Re: Fiberglassing and hardner mixing?
And More:<br /><br />Some things bothered me about your post because they hinted that you might be getting ready to make a mess, but that maybe it doesn't have to be that way.<br /><br />First let me tell you a couple of things about resins that you really need to understand. Let's start with one of the real basic differences betweem epoxy and polyester resins. With epoxy you control how long it takes for the resin/hardner mix to set up by using different hardners. Some are very fast and some are very slow. With most epoxy's you can mix hardners to adjust the set time, which is to say that you can mix half fast hardner with half slow to get a medium set time and you can vary the proportions to suit your needs. In general slower is actually usually better. In any event it is very important that the proper ratio of hardner and resin be mixed together. Too much or too little hardner and you end up with a mess that generally won't set up at all. <br /><br />Polyester is much different in that reguard. With Polyester you control the set time by how much hardner you use. More hardner means a faster set.<br /><br />Temperature is a governing factor in set time too. Hotter equals faster. No suprise there. Well, sometimes there is a suprise. Resin/hardner mix generates heat as it sets up and that heat will speed up the set. The thicker the application the greater heat is retained and the faster the set. Here is how it works in practice. If you were to take one of those generic plastic paint cans that Lowe's and Home Depot sells with their graduated sides (get a half a dozen of these things along with rags and hand cleaner before you even think about starting) and mix up a quarter inch of resin/hardner it might take a half hour to set up on a good warm day. Take that same can and fill it up half way with resin/hardner and I can guarantee you that in 10 minutes it will either be hard as a rock or on fire. The deeper the mix is in the pot the faster it will set up and the hotter it will get. In the worst case the top of the mix will actually begin to bubble and turn brown from the heat, in many cases it will smoke and rarely, but occasionally it will actually burst into flame. Both epoxy and polyester will do this. On the other hand if you were to mix up a batc of the stuff inside of the tray for dipping a roller and have it very shallow, say 1/8" deep or so, it might take it a day to set up. Thin applications of resin/hardner take forever to set up.<br /><br />I only said this stuff because you mentioned that 5-gallon pail. If you mix up your resin in it with the thought that you are going to have time to then use that stuff to glass your boat you are mistaken. You pour a gallon of resin in there along with its hardner and what is going to happen is that its going to become unusable in mere minutes, unless you happen to be in the artic.<br /><br />Next. Fiberglass is strongest when the least possible amount of resin is used but still fully saturates the actual glass. That is why application of the resin (when I say resin from now on I mean resin which has been mixed with the appropriate and proper amount of hardner) using either a paint brush or a short-napped roller works so well. It tends to limit the amount of resin you can carry to the piece of work and that is to your advantage. Dipping the glass in a vat of resin almost always results in a couple of things. The first is one of the worst messes you'll ever see. The second is cloth that stretches and becomes essentially unusalbe. The third is most important. It results in a mix that is far to rich in resin and lean in cloth and the result is a much weaker peice that would otherwise have been the case. Don't dip it.<br /><br />As for the application technique. Try this, staple the cloth to the stringer and then wet it out. If you don't like that one try smaller strips of glass and apply them overlapping. By the way, don't overlook the use of fiber glass tape, something around 4" wide works wonders. There is also bagging and its really the way to go if you have anything you can use as a vacuume pump and are somewhat innovative in your approach to things. I will say this, if you can rig up a bag system, which can often be done with simple plastic and duct tape, the quality of the job you turn out, both in appearance and strength, will be greatly improved.<br /><br />So those are some hints that I would give. I would absolutly love to see some from guys who do a lot more glassing than I do. I know there are some builders here, and of course they do a lot, and there are some real serious hobbiest here, and you know some of those guys are turning out some outstanding work (I know becasue I've seen the pictures here) and should be able to give you, and me too, some pointers.<br /><br />Thom
