Like so many other people, I wanted to make the Bose system sound thicker, yet I still wanted to maintain most or near all of my trunk space. The only solution I could find is to build a fiberglass box as a false floor in the trunk and fill in that nice hole with two 12" orion xtr pro subs driven by an Orion 900 amp. And to do something with the pathetic 6x9's in the rear deck.

The following posts will be a step by step instruction on how to build fiberglass for the amateur and 'hopefully' make it look good. I say hopefully because I have not finished mine yet.

I will walk through where to get the components, and how to do everything in one thread with photos. So without futher delay, let's begin.

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The first thing to do is get all of the equipment you will need for fiberglassing the floor. It will require two stops and about $150 or $200 out of your pocket. You will need the following components from the following stores.

Home Depot

2 rolls of 2" painters tape
8-10 2" cheap as they get paint brushes
about 5 little plastic buckets (1 or 2 liter) to mix the fiberglass resin
dust masks, the little ugly white ones
latex gloves several, several pairs
3/4 MDF 4'x 8' piece cut into two 4'x3' pieces and the leftover as well
another small sheet of 3/4 MDF about 2'x4' will do.
Paint mixing sticks
about 4 garbage bags.

Your local boaters supply store (I used West Marine)
Fiberglass Mat 3-4 packs of 3/4oz weight,38"x90"
Fiberglass Cloth 1 pack 6 oz, 38"x90"
the big jug (about a gallon) fiberglass resin (epoxy will work)
one fifth of a gallon or similar amount of hardener. (don't get the fast hardener, I will explain later.)
carnuba wax (boat or car wax, not the liquid)

EDIT:
Home depot actually has fiberglass resin as I found out about two months too late. It is a little less expensive as well. Please read all of this post before you begin. I made mistakes along the way. Learn from me.

Then you need a lot of patients.

And Please do not destroy your car. This is a map of what I have done, I will not be resposible for damage to anyone elses property from the use of this thread. (It is a shame we have to put stupid disclaimers in things nowadays.) But have fun.

First I left all this equipment sitting on the garage floor and went for the 6x9's. I used the instructions found on another thread here. If someone would be kind enough to post the link for me I would appreciate it. Here is the finished product.

I remember reading that the rx8 has 8.9 cubic feet of convoluted trunk space. Well now I want to reap the rewards of that space to enclose about 1.4 cubic feet of space without comming more than 2" off the floor of the trunk (the sides and front, not the hole of course).

I am interested in building a false floor so my golf clubs and/or suitcases will still fit below the 6x9's. I have also decided to build the floor in two sections so the box can be removed if it needs to be, and to build three of the 6 sides out of MDF for the cost savings. Here is the gear that I have to work with.

First, you have to make sure that none of the fiberglass resin touches your car in any place. If it does, it is ruined. There is no getting it off. Take the time to do these steps carfully.

Take the Painters tape and tape off the area that you will fiberglass. Tape off a much larger area than you will need to fiberglass. There will be oversplash I promise. Use long strips of tape because the fewer ends that are under the resin, the easier the tape will be to remove from the glass once it is set.

Once you have laid all of the tape over the area that will be covered, make two more layers. If the first layer was lengthwise from the front to the rear of the car, the do the next one side to side, and the third front to rear. This will criss cross the pattern and make it more leakproof.

At this point it is time to make use of the MDF we bought. First take some old cardboard and cut out models of the side pieces that you will need. Cardboard is easier to trim to proper size.

Once the cardboard is cut into shape, the use it as a stencil to make the cuts on the 3/4MDF. Make sure you use the small pieces of wood to cut these parts from. You will need the 3'x4' pieces to make the baffles. Another thing to consider is the space that will be needed between the boxes (left and right) to remove them once they are in place. They will need to be lifted at an angle to come out of the trunk so at least 1.5" of dead space is needed in the middle. In other words, make the boards across the back of the trunk shorter than what is needed to come to the middle line. They do not have to be perfect, just rough outlines of what they should look like. You will need to cut them again once the fiberglass is laid. Make two pieces of each board as well. One set for the left, and one for the right.

Here I have also decided to make the false floor stop short of the back of the car. I would like to be able to get to the Jack and crowbar if needed.

Once you have them in about the right shape take them out and set them asside.

Once you lay down the three criss crossed layers, you will want to coat it with a releasing material. This is something that will allow the fiberglass to be pulled free of the tape. I have seen people use Pam cooking spray, and many other things, but use carnuba wax. It is much nicer to work with. When you think you have covered the entire surface with carnuba wax, coat it again. It will make life easier when you go to pull the tape free from the box.

There is no need to wait for the wax to dry, you can begin placing glass immediately.

Next is the fast part. I say fast because if you are not quick your glass will harden while still in the bucket.

First thing to do is take the fiberglass mat, and gut it into manageable strips. Well, the first thing to do really is put the latex gloves on unless you want itching to be your new hobby. The strips do not have to be equal in size nor do they have to be clean cuts. It will all be just one big piece when you are done. I used strips about 5" by 8", it seemed to work fine. Cut the entire package of mat up into these pieces before you go on.

Now that the mat is cut, take two garbage bags and cut them opened. Cover the bumper of your car from the outside down into the taped off area, and the opposite side from the part that you are glassing. Cover the floor with something just incase you drip. It looks bad on the garage floor.

