its a 1987 or 1988 Macgregor 26D (blue stripe vs later black stripe).
the only ballast THIS model has is the water, and if it leaked out, it could capsize.
(no relation to the current model for sale on the mfg website... a very different boat)
I can't imagine them leaving the dock with NO ballast, its just very very tippy. but if they didn't seal the vents or close the air vent, and it was heeling water could leak out, to help cause a capsize.
however, the hull would not want to float upside down, where the weight was the highest.
like most of the accidents for macgregor, I think it will turn out that the balast was not full and that error in use, caused the incident.
-and that is way to many aboard! 6 is a normal limit, 8 maybe if there are several kids. but 8 is a lot, and 10 is just foolish.
prayers for their families! so sad.
I really think they didn't have the ballast completely full. The amount of bodies on the boat certainly contributed to the capsize, but the fact that the boat didn't right itself points to an empty or mostly empty ballast.
I know water ballast boats are known to be tender, and they are up to a point just because the center of gravity is a little higher. But with a full ballast (unless it's a bad design) they don't turtle easily. Mine stiffens up like a keelboat at 15 degrees.
If there was any kind of thought to the design, the valve would be near the midline of the hull. It would need to have it up and out of the water before leaking from heeling. That would be near 90 degrees. It it was a severely leaky valve, water going by the hull might drain it. But that would probably take speeds faster than that boat can go since the valve wouldn't be designed like a self bailer. I know of a few water ballast boats with mildly leaky valves that still remain full.
Though, if you don't check to make sure it's full, they can fool an idiot. Mine will fill by itself to about 1/3 of capacity and take it's time doing so. I have to physically push down on the rod to hold the valve open to get it to fill completely because the pressure of the water closes the valve. It's a fair amount of pressure as well. I wouldn't have known to babysit it if I didn't check with lowering a rope down the vent hole to check the water level. I also know how low the boat should sit in the water, but a renter might not be privy to that.
If it was indeed a rental boat, surely they would have filled the ballast at launching before allowing anyone on the boat. But I have seen enough stupid with rental companies that it wouldn't surprise me if they didn't.