Help me understand vacuum bagging

[cdory dude]

So I am building a curved piece of fiberglass that I need to vacuum bag. I will be putting the whole piece inside of the bag. But how do I layer it? Do you put a breather cloth on the bottom then your nylon sheet then your wet layup, followed by another nylon sheet then breather cloth?

Summary:
Bottom of vacuum bag>breather cloth>nylon cloth>wet layup>nylon cloth>breather>top of bag

If so what do I use for a breather cloth? That thick stuff that is inside of blankets? I believe it is cotton.
And what type of nylon do I use? I went to the fabric store and they have a very fine bridal weave to a coarse porous dress lining weave and then a very thick cloth that is also very fine like the bridal stuff.

Thanks, this is my first time doing this and I don't quite understand the concept of the layers...and what materials to use for them.

 

[Georgesalmon]

Re: Help me understand vacuum bagging

What are you doing? If your going to layup something and roll it out then all you need is the bag. The bag just pushes against the part to get a lot of pressure on it. Typically vacuum bagging is used with core material. Do you have a mold? Curved pieces don't require bagging normally. Now if your talking resin infusion or SCRIMP that's another story.