FIberglass Enclosure DIY

[immorality]

Guys, I'm in the midst of doing a little audio upgrade to the Cressida, and I thought that I'd spend a little time to give you more insight into building a fiberglass subwoofer enclosure. Working with FG is stinky and messy, but it's light, strong and a great material to use in many applications. I like to use it for enclosures because you can make a box tuck into tight spots. I have previously made a box for a mk1 MR2 to fit behind the seat. It was compact enough to allow 100% range of seat sliding motion and over 90% recline ability. Anyways, I wanted to use FG in the Cressida to fill up the right side of the trunk since I have a full size spare on the left side, and of course my car needs a fuller sound.

Here's a general list of supplies and tools.

- FG Resin
- Hardener (MEKP. Methyl Ethyl Keytone Peroxide, you can often buy this together with the resin
- Fiberglass mat
- Stir stick
- Scissors
- Hot Glue gun
- Wood for making a trim ring
- Painters tape (2" wide x L=15m, I used 3 rolls)
- Old wax (Nothing fancy, and not 100% required)
- Plastic sheet
- 3M Spray adhesive, Foam & Cloth or bondo, Spot putty & paint

- Paint brushes (Get about 3, I like mine with shorter stiff bristles. That makes them good for pushing out air bubbles)
- An old container for mixing resin & hardener
- Gloves (cheapie one use throw aways)
- Wiring terminal & wire
- Dremel with sanding wheel
- Measuring tape for making the trim ring
- jigsaw for trim ring
- Drill with bits for screw holes, hole saw for wiring terminal if round, maybe a jigsaw for a square one
- Sander/grinder
- Soldering Iron/crimper
You will also need a subwoofer, but that is generally understood.

I recommend getting the tape, glue sticks, plastic sheet, brushes and gloves from the dollar store since these are going to be one use only.

You can see the cans of resin that I had purchased. I completely used both of them and my box is on the thin side. For the mat, I suspect that I used maybe 15sq.ft. I don't know exactly, that's just a guess. I've got lots here anyways.



Day 1

Step 1: Find a suitable location for a fiberglass enclosure.
I choose this corner of my trunk. The other side holds a full size spare, and I'd like to keep it there for the time being.


Step 2: Tape the hell out of it!
Start by gathering supplies;


Use lots of tape as you don't want to have resin seeping though into your trunk carpet! I did 3 layers here. Work from the bottom to the top and overlay the tape by half it's width.


I ended up using 3 rolls of 2" x 15 meter rolls of tape. I recommend getting tape from the dollar store. There's no sense spending $4/roll at Canadian Tire for painters tape.


I also laid down some plastic drop cloth to help protect the surrounding area and to give myself some more room to work. I've also marked a rough outline to give myself a rough idea of where I want the edges of the enclosure to be.


I've also added a layer of old cheapo car wax to my tape layers. In fact this wax was so old it had started to grow mold? I had no idea that would happen! This helps to aid in making the FG easier to remove from the car


Step 3: More supplies!


I cut up the fiberglass mat into strips and squares. This is an inexact science so the sizes are irrelevant, but the squares are about 4x4". The squares are for corners and sharp changes in shape.


Step 4: Get messy
Now is the time to mix the resin and hardener together. You can follow the directions for the right amount to mix together. I like to put a little less hardener in the mix so that I have more time to work. I have made a sub box for a mk1, but I'm still a FG noob, so a little extra time works for me. I'm not in any rush. Brush one coat of the mixed resin and then start putting the mat on top and brush more resin into it until it's completely soaked through. Keep repeating the process until you have covered the entire work area. Repeat this as many times as you'd like. I've heard that 3 layers is good.

This shot shows the end of the second layer


Here is the third layer. There's still some white mat showing, but I've run out of resin.




More tomorrow!

[immorality]

Day 2

Step 5: Prep

Now that your box has hardened, gently, but firmly remove it from the car. Watch out for sharp corners! Once you get it out and remove all the tape and plastic, it should resemble something like this;

You can now add a layer or two if you with to the thin sections.

Here you can see the straight lines that I've added so that I can get some nicer edges while trimming. You can use a dremel here, but I used a grinder with a cut off wheel, it goes much faster. You should also be wearing some kind of mask at this point, because you don't want to be breathing in dust glass particles.


Trim those ugly edges until you get this;


Step 6: Trim ring
Once the edges are trimmed make a ring for your sub. Measurements are usually on a sheet that comes with a new sub. Otherwise measure and cut. I used some 3/8" plywood and made it out of two layers so that the sub would fit flush to the edge of the box. In this case it doesn't need to be pretty as it's just going to be covered up with more fiberglass. Here I've cut a few little pieces of balsa wood to make a stand for the trim ring and glued them in place with a hot glue gun. (as a side note, in my infinite wisdom I bought glue sticks that were too big for my gun, so I lit a candle and melted then end of a stick and smeared it as needed )


Step 7: Wrap
Now use some stretchy cloth to cover the trim ring sides of the box. I had this handy dandy GM Tuner Experience T-shirt from the Autoshow several years ago. Since I don't wear an XXL, I decided to cut it up,


Again using the glue gun, stretch the cloth over each edge and glue it down;


Then trim off the excess;


Step 8: More mess
Gather up your supplies for another round of messy, stinky fiberglass. Paint on a layer of resin and then start putting down more fiberglass mat.


