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Cmarois
6th July 2010, 11:41 PM
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.

Unregistered
7th July 2010, 12:54 AM
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

Farlo
7th July 2010, 01:03 AM
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 mē. This been said 4.11 sounds very compact for a 2.13 boom. I have a 7.3 mē sail with same boom length and 4.86 mast luff. What type of sail is yours?

Cmarois
7th July 2010, 04:46 AM
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.

joe_windsurfer
7th July 2010, 07:32 AM
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 ??

Ken
7th July 2010, 09:47 PM
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?

Cmarois
7th July 2010, 11:25 PM
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.

nonopr
7th July 2010, 11:55 PM
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/sailpaddle/sailcalculator.xls
http://www.vims.edu/general/sailpaddle/sailcalculator.xls

Unregistered
8th July 2010, 04:23 AM
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.........

Floyd
8th July 2010, 05:01 AM
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.

Unregistered
8th July 2010, 04:00 PM
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.




580*210 /1000 = 121.8
500*244/1000 = 121.8


475*210/1000 = 99.75
445*224/1000 = 99.75


nah forget it stick with area......

Farlo
8th July 2010, 09:20 PM
Hi Floyd, I've done similar statistics on my sails collection, basically calculating the ratio between claimed surface and inner triangle area. Overall I've found numbers around 1.4 with wave sails having (logically) a smaller ratio than freeride/race sails. But also it can vary sensibly from one brand to another, one model to another, and even one year to another. Sail surface seems to be affected by same marketing tricks than board volume.

Floyd
8th July 2010, 11:16 PM
Hi Farlo
Yep;its why I started with the calculations.
I have 2 "5 metre" sails.
A Gun MC wave and a NP Combat. The Combat is lots better in strong winds; the Gun loads more bottom end.In theorey both 5 metres but on my scale the MC comes out around 75; the Comat around 70.(Similar aspect ratios too !!!) So obviuosly the Combat is better in strong winds ; its smaller !!! (Both 5 metre sails can go in same quiver !!!)

My biggest sail is 7.5 metre (107) but compares favourably with most 8 metre sails on my scale. My 7 (in theory only half a metre smaller) scores only 97; so it fits in my quiver.
Floyd

Farlo
9th July 2010, 12:49 AM
See what you mean. I have a Naish 6.6 hardly larger than an older North 6.0 but with much more grunt. Looking at them you would not say one has 10% more surface. The 6.6 is probably exaggerated to reflect the sail power, so that it fits nicely in the product range compared to other sails.