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Old 03-07-08, 09:52 AM   #1
dragracer
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Anyone built a sub box out of fiberglass??

Son is wanting to build a custom sub box for his car and thinks he'd like to do it using fiberglass. Anyone ever done anything like that? If so, do you have any tips??

I built a couple of fan shrouds and a few other things out of fiberglass but I think a sub box is gonna be a bit more involved. To be honest I really hate working with fiberglass. It's just nasty stuff.
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Old 03-07-08, 09:55 AM   #2
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I did a few years ago, built it so that it would fit in my spare tire well. To start buy a bunch of saran wrap and vaseline. Coat the whole trunk in vaseline then apply the saran wrap. After that start laying down fiberglass mat and resin, do a few coats of it then add the top. Mine worked out great.
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Old 03-07-08, 09:59 AM   #3
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The boxes I have seen made of glass have wood bases, with raised wooden rings to hold the speakers. Then some sort of elastic fabric is stretched and and stapled over the top of the box to form the raised and curved form. Then fibreglass resin is simply brushed onto the cloth and allowed to harden. After this, then body compound is used to smooth the glass out and final sanding is done. Seemed pretty straight forward. Watch a few episoded of Unique Whips on SpeedTV, they do this pretty often.
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Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.
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Old 03-07-08, 10:20 AM   #4
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Yeah that's what I remember seeing them do too Jeff, but it doesn't seem like fiberglass alone would be rigid enough by itself unless you built it up extremely thick. That would cost a fortune. Hell I dunno.
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Old 03-07-08, 10:24 AM   #5
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That is why the box is wood, with the speaker rings supported by wood. I think the glass is basically cosmetic. If concerned, do the stretchy fabric, brush on one coat of resin, then lay on a layer of heavy fiberglass woven roven, and another layer of epoxy.

I repaired a deck hatch on my Cal 20 with two layers of mat and resin and it was pretty dang strong.

go get a quart of resin and a bit of woven roven and some stretchy cloth and do a small trial to see how strong it gets.

Once the mat and resin bond to the wood rings and stiffen up, you will be surprised by how sturdy and strong it is I think.
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Old 03-07-08, 10:32 AM   #6
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I'd suggest a nice nonresonant wood like Oak. Calk rthe seams to eliminate seam buzz and make it an isobaric enclosure. 1'X1'X3' for frequency response to below 50 hz and a crossover at 100 hz on the high freq side. Either 2 12" speakers mounted in a push-pull or a face to face array, or a single cone double coil speaker with a very rigid cone.
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Old 03-07-08, 10:52 AM   #7
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here is a decent article.

http://www.garbled.net/tim/fiberglass.html

BTW, most of my fiberglass work was on rental boats, primarily jet skis. All I was concerned about was fixing small holes and cracks to get them back to rentable condition.
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Old 03-07-08, 11:27 AM   #8
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There's a reason most speaker and subwoofer enclosures are made of wood.

Of course, very little attention is paid to sound quality in most car audio installations, so that reason is fairly irrelevant in this case. I'm sure a well-made fibreglass enclosure would be plenty strong to house a few subwoofers, and you could even get crazy shaping it, if you wanted.
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Old 03-07-08, 12:06 PM   #9
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My advice is for you guys to wear a face mask, eye protection, and long sleeve clothing. Cover as much of yourself as possible so you limit skin exposure. When you work with fiberglass, there are microscopic-sized fibers everywhere. You can easily breath these fibers into your lungs/eyes. Likewise, skin exposure causes itchy skin.
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Old 03-07-08, 12:09 PM   #10
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Carbon Fibre....definitely CF. and if you have any left over you can build yourself a nice bike frame to.
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Old 03-07-08, 12:52 PM   #11
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I vote for a bamboo frame, hemp T-shirt for the stretchy material, then hemp fiber laminate over that, using all organic resins...


Oh wait, it's for a car. Use PVC, fiberglass cloth, the nastiest epoxy you can find and be sure to spray it with an aerosol paint.
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Old 03-07-08, 12:54 PM   #12
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I say cover it in snail darter skin and decorate it with snow owl feathers and California condor beaks also. Animal motifs are big in the car culture.
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Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.
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Old 03-07-08, 12:58 PM   #13
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I say cover it in snail darter skin and decorate it with snow owl feathers and California condor beaks also. Animal motifs are big in the car culture.
Jsharr can provide snail shells...these should make excellent sound chambers.
Just need a really tiny speaker to place on the cone of the shell.
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