View Full Version : detailed fiberglass box construction ??

01-03-2003, 09:10 PM

I'm getting close to building my box (parts are already under construction).. but I have 2 questions..

First, where can I get those round speaker moutns? or are they made ( I have some scrap I can use, not MDF though, subfloor material 3/4"..)

Second and more importantly.. I was looking over some fiberglass supply companies stuff and see that there are a LOT of different options for glass and they all have differing costs.. I could run from Kevlar and ~$350 for my box to Carbon Fiber for ~$700 for the box to various types of 'mat' and 'fabric'.. So, the question is...

How many layers of what kind/size/weight mat/fabric would I need? mat is a lot cheaper than fabric but would require more layers I think.. Then, there is carbon fiber 'cord' or stranded stuff (not that expensive when you think about it) that can be used like one would use rope I'd immagine, but the carbon fibers should be a lot stronger.. so, if I used a fabric outershell for smoothness, then put some fiber strands in (not too thick like a rope, but kind of like a thin meshish thing) and mat, fibers, mat, etc.. About how many layers would one need if they put in a little carbon fiber stranding between layers? What weight mat and how many layers if just that?

And, also.. most supplies are listed as sold in x yrds.. yards I'm presuming.. is there a standard(ish) number of yards needed per cubic foot? I know shape has some bearing on surface area over volume.. but there has to be something that gives me an idication.. would I need 5 yards for a 1 ft^3 box? 10, 15, 20 yrds? This all has a bearing on what material I get (obviously).. Is there a general rule of layers/thickness for different mats/fabrics that would make a difference? For example, I could run 3 or 4 layers of 6K heavy mesh Carbon Fiber and I think that would be thick enough, but that would cost ~$450.. a bit more than I'm looking to spend on a glass box.. the cheapest mat (guessing 8 layers, and 24 yards total) is something like ~$40, but that's only just over 1/8 inch (or so it seems) and that seems thin.. unless 4 oz mat (4 oz / ft^2) is that much stronger than ckeapo stuff from WalMart, for example..

The big reason I'm asking is, I can't just run to the store if 8 layers isn't enough (since I'll be ordering it online), and I'd hate to buy enough for 8 layers (with carbon fiber strands intermixed) if I only need 4 layers if there are fibers..

*sigh* Hate to ask another fiberglass question, but none of the tutorials I've looked over really specify anthing specific on what type of glass, weight etc..

Any info would be helpful,


01-03-2003, 09:39 PM
first off just buy mdf for the speaker mount....thats the leats of your cost. mat vs fabric....thicker does not mean stronger and mat is actually stronger, fabric is used to build curves and such. the reality is, the stuff you buy at walmart is not that bad....i picked up matting and resien from home depot and its great. dont buy rope, cause this is how that works: you need a "chopper gun" it chops and sprays the rope, you need a second gun, much like a paint gun, but ment to handle the resien, and you spray with both at the same time, this is generally used to build rediuclous thickness (boat hulls and such) it sounds like you are doing you 1st glass job and thats just going to create a mess for you. the diferent wieght mats (4oz/ft...6ozft, ect) build greater strenght, but are not nessasary for your use.....remmeber that a box is one of the weaker things fiberglass is used for, your going to need to do 8-16 layers (depenent on the sub thats going in there, 8 layers for a jl w0, 16 for a jl w7 :) ) dont used the random matting, its a mess and not strong.

01-03-2003, 09:49 PM
Originally posted by evo2k3
dont buy rope, cause this is how that works: you need a "chopper gun" it chops and sprays the rope

Yeah, I saw a 'bolt' of glass 'string' they had for guns.. The carbon fiber ribbon seems more to be used like I was saying.. I could be wrong.. the string specifically mentioned even cutting for guns, the carbon fiber ribon specifically says it's intended for selectively reinforcing fiberglass or carbon and for fabricating small, high strength, low weight structures.. that's why I asked about it.. supposedly I'd be able to use less matting, etc (especially since carbon fiber is stronger than glass rope or regular rope I'd immagine, and I've seen suggestions of putting rope in the mix to strengthen/support a box)..

The Home Depot here in town doesn't have fiberglass mat or resins, that I found.. what department was that in?

01-03-2003, 09:57 PM
i have 3 stores within 20 miles and only one caries it in the paint area....1 gallon jugs....try asking sometimes its up in storage.

01-04-2003, 05:11 AM
I asked when I was there getting lumber.. they said no.. *sigh*

Looks like it's back to the net.. just have to figure out what and how much now.. I think I'll put some paper in the area that I need to glass and try to get a feel for sq ft that way... so, how many ft^2 in a yard? is it just 3ftx3ft? 9 sq ft per yard of glass mat?