Now get one of the buckets, a paint stirring stick, paint brush, and your resin and hardener. Into the bucket mix the resin and hardener at a ratio of 5 parts resin to 1 part hardener. They sell pumps to make sure this mixture is correct, however, it does not have to be exact. Extra hardener will make it harden quicker. But be careful. Too much hardener will cause bad things to happen. The hardening process is exothermic and creates heat. Too much hardener and there will be too much heat causing the bucket to melt and spill fiberglass resin all over your trunk. The fast setting resin almost caused a catastrophy for me. Take a look. There was smoke from the heat and everything.

Now that the resin is in the bucket, at the proper mixture, use the paint stir stick to mix them evenly. About 15 or 20 seconds of stirring with an upward motion should be sufficient. Also, be sure not to mix too much. I never went past the 1/2 liter line on the bucket and had about half of the mix harden before I could use it.

Once it is mixed, set it inside the trunk on the garbage bag side. Lay a piece of fiberglass mat on the area and use the brush to paint the resin on the mat. In a few seconds it will turn from white to a clear color. This indicates that the resin has gone through the mat, and that the piece is saturated. Stop here with this piece. Don't overload the mat with resin, it will just take longer to harden. But at the same time, don't use too little.

Take the next piece of mat and lay it next to but overlapping the first section by about 1/2 inch. This will ensure a good seal. Continue this process untill the entire area is covered including the side wall. Here it may be easier to paint a bit of resin on the taped area so the mat will stick to the side when you put it in place.

By now the resin in the bucket has hardened and is useless, along with your paint brush. Throw the brush away and start with a new one. Lay down a second layer immediately, while the first is still wet. This time, turn the mat pieces the other direction so they're seams criss cross like the tape.

Try to get the airbubbles out as well, however, this is not terribly important because you can just fill them later.

After the first two layers are sealed, go to bed. Come back tomorrow and they should be dry. In this process you will need to remove the fuse that runs the light in the trunk or your car will be dead tomorrow.

I did not do this. But managed to remember that the light was on after about two hours and started the car, let it run for a while, and then realized that it was mostly dry, and closed the trunk lid. I still left it sit untill the next day. Odds are, you got some resin on the garbage bags. If you are going to close the trunk to keep the light off, make sure you remove the bags so you don't get resin on the trunklid.

Now that it is dry. Lay down two more criss crossed layers and you will be done with the first portion. Then again, go to bed and come back tomorrow. You can use the car inbetween all of these steps, just make sure you air it out and there are no fumes in the cab so you won't pass out at the wheel. I did not have this problem because I left the center cover in place and was able to drive to work everyday.

I ran out of plastic buckets here because I melted the first two due to the accidental purchase of Fast Setting Hardener. Note the salsa container.

Now you want to mark off where the side boards will go for the box. Take the 4 boards and put them where you want them to go. Remember you need some space in between to get them to fit in and out of the car, and the size of needed board has changed due to the glass. Measure out the proper center space from the boards on the side of the car that does not have the glass in place. Then use a marker to draw lines where the boards will attach to the glass. Mark both the inside and outside of the board on the top of the glass.

The next thing to do is to pry the glass loose from the car.

Once the glass is dry, remove the garbage bags, and then begin to peel the tape from the carpet in the trunk. And yes I left the carpet in because the stock deadening material in the 8 is not too shabby. It is also less expensive than buying a ton of dynamat.

Peel the edges of the tabe back, and then start to peel the tape under the glass off of the carpet as well. Keep peeling one part at a time untill you can wiggle the whole glass section loose. Then take it out.

Once it is out. Turn the glass over and peel/pry as much of the tape off of the glass as possible. If you did a good job with the carnuba wax then it will all come off. Now you are left with a big piece of fiberglass for your subwoofer enclosure.

There will be a large amount of extra material at this point. That you will need to remove on the next post.

Now you need to cut the excess material off of the box. I tried several methods but found that a Dremmel rotary tool is appropriate, and effective. I normally hate Dremmels, it is the most useless tool in my garage, but for this it worked, so, so.

Use the fiberglass cutting attachemets. They are round flat pieces that look like firm sandpaper. It is a good thing they come in packs of 14, because you will break at least 8 of them. I got fed up and used the bigger one after a while, but the small ones cut better.

Start at one of the corners of the box and cut along the outside of the sideboard lines. This will make the box the shape you need along the two sides that will have MDF pannels. I have left the other side (along the wheel well) alone for the time being. We will come back to them later.

Now sand just a bit on the surface to remove any stray glass that is sticking up off the box in any area top or bottom except for the part that we did not cut yet. Don't sand too much. You do not need to weaken the box. In fact we will be adding another layer soon to make it stronger when, the supports are added.

Since there is a nice edge on the side of the box here, we can make adjustments to the sideboards so they fit nearly flush. Lay the sideboard down and then prop the glass up on it on it's very edge, and then trace the line that the top of it makes. In the end, you will need to cut about the glasses thickness off of the MDF sides. Makes sense right? See the picture above for the pencil lines of what I am talking about.

This is where I am at for now. I am going to bed, and will cut them tomorrow.

A belt sander works AWESOME for this...nice job so far...cant wait to see your end result...

I've done a few fiberglass projects. Your instructions are nice but the work could use improvement. First some technical considerations for the novice:

Protection
Proper protection is extremely important. Fiberglass dust will cause bad rashes on exposed skin. I don't even want to get into what it will do in your eyes or lungs. Organic solvents found in the resin are also bad for your lungs. Make sure to use a good two-part respirator designed to filter particulates (fiberglass dust) and organic vapors (resin). Wear a bunny suit if you can--washing fiberglass dust out of clothes doesn't work very well. Coat all exposed skin (including face) with talc powder before donning protective gear. This will help clog your pores so fiberglass dust doesn't penetrate. Take a cold shower afterwards to wash off everything.

