How To: Fiberglass Sub Box Build-Up

[Rinkrat456]

Alright guys. Thanks for waiting so long. I've finally found enough time to get my box heading in the right direction, and also enough time to start writing this build up. You guys can use it as a how-to, or just view what I've been working on for the past 3 months.

To start off, Part I is all about the materials and tools that I used while building the contruction portion.

Materials:
3/4" MDF (medium density fibercore or fiberboard) 4x8 sheets
Gorilla Glue
Clear Silicone Caulk
Wooden Dowels
Hot Glue, Clear
Minwax Clear Coat

Tools:
Table Saw, Rip/Crosscut combo blade, and Dado blade
Radial Arm Saw
Jig Saw
Scroll Saw
Router - flush trim bit
Roto-zip- wood cutting bit and circle cutter attatchment
Dremel
Bandsaw
Hot Glue Gun
Caulk Gun
B.O.S.S. Sander
Paint brush

I started with large 4x8 sheets of the MDF and cut out my amp rack first. To do this I had two guys help me on the table saw for balance, and cut the sheets roughly to the size I knew they'd be leaving a bit over for error. After the cut pieces are managable I cut them all to actual size.



To make the pieces stick in there without glue yet or screws or anything, I cut dados inside the wood at an angle with the table saw. A dado is a cut groove inside the wood, and a rabett is a groove on the outside of the wood.

When combined together, they make a nice ridge for the glue to hold to rather than just face glueing the pieces together. I have never used screws before on any of my box build ups because screws dont hold as well, and actually crack the wood and becomes a stress point due to the hole made. All the dados and rabetts are 3/4" wide, and half the thickness that the wood is deep - so 3/8ths deep.

[Rinkrat456]

Starting where I left off in Part I, this is where the woodworking fun began.

After my amp rack was cut I needed to cut out the bottom piece and angled side pieces. To cut the angles the table saw blade was angled to the side as needed - I think it ended up being a 15 degree angle.

The back was simple, all that was done was I tipped the sides, bottom and amp rack on it's back and trace the figure on a full sheet. After a medium sized bottle of gorilla glue and 18 clamps, the box started taking shape.


I cut little triangle support pieces just for my own comfort and security. I'm positive it's over kill but the front didn't have a board to connect the side pieces to so I thought it wouldn't hurt. I also took this time afterwards to seal up the box using silicone caulk and put it in every joint there was. Remember, you want the air coming out from the sub or out the port and no where else.

[Rinkrat456]

Man, I wish there were more pictures allowed, but oh well..

continueing...
Afterwards, the rings were up next on the list. These got tricky at times but with the right tools they turned out really nice. I flipped my sub over and traced the outside diameter. That was going to be my flush ring that gives the sub a set back look - also looks cleaner IMO. The inner ring - also the largest - I used the sub's manual and looked up the cut out diameter needed. Using a 2' arm compass I made the inner diameter the cut out diameter, and the outside 1" wider than the sub is total. That way when the two rings are glued together one sits ontop of the other while still giving a lot of support. I used two methods to cut the rings, just so I could show both. To cut the first ring I used a bandsaw on the outside to get the general shape needed and a skill saw afterwards for the inside, keeping tight to my line but on the outside so I could sand to actual size. The other set was cut using a router and a circle jig. Afterwards, both needed to be sanded down so I used the B.O.S.S. sander and the largest drum there was. A smaller drum will make more grooves as you go around so use the largest one possible.





Next it was time to put it all together. The rings, the box and and the ports.
Using dowels 1/2" thick and hot glue, the rings stayed up there with no problem. To get the rings the same, a level was used on the front to get them even, and also on the top to get the heighths the same.

[Rinkrat456]

The ports were by far the trickiest things to cut. Not only because I only had one clear tube to use that was $160 bucks for it, but also because of the angle.

The tube I bought was a 4" inside diamater, 4.5" outside diameter 3 foot long clear acrylic tube. Why clear? Because I would like to have green neons in side the port area (not inside the port but where they come out) so a green glow will come through there. That I used an acrylic table saw blade and a belt disc sander to make them smooth. To cut the holes, a 4.5" hole saw was used with a high output drill. In this picture I have them more upfront, but I ended up making the holes furthur back on the divider so the angle coming out would be to my liking.





Also, while I was doing all this cutting I cut out a slot in my shelves so wires can be run through there and also a hole out the back. You're probably thinking that's a huge hole but it didn't matter how large that hole was because no air passes through that area. I also took this time to clear coat everything. I found that wiping spilled resin is a lot easier when the surface isn't porous and the pores in the wood have already been sealed.

[Rinkrat456]

Now comes the sticky part! Fiberglassing is a two part deal combining fiberglass cloth or mat, and resin.


I have noticed that there are a few brands out there, all work just as fine as the next. I have also heard that there is some high buck resin you can get in 5 gallon pails - something I probably should have done but making a few trips out to Autozone and Fleetfarm is alright with me.


For starters, fiberglassing requires a mold. Either concave or convex. In this case I used a T-shirt material to pull over the box and staple onto the sides. It is best that the material is pulled extra tight because every wrinkle will take at least 2 layers more to get out, plus more bondo - but we'll get to that later. Also, it's ok to use more than one piece because after the first layer of 'glass you can't see the seem anyway.

