I want to measure the total area of the spinnaker that came with my boat so I can compare mine with those of others with the same boat, and the area specified by the boat's designers. What are the standard measurements I need to make, and how do I do the calculation? Thanks, Neil
Measuring spinnakers
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mid-girth
The main measurement is the foot, which you translate into percent of J. My asymetrical cruising spinnaker, for example, is 165% of J, while most racing spinnakers are in the 180-185% range. The second measurement would be the mid-girth, which is the distance between the half-point on the luff to the half-point on the leech. If the mid-girth is larger than the foot, you've got a sail designed more for downwind conditions, one which will usually have larger shoulers. If the mid-girth is smaller than the foot, you've got a sail designed more for reaching conditions, one with less power for the type of DDW sailing done in round-the-buoy racing, but which will point higher on a reach. These measurements apply equally to symetrical and asymetrical kites. Total area is not a significant measurement, because light-air spinnakers are often smaller than heavy-air chutes. This is because the spinnaker is a sail that supports its own weight, via the shoulders, which means that a light-air sail needs to be able to float up out of the mainsail's shadow. Total area, therefore, is both a function of fabric weight and designed angle of attack. The first thing to understand is that there's no such thing as an all-around spinnaker for all conditions. Start with the type of sailing you intend to do, factor in the conditions under which you'll be flying the chute, and proceed from there.
The main measurement is the foot, which you translate into percent of J. My asymetrical cruising spinnaker, for example, is 165% of J, while most racing spinnakers are in the 180-185% range. The second measurement would be the mid-girth, which is the distance between the half-point on the luff to the half-point on the leech. If the mid-girth is larger than the foot, you've got a sail designed more for downwind conditions, one which will usually have larger shoulers. If the mid-girth is smaller than the foot, you've got a sail designed more for reaching conditions, one with less power for the type of DDW sailing done in round-the-buoy racing, but which will point higher on a reach. These measurements apply equally to symetrical and asymetrical kites. Total area is not a significant measurement, because light-air spinnakers are often smaller than heavy-air chutes. This is because the spinnaker is a sail that supports its own weight, via the shoulders, which means that a light-air sail needs to be able to float up out of the mainsail's shadow. Total area, therefore, is both a function of fabric weight and designed angle of attack. The first thing to understand is that there's no such thing as an all-around spinnaker for all conditions. Start with the type of sailing you intend to do, factor in the conditions under which you'll be flying the chute, and proceed from there.
Sail Care Says
Measure the foot x height x 80% = square foot thats what they have for measuring a spinnaker. I don't know how accurate that is I'm assuming this measurement is for a radial spinnaker from looking at the picture in the sailcare catalog. I know on my North Sails Spinnaker it is written in ink at the top of my sail with a date of manufacter. Tim Welsh H34 AKA Cabo Wabo
Measure the foot x height x 80% = square foot thats what they have for measuring a spinnaker. I don't know how accurate that is I'm assuming this measurement is for a radial spinnaker from looking at the picture in the sailcare catalog. I know on my North Sails Spinnaker it is written in ink at the top of my sail with a date of manufacter. Tim Welsh H34 AKA Cabo Wabo
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