Long Island cabernet can be a not-very-tasty proposition. As consistently as vineyard managers can ripen merlot on this overgrown sand bar, cabernet does so just as inconsistently. Often, it doesn't ripen fully at all, leading to wines with overwhelming green flavors that are almost unrecognizable as cabernet sauvignon. As you might expect, a lot of this under-ripe cabernet ends up blended into other wines to mask its faults or is used to make rose or blush wines. Even at its best, Long Island cabernet sauvignon bears little, if any, resemblance to the hulking, muscular wines of Napa or Sonoma. Instead,…