What are IOM hulls made of?

From a glance at the original rules for the IOM class, it appears the idea was to encourage fiberglass hulls, although metal (unspecified) seems to be permitted.

Is this still the case? Are there any metal hulled IOMs? Anything other than GRP?

Thank you for your insights.


Hulls are fiberglass or wood. Not aware of any metal hulls, but it doesn’t mean there isn’t one out there somewhere…

The benefit of specifying metal in the rules, is that a builder can integrate aluminium into parts of the hull - say as a load-spreading beam or such - without concern about a breach of the rules. It would be an interesting exercise to build a hull in aluminium, but I can’t imagine it being easy, nor do I think I would produce a better hull than the fibreglass and wood alternatives.


are you not aloud carbon fibre hulls at all???

Not in the IOM class

I am no IOM pro at all, but it seems: no carbon in the hulls, though rudder and keels are ok (I hope i am correct on this one)


_/ if it isn’t broken, don’t fix it! _


Correct Wis,

For a chine hull design, it would be pretty straightforward to substitute sheet aluminum for wood.

For a curved skiff hull, or “triangle boat,” it would not be a daunting project. Hulls are basically reinforced a “U”. If you had access to an English wheel, you could also form compound curves.

Finally, if you wanted to industrialize the process, you could job it to a stamping machine. Raising the prospect of IOMs produced like salad bowls.

But the question is, can you make a lighter hull in this way, and thus shift some of that 4 kilograms down to the bulb. The advantage, if any, would be marginal. But it seems to be a class where marginal advantages matter.

In any event, and whatever the outcome, it would be kind of a kick to build a boat with tin snips.

Best, mcg

Ballast ratios are already set by the class rule.
So a lighter hull ends up with lead in its bilge.

A waste of time, then. Thanks for the info. mcg