Originally Posted by Boasun
Stay close to shore on a hot day and deliberately plunk the boat over and right it. Just be sure that there is more water under the boat than the mast is long. Rotate all of your family through this drill as the person in charge.
This way you will see what comes loose and starts to float far far away from you.
Take a look at these pics. Mistral 16 sailboat for sale
You can see that the boat has a cover over the aft compartment that is missing from this boat. Now I've not had Mistral a but I am familiar with the boat it's cloned from, the Wayfarer. The Wayfarer's aft compartment is crucial for buoyancy. In fact they won't let you race unless you have had a leak test done on the aft compartment.
I also believe that the forward compartment should have covers on the inspection holes and shouldn't have a hole drilled in it for a spinnaker pole unless it's a sealed tube! Again the forward compartment is partly for buoyancy. My Wayfarer had a couple of inflated beach balls in the forward compartment as a cheap buoyancy measure.
On later Mk II Wayfarers they added some foam between the floor and the hull giving them some intrinsic bouyancy but a notorious tendency to turtle. This Mistral looks like a Mk II clone. Most Mk IIs have added sailtop bouyancy, a small inflatable bladder in the top of the sail or similar. I added this to my Mk I.
So before deliberately capsizing it I would :
Investigate the designed buoyancy measures on your boat and restore compartment covers if they are indeed necessary.
Get sailtop floatation.
Even then I would do it first in a lake with a second boat standing by to assist.