Materials
There are two basic kinds of fiberglass--mat and cloth. Mat has strands in a random pattern and is good for conforming to compound (multiple curve) surfaces. Cloth is woven and is good for quickly laying up large flat (or single curve) areas. Both are specified in terms of ounces of weight per yard of cloth. 3-4 oz is a good weight to work with. There are also two types of resin; polyester and epoxy. Normally epoxy resin is used for carbon fiber and polyester for fiberglass. Part of the reason is fiberglass mat contains styrene as a binder. Styrene softens/melts in polyester resin and helps make it conform better. Epoxy is more expensive. Polyester resin comes in different grades. The clearer the resin the higher quality it is. Surfboards use the highest quality resin. The brownish stuff you find at most hardware stores (Bondo brand) is pretty low quality. Pot life can be a problem and is compounded by the amount of mixed resin. One quart of mixed resin will set much quicker than an ounce. I like to set up a bunch of paper cups with 100-200 grams of polyester resin in each. I then add catalyst to one cup, use it up and then mix the next cup. It goes fast and you don't have to worry about pot life as a result. You can also use the same brush for the entire layup.

Layup
One key advantage to mat is if you rip pieces off it has a fuzzy edge. Overlapping that fuzzy edge with the previous piece provides a secure join that doesn't have an obvious seam. Use the largest piece that you can easily work with. That minimizes the seams and overlap. Paint the surface with resin before laying the first piece. Use a jabbing motion with the brush to work out all air pockets. Air pockets look lighter than wetted out fiberglass and really should be avoided. Aside from looks they are significantly weaker and the uneven surface can cause construction problems later on. You want to use barely enough resin to wet the fiberglass but not so much that you have puddles of resin. Resin is actually weak and brittle. It's the fiberglass that provides the strength. When you place a new piece over another, use the brush "dry" to see if any resin wets through. If it does then you know you've used too much in that area before.

Originally posted by Bob The Eskimo
I normally hate Dremmels, it is the most useless tool in my garage, but for this it worked, so, so.

Here I disagree with you. Dremels with either a sanding wheel or fiberglass reinforced cutoff wheel are the single most important tool in my garage. I've burned through several of them before finding the Black & Decker RTX rotary tool. It has better ergonomics and torque so it doesn't bog down under load like a Dremel. Fordhams are even better but also cost $300. (I have one of those as well.)

Finishing
Cutting fiberglass with a cutoff wheel or sanding it will produce tons of dust. This is where it's really important to wear proper safety gear. Fiberglass dust is abrasive and will quickly kill a dremel if it gets into the motor. Use the flexible shaft attachment to help minimize this by keeping the main unit as far away as possible. After sanding use tack cloths to grab all the dust off the part. Once you have a finished part it's safe to handle normally but until then I can't stress enough proper safety precautions.

Other comments
This is a nice writeup Bob and I look forward to the rest of your installments. I can't wait to see how it all turns out.

FYI...a Laminate trimmer works very well in trimming fiberglass...as long as you have a guide...i always cut pieces of 1 by and clamp them to the piece, works great...

PUR NRG

Good points.

The protection thing is one point that I meant to include but forgot in my haste to post the work. My tool and saftey supply is much more limited than yours is. I simply used a thick long sleeve shirt that can be trashed with the sleeves tucked into the latex gloves. The dust mask got rid of the shavings from the dremel, and the breeze in the driveway was the best I could do for the fumes.

I like the idea of tearing the mat. I was affraid to try this as I only had one pack of mat to begin with But I will give it a try with section 2.

wow, this is gonna be sweet when it is done
but its a lot of work

how much money are you saving by doing it yourself?

coming froma custom shop background...$1000's

A tyvek body suit is maybe $5-10 depending on where you purchase it. It's reusable as long as you take care of it. If you're using throwaway clothes, don't try to wash them. It will contaminate your washer and you'll get fiberglass dust in all your clothes. Use some of that blue tape to tape the gloves around your shirt if you aren't doing that already. Then wear another set of gloves on top that you can easily dispose if/when they get too dirty. You'll find that tearing the mat produces a lot more loose strands that get messy. Don't forget fully enclosed eye protection (goggles) to prevent dust from getting into your eyes.

You tear fiberglass mat the same way you tear sandpaper. Place a long flat board as a ruler on top of the mat and tear. For detail work I like to tear 4" wide strips. I can then tear them into smaller lengths as needed during layup.

Use the flat edges of the mat along the lip of your part and the fuzzy edges on the inside. For the part you're making I'd suggest a single "strip" as wide as the bottom with the fuzzy edge overlapping the vertical wall. Then use 4" wide strips for the rest. That will save you a lot of time. Another technique is after the first layer is applied, put all the strips in the next layer down before wetting any of them.

If you're buying mat in packages it's probably more expensive than if you bought a length off a roll. Fortunately I live in Santa Cruz so I have several surfboard supply shops that have a wide range of fiberglass supplies. If you're on the beach you might find similar shops as well. Good luck with your project.

Well I have finished cutting the sideboards and temorarily attaching them. Now I will cut the baffle and supports and begin to post the photos tomorrow or Wed.

