LIGHT SANDING FOLOWED BY CLEAR TWO PART URETHANE. uSUALLY ON MASTS AND STUFF IT IS BECAUSE SUNLIGHT HAS ETCHED AWAY THE SURFACE AND EXPOSED THE FIBRES. DONT WANT TO APPLY A LAYER OF SOMETHING THAT MIGHT EFFECT THE STIFNESS. (LIKE EPOXY) Also, typically, old fiberglass battens get really stiff too, so you might want to sand, taper and tune them. Catsailing for the nineties has a section on that, if I remember.