How much did a medieval fail weigh?

First, it is the medieval and it is flail. To answer your question, the average flail weighed 10 to 20 pounds depending on who was going to use it and if it was for cavalry or for hand to hand combat and if it needed to be armer piercing. Flails could also be thrown to ensnare enemies but that takes extreme practice and true aim and skill. Hope this helps!