DerrickM

Hi. I'm considering making a custom box out of fiberglass, and have never worked with it before. What I'm wanting to do is make a custom impression of an area in my trunk with something like expanding foam inside a plastic bag, then glass over this impression, cut out the hole, then dig out the foam. This would allow me to create an enclosure that perfectly fit into an odd-shaped area.

Has anybody ever done anything like this? What kind of expanding foam could I use that would harden inside a sealed plastic bag? How many layers of resin and glass would I have to use to make it strong enough for a sub?

I'm planning to make the box, then measure it's volume with water, then pour something (resin, lead, etc.) in the bottom to bring it up to exactly 1 cubic foot.

Thoughts?

elduderino

The more "traditional" method seems simpler:

Mask off the trunk area you want to fit with blue 3M tape

Spray it with some release stuff

lay down a couple layers of glass in small dabs and pieces so that you have a shell that fits the area.

Cut a baffle-front panel with a hole for the woofer.

Remove the vehicle matching "tub".

Mount the baffle in space on the tub with short sticks and hot glue. Make it firm.

Wrap some grille cloth around the whole thing, and using a staple gun, staple it to the baffle and to the edges of the tub. The cloth serves as the final surface shape that makes it an enclosure.

Now resin and glass the cloth a couple of layers.

Now glass it from the inside thru the woofer hole.

Now bondo the bumps outside, sand it, and paint/upholster it. Voila.

DerrickM

Okay, I did some looking around and found this link, which describes the proper way to do what I'm after:

http://web.njit.edu/~cas1383/proj/Glassing2/index.htm

I only need to form-fit the part that touches the car. From there I can build the other sides with fabric and wood and continue glassing.

DerrickM

Ken, looks like I posted right about when you did--this is exactly what you're recommending.

DerrickM

Ooh, one more question: would chicken wire be easier? I mean if I could get it to shape in the trunk, then remove it and glass it.

elduderino

Yeah, those are good pics (for crap woofers too: )

I would definitely use the Blue 3M tape (the non-3M is NOT as good) and I would go to more trouble to drop-cloth the trunk, and the baffle CAN be a ring but doesn't have to be (more sanding/finishing if it is, actually). I like a flat front for a OEM look...: )

Edited to add... I think the chicken wire would lose its shape. For a perfect fit I think you gotta do in in situ.

DerrickM

Thanks bud.

NYZGREATST

in that setup, he was able to remove the glass from the trunk. what if you do the WHOLE trunk? how could you pull its out?

elduderino

In pieces.

I've seen people glass INTO the floor of the trunk and the spare well for a floor-box... when they take it out, they have to break it into pieces, and that ain't easy.

DerrickM

Just back from Home Depot--$100 for the supplies. Ouch. I bought a gallon of resin, 36 square feet of fiber and cloth, and a $30 respirator.

elduderino

Hey, Derrick, a lot of people make a mixture of sawdust and shavings and resin and use it to do the last coating inside... some put sand in it for low res/low "Q" but the weight is a factor. FYI... I'd get some shavings from a furniture shop or something...

DerrickM

Okay, the project is well under way: I have the first layer setting up inside the car. I didn't know how much to mix, and ended up having to remix during my first coat. Anyway, it looks like it'll form a nice shell for me to work with outside of the car later. I'll post some pics later.

DerrickM

Here's three pictures of the first steps.

Masking tape:
http://img.photobucket.com/albums/v6.../glass0001.jpg

Closeup of masking:
http://img.photobucket.com/albums/v6.../glass0002.jpg

First layer drying:
http://img.photobucket.com/albums/v6.../glass0003.jpg

I was too cheap to spend $12.00 for a roll of the blue tape, so I imagine this is going to be pretty damn hard to get out of the car. Another hour or so and I'll be ready to pull it out.

DerrickM

Another question:

As I make the other three sides out of wood, are there any tips and tricks for attaching to the wood sides? (I don't want to have to cope the wood perfectly to fit).

Thanks!

DerrickM

I'm going to put fiberfill inside about 1 or 2" deep all the way around, so do you think it would be necessary to add sawdust to the last layer?

DerrickM

This is harder than I expected. One batch gelled up on me before I could get it done. I'm having way too many air bubbles. I guess it's like anything else in life: experience counts.

DRM600

interesting project. thanks for the pics and info so far. please keep us well posted as you progress.

Titand19

it will be hard to get that shit off, shoulda got the blue, nice job though

DerrickM

Naw, it came right up. But I made plenty of other mistakes. Too much hardener, too many airbubbles, etc.

elduderino

I would use a heavy-duty staple gun or screws to attach the wood...you're just wanting to hold it in position, remember...

elduderino

Fiberfill is cool and all, but I like having non-flat internal sides and the sawdust is cheap and easy.

But neccesary? Naw.

You're doing great BTW...

NYZGREATST

so how will you get out those bubbles?!

ResidualFreedom

Great Walk through.... enjoy... oh, and take your time.

http://web.njit.edu/~cas1383/proj/main/

DerrickM

Here's where I'm at now. Have two flat sides added, and next is the top with the hole for the subwoofer.

http://img.photobucket.com/albums/v6.../glass0006.jpg

http://img.photobucket.com/albums/v6.../glass0005.jpg

elduderino

Looks great! (And think, when you're done, you'll have character coming out of your ears!: )

You'll do these for other people for $200 each, right?

DerrickM

Hell no! I've been working on this all weekend and it's still only half finished. No way I could make these for money.

DRM600

are you finished with it? how'd it turn out?

DerrickM

Still working on it. Really only have time on the weekends. I've got the top on, and i'm glassing the inner corners using a mirror to see what I'm doing in there. I should have it done this weeken. Amp won't be here for a week, and I'm out of town next weekend, so the final product won't be in my trunk for two more weeks.

Here's a picture:

http://img.photobucket.com/albums/v6.../glass0007.jpg

DRM600

looks good so far. how did you attach the baffle board?

DerrickM

Attaching the boards to the uneven glass surface was the hardest part. I coped the boards best I could to fit, then used Liquid Nails and drywall screws to attach the boards. After the LN was dry, I glassed over the inner corners several times. One mistake I made was not routing the outer edges of the boards--fiberglass doesn't like to make sharp corners, and rounding over the outer edges would have helped a lot. I'll be much better at this if I ever do it again...

dark inspire

wow that looks slick! i wish i had the balls to do somethin' like that. maybe in a year or so...

ResidualFreedom

why the mirror?

DerrickM

So I can see to put glass on the inside corners. It's not permanent, of course.

ResidualFreedom

ok .. understood.. I was thinking it was permanent, and I was trying to figure out why.... looking good!!

dark inspire

to reflect the sound!

DerrickM

I think I'm done glassing. In a couple of hours I'll fill it up with water to make sure it doesn't leak. I cannot imagine how it could, but my inner corners aren't as clean as they could be and I want to be certain.

I'm off to find gray carpet to match the trunk. Home Depot didn't have anything; I'm hoping Lowe's will.

dark inspire

awesome! are you gonna post a DIY?!

DerrickM

Pictures are about all I'm going to post. The link posted near the top is pretty comprehensive--no way I could compete with that! Besides, I'm not in a position to claim any expertise at this...

dark inspire

sounds good

DerrickM

Nearing completion. Shown here with carpet on the sides that show. (Didn't attempt to put it on the uneven sides that go towards the car sides/floor). I also took Elduderino's advice and put a layer of resin/sawdust on the inside, but it's not in this piture.

http://img.photobucket.com/albums/v6.../glass0009.jpg