Noob Fiberglass Enclosure?

I need to create a FB enclosure about 1.75 cu. ft. ported.  There would be big parts of the enclosure that would be flat.  How do you reinforce the flat areas? I have read that flat areas for FB is bad.  And what is the ideal thickness? For MDF it is 3/4 inch, would 1/2 inch for FB do? Does FB need bracing? I have experience making MDF enclosures, but not FB..

For flat areas try to use MDF, Fiberglass is brittle when its all flat. Make a MDF frame then wrap it in fiberlgass...Here is an example HzEmall For thickness its can be hard to tell sometimes, I do what most do and go with the thumb test, after you have a few layers on let it dry and then start pressing all over it with your thumb where it flex's down I ad a few more layers. Fiberglass won't need to be 1/2inch think though, about 6-9 layers with a thick matt should do the trick. Hope this helped :)

Thanks, this helped a lot.. But I would prefer a pure FB enclosure.. Is there a way to do this?

Yeah you can but the safest way to do it is use MDF, if you want all fiberglass one trick is to add some robe to make ridges in the flat areas. The more ridges the better, FG is much stronger with curves. Lay one or two layers down then while it is still sticky lay down the rope or anything else you have, I would say about 1-2 inches apart across the whole flat portion, then add a few layers to cover the ropes, but remember to let the FG harden between the layers (not fully but atleast to where it is stiff) GOod luck with it :)

Ok, you do NOT have to use MDF. It defeats one of the main purposes of FG, which is light weight. For the flat areas I have found that putting cardboard down, and then coating it on both sides makes it as hard(er) then MDF

Yep, I need it to be thinner than a 3/4 mdf so that I can have more volume for my SUV. Thanks, maybe I'll try the rope thing to strengthen the FB, by the way do I need to brace the FB enclosure(it's about 1.75 cu. ft.)? Thanks

Ace, as long as when you push on the fiberglass with your thumb and it doesnt flex. Then there is no need to brace it.  If it flexes then try some of the tricks they're talking about. The rope, or taking cardboard and painting resin on both sides of it then put a layer or two of glass over it. Learning the trade one fiberglass creation at a time!

djrcustom wrote: For flat areas try to use MDF, Fiberglass is brittle when its all flat. Make a MDF frame then wrap it in fiberlgass...Here is an example HzEmall For thickness its can be hard to tell sometimes, I do what most do and go with the thumb test, after you have a few layers on let it dry and then start pressing all over it with your thumb where it flex's down I ad a few more layers. Fiberglass won't need to be 1/2inch think though, about 6-9 layers with a thick matt should do the trick. Hope this helped :)

Sweet install.  How many people did it take to carry that in there?

I am planning to make a FG enclosure and it will be attached to the back door of my mitsubishi Pajero(montero in the US).  How do you go about using bolts for your enclosure?

washers... big washers