can I use a b-50 Dacron bowstring on my Kota prairie swift recurve or are they fast flight only

You can use B-50 on any bow.

ttt

L82HUNT had it right.  B-50 is heavier and will slow your arrow some.  It will, however, be quieter.

b50 ("dacron", actually polyester) can be used on most any stick bow.  

you can make a far lighter and faster string using modern hmpe fiber ("fast flight", et al), as long as your bow can handle the modern fiber.  

as to dacron being quieter than hmpe, only you can determine that through testing.  in many comparison tests, modern hmpe fiber strings are definitely quieter than dacron.  particularly those "skinny" hmpe bowstrings.

as always, do your own testing and make up your own opinions and use whatever you think is best.  any of these string types will get the job done for all of us.

ttt