rapiers were in use (as the primary weapon throughout europe) from about 1500 to 1700. that is quite a period of time!

most rapier users would have destroyed a longsword user. it's faster, lighter and a thrust weapon (organ puncture). this is partly why it replaced the longsword.

however, a good sabre user could probably defeat a rapier. a rapier (or other thrusting weapon) relies on the lunge to gain distance, but this leaves the arm exposed. a quick (and accurate) slice will take care of the arm holding the blade. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />

also, i would happily take a sabre and poniard against a longswords (as you refer to it).

oh BTW modern fencing is based on a weapon that would kill you in a second. just because fencing uses dysfunctional (mostly) weapons - in the sport! - does not by any means mean that a 'real' version wouldn't leave you weeping in a puddle.
that's nearly as silly as saying that police practicing with paint bullets couldn't kill anyone with their guns!