So with IOM boats carbon masts are not allowed, but are fibre glass masts okay?
Also with aluminum masts has anyone trieg 9.5mm mast I found some tent pole material looks good. They also have tent poles 11 and 12 mm but come in two foot sections, is this class legal or do they need to be one piece?

alluminium alloy or wood is allowed, see , rig section…

-Wis (aka Laurent)

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Please do read the class rules - they are are really not very complicated.

In addition to the mast diameter, you should also check the wall thickness of the section you are considering. I think most IOM masts are about 0.5mm - 0.8mm in wall thickness. The issue is the stiffness of the mast, and therefore it’s ability to accept plenty of backstay tension. Have a look at Lester Gilbert’s site for some information on applying pre-bend to the spar. My “A” rig mast is 11.1mm round with a 0.5mm wall, and is really a bit too light and bendy. The Sails Etc 11.1mm round mast has a 0.7mm wall thickness (this is a popular IOM mast). In my local hardware store there is a standard 12.7mm extrusion that has a wall thickness of 1.2mm - stiff, but IMHO much too heavy to use as an IOM mast.

Unless the 9mm section has extraordinary stiffness, I’d be surprised if it’ll do the job. The rules allow joiners in the mast. The joiner should also be aluminum or wood.

…hope this helps.


This really shouldn’t be an issue, aluminum masts custom made for IOMs are available from a number of suppilers for very nominal charges. Check with Great Basin, Sails etc. for starters. The masts avialable are thin, light, stiff and comply with the class rules.

Great Basin still carrys a 7/16 OD aluminum mast in T-9 temper which is quite stiff, they mat still have some 1/2" in the T-9 also.[8D]