Woven Glass Tapes
Woven glass tapes are electrical grade fiberglass fabric tapes that come in various widths: 729 (2″), 731 (3″), 732 (4”) and 733 (6″). They weigh 9 oz per square yard. These woven glass tapes have a selvaged edge that prevents fraying. These tapes are ideal to toughen and protect corners as well as for a myriad of other applications. Corners must first be rounded about like the radius of a dime (minimum) because the tape will not make the turn of a sharp corner. I take a short sample of the tape, fold it in half to find the center and then mark it. I center the mark over the apex of the corner. I then mark where the edges lie.
Now, I’ll take a combination square and mark the two edges along the entire length of the corner (above). I wet the substrate between the marks with mixed resin/hardener along the entire length. Then I roll the tape, placing the edge on the mark and smooth it down. Usually, I’ll place just one surface (the easiest) down first. Once its entire length is in place, I press the remainder down. As the glass tape is negotiating the corner, it may not want to stay put. I’ve found if I just let it set for half an hour, the epoxy gets stickier as it begins to cure and then the glass stays down. I’ll re-wet the glass tape as required (it will be white if it is not wetted properly).
When covering the corner of an arc shape, the edge may still not stay down. In these instances I’ll slit the edge, producing a dart, until it cooperates. I’ll wait a few more hours and then apply another coat to fill the weave of the tape as well as to inspect for wrinkles or bubbles which can be resolved at this time.
Sand the cured tape with 50-grit sandpaper on a sanding block to feather the selvaged edge. If the edge has got to blend, thicken a mixture of epoxy with 410 Microlight® and apply it with a wide putty knife.