At this point however, I would like to ask a favor of some of the people who have spent some time behind the dashboard or under the hood. I have this dislike for drilling into the 8 to run a powerwire from the Battery into the cab and to the trunk. Does anyone know a way to get the 4 gauge power into the cab without drilling into the firewall? I have seen the post going through the space for the UK and Japan steering solumn, but man I will hate to do that.

Any suggestions?

Run it outside and in through the trunk lid! ;)

Good luck finding a way to get that wire that big in without drilling. That spot was the best one I could find. It isn't in the way of anything else and you can't see it without taking the washer fluid reservoir out. You may be able to find another grommet that already has wires running through it and force it in with them. It's been done before but I have damaged other wires in the bunch this way before and that is an even bigger PITA to fix.

"Run it outside and in through the trunk lid!"

I could turn it into a spoiler!! Great!

But seriously now. I have another question. The 8 has a 100 amp alternator. Cars (piston engine cars) normally draw ~30 amps to run, the Orion amplifier is fused at 60 amps, which leaves 10 for recharging and putting the windows up, so the question is; do rotary engines (renesis specifically) draw 30 amps to operate? If they do, then I have no need to get a stronger alternator. If they draw more than that, then I need to replace it.

Does anyone know the running apms of the engine? With/without lights and foggies on?

Thanks,
bob

Originally posted by Bob The Eskimo
"Run it outside and in through the trunk lid!"

I could turn it into a spoiler!! Great!

But seriously now. I have another question. The 8 has a 100 amp alternator. Cars (piston engine cars) normally draw ~30 amps to run, the Orion amplifier is fused at 60 amps, which leaves 10 for recharging and putting the windows up, so the question is; do rotary engines (renesis specifically) draw 30 amps to operate? If they do, then I have no need to get a stronger alternator. If they draw more than that, then I need to replace it.

Does anyone know the running apms of the engine? With/without lights and foggies on?

Thanks,
bob

30 amps to run? Are we talking spark plugs, ECU, electronic power steering, Exhaust air pump, HVAC, all with the rear defroster on?

Lets face it, 30 amps would probably be a 'idle' situation, but I'd be willing to bet that it'd be closer to 10A at idle, sitting still, with few to no accessories on, + there are several lights on that you can't turn off (like the console and the center LCD display).

I'd bet that the RX-8 can draw ever one of the 100A that the alternator is rated for, plus the other 60A (US models) that the battery is rated for, with an appropiatly powerful sub-amp...

Normally, just because you have an amp rated for 60A, doesn't mean you'll pull that much power.. That's close on 858 Watts at a nominal 14.3V system voltage. Can you say 'Deaf'.. That's loud. Typpical amps that I've seen measured will only draw about 10A in a normal 'subjective reasonably loud' scenario. 140Watts of sound, even going through a 50% efficient (most are at least 50 to 70% efficient) Amplifier will give you close to 100 DBA of sound level through even mediocre speakers.

edit: sorry maybe I should elaborate, current draw is proportional the the listening volume..

On the other hand, If you want to cruise down the road, with people in the car next to you plugging their ears, you might need more than a 200A alternator.

I'm planning on adding a 600W max output amp to my trunk, and I'm definately not upgrading the alternator, unless it breaks and needs replacement anyway, long after warranty, but my listening habits may be different than yours.

To more directly answer your question, it would probably be pretty difficult to get an accurate measurement of the nominal current draw of the RX-8, since the alternator and battery are working as separate, but cooperative power supplies, you'd need to probably use two, or three current probes, one on the alternator +, and one on the battery +, and then you'd need to figure out how much current the battery was consuming during charging (since it almost always is, but at varying degrees), so the third one on the battery - terminal to subtract from the + battery terminal to get toal system consumption (Alt+ plus Batt+ minus Batt-)

;)

OverLOAD

Yeah, I know the car and the amps will have a variable ampre draw over time. I am just weary of this because I went through two batteries, and one alternator in my old cavalier before I wisened up and found my problem.

I am just making a guess that average driving at about 3500 rpms with the lights on, will draw about 30 amps. The Amp I am running is rated 900 w Max and 225 rms x2 On average I will expect about a 35 amp drain (I am not a deafining listener either, about 20 on the stock bose is my loud limit). So I do not expect an issue.

After install, I am going to check volts and amps in the system at several points. This should let me know where things stand, and if I need a new Alternator.

bob

The next step is to trim the sideboards into the shape of the trace that you penciled in on them in the last photo post.

Once you use the Jigsaw and get the cut correct, there are a few options to keep the sideboards in place. You can either use a few screws to hold them in place or you can fiberglass them in place directly. I chose to use a few screws for simplicity's sake. Just dont screw too tightly and risk cracking. First you will want to screw the two sideboards together to maintain shape. Drill primer holes and then tap screws into the boards. Once the two are attached, drill primer holes in the glass as well as in the boards and attach to the glass. In the photo below you can see how much room was leftover. This space will be filled in with more resin and cloth.

This image is mainly just for fun. This is somewhat what the speaker will look like placed in the box. There will be a bit more room in the corner when the speaker is lifted above the back pannel.

But I think you get the idea.

The step that did take place before I placed the speaker is triming the extra glass off of the top(wheel-well side) of the box.

This was done by laying the box upside down with the sidepannels attached, on a piece of the MDF that had not been cut. The portion of the glass that was not cut to shape was left to hang over the side of the MDF. Then the box was rotated so that all overlapping glass touched the MDF and a mark could be placed on the glass. Connect these dots, and you have a line to cut with the dremel or B&D rotary tool.

