By Lenn Thompson, Executive Editor With the accelerating success Long Island wine has enjoyed in recent years, it's easy to forget that the industry was only founded in 1973. Several grapes have come and gone over the course of 30-plus years — zinfandel was even tried early on — and a handful of grapes have emerged as those showing great promise here including merlot, cabernet franc and sauvignon blanc. For a variety of reasons — and with a few notable exceptions — variety experimentation has slowed in recent years, but Palmer Vineyards and winemaker Miguel Martin aren't done exploring. This…