He's the IT director. He's on the board and he's responsible for the company IT. It's his role to decide on the direction of IT for the organisation and how things should be done. It is your role to implement that decision. Certainly you should be giving advice and, if you see a potential problem, you should raise it. But, if he chooses to ignore you advice and warnings then that's his perrogative and, ultimately, his responsibility if it all cocks up.

Depending on what sort of a bloke he is you may want to cover your self by sending concerns via email so you can demonstrate later that you were dilligent if he turns out to be the sort that blames his mistakes on those below him. Be freindly rather than officious about it, though. You're just raising a concern in the normal way. The fact that it happens to leave a trail you can use to cover yourself later is entirely incidental.

It can be soul destroying to work for someone you think is taking the wrong aproach (it's the main reason I left my last job) but if you try and 'take them on' in some way then you are bound to lose. The only people you could raise your concerns with are the rest of the board and I doubt very much they'll respect your opinions over his - after all, they hired him, rather than you, to make these decisions. If you really feel you can't work under him then move.