boat itself is a limiting factor. The minimum dimension can be your decision, based on many facts, the sails available or the price.

Our staff has many years of sailing experience. If you have any question, please let us know.