srm is right, get ready for a new sail. In the meantime take care of the "newer" sail. You could try not allowing it to flog on the beach, let it down when not sailing. Roll it up don't fold and store it out of the sun. The old sail might make a shade sail.
The sail material is a laminate of (probably) Mylar film and Dacron. They were bonded together with glue, pressure and heat. The Mylar helps the sail keep its shape. Over time the bond fails and the sail material de-laminates. As srm said though, the modern materials are far better.
Very rarely a used sail is offered for sale but you could ask the forum if anyone has one they would sell.