Pretty simple.

Nice feet! :D

"Nice feet! "


Scary. . .

Here check this setup

drool . . .

but I need practical as well.

thats macnific!!!!

I have a question to ask.

I have been sealing the box lid in place over the past few days and have found it to be a bit more time consuming than I first imagined.

I began by tapping and screwing the baffle into the sideboards, then I began to wrap fiberglass on the outside just thin enough to get a seal (i used the cloth rather than the mat which seems to flex a bit more), and tonight I will fill in the open places on the inside with more fiberglass resin. After that drys, I plan on using clear caulking to fill in any remaining gaps.

Does anyone have a better way of sealing the box?

I think for the second section of the box I will try to set the sideboards in place while the fiberglass is still drying. I may even try to have the sideboards, and the baffle already screwed together and place it all in one piece. Any thoughts?

Ok, I probably chose the hardest way possible to seal the box up but I am going to work through it. Let's start with a photo.

What I have done in the above picture is as follows.

Once the fiberglass is cut so that the baffle board lays as flat as possible on top of the box, begin to seal the outside edge of the box as air tight/water tight as possible. I was careful not to go higher than the baffle. You may find it helpful and adds extra strength to go higher than the baffle, but The second portion of the process is what will hold the pressure, not this layer.

Go the whole way arround the box and seal it as well as possible. Then go to bed and come back tomorrow.

After the glass has dried, come back and we will work on the inside of the box. Take some fiberglass mat and in any large areas, stuff small shreds of the mat. Then mix up some resin and strategically pur the resin into the cracks or opened spaces. Don't be afraid to over pour the spots. It will only add thickness to the box. You will also want to pour resin arround all of the openings/cracks/seams or whatever holes may exist. This when hardened, will give the box a perfect seal.

At this point sleep, and then come back and go over these areas with caulking. This is an extra seal that never hurts to have.

Okay, now I can visualize what you are doing.

1. By glassing over the wood, won't it prevent the two halves from fitting together snugly?

2. Have you heard of the stuff they use for automotive window calk? It's a black urethane that's flexible but adheres well. You might try using that as glue to attach the wood to the fiberglass. You can also use it as "regular" calk afterwards.

3. There is also a type of bondo that contains fiberglass strands mixed in. I hate working with the stuff but might be what you need for sealing/reinforcing. However I'd still recommend the window calk. It seems like flexibility would be good to help absorb woofer vibrations and it's lighter than bondo.

Yeah, That's exactly what I wanted to do with the window caulk. The thought was to seal the outside with fiberglass cloth, let harden, then pour resin in the sides (from the inside of the box) to fill up any major cracks. Then the smallest holes will be filled with caulk.

Plain resin is brittle. How will to hold up to continued vibration from the speaker? It isn't a very good adhesive on its own either.

That's why I recommended the automotive urethane window calk. You could apply a thick bead along the board's edge, press it into place and after it cures use a razor blade to trim the excess that squeezed out. It would give you an airtight, strong yet flexible bond.

I agree with you. Caulk is probably the best way to go. I was just affraid to do this in the larger gaps that were left between the board and the glass. The caulk has some flex that I was concerned with under SPL, but I think I overcame that with the outside layer of glass.

Resin is brittle by itself, but it bonds very well to other glass and to pourous wood surfaces (MDF). I should have some more photos this weekend.

On a side note, I feel like i just graduated. I got rid of that 'junior' next to my member status. I finally have enough posts!!!

PUR NRG

I forgot to post a reply to question 1.

The two halves are not going to fit together snugly. There will be about 1.5 inches of space between them, with the passenger side baffle board being larger than the box. This will allow the appearance of two connected boxes for the false floor, but allow enough wiggle room, that the boxes can be moved and removed from the trunk easily.

I would be on the second box by now, but sealing this thing up takes one day per side to dry. What a pain.

Well if you are not concerned with looks, I would say as long as you can get the edges of the MDF to get pretty close to the fiberglass, you could put a fat bead of liquid nails on it and then run screws through the fiberglass and into the MDF. That will seal it perfectly. That is how I have always connected my pure MDF boxes together. I am looking for measurements of just the little recessed area in the floor so that I can see how much airspace is in that and also what the depth is. I am thinking about just building a box for a single 12 in the recess if I can get enogh airspace and depth.

If I remember correctly the recess is about 1,592.5 cubic inches if you leave about 2 inches at the back for the opening of the jack hatch. This is about .9 cubic feet. The 12' would need about .75 feet of breathing room after you take into account the displacement of the magnet and shell. The two 12"s that I have require about 1.25 feet each. There may be models out there that requre that amount.

Also, The look of the box will be carpeted to match the rest of the trunk. You will not even be able to tell that it is glassed.

Ok, it's been a while because each step I had to seal one side of the inside of the box. I used fiberglass resin and cloth, and then in the small areas with holes I used window caulk to fill in.

Now I am left with a perfect seal. It just took forever because each side took a full day to dry.

Take a look.

yes I know it looks like crap, but it will all get better soon.

I was not concerned with the image of the box without the carpeting on it, just that it had a perfect seal.

In order to double check that I had a perfect seal on everything, I lightly placed the speaker in the box. With a flat hand I gently pressed on the speaker cone and listened for any leaks that were audible. I also ran my hand around the box slowly to detect any leaks by touch.