01-04-2003, 01:16 PM
You really cant talk about how thick something is by just layers. Fiberglass mat comes in diffrenent Oz. thicknesses. Most of that stuff you buy at the like walmart is thin stuff. I buy 2 oz. mat and 3 layers of this stuff is strong enough to stand on. And i have found that is is WAY cheaper to buy a yard of 2oz. mat than it is to buy one of those little packages from a store

01-04-2003, 04:30 PM
Originally posted by Everclear
You really cant talk about how thick something is by just layers. Fiberglass mat comes in diffrenent Oz. thicknesses. Most of that stuff you buy at the like walmart is thin stuff. I buy 2 oz. mat and 3 layers of this stuff is strong enough to stand on. And i have found that is is WAY cheaper to buy a yard of 2oz. mat than it is to buy one of those little packages from a store

Do you have any expierence with 'fabric' versus mat? The site I'm looking at has 1 1/2 oz mat (no 2 oz) but there is no 'break' values listed like with the fabric/cloth. The 1 1/2 oz (per sq ft) mat is $5.15/yard and the fabric I was looking at is $4.90/yard at 7.5 oz/sq yd.. Does that mean the mat is 13.5 oz / sq yrd (9x the sq ft value to get sq yrd value)? Here is the fabric description:

Commonly called "Boat Cloth", this fabric is excellent for covering plywood, plug shapes, and moldless foam designs. 1-2 layers will waterproof and protect boat floors and roofs.

But, I'm thinking this is over wood. Would that be good stuff for building a box? It's a lot thiner than the mat (fabric is .011", mat is .045") so I would be able to keep more volume in my box (very tight fit where I'm building this)

Here is the link if anyone cares to look and offer suggestions for what would work well and still be cost effective..

http://www.fibreglast.com/products.php?session=2c3783f90ba366efe1710071d8d94 949&area=4&PHPSESSID=2c3783f90ba366efe1710071d8d94949

Another thing I was thinking was using that carbon fiber 'tow' (under the kevlar/carbon fiber link I think) to put some extra stiff in the layup.. figured I'd use the whole 10 yard roll since I'd not have anything else to use it for.. spread it out to a thin fan(ish) layer duing buildup.. The question I have about that is, is that 10 yards length of 1" rope? or 10 yards like the fabric (sq yrds I'm presuming, but that seems to be way too much for a 'rope')..

Also, I still don't really know how much coverage a 'yard' is.. or to figure out how many 'yards' of material I would need (I'm thinking about mocking up paper in the space that I'll be glassing, then trying to get sq ft.. then I'd have to convert that to yards, would that be 1296 in^2 per yard?)

Sorry for all the questions, but I'm very close to ordering stuff so I have it for next weekend so I can start building. I really don't want to get 1/2 way through and find out I don't have enough stuff, or finish and find I have tons of extra.. This project is already over budget since I bought some power tools for the wood fab I've done ;)

Thanks again :)

01-04-2003, 04:55 PM
like i told you before.....fabric has little strength its for building thickness to create curves and such....i dont know what kind of equipment your running, but you should buy the thinest stuff possible (2 oz/ft is fine) and do somewhere between 8-16 layers....i was going to buy all my stuff from fiberglast.com too, but found home depot was more convienent and cheaper....look around, lots of stores carry it. thats the right conversion for sq yards.....dont worry about running out anyways, amature glassing takes a shitload of time and patients, thats also why i recomended finding a hardware store that caries it.

01-05-2003, 02:24 PM
basically, if you when you are done and you think it's thick enough, stand on it....thats how we do it, we had a 198lb buddy stand on the fiberglass enclosure for my type r 15 and the **** thing didn't even flex......and i stood on on the one for my 8inch sub....163lbs.....definetly strong enough.....(obviously you wouldn't wanna do that for kicks cause kicks don't have to be that strong....same with ampracks) we always go by that rule and have never had a problem.....perfect every time...

01-05-2003, 03:54 PM
i understand that rule, but dependant on equipment that may not hold true.... i had a small piece (14"x16") peice of 3/4" plexi that i could easily stand on with it flexing the slitest, but in its prt of my w7 box and i just watched it flex unltill it finally broke.....so yeah thats a decent rule of thumb, just know there are ecceptions.

01-05-2003, 04:48 PM
when I had my solo baric L7's I used fiberglass on the front of the box. I bought the stuff from autozone and used it. First the clothe stuff to get the shape I wanted, painted it with the resin, let it get hard. Then I went back and put 3 layers of Mat on it. This was extremely strong and did not flex. Just make sure you get a fiberglass roller or something to get the air bubbles out. I found a local distributor that sells fiberglass, the resin is 18$ a gallon(7$ cheaper than autozone i believe) and the mat for 3.99$ per square yard. Not sure what weight though. Either way, fiberglass is used to repair vehicles and it almost like metal when it is hardened, every shop I talked to in my area said 3-6 layers is generally plenty. Everyone said to get it over a 1/4'' thick preferably 1/2'' thick and you'll be fine. www.caraudioresources.net has a lot of fiberglass tutorials if you need them.