What is a dinghy??

That would exclude traditional boats like the Brighlingsea One Design and others of the same ilk..

That's the Albacore and GP out then.

OK, add categories Scow (incl. Topper), Catamaran (incl. Vortex) and swing keel/water ballast keelboats. Heavy c/b boats are generally sailed upright, are they not, so comparable with F15?

Alternatively, maybe a dinghy could be defined as a boat whose righting moment when raced by 'those who know' is mainly achieved through crew weight. Might need further definition of 'mainly' as a percent. Certainly, when I was trying to come up with a reliable indication of righting moment for the purposes of my comparative performance spreadsheet, I found that the proportion of crew weight to all-up weight alone tended to be a reliable discriminator of which boats could be regarded as dinghies and which, as keelboats, had to have the boat weight taken into account for sail carrying power.

For me the F15 is still a self-righting dinghy, albeit one which could do with a harsh diet...

Maybe a reasonable definition would be that you race a dinghy upright, thus deriving no righting moment benefit from any keel weight, whereas on a keelboat is sailed heeled to use, at least partially, the keel.

On that basis, I guess the F15 is a self-righting dinghy if you watch the top guys, or a kelboat if you observe the tail enders