n00bish ? - Fiberglass box

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#1

So i’ve been lurking around the composite world and i’m getting ready to start my own project - If possible I would like to make a box (cube) for a subwoofer using fiberglass. I have made subwoofer boxes out of 3/4" MDF but I would like to start using a lighter material for obvious reasons.

Well heres my plan, the box would be about 1cu ft sealed so 12X12X12
I would make a cubic skeleton and a circular ring out of fiberboard, lay some fleece over it, apply epoxy and lay the Fiberglass mat.

Now the thing is I would like to know if this project is worth wild because I’ve never seen it done, and probably theres a reason for it? I would like to know if the fiberglass can keep it’s shape and support a heavy subwoofer (almost 20lbs)? Please leave some feedback, thanks!

#2

Yea it can easly be done… For the last few years it has been the big thing in car stereo’s… Most usuall build the bottom out of mdf and then make some funky top with speakers and amps facing different ways out of fiberglass…
I built fiberglass enclosures for my car. since i didnt want to take up all the trunk with a big square box. i just made fibergalss ones that molded to the sides of the trunk. i’ll see if i can dig up some pics tonight…

#3

thanks for responding, oh yes I have seen thes custom shaped enclosures, but I think i’ll be designing mines kinda wedge shave with a sloping top for the amp.

So it’s best to make the bottom out of a solid piece of MDF and wrap the fg around? I’m hoping I can easily make the side panel straight with fiberglass… perhaps if all goes well I might like the exterior with a layer of CF for some eyecandy… Tho i might be getting ahead of myself here.

#4

Are you tight on space for the enclosure? If not then i woud suggest using mdf on all the areas that will not be seen. Since you can build that fairly simple. Then for the area of the speaker or amps that will show, do that in fiberglass… It will make the project go a lot quicker and easer.
Also if your molding the enclosure into a certian area of your car, ie. side panel, small nooks ect… make sure to leave the glass in there over night to cure. Cause if you pull it out too soon it can warp and when you put it back it will not be a perfect fit… I know, it happend on my 1st one…

#5

no I have a typical sport sedan trunk… But I have got into autoXing and I want to do a box which is as light as possible so that it dosen’t weight down the car… or at least a lesser PITA to take out… My current MDF enclosure +sub and amp weight about 70lbs and I had enough of lugging it in and out of the trunk every couple of weeks…

Anyways no molding… it’ll be pretty much just a wall in the back of my trunk, so cubeish or rectangleish… Is there any trick to making a panel flat? should i work on one panel at a time? How many layers would be sufficient?

#6

Hello firebert,

Ive been doing car audio install for about ten years and ive run acroos this request from customers before. The easiest way I have found to build this box is to first build thebox out of 1/8 or 1/4 inch masonite(rough side out) and gluing it together using Cyanoacrylate glue (super glue) and an accelerator to bond the edges together to make a cube. This will be very light but not to strong. Next you will want to apply three to four layers of fibeglass matt to one side of the cube. An easy trick to make it as flat as possible is to take a board and cover the surface with masking tape, then when the fiberglass is applied to the side place the cube fiberglass side down onto the masking tape board. start on one edge and pivot it down so you can minimize any air being trapped in between. push the cube down and put some weight on it to hold it in place. Once the fiberglass starts to set up trim the edges with a razorblade knife while it is still attached to the board( see posts on how to cut fiberglass easily). Once completely cured you can remove it from th board and you will have a flat solid panel. Next repeat on the opposite side. Once both sides are done start on the rest of the panels making sure you over lap the new fiberglass onto the trimmed edges that have already been done. Doing one panel at a time allows you to minimze the grinding and sanding you will have to do.

Good luck and let me know how it turns out.

#7

one4snow, thankyou very much for the walkthru, I have a much better understanding and feel much more confident in the project - but just a few question.

  1. where can Masonite be purchased
  2. Can you recommend a brand of glue and accelerator?
  3. I am supposed to lay the fiberglass mat in one solid piece (on each side) as oppsed to using seperate tear-outs, correct?
  4. For the edges/corners do I fold the fg in or just leave it as is and trim? -pardon me for this rudimentary question since I have never worked with fg before (only read tutorials) and it seem that there wouldnt be enough intergry in the corners if i just leave it as is and cut.
#8
  1. where can Masonite be purchased
  2. Can you recommend a brand of glue and accelerator?
  3. I am supposed to lay the fiberglass mat in one solid piece (on each side) as oppsed to using seperate tear-outs, correct?
  4. For the edges/corners do I fold the fg in or just leave it as is and trim? -pardon me for this rudimentary question since I have never worked with fg before (only read tutorials) and it seem that there wouldnt be enough intergry in the corners if i just leave it as is and cut.

1)masonite can be bought at most hardware stores such as lowes or home depot( whatever you may have in your area). It is used to build the bottom and back of cabinets and is brown in color with a shiny side and a rough side that has sort of a square hatch pattern that the fg sticks to nicely.

2)I use the 2p-10 solo kit from www.fastcap.com which is the activator and the thick glue in a kit. I buy it locally at a laminate store called Austin laminates and get it for about the same prices. You can also find zap glues (www.zapglue.com) at rc car/plane hobby shops. Just make sure you buy the thick glue for this, it wont soak into the wood like normal superglue does.

3)you are correct. cut three to four layers of matt slightly larger than the sides and wet out each piece until they are all on the box.

  1. I would just leave it and cut off the excess since the fg matt does a horrible job of fold ing over corners. It will just lift and create air bubbles, then you have to grind and sand the fiberglass smooth
    (itchy!!!). It will be strong enough for your application as long as you over lap the cut edges with the other side layers, but if you are still concerned after it is built just take some 2" strips and wet them out into all twelve corners inside the enclosure.

Feel free to post any questions that you might have. If you have an email address send me a private message and I will send a couple of pictures of fiberglass boxes since I have not figured out how to post them on this site yet.

#9

Thankyou very very much, you have been extremely helpful… I think i grasp the concept 100% and now to start the project on my own :smiley:

If you have some pictures that would be wonderful, perhaps i can grasp some inspirations from them.
deltawc@pacbell.net - no need to worry about file size, i have almost unlimited storage.