The Gowanus Yacht Club, a warm-weather favorite in Carroll Gardens, is opening this weekend and inviting the whole neighborhood — provided you have a strong back. “Your participation in helping us set up is greatly appreciated,” says a sign on the fence. But not for nothing! Gowanus is offering free beers and hot dogs, a step up from Tini Wine Bar’s coffee and pastries gambit. The physical exertion starts on Saturday and Sunday at 11 a.m.