Summer racing on a downwind beat from Annapolis down the bay, in a 35 foot sailboat with a ½ oz. spinnaker flying nicely in 35-45 knots of wind, we were suddenly sailing by the lee when a 55 foot Swan sailboat behind us took a full broach knockdown. Less than 2 minutes later we took a knockdown from the same wind and broached with the mast and all sails under water. It was a complete whiteout from the thunderstorm, nobody had on a lifejacket and we were all hanging from the rail as the boat slid downwind. We struggled to get the mainsail back into the cockpit, the spinnaker had been shredded into a 1000 pieces and we finally righted the boat. With only 100-200 feet of visibility in any direction, trusting to our instruments, we got back on course, put up a ¾ oz. spinnaker in 50-55 knots and proceeded on. We finished the race 6 hours later, still in a full gale and corrected to 8th place in class, in a fleet of 105 boats. Lesson learned = with a thunderstom approaching put on that lifejacket.