The sail old gent who bequeath me that aluminium trimaran that looked more like a pirate ship as gave me a little aluminium sailing dingy.

I've found that my 5.8m winsurfing rig drops straight into the mast track so I'm going to clean the boat up and let my son learn to sail in it.

My question for the brains trust is about the suitability of using that expanding type foam found at Bunnings to refill the cavities under the seats. Is there a particular type that can be used to provide bouyancy?