The matching of a sail’s luff curve to the mast bend characteristics has always been a Finn art from the earliest days when Elvestrom realised its importance. This makes sail selection for the classic Finn owner a bit of a problem because of course no-one still makes sails for alloy masts, let alone wooden ones. My own opinion, without prejudice, is that a new sail is probably better than a well used one even if in theory its’ luff curve doesn’t match the mast. I know a 70s Mader Finn that sets a 2004 North Mylar sail on a Needlespar 3M and sails significantly faster than it did with an old sail designed for the mast. There are a few unused Dacron sails from the 80s still about, whether they’d be faster on a Needlespar mast than a good modern plastic sail I really wouldn’t like to say.
In the late 60s and early 70s many club sailors used Seahorse or Banks sails on a Collar mast, with Musto sails becoming popular, often with a Boyce wooden mast.
With the introduction of alloy Needlespar masts Musto initially were the common sailmaker but from the mid 70s onwards North became dominant. Musto continued Finn sail development however right up to the present day and have always produced fast sails alongside North. No other sail maker in the UK has invested as much in development as these two sailmakers so with the odd exception (say Sobstad for early plastic sails) no other sailmakers have managed to produce significant numbers of fast Finn sails.
classic Finn sailor with a Needlespar mast therefore needs to look for a good
condition Dacron sail ideally from North or Musto. A good plastic sail on
a Needlespar seems to work reasonably well although probably less in the spirit
of a classic (whatever that means). For a wooden mast the options are much
less clear. An original sail, even if perfectly matched to the mast when made,
is likely to be in pretty poor condition and a later sail is very unlikely
to set well on a wooden mast. My view is that a wooden mast can be used for
vintage (CVRDA) events provided the handicapper gives you an allowance, but
for club racing only a Needlespar with a good condition North or Musto sail