I have a few questions here.

two different issues here, also.

1) What is the difference between a "laminating" epoxy, and a "finish" epoxy?

2) How much material is consumed when glassing a (lets say) a 2 meter sailplane?

3) Do I or better yet, should I use different weighted glass?

4) How do I choose my epoxies? I find as a hobbiest, we mix part A & B -- 1 : 1
If I buy commercial,, the catalyst is MUCH less.

5) WHY is there so much price variance between the above?

I have found here locally that a "finishing" epoxy is selly for $20 for 6 oz.

I go commercial and I pay $45 for a gal.


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6) Which product(s) do I use for making a plug?

I guess the list could go on but I think that's plenty for now

I would surely appreciate some straight answers.

marwen

PS Happy Holidays to you you folks down there in the US.

I lived there for almost 4 decades -- came back up here to CANADA in '92


marwen

1. Laminating epoxy is a glue that's used to bond things together. Finishing epoxy has waxes etc in it that cause it's surface to level out and look pretty for the "top coat" and is not good at all for bonding things together. Matter of fact, if used as a glue it's often much less strong than regular epoxy.

2. There aren't any rules of thumb that are meaningful that would answer that question. Your skill at application has a lot to do with it. Your techniques have a lot to do with it. How thick a cloth you use etc etc...

3. You should always use the appropriate weight cloth for the job. If you've got a balsa fuselage that you want to strengthen you'd probably use anywhere from 2oz or 4oz or 6oz or a couple of layers of 2oz or maybe a layer of 4 with a layer of 6 or..... And if you were just looking to make a sheeted glider wing somewhat stronger you'd use 3/4oz and maybe mix some microbaloons in etc etc. How do you decide? Be specific about what you're planning to do and ask for suggestions.

4. Hobby shops also sell the West System epoxys and that adds a third price structure. It's usually a good idea for a beginner to buy hobby shop sizes of components to use on smaller projects to see if they have the patience and ability and talent to work with the stuff. My local hobby shop has West Systems and they have a stack of free "how to" booklets and pamphlets that're really worth your time. Look for the West System stuff and the booklets.

5. Availability and demand. Most modelers aren't ever going to use much more than what's sold in the LHSs packages. And most modelers aren't going to put out the time, effort, and frustration of searching out the retail sources that sell "cheaper" components. And if they do, they often run into less than pleasant retailers who don't want to mess with miniscule sales to people who have little or no experience using the components. Did you know that a lot of the glass cloth available outside the hobby shops is treated to work with polyester resin and when used with epoxy results in very weak structure? Things like that make blazing your own trail risky.

6. You can make a plug out of anything that will hold the shape you plan to create. You're going to have to finish your plug and that finishing is what makes your plug a useful plug.

7. I'd suggest that you really should try out a small project to start your learning process off. If you have a balsa fuselage glider right now, get enough 3/4 oz (if you want to make it strong AND light) or enough 2oz (if you want to make it STRONG and not heavy) and a box of Z-poxy finishing epoxy and have at it. You'll answer a lot of your next set of questions by actually experiencing that little project. Working with epoxy ain't for some people, while others find it's wonderfully simple (which it isn't).

BTW, every human on earth will develop a sensitivity to epoxy if they don't protect themselves from direct contact with the uncured resin. That is, they will if they continue to do so, it just depends on when and how much. So don't go spreading it with you bare hands.

BTW, if you'd like to get a feel for what plug making and use are like, read the thread on this same forum that is titled something like "anybody use just wax on their mold". It is not for the faint of heart.

And happy holidays to you guys up north. May your winter be only 10 months long and all your snows only a few feet deep.

If you want to try your hand at plug/mold making you'll want to buy larger quantities of epoxy (gallon) as the price is reasonable and you'll use it for plug, mold, and final parts. There will be other expenses to gear up such as cloth, brushes, mixing cups, fillers, etc but well worth the ability to produce your own parts.
I did a little demonstration recently for some students and used a nose section of a large model they designed. They will use the part as is but the process is the same one I use to make plugs. Materials are, blue foam, .75 oz fiberglass cloth, overnight-cure epoxy resin, hobby filler (lightweight spackle would do), and high-build lacquer auto primer.
There are many ways to do this but here is a simple process that works.
Paul

Blue foam can be sanded and if you're careful it will yield a nicely shaped part. Gaps were filled with model filler but lightweight spackle would work. For this part I used 2 layers of .75 oz cloth put on at one time ( I didn't let the first layer cure, sand, them add the second ). After it cured I sanded with 80 grit paper to get a uniform dull surface. The high-build primer/surfacer was brushed on without thinning and sanded out. Another coat of primer slightly thinned was brushed on and wet sanded. I finished up with a white sandable auto primer in a spray can to provide a white base color which was wet sanded. If the lacquer-based primer seeps thru the fiberglass layer it will attack the foam. In this case I used two layers of cloth; another way would have been to use one layer and put another coat of epoxy after the first one cured and was lightly sanded. I didn't have time and needed to have it done with one epoxy application. Brushing the first coat of primer without thinning helps prevent the solvent from getting to the foam; the thinner would certainly get through any pinholes (ask me how I know!).
If this was a plug I would have used heavier cloth such as 2 oz. to make a sturdier part.
I also made a sample aileron to show that the process will work with control surfaces as well. It was made by glueing templates to a foam block and sanding out. Same process on the glass cloth. Quick, strong and light.
Hope this is helpful.
Paul

Another important consideration when choosing glass, besides weight, is thread count. Check out http://www.cstsales.com/FGDataTable.htm.

If you are glassing sailplane wings, I would suggest a higher thread count. You will get better tensile strength, and it takes a little less epoxy to saturate the fibers. That saves you some weight.