PRIVATE PLT OF SMA ACFT LOST CTL OF THE ACFT DURING LNDG RESULTING IN MINOR DAMAGE TO THE ACFT.

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I FLEW A STANDARD PATTERN AT STANDARD ALT AT THE CORRECT AIRSPDS AS PER MANUFACTURER -- THE ACFT IS A SMA SINGLE ENG LAND ACFT. MONTAUK ARPT IS ON THE WATER WITH A SAND DUNE BTWN THE BEACH AND THE RWY. WE WERE 2-3 FT AGL WHEN WINDSHEAR OCCURRED. WE WERE BELOW THE TREE LEVEL AND BELOW THE TOP OF THE SAND DUNE. THE L WING DROPPED WITHOUT REASON. IT STRUCK THE GND. I TRIED TO CORRECT WITH R AILERON AND RUDDER; BUT NOTHING HAPPENED. THE AILERON WAS JAMMED BY THE STRIKE. I LANDED THE PLANE. AS WE WERE ROLLING OUT; I HAD NO CTL OF THE NOSEWHEEL. I TRIED TO BRAKE BUT AS WE SLOWED; THE ACFT TURNED SHARPLY TO THE R; WENT OFF THE RWY INTO A DITCH. NO ONE WAS HURT (I USED L RUDDER TO CORRECT; BUT NOTHING HAPPENED) -- CAUSE WAS CLRLY WINDSHEAR THAT CAUSED THE WING TO DROP. THIS ARPT IS RIGHT ON THE WATER. THERE WERE NOT ANY NOTAMS FOR WINDSHEAR -- THIS ARPT NEEDS MORE WIND SOCKS AND WINDSHEAR DETECTION DEVICE. UPON READING FAA AND NTSB RPTING GUIDELINES; THIS APPEARED TO BE AN INCIDENT WHICH DID NOT REQUIRE NOTIFYING EITHER THE FAA OR NTSB. MY LAWYER AGREED IT DID NOT REQUIRE NOTIFICATION TO EITHER FAA OR NTSB.