Once you have a seal in all areas so that you are comfortable with it, we begin smoothing things out. Take a sander and sand out all of the rough spots, high points, outcroppings, and other stray pieces, and make it fit your trunk perfectly. Have the whole box smooth to the touch. At this point it still may not look perfect, but that is ok.

now that the box is sealed and sanded, it is time to puncture it for the wires. I was never a fan of placing any un-needed connectors, so I opted to run wires from the speakers directly to the amps rather than a connector at the side of the box.

Simply drill a hole in the sidewall of the box wherever you see fit, and then run wires to the speaker. Internally, I made sure the wires dont rattle against anything by running them through the speaker frame and removing any slack that would be available. Once you have the Wires in place and the speaker in, use window caulk from the inside and out to seal any remaining space in the hole.

now, bolt the speaker in.

Here is a pic of the setup in the trunk so you can get a feel for what It will look like when the entire setup is done.

Here is another angle. i built it this size for easy access to the jack if needed.

I also have about 11" of clearence over the top of the box (and amp when installed) so that golf clubs, or luggage would fit.

I could have mounted the speakers inside the box for added room, but decided I would rather have removable speakers than, recessed subs.

I will install a grill or plexiglass cover after completion. for now, there is a large amount of room in the front end. The amp will ride across the top of the boxes, but will still allow 10"-11" clearance.

Over the next few nights, I will carpet it and finish it up before begining on the other side.

I wish I would have seen this earlier. The easiest and most sure fire way to seal up the inside of your box is with a combination of bondo and fiberglass. This is something that we just experimented with one day at the shop and found works extremely well.

To do this take a large plasic cup and fill over half full of just pure bondo. Then add a small amount of fiberglass resin to the cup. It doesn't take much. You want just enough that it will run but not so much that it is watery. Now add the Bondo hardener only. Do not use the mekp fiberglass hardener. Mix this together and then pour it into you box. Now hold you box up and turn it around watching the mixture coat everything inside. It is pretty neat to see since it sticks to everthing inside. You may have to do this process a few times to make sure you coated the entire inside well. It hardens within only a few minutes just like bondo does so you've got to be pretty quick.

Your box will never leak with this method. It is very easy to do. It also adds a little thickness to the box as well as giving the interior a very nice smooth finish. I never use caulk in a fiberglass box. Try this method before you carpet it. Remember it is easier to do it right the first time than it is to do it again.

now that sounds like a good idea. Thank you god.

rotary god that is.

Did you try the bondo/fiberglass mixture? Most people that try it make it too runny the first time. I'm curious how you did.

What I've used to good effect is a bondo/gelcoat slurry. Use a 1:1 ratio and add 2% (by weight) fiberglass resin catalyst.

Hello again. I had taken a stereo break while I busted ass for my company. but now I have a few minutes to update everything.

Rotarygod, I will take your advice on my next half of the enclosure but testing this one proved that the glass that took me forever to lay, actually worked for a perfect seal. I placed my hand on the speaker cone and could not find any leak points once the speaker was tightened in place. So, I moved to the next step.

I went to the local audio shop, and purhcased about 12 feet (way more than enough for both halves) of stretch carpet, and then to Home Depot for some spray adhesive. I sprayed the back side of the box first (the side nearest the back of the car). This allowed me to stand the box upright to smooth out the remaining sides.

Take the speaker back out of the box and spray one entire surface at a time. However, you want to leave a ring arround the speaker hole without any adhesive. Stretch the carpet the whole way arround te box spraying in sections as you go. Then go back to cut the speaker section out of the carpet.

Once this is complete, cut about 1/2 inch outside the speaker hole, and seat the speaker. Pull the carpet on top of the speaker so the box and the speaker create as perfect a seal as possible, and then trim excess away. Don't forget to cut the hole for the wires as well.

What you are left with should look like this.

Here is another angle. Again, There should be plenty of usable trunk space once the other half is completed.

Now comes the tedious part. Figuring out where to run the power wires. I have this aversion to drilling into my brand new car, so I scoured the firewall for rubber grommets.

I only found one.:(

But it was useable.:)

Here is the location just to the left of the clutch, and behind the wheel well.

Here is from the cab.

The rubber has two sections to it. There is a center tube for the stock wires, and there is an outside area that can be used for your power wires. Mine went half in the center, and half outside but once it was through without damaging the stock wires, I was happy to leave it this way.

Here is an image of how I ran the line to the trunk. It will fit in the door jam, but just barely. To remove the jam, start at the front end and lift from both the left and right very carefully. Then gradualy move back as the snaps let loose.

After laying the cable, carfully move in reverse in replacing the cover. You may have to move the cable from one side to the other, but this image should be almost exact.

Oh, and I forgot, Nice feet again, eh?

This is a critical thing that I left off of my cavalier. I lucked out because I never wrecked my car, But it could have been pretty bad if I would have.

I am concerned with the distance of the fuse from the battery, but this is better than nothing. It is about 22" from the battery. I am using 80 amps.

In attaching to the battery, you simply remove the large cover, and then the terminal cover, you will need to cut a section off. Remove the corner nearest the engine, and the rear snap on the fold up piece. This should give you plenty of access.

Now I am in the process of PMing people to find the best way to tap the RCA lines into my amp. Thank you all who have helped.

I will run the lines over the next day or so, and then attach a small Precision Power amp to tide me over until the whole floor is complete. With any luck, it should be deafening, yet crisp.

