Hi:

I tryed to post this at the IOMICA forum, but it is quite technical and have been waiting for days they process my registration in order to post, but that has not happended yet.

I wonder wich one is the benefit of using flat rigging wire in a IOM sailboat. I use 0.5 mm stainless steel round wire but at Barbados World Championship seems that everybody was rigging with flat SS wire. I mean 0.9mm thick x 0.25mm.

I Just can guess that will affect the curve in the mast...or give more stiffness to the mast...any input will be useful.

Tato Lazo.

The principal advantage of a flat wire is there is a little less drag.
Possibly it is also less likely to break than a stranded wire.
I don't know whether it is more or less likely to kink than ordinary stranded wire.

SailsEtc sells the flat stainless steel wire and it does not seem too expensive, so why not use it for shrouds, jib topping lift and perhaps backstay?

I don't understand why you think it will alter the stiffness of the mast.

The flat wire might improve tacking ability by reducing forward surface area by a few square millimetres while crossing the headwind.
That, and it probably looks cooler.
When Lotus had an F1 team, legend says that Colin Chapman would start development by asking his designers what unfair advantage they could use in the coming season. This could fall into that category, but any advantage will probably be negated in identical boats by a better skipper.