No, but it is best to use a slow cure epoxy, at least 30 minute. I put on as thin a coat of epoxy on the area that I can then lay the cloth over it. I then take a heat gun and gently heat the area; you will see the epoxy flow out and saturate the cloth. If any area does not appear to get wet with epoxy, apply a bit more in that area and gently heat again. Now cover the entire area with one piece of Saran Wrap and smooth it out to eliminate any wrinkles or uneven areas. You can feather the edges very easily so that, when it cures and you remove the Saran Wrap, very little if any sanding is required: a glass smooth surface results.