[bobmcgov]

what is to stop this simple 13' sloop from going completely over?

Nothing at all. And it's no big deal. Multis can be a bugger to right from full inversion -- hence the mast floats on some beach cats. But a dink like the Pirateer? It's not much harder than righting it from 90 degrees.

Try to ensure your mainsheet is floppy, which it ought it to be if you rolled it in a gybe or were in the process of blowing it when you flipped. Jib sheets, not so important. In fact, while you are dog-paddling around the upturned hull, try to snag one of those sheets (doesn't really matter which) and toss it over the hull. Flop your body onto the hull after it, grab the sheet, stand as close to one gunwhale as you dare (I like the leeward side, but things will happen faster when they happen) and lean back against the jib sheet. Wait.

And wait. Wait some more. Like hoisting a windsurfer sail, ya gotta give the rig time to move thru the water. Jerky motions don't help. Straight spine, hips in, lean back. Wait. Eventually, the mast and sails will come up to just below water level. Now is the time to dash for the centerboard. Keeping hold of the sheet, get established on the board, lean back against the sheet, and wait. Once the sail sheds its water, the boat will come upright fast. With practise, you should be able to fling yourself over the gunwhale and into the cockpit w/out going swimming again. Bail like hell, get the boat moving, and open the floor bailers if you got em.

I'm about 140lbs & can right the Pirateer's big brother, the 500# Buccaneer, by myself from full turtle. It's takes longer than a Sunfish or Laser and the big cockpit holds a lot of water, but it's not especially technical.