Measuring the IOM Mainsail

Discuss measuring an IOM and being a measurer

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Joined:11 Apr 2016, 07:23
Sail number:SWE 58
Design:Kantun S
Measuring the IOM Mainsail

Post by magnusmodig » 26 Apr 2016, 13:47

Hello IOM lovers,

Since I am planning to manufacture IOM sails just for fun I would like
somebody to again confirm the exact rule of measuring the main sail.
I find 2 different way of doing it on the internet.

1. To find the leach 1/2 point you use the method of Lester above.
The mainsail leach midpoint is found when you draw a 90 degree
line from the midpoint of a strait line between the forward Head point
and the Clew point.

2. The leach 1/2 point is found as the mid point if you fold the sail holding
the aft Head point and Clew exactly aligned. This is the exact leach 1/2 point

Whick one is the correct one ?
Since the IOM mainsail leach does not bend much the result is almost
the same. The difference is only a few millimeter.
When I measured my existing sails they were approved with either
When I got my sails approved by a measurer guy he used method 2.

Still I would like someone here to confirm what method 2 SHOULD be used.

I put this question on the international IOM facebook group.
I though I would get the correct answer within 15 minutes.
NOBODY answered !!!

Thanks in advance
Magnus Modig

CHATIN Achille
Joined:19 Feb 2005, 21:11
Sail number:FRA 16
Club:CV Cazaux Lac
Location:Bordeaux FRA

Re: Measuring the IOM Mainsail

Post by CHATIN Achille » 09 Jun 2016, 10:19

Last but not least, as there is no answer, here is mine with little experience even if I am not an official ISAF measurer ;-)

As far as I know, Method 1 is the right one. Then to find 1/4 points you repeat the same method from the 1/2 origin founded on the edge of the sail.

Is that clear enough ?


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