I got a lot of hits on my blog about PVA glue and the fact that it acts like a hot melt a few days after it cures. I have used this factor for years when gluing down thin materials that, other wise, would require complex clamping. I put PVA glue on both surfaces and let the glue dry. I then put the two pieces together and use a hot iron to press the two surfaces together. I get an instant permenet bond. That was the first blog. Now I have a new concept.
For some reason when we deal with fiber glass cloth, we always go with either polyester resin or epoxy. The only reason that I can see to do that is that they cure clear and don't shrink much. This new concept is to use cheap PVA like Titebond II in place of the expensive epoxy. Titebond II is almost as water proof as epoxy and a lot easier to work with. What I do is combine the concept in my first blog and apply the PVA to the fiber glass fabric in a thinned down layer. What this does is to make the fiber glass fabric stiff. It is like using starch on your dress shirts. Once the fiber glass is stiff, it can be cut neatly with regular sissors without fuzzy edges. This is just the first step.
Once you have a sheet of cured fiber glass fabric coated with PVA, you can use it in many ways. Here is how you can splice two pieces of plywood together.. Cut a strip of cured fiber glass about 3" wide and as long as needed. Coat the edges of the plywood with PVA glue from the joint point back about 2" and let dry. This is an interface coating, or priming of the plywood. Next put some PVA on the edges of the two pieces of plywood and press them together. You know that this is not going to work and will only produce a weak bond. Next, take the strip of cured fiber glass that you had prepared earlier and place it over the crack between the two sheets of plywood. Since all the glue is dry, you can move the cured strip of fiber glass all around. When you have it is centered, take your hot cloths iron and iron the cured strip of fiber glass down into the dry PVA glue on the plywood. If your iron starts to stick, put a strip of aluminum foil over it that has that release coating. What will happen is that the heat will reactivate the glue and the fiber glass will bond the two sheets of plywood together. Next, do the same thing to the other side.
What you will notice compared to doing this job with expoxy is that it is a lot faster and the amount of PVA used is a lot less. The fiber glass is a lot thinner since it was pressed down with the hot iron, but it is just as strong. When you consider that the failure mode with epoxy is going to be the bond between the wood and the epoxy and it is going to be the same with the PVA, any extra strength that the epoxy has is wasted.
Think of how complicated it is to use epoxy on a vertical surface or the fact that you have to hold the objects in position while the epoxy cures. With this method, you get an instant permanent bond. I used to use a lot of expensive epoxy and polyester resin in my wood working, but not any more. I use Titebond II for almost every thing now, even with fiber glass and Kevlar. Because of the simplicity, I use this concept a lot more to maximize the strength of many things that I make. I use Kevlar and Graphite in places that I had never dreamed of before and at much less cost and complexity.
Have fun!!!!
PS--Experiment. It is amazing how thin and how little PVA glue is needed when the fiber glass is pressed in place with a hot cloths iron. It is like cheap "pre-preg". This procedure eliminates the shrinkage normally associated with PVA glues.
