got a couple of ?'s cus im undergoing a real nice custom box for my car. i love ported boxes so i gotta make 1.5 cuft in this small a$$ space. 1. how do i calculate for weird shaped boxes i.e im using a stock panel (cheorkee side panel in back. if u ever seen one it has a indentation in it) and glassing mdf to it and junk. 2. as a backing, would a plastic panel work or is it too flimsey. would fiberglassing the back of the panel make it strong enough. 3. can fiberglass stick to plastic? 4. say i need the 1.5 cuft box but only get just saying 1 cuft but polyfil is in the box. will this mess up the sq or even spl?
Fiberglass really doesn't add much stiffness to flat surfaces. Rounded, yes. Flat, no.
Your best bet is to use mdf for flat panels.
The easiest way to figure out volumes of weird shapes is to break them up into small sections and then add the volumes up. If you're not doing any funky curves and can figure out the area of a right triangle then its pretty easy, but can get a bit tedious.
Funky curves? I filled my stealth box with water to figure out its internal volume.
yea...fill it w/ water or sand if you have funky curves. Just make sure the MDF has a few layers of fiberglass on it if you use water. MDF and water dont mix.