There is no "offical" weight for the J30. The basic specifications list a factory weight of 6000 lbs. and a sailing weight of 6700 lbs. The draft or float lines are the only official way to ensure the boat is legal. I have some weight data from boats that have been weighed but the equipment and sails on board were not controlled so it is just a range of weights.
Re: Official Weight of a Dry J/30#6621 02/11/0712:32 AM02/11/0712:32 AM