Blue Water Cruising the Cal 31
airdog07 is correct, there are many boats smaller than the Cal 31 which have circumnavigated. And some very small boats have made blue water crossings of both the Atlantic and Pacific. I know of the Cal 20 which was in the race to Hawaii and the West Wight Potter (14 ft?) which sailed across the Atlantic.
The Columbia 26 from the late 60's was also a small boat which has a reputation of being strong and stable in a nasty blow. I had a dock neighbor buy one for a song and fix it up really nice. He sailed it to Cuyler Harbor on San Miguel and, in the hands of the right sailor, it could potentially circumnavigate. Even in the hands of my novice neighbor the boat and crew made it through a really nasty blow coming back to San Pedro from Avalon, Catalina. It is, however, tiny inside with barely seated head room for me.
Then there is the Contessa 26. The Cal 31 isn't a Contessa 26. Not even close. If I had a chance to sail either on a long offshore passage I might hesitate to give up the 6 extra ft (the Contessa is 25.5 lod and the Cal is 31.5) and the speed that comes with a fin keel, also the head room, the interior space, etc. to sail the Contessa. However, the Contessa's a real blue water boat born and bred with a full keel and built like a tank. The mold was taken from a wooden hull and the original scantlings in fiberglass were based on the strength of wood not GRP. It was designed in England where coastal cruising can mean the North Sea. The Contessa (and later J.J. Taylor 26 - the same boat) had a production run in the hundreds over forty years. As they say in the UK, this is a case of "horses for courses."
The Cal 31, and remember, I love mine, was built to be a performance coastal cruiser. Raced on Wednesday night and sailed by the family on the weekends on passages of 20 to 30 nm. She does this VERY well, has done so for 30 years and will, God willing, continue to do so for some time to come. But she was built to meet a certain price point and to sell in quantity. Jensen and later Lear Siegler made 360 of them in four years. These boats spend the vast majority of their lives tied to docks in modern marinas. I would have been very unhappy to have bought the Contessa 20 years ago. It would have been slower, smaller, and in most ways the wrong boat for the sailing I have done. Again, horses for courses.
Another note about the Cal 31 as a world cruising blue water boat: Among the things I would worry about (in addition to those I mentioned in a previous post) it just how well the bulkheads are tabbed to the hull. In the nearly twenty years I have owned my Cal 31 I have never been underway for more than 16 or 17 hours at a time. My usual passage is 4 to 5 hours one way. I do this once or twice a month. So, a single four day passage like non-stop to Turtle Bay on the Baja coast is the equivalent (96 hours) of nearly a year of my ordinary sailing (not counting my annual long term cruise to either San Diego or Channel Islands NP). Time at sea, particularly going to weather will work the bulkhead/hull joint and is something I am now conscious of - preferring to reef early and put less wear on the boat. Should this joint fail while in bad weather (when else would if fail?), the boat could work itself into catastrophic hull failure rapidly.
When looking for inexpensive small boats for world cruising, folks turn to mid to late 60's boats, before Lapworth (may God rest his soul) revolutionized the sailing world with the fin keel, spade rudder Cal 40 that swept the Transpac and many other races, and before builders figured out that fiberglass was stronger than wood and the hulls could be made MUCH thinner. These boats were "built tough" because the builders hadn't yet figured out how to do it any other way.