An important thing to note here is that when working in bright, warm sun the mixture will harden MUCH faster than normal! Hence there's only one picture and my box kind of looks like ass.


Now let that sucker bake in the sun for a while.

Step 9:Clean & Test fit
Here I've gone over it already and cleaned up all the sharp edges.



Test fit in the trunk;

[immorality]

Day 3

Step 10: Wiring

You need some way to get signals to the sub, pick up something like this;

This one is a little fancier than I would have purchased, but it was all the audio shop nearby had. The extra wires are to power any accessory lighting one might want to add.

You need to measure up a hole for the connector plate and cut it out;

I don't have a hole saw large enough for this one, so I just went over it with a dremel after.

I added a little silicone around the edge just for good measure. The paint thinner is there to help remove some of the dust from the box.



Step 11: Covering

Here you have a choice to cover with cloth or smooth out the box and paint it. Wrapping is much simpler and I think it goes better since the trunk is covered in carpet as well.

Here I've got a thin layer (1/4") of foam to help smooth out imperfections. I used a 3M spray adhesive on both parts. The instructions say to let it sit for a couple of minutes and then put the two together. Do the same thing with whatever cloth you have to cover the box. Since I'm broke from school, I used more of that huge ass GM Tuner t-shirt;


Cut out the area where the sub will sit.


Step 12: Insert Sub

Here there's not much left to do but attach the wires to the sub, and drill holes for the screws and put the sub in. Here's my old RF from about 1998! I'm hoping to get a newer sub and amp when the paycheques start rolling in again.


I still haven't had a chance to test it out because I haven't wired the car yet. I'm still waiting on an ipod cord and a PAC SWI Jack so that I can use my factory controls. I've also got find myself a 4 channel amp one of these days.

[Saiko]

hey Russell, funtastic, that looks funnntastic!

Nice craftsmanship thurr man.. Can't wait to hear your setup once you have it all sorted out. This is going to be very handy for a lot of people. THANKS!

[1985 Silver MKI]

wow...that looks sweet! good write-up too easy 2 follow...just add wildcats!

[bbarnumboy]

u inspire me to remove the 3/4 inch high density 200 lbs of wood from my trunk

[immorality]

I want people to realize that it's not that hard to do and it's great for using up underutilized space. I could have put a huge MDF box in my trunk, I even have one at home, but I think this works so much better. Martin, I think without the sub the box might weight ~5lbs max, it's basically nothing.

[macatak]

yeah, I was looking at the box last night at Russ's place
looks really good

gave me an idea for the SC which might give full seat motion and still allow the t-tops to
fit behind the seat correctly
( and one for the lump, it's got a useless corner in the trunk and I have an 8' Omega boom tube just sitting around)
wtf, just another couple of projects for the list
( it's starting to make the old "Honey do" list look like a piece of cake!!

btw,
don't buy stuff from Russ, he keeps giving you other stuff you might find a use for

[immorality]

btw,
don't buy stuff from Russ, he keeps giving you other stuff you might find a use for

Oh Duncan, I've got an extra washer fluid reservoir that you could incorporate into a methanol injection system! Maybe it could be used for alcohol in an intercooler spray setup?

[bbarnumboy]

ohhh good idea russ yeah maybe someday i will rip the 200 lbs of stereo out of the bmw and redo it. as for the mr2 i think i am happy with my boX in the frunk unless it gets i the way of my 3 hallon resovoir for my a2w system thats going up there....methanol is going behind the seat i think

[bbarnumboy]

i am definately happy you made this post. becasue it really does show how easy it is and shows that anyone can do something like this. i have been meaning to explore with carbon and fiberglass sometime and now i know that it will not be as hard as one could think. although i never thought it was that tough but u answered some questions. how many layers of fibre did you use? hope you dont rattle the box apart.

[immorality]

I think I used about 2 layers of mat. I would have liked to use more, but FG is pretty strong stuff. I've got a can of pre-preg that I though about using, but I just wanted it finished. I can stand on this puppy no problem, so I'm not worried about rattling it apart.

...and pre-preg (Pre impregnated) is a term used for short fiberglass strands mixed with a thick resin. You add a hardener to it and apply it kind of like bondo. It's good for adding thickness in places that are a little thin.

[bbarnumboy]

is that a 12" or a 10" we should have a fiber glass party and redo my whole stereo

[immorality]

...just add wildcats!

...or Fundador!

is that a 12" or a 10" we should have a fiber glass party and redo my whole stereo

It's an old ass 10", and I'm always down for a good party, although I'm no longer allowed to cross the border.

[bbarnumboy]

i found out yesterday they are being nice for a while and letting me peopel cross. i accidentally went into canda on tuesday lol and had to come back with no documents. dont ask. but yeah they said they are in a grace period for a while.