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.

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.
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COACH PURSES

 

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.
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OUTDOOR YOUNG

 

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

 

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.