Ok, I don't know a darn thing about using epoxy as a resin in a "fiberglass" componant. Barry, can you clear something up for me? I have been around a lot of fiberglass Rod body manufacturing, architectural manufacturing (come on now guys, you don't really think that ornate new building in town is really granite did you?
) , and the like, I have never seen epoxy used.
It makes sense that it would be stronger, but is it really being used in boats? I use to service a pretty high end boat repair shop in the Sacramento delta and all the boats appeared to be regular old polyester resin glass and the repairs seem to be made in regular old polyester resin. These were BIG buck yachts. Could these have been epoxy and I just don't know what I am looking at? Is the epoxy used for such a project different in appearance than the dark gray,white, blackish opaque looking resin we see in other epoxy products like adhesives?
And for goodness sakes, how the heck to you spell it "mould or Mold"????
Psionic, I am miles from being a glass expert but I would like to take a stab at your questions.
1. The gel coat isn't to cover up defects in the mould, but to "cover up" defects in the surface of piece you are making in the mould. When the glass is laid in the mould, if there are any air bubbles or flaws where you can't get the glass tucked into a nook or cranny the gel coat covers it up. There may be this void under the gel coat in the glass but you don't see it.
Willy's, Barry? At least that is what it looks like it is used for in production parts.
2 I have never seen gel coat sprayed after the part is pulled other than to repair something.
3. It isn't another name for resin,but it is made largely from resin. Resin and pigment color. Barry, Willy's , maybe some "talc" for body?
4. I imagine you are correct, but I have never seen a company make anything where it wasn't used. Those "carbon fiber" (something makes me doubt it really is carbon fiber) hoods you see on the little ricy cars, they have a clear gel coat I believe.
I don't think the smoothness of the mould is as critical as the smoothness of the application of mat, cloth and resin into the mould. If you don't get it down smooth, into every nook and cranny, pressing out every single bit of air bubbles and so on, you will have flaws in the outer surface of the part you pull out of the mould.
The "visual" difference is the part looks "painted" when pulled out of the mould if it is gel coated. MUCH better surface other paint products if you plan on painting it an automotive paint later.
"Structual"? I don't think one single iota.
The manufacture really uses the gel coat for a number of reasons, one is to insure the part will be smooth and free of defects. The other is what I just mentioned, it is already painted!
Here is little riddle you can ask your buddies.
What is painted before it even exists? A fiberglass boat!
Yep, before it is even made, it doesn't exist, the gel coat is sprayed in the mould. Thus it is "painted" before it even exists.
I just looked "mould, mold" up in the dictionary and found both are correct!
I will be using "mold" from now on, one less letter to type.