Re: Is external rudder a good idea?
There is absolutely nothing wrong with having a transom-mounted rudder for racing or cruising, coastal or ocean voyages - and whoever said there was knows nothing of what they speak..
There are major advantages - like less holes in the boat and the ability to repair or jury-rig something without having to haul the boat out to do so - and perhaps some minor disadvantages if you're hanging an outboard on the back also, but from a performance point of view it makes absolutely no difference at all... it simply comes down to personal preference and the abilities of the yacht's designer.
From RFC 1925: "(3) With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead."