As it happened it turned out quite well, the second side was clearly better than the first. I was actually considering using it, until I realised that I'd put the leading edge on the wrong side, and since it is a kick-up rudder, it's not even close to symmetrical. Oh well, you learn.
Things I did learn,
- on the first side you must leave pillars to support it when you flip over to do the second side.
- mill the foil shape from an over long rectangle leaving the ends untouched, then cut the rudder out afterwards.
- small wooden wedges keep the stock hard against the base and give more consistent results.
- two small pieces of perspex set up on a cord hinge run along the rails, avoid bits being kicked everywhere
- cut towards ourself, the sawdust shoots down the channel between the guides to your waiting hoover.
- Make sure the wood is the right way round.
I guess the production run will be better !