Since folks crossed the pacific a few years ago with a rowing ship (From Japan to san francisco bay area) and the typical measurements of sailing boats involved with a circumnavigation, is 34 base and I came across individuals cruising the pacific with a 21 base sail vessel, my first sailboat ended up being a 22 footer, I would be tempted to say a 10 - 15 foot sailboat is the tiniest you can get for an important circumnavigation.
The reason why We state that:
1) You will need a vessel with a cabin. So that it can capsize and you may nevertheless endure - at that dimensions you might once or twice - exactly what the heck its less of a deal after you performed when LOL. To my understanding the smallest cabin sailboat is a 15 footer - so you might should grow your very own if you want to get smaller.
2) you'll need some surface area where you could capture enough water starightaway maintain you from dehydration, as you cannot just take adequate fresh-water with you and your solar powered water maker. well you do not want to depend on it 100per cent. Remember a 10-15 base waterline could keep your average rate perhaps right down to perhaps 3 knots - you perhaps on the market for 2+ many years
3) you will require some storage space to keep the very least survival package, an initial help system, several rods to fish and so forth - and you'll need hold a resting bag as dried out that you can - it not only sucks if you should be damp 24x7 for per week or two it might probably allow you to get inoperable :)