It is true that the sizing on the fiberglass cloth does deteriorate with age and the sizing is on the cloth to help the cloth wet out with resin. ?But, it will still wet out and produce the same strength composite structure as there is no shelf life for glass fibers. ?However, old cloth with degraded sizing will not wet out as readily, so it is easier to make a structure that isn't fully wet out. Or you may end up using more resin while attempting to get the cloth to wet out, making for a heavier structure. ?
If you don't have a lot of experience with glass, you really need for things to go right as you'll make enough mistakes without having the cloth fight you. ?Much of the glass I am using for my modifications is quite old (purchased in 2005). ?I can see the difference in that it takes more effort to get it to wet out thoroughly, but it does still work just fine and once wet out, the glass fibers bonded together with the resins should be the same strength as when the materials were new. -Jeff Scott Los Alamos, NM > ----- Original Message ----- > From: smwood > Sent: 03/26/13 04:04 PM > To: krnet at list.krnet.org > Subject: Re: KR> Glass cloth shelf life > > Fiber glass cloth has a sizing coating on each strand to help the epoxy > resin to bond to the glass. The shelf life for most fiber glass sizing is > five years. After that time the wetting out with the resin becomes more > difficult and will result in a weaker structure. The older the cloth the > worse the situation will be. > > Sid Wood > Tri-gear KR-2 N6242 > Mechanicsville, MD, USA > ----------------------------------------------------------------