I am planning on building the second half arround the oil bottle and the tire repair kit. This will do two things for me. It will make a nice built in place to stick the oil and repair kit, and it will make a slightly different resonating note for the second box. I should be able to flatten the frequency response quite well with independent gain and InelliQ.

We will see.

you did a amazing job
looks perfect

thats lewks soo freakin good man!!nice work!i wanna do that with mines..how long did it take for you to do?

2-15-04 thru 3-26-04. But I only worked on it a few days for a few hours (if that). I worked 1 hr on one day 30 minutes the next, 2 hours the next, then went to Atlanta, and Jacksonville etc.

All in all I would say about one week working about 2-3 hours per day. But before this, there were many days of planning and learning how to lay fiberglass.

Tonight I tested the volts on the 8 and noticed that it seems to be running about 14-15 volts with the healights, radar detector, foglights, and stereo on at about 10 volume. Has anyone seen variances from this or should I use this as the basis for when I attach the amps and check for drain?

I honnestly expected about 13 volts, but hey, that's ok as well.

bob

Here you can see the base of the second half.

Here is another angle. Notice the Oil can and Tire Kit.

Now that side two is layed and hardened in shape, trace the sideboard location as in the photos above, and pull it from the trunk to work on it outside the box. Once it is cut to shape, then screw the sideboards together and then into place. Trim the glass to height and cut the baffle the same way side one was made. Once this is complete cut the hole for the speaker and make sure it will sit together correctly. If all is well, then seal the box up.

This time I got smarter and sealed as much as possible before I layed the baffle in place. I will also seal the baffle with a layer of glass between the sideboards to make sure it is easy to seal.

Trim the glass sections to small enough pieces to go arround corners and bends. Fold them in half and stick them in all of the cracks so they fold open and half on the glass, half on teh boards.

This time around I have found a way to reduce the headache and itching that results from this portion of the project.

After thickening the inside of the box before the baffle goes in place, and taking the time to ensure that all of the margins are sealed well, add resin and glass to the top edge of the box.

The top edge of the side boards will contact the baffle board. If you paint this top edge with resin, and then lay down some fiberglass mat or cloth cut into 1/2" wide strips, then resin this glass, you can form a perfect seal with the board when you screw it in place. Just make sure you seat the baffle board in place while the glass is still wet. It also helps if you have pre tapped the screw holes before you lay the glass. I will post photos very soon.

This leaves only one side of the box that needs sealed once the baffle is in place.

It is beautiful. Pics tonight. . .

very good

It is in. Attached is a photo of the sealed sides. This will make life easier in trying to get a good seal between the baffle and the sideboards.

another

Now comes the time to seat the speaker and run the speaker leads. I had to drill two baffles because I drilled the opening too large. This one is perfect however.

Now we carpet

Before I began this fiasco, I ran wires and attached the other sub as a test. The wires have been a disaster in my trunk for days. Take a look

The ground point I found was perfect. I did not even have to drill out a spot. If you pull the side carpeting away from the trunk, and look on the right hand side out near the side pannel (the farthest part from center of the trunk) there are two holes with screw taps already in place. Just get a screw that fits in these, remove some paint, and connect your ground. Easy as pie.

Next comes the placement. and attachment. Don't forget to put your gains as low as possible and then work your way up.

Another angle.

Believe it or not the speakers are acutally centered in the trunk, and in the boxes. The line between the boxes is off center. I guess in retrospec, I could have made this an even center line by halfing the cover. Oh well. It sounds insane.

One more view.

The amp is a bit crooked but that is easy to fix.

The oil bottle and tire kit fit perfectly. Speakers are within .1' of perfect breathing room. I have a S#%t ton of trunk left. I can get to the jack if I need to.

I will eventually build a center piece for the back side to block the view. It doesn't need it however.

And now, I need another project.:cool: :D

From here I will have a local plexiglass shop build me two (or one big) grate to cover the speakers so the golf clubs will fit on top.

I am in bass heaven. The only problem is that the amp has so much power I have the gain set at about half to balance with the rest of the system. Anything more and I can't hear my mids.

Also, The rx8 runs at about 14.5 amps nominal from the alternator and battery. This system is running 445 watts at 2 ohms. With the lights on and the AC on, when the bass hits the system drops to about 14 amps. Does anyone think this will be damaging? Please help on this. I don't want to get stranded on any long trips.

I'd be more concerned about the short trips adding up.. but 14 amps isn't all that bad. The alternator is rated for 100 amps. it can handle it. It just emphasizes the need for a batter gauge.

If you were cranking out 30+ amps on that line, I'd start to be concerned. I ran a big 600Watt amp on dual 10's in my MX-3 with only a 90 amp alternator for years. The battery died after 8 years, but (some) batteries should be replaced much sooner anyway. If anything, there'll probably just be a little deeper cycling of the battery, slightly reducing it's life expectancy.

If you really want to keep an eye on if you're slowly depleting the battery, get a decent charger and see what kind of current it draws when charging (but don't change it for long, just long enough to get a reading). If it starts to take more and more current, it's slowly getting depleted and might leave you stranded.

It probably makes a big difference how long your average trip time is than anything else as long as the system has reserve capacity.

The battery will get hurt from deeper cycling, but the alternator should be fine as long as you don't draw more total current in the system than the alternator is rated for. Even then it's supplemented from the battery, but when you stop you can have no power left to get going again.

