About the same size and hull shape as a Wayfarer, Black Jack differs in thee important ways:
The cuddy or 'cabin' just gives you room to sit with your feet in a well by the dagger-board case, and your head and shoulders filling the raised portion. Sleeping is like lying in a coffin.
The design is self-righting and there is enough built-in bouyancy to float when full of water. My only modifications have been to fit a floor and pump in the cockpit and a 12 volt battery to power navigation lights.
Sailing is 'stiffer' than a conventional dinghy, but even so, in a good wind Black Jack will plane, particularly on inland waters like Coniston where you can get a strong wind without big waves. in very light airs before the wind, Drascombes and the like will begin to catch up, but my secret weapon against this eventuality is the £10 spinnaker I bought in a boat jumble...
The one disadvantage of the hard chine hull is that against the wind with waves and when the wind is dropping Black Jack begins to stall. With a decent wind however, it's a different story... Bob has suggested that a finer entry would have helped here. Apart from that, I couldn't wish for a better boat.