How to calculate the sail size
 

Hi everybody,

I have a sail that I wish to sell, and I'd like to provide the size of the sail ( which I don't know and it's not indicated).

I originally searched online for the methods, which I did not find, so I guessed it was similar to calculate the area of a triangle.

So here is what I came up with:
My sail is 13.5 feet tall, 7 feet at the boom. I converted that to meters which gave me 4.11 meter tall and 2.13 meters at the boom.

After doing the calculation : (4.11*2.13)/2, it comes down to 4.3 square meters.

so I thought my sail was of size 4.3. But someone came and compared what is supposedly a 4.5 sail, and it's half the size of mine.

So therefore, how do I calculate the size of the sail, since apparently it's not what I thought.

Many thanks in advance.
Chris.

Well if the 4.5 is half the size of yours that would make it a 9 meter! But with a 411cm mast that's pretty doubtful :) I'm guessing that the shape of your sail and the 4.5 are quite different, so it's difficult to accurately compare their sizes.

This is probably a pretty old sail? Does it have any full battens; ones that go all the way from the leech (trailing edge) of the sail all the way to the mast?

One minor adjustment would probably be in the mast sleeve - it's probably curved so it's not quite a triangle.

If it's old enough, it might be marked with the area in square feet. Then you can convert using: sq ft x 1.1 = sq meters

You can always just sell it with a picture and the mast & boom measurements.

Drew

Hi Chris, unless your sail is very old fashioned it has not a triangle shape and there is much surface outside. Based on my own sails collection I would suggest a x1.4 factor so ~6.2 m². This been said 4.11 sounds very compact for a 2.13 boom. I have a 7.3 m² sail with same boom length and 4.86 mast luff. What type of sail is yours?

Thanks for the replies.

I think it's somewhat old. I am not the original buyer. And it's a NeilPryde (or something like that).
The battens are not full length (3 in total), and it's not far off from a triangular shape.
I looked everywhere on it, and it does not say anything about the size.

The measurements I took are approximate with a measuring tape, but I mean, in worst case it's an error margin of 1/2 feet.

As for the other 4.5, you could clearly see it had a lot less surface. It was approximately the same luff length, just half the width.

I'll try to post a picture to give a general idea.

did an experiment since i have my sail specs in a spreadsheet

did reverse engineering and discovered luff * boom / 1.5 is REALLY close to sail size

so, in this case ...

4.11*2.13/1.5=5.836 sq meters
rounded up that's a 6.0 sail - make sense ??

Sounds like a 25 year old regatta sail. Short mast and long boom with three short battens. Is the sail all Dacron (no plastic laminate on the sail), with a thick flexible window?

Given the mast and boom sizes, it my be around 5 - 5.5 meters. I still have my 1985 Superlight regatta sail and use it on the original board.

Are there any markings on the main body of the sail (numbers or a design)?

Any pulleys or just a grommet at the foot of the sail?

Joe and Ken, thank you very much.

The sail is pretty much how you describe it, Ken: no laminate, small plastic window, no marking or number, and it's a grommet at the bottom.

Joe, I was dividing by 2, so your 1.5 is probably what I had wrong.

With a visual comparison (from memory) with the 4.5 sail, 5.5 or 6M would make sense.

I'll go with that.

Thanks for all the help, guys!

Chris.

There is an Application on iTunes that gives you the sail size depending on your weight and wind velocity.
The name is Sail Size.. Check it out. They also offer a windows excel program with the same things.
http://www.vims.edu/general/sailpadd...calculator.xls
http://www.vims.edu/general/sailpadd...calculator.xls

Good Lord Sir !
By the sound of your sail, it is more likely you will be paying somebody to take it away !
I recently saw some wallets in Tarifa made from "old sail cloth".
You might do better to "recycle" it some other way.........

Hi
Its a little off topic but a technique I use to compare my sails (from different manufacturers/ranges) is boom length x mast length (in cm) divide by 1000.

A 7 metre comes out around 100. A 5 metre around 70. Its sort of a power index which I find better for comparing sail "sizes" than quoted areas.

See where yours comes out and then work backwards to size.