Regards,

OverLOAD

Thanks for the info. My daily trip is about 4 or 5 miles to and from work. The car has plenty of time to get warm by the time I am out of my neigborhood.

Thanks,

looks like all the hard work
paid off


looks very sharp

<drool>

Looks amazing. I'm impressed that you even built in the little nook for the tire repair kit and oil.

If you could make more, I'm sure folks would buy them.

Oh... My... God... You have done a great service for those who are compitant enough to complete this, but wouldn't know where or how to begin... Thank you... From the bottom of my heart... Thank you!

If you're getting 14v or over at idle with full load (all accessories on, bass hitting) you're golden. Hell, even in the 13v range you'd probably be OK.

I'm assuming that you're checking voltage at the battery with a meter - that's the best way to check.

They probably used the same alternator in the RX-8 as they did the 3rd gen RX-7 - that sucker puts out a LOT of juice, I think it's actually under-rated at 100amps.

BTW, cars with Bose/nav/etc. will likely draw more current than less-equipped models. Also, I seem to remember the automatic might have a different alternator - anyone know?

Anyhow, good job! I've always wanted to do something with fiberglass, and it's neat to hear of other's adventures :).

Dale

It has been some time since my last post on this thread but I have to complete the project. I have been searching for a plexiglass cover for the speakers so I can use the space for luggage. Unfortunately, everyone wanted a fortune for the work so I must do DIY again.

Does anyone have any tips on gutting plexiglass to get smooth edges?

bob the eskimo...I work in non-ferrous metalsmithing and I have to cut plexiglass/fiberglass for metal die forming...

You can use just about any saw, even a jigsaw as cutting it is like butter...BUT just like butter it will melt and create a mess...specifically the synthetic glass will melt down and gum up the saw if you don't keep the saw at an extremely low speed. You must be patient or the jigsaw (or bandsaw, whatever)...will as it is cutting through, heat up through friction, and you will find the cut will melt back together as the blade passes through it...\
another trick is keep a fan on you cutting or many jigsaws have a blower built in...aim it not so it will blow particles away but blow on the blade and the cut to keep it cool.

Practice with a piece of scrap first to get the hang of it...oh and if you don't have a jigsaw or the like...use a jewlers saw, it is slow but flawless and you can control the cuts much better.

More CRITICAL info on cutting...you will scratch the hell out of your project if you remove the plastic coating on the synth. glass. Also use a buffer bettween the saw table and the project to prevent scratches....and keep the project flat as you cut it...severe vibration will prevent an even cut and possible cause cracking.

ON SMOOTHING THE EDGES...if you cut extremely carefully you may not need to do this (but that is unlikely) so...this is easy...Sand it!

Start with a 200 grit silican carbite paper....break glue bonds on paper by pulling along a 90 degree edge (like the end of the table), this makes the paper more durable...wrap paper around a small block of hard, smoooth wood...sand edges till relatively smooth...

if you wish to have a beveled edge...carefully angle the sanding block (with 200 grit paper)

Then move on to 300 grit silcan carbit paper...sand till smooth

then 400 grit...you can probably stop here as the edges will now be smooth with a slight haze to them

if you really want perfection do a 600 grit...and finish it off with a 1200 or more grit...this will polish it (but both 600/1200 are hard to find at most hardware stores...but look around)

one alternative...is at around 400 grit...if you have a polishing wheel...get a synthetic glass polishing disk that will finish it beautifully...and fast!

Good luck Bob...and anyone else with you DIYs!

A couple things to note here and to help improve upon and hasten the finishing of acrylic plastic edges. If you want to skip a lot of sanding, and you do not need an edge that is optically clear, use a small blow torch to heat up the edges, this will melt the roughness and produce a very smooth edge that will not show a lot of marks to it. Do not over heat it to the point that it actually turns to liquid and melts. Just heat it gently and as you apply the flame at the right moment, it will turn clear. Always move the flame back and forth along the edge so as not to overheat in one area.

If you want to get a glass like optically clear edge and you do not have a polishing disk on a grinder, buy some 3M rubbing compound (Professional Formula) at your local auto parts store in the paint section. This you work with after the 1200 + ( I use 3M Imperial WetorDry 1500) grit sand paper. You can also obtain this readily available at the local auto parts store in the paint section too.

For projects that I work on, I first use the ban saw, then shape with a belt and disk sander. After that it is sand sand sand. As truemagellan said above, graduate up with the grit as you go along.

Here are a couple of pics of a project that I did with my K&N intake window and unpainted rough and smooth sanded fog light accent strakes that demonstrate this.

That, Dennis, is VERY slick! :D Got a thread going on it somewhere?

That, Dennis, is VERY slick! :D Got a thread going on it somewhere? Yeah, I posted on it before. Took a lot of pics and stuff but do not remember the name of it. Took me a while to find the original thread but here it is: http://www.rx8club.com/showthread.php?t=28185 I know, I owe a few DIYs for a few of these things I am guilty of. :D

I just finished my amp install. What I noticed is that the grommet on my 05' is different what is depicted in this thread. I had to cut a slit on the side of the grommet and squeeze my power wire in through.


Not sure if Mazda changed the design of this part at some point.

Brett

I just installed 2 infinity 10" subs in my 06 last week. I found that the easiest route for the power wire was to drill a whole right behind the washer fluid holder. That way I didnt have to worry about damaging the wires in that gromet. Just a thought.

How did you end up hooking up the rca's to your amp?