I'm strongly considering creating a custom fabricated fiberglass subwoofer enclosure for the "hole" in the trunk of my RX-8...

It seems like the ideal location.. and the appropriate size..

I'm thinking about mounting a 10" sub & the amp on the same box. Does anyone have any experience with fiberglass enclosures? My main reasons for fiberflass are reduced weight, and the capability to finish it like a body panel.. to make it very slick looking when i'm done..

OverLOAD

 

I have tons of experience with fiberglass boxes. What do you want to know?

 

Well, basically, what would you suggest for the skeleton of the box, and the best method to laminate the two halves I will have together. I'm planning on making top/bottom pieces, and I'm wondering if some wooden support members, or other pieces to support mounting the amp directly into the fiberglass is a good idea.

A one piece is probably a better idea, but it will not be too easy.

what type/size skeleton, if any would you recommend, and what type of glass mat & how many layers tend to work best?

Thanks,

OverLOAD

 

The "hole" that you are refering to has the aproximate following dimensions:

26" X 14" X 5.5" (this is from memory)

The killer is the 5.5" because your internal dimensions will become something like .84 cubic feet before you factor in where the amp is going to go. You also have to worry about putting stuff on top of the woofer, etc.

That was the first place I considered putting a box but I decided that the space could be better used for other things.

-Mr. Wigggles

 

Well, to be exact, the 26x14x5.5 you mention works out to be exactly 1.1586 Cubic feet. That's plenty. I thought about to potential problems with the loss of usuable space but just because the space is so enticing to put a sub in, I don't think I can resist.

I'll most likely be going with a configuration where the amp is mounted to the top of a ported enclosure, and the sub (probably a 10" Infinity Kappa Perfect Dual voice coil model) will be mounted slightly to the side.

Then If I still need a special utility space in the trunk, I may fab some guides or rails to fit in the trunk.

I just keep thinking about how a matching body color, curvy sub enclosure sitting in that well would look, and it brings a smile to my face.

OverLOAD

edit: ps. There's nothing stopping me from making the enclosure rise a little over the space as well if I need a little more volume. It just makes a better place to just 'plunk it down'.

 

OverLOAD,

I was refering to internal volume.

-Mr. Wigggles

 

When I do fiberglass enclosures, I do the main baffles as well as any flat sides out of wood. If the front is the only flat side then obviously this is the only piece of wood. If I am trying to conform to a certain shape that I want the fiberglass to form to, I line the entire area in masking tape. Covber completely with several different layers. Make one layer of tape all go in one direction and the next layer in a different direction. About 3 layers is plenty. Do not use Duct tape. Save that for when you need to fix the car After the entire area is taped up really well so that no fiberglass can penetrate it, wax the tape very thoroughly with a carnauba car wax. Do not use the liquid wax. This will serve as a mold release. Mold release is also sold at various locations that also deal with fiberglass but if you can't find it use wax. Now set some old towels down around the area to be glassed. Hopefully you will have taped a MUCH larger area than was necessary just in case of a spill. Now cut up your fiberglass into small sections. Use some good judgement here. It doesn't need to be exact. Generally about 2" X 5" or so pieces. Cut up more than you will ever think that you will need. Use 2 different kinds of fiberglass mat. The first 2 layers should be with the woven looking thin mat. This is very flexible and is a perfect base. As with the tape do 1 layer all facing one direction and the next layer a different direction. 2 layers with the woven mat is fine. Now do about 4 layers with the "kitty hair" type of mat. This is the stuff that likes to fall apart and stick to your fingers. Oh yeah, wear rubber gloves and use a paint brush to paint the resin on. Do not dip the strips in the gel. Best results come from using only as much resin that is needed to soak into the strips and no more. You do not want excess resin so do nomt go back and paint on the excess. Either use more strips or throw the leftovers away. You need about 30 min. between each layer if you mixed it properly. Now back on track. Lay the kitty hair mat down in about 4 different layers. If you have to ask if you have enough layers just remember that you can never have too much but too little is hard to fix later. After the last layer dries, go back and remove any awkward pointy resin spots with a sander or die grinder. Now go back and do one more layer with the woven mat. Attach your wood baffle to you newly formed enclosure by overlapping the wood over the edges of the fiberglass that sticks out on the edges, or vice versa depending on how you did it. Hopefully you will have fiberglassed a larger area than you needed. You can always cut it off. Attach the two together with screws. There will still be some holes to the inside but this is OK. Lightly fill in the area with Bondo and maybe a single outside layer of fiberglass. trim away any excess to get your finished box exterior. Now we need to finish the interior. Get a big cup that you never want to use again.Pour some regular Bondo into it filling it about half way up. Now add some fiberglass resin to the cup as well. Only add a little at a time. Stir it to mix well. When you can easily pour it but it isn't too runny you know you have it right. Now add only Bondo hardener to it. Mix well and then immediately pour the concoction into the box. Turn the box around to make the mixture run to all corners of the box. This mixture will stick to every surface in the box making it smooth and sealing it at the same time. If you didn't make enough the first time then do it again until you finish. The mixture will harden within a few minutes. There you go. A fiberglass enclosure that is totally sealed. It seems like it would take forever but can be done in a day. Try that and tell me how it works out for you.

 

I haven't had the mat up in the boot, so this may be a useless suggestion...

Is the well in the boot sealed? If so, why not just build a flush baffle and line the well. A custom mat to cover the then flat boot floor possibly?!?

This is the path I was planning for a dual v/c 10 inch JL. Maybe it's less than perfect, but I'm also weight sensitive - particularly in the overhang areas.

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