[Rinkrat456]

After the material is pulled over the box, out comes the resin. You only have about 5 minutes to work with the resin before it gets really hot in the bucket in your hand because of the chemical reaction and becomes hard. I used quarts at a time, which equates to about 5 minutes of working time. By the way, you use half that tube of hardener for every quart of resin mixed. The best way to do this is buy a mixing container, fill it up to a quart with water and find an ice cream bucket or large cool whip container and poor the quart into that. Mark the line with a pen/marker and that way you dont have to buy so many expensive mixing pails. After the hardener is squezed into the resin, mix extremely well. If you miss any part there will be little drops where the hardener reacted too quickly and also the resin wont dry if there is no hardener.


Lay on a wet thick coating of resin. When this dries you will have your mold that you can start laying the fiberglass over.


Cutting up the fiberglass mat or cloth takes some thought before. Depending on what shape you're doing or on what portion of the box you're laying it on depends on how you cut it up. Any curved sections, rip 4"x4" sections by hand so you get frayed edges that overlap much better over cutting them. If you're laying over a completely flat section, scisor cut strips work fine. Just laying the mat or cloth down in one piece will not work. You will get to many air bubbles underneath and that's where you loose your strength.

[Rinkrat456]

Now onto the big question...how many layers do I need? I'm not going to copy and paste this article into here, but I'll link to it.
http://www.caraudiohelp.com/newslett...ass_layers.htm
This article is amazing in giving the low down on everything you need to know about determining thickness.

How thick am I going you might be wondering? After determining the power handlng of one layer, the number of curves vs. flat areas and the weight of the sub in general I found I needed 7 layers but me being me I'll go with 8 just to be sure. One layer is composed of first painting on resin to the spot you're doing, laying down the fiberglas mat or cloth, then pooring on the resin and letting dry for 20-30 minutes or until it's no longer hot. After about the 4th or 5th layer I started sanding down the large bumps and cut off the excess on the sides and around the rings.

After 1 layer:


This is after 5 layers and just after sanding:


This was taken after my final 8th layer - just as she's drying.

[Rinkrat456]

Just letting everyone know right away, the bondo process is never complete, when you think you're "done" is only the point at which you give up. This I have found to be very true and should be made into a general law of customization. Same goes with sanding. "When you think you're done sanding, sand some more." my shop teacher used to say.

But anyways, let me explain what bondo is for all of you who are still a little hesitant on using it. Bondo is a body filler. What I mean by body filler (and the can says that too) is that it takes an uneven surface and makes it smooth. Whether that surface be flat or curved, you spread bondo on to make the area uniform in texture.


There are really two types of bondo that you should consider. Original body filler (red can) should be used to make everything uniform...or do what the can actually says and be used as a body filler. The first layer just lay it on thick. 1/8" thick would be ideal, but a 1/4" thick isn't unheard of. You sand this stuff down anyway, trying to keep the thickness uniform as you sand. I keep using the word uniform, because you dont want waves and ripples and ridges as you go. Imagine your own truck's paint job. (hopefully it's not full of holes and rust otherwise this doesn't work) You want the final product to look like that. Smooth, free flowing, uniform. To mix bondo, find something like a pallet or a piece of CLEAN cardboard and open up the actual container. It's white and will never harden without the other little tube. Take out as much as you think you can spread in less than 5 minutes. If you mix it right, you're actually looking at 3 minutes tops. A good color of the bondo should be similar to this:



After this part of the bondo is to your liking, go out of the usual frame of the typical to-do list and take this tip from me. Primer brings out every little dimple, imperfection, pock mark and blemish. Lightly primer the entire area and you will see everything you missed. That's ok though - the next step is for all you perfectionists out there.

The second type of bondo is the Ultimate (black can). This stuff is amazing. Lightly scuff up the primer with 180-220 grit sand paper and lay on this ultimate bondo similar to how you spread the original on. But go lightly! Many quick thin layers of this stuff will be better in the long run over one thick layer. This mixture is yellow out of the can, and right away you'll tell the difference due to the thinner mixture. The hardener is blue, and when mixed you get a blue-ish green mixture that smells like skittles in my opinion. Sanding between layers, fill in each little pock mark that you dont like. Paint and clear will magnify every mistake you make or leave in the end, so take care to pay attention to the smallest detail.

[Rinkrat456]

The last little part of bondo-ing is for you even more nit picky perfectionists. This part is utilizing the bondo brand glazing putty. It goes on similar to the previous two mixtures, but is even thinner than the ultimate.



Spot glaze any little imperfection that you weren't able to get out with the ultimate. Sand so lightly, using 400-500 grit sandpaper if that. It comes off really easy and sands quickly so dont press hard.



Here's another quick tip. The bondo brand spreaders might come off to you as a cheap scam to buy more of their stuff, but take it from me....these are the nicest spreaders you will find. For under $5, three different sizes you can't beat it. Also, another time saving tip that I found, is use/purchase a random orbital sander for all bondo work. Get the hook and loop type pads since they're less expensive, work better, and hold longer than the stick on pads. They make quick work of bondo, yet can be used to shape and lightly touch up the most crutial spots.

[Rinkrat456]

This is where you get excited, believe me. All your hard work and time go into the preparation of painting. The finishing process can be cheap, or extremely expensive depending on your tastes and your wallet. You have 3 main options you can choose. Carpet, vinyl, or paint. That's just about the order of cost too, carpet being the least expensive up to paint which is the most expensive. There are exceptions to every rule, so if you find a good deal on one of them, good for you. Or, if you paint using spray cans...that's another exception. All will look good but you are the one who needs to decide what looks and fits with your style of truck, interior and exterior; cost of materials and the amount of time you have to dedicate to this.

Carpeted box:


Vinyl box:


Painted box:


Or a combination.