Mixing fiberglass and MDF... need help.

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03.5 Lsr Blue P5
Mixing fiberglass and MDF... need help. (aka fiberglass box progress)

Alright I've been talking about it forever, but hopefully monday I'll start on my new box. I'm just gonna do a simple sealed enclosure. However it's with my 1KW eD 12a, so I want to make sure it doesn't 'splode...The larger MDF components I'm currently planning on are the bottom, face, and mounting plate (I'm borrowing the bolt it to the jack-holder idea) I figure with everyhting else,I'll mostly see what's looking potentially weak and try to re-enforce it from there (hopefully those seemingly wasted engineering courses'll come around)

Sothen what I need help with is joining the 2 materials together... let's start witht he bottom plate. This is going to be a large flat area, and thusly succeptible to flexing, so I'm pretty sure a sheet of 3/4" MDF cut to fit the floor of my car in the area would be the best idea for the bottom of my box. Would I be wise to put down a layer of fiberglass first, then wood, then fiberglass over it to sort of "encase" it in a cocoon, or would I be better to just have the wood in there to begin with, and sort of fiberglass up and over the edge? My thoughts at the moment are to laydown a layer or 3 on the bottom, then place the wood on top, then try to "sandwich" it into place with a couple more layer on top (atleast up and over the sides a good couple of inches), but this may be overly redundant.

I'm not really too concerned about the faceplate, (woofer mounting ring) eventhough I WILL have ALOT of magnet hanging off of the back of it. I'm pretty sure the resin-soaked fleece will saturate into the wood well enough to get a good bond. But my mounting plate kind of concerns me... Basically I want to mount my wire terminals in a chunk of wood that will also have a mounting hole to bolt into the jack-holder. THis way the loads of the box trying to shift will be spread throught he wood instead of jsut to a small hole drilled in fiberglass. So far my thought is to make the plate, Mount my terminal plat eon it, then tape off my area, and bolt it to the wall, then Fiberglass over it, I guess?

Prettymuch I'm mostly concerned about how well fiberglass will bond to wood. Should I even be worried about this?

Edit: this has kind of turned into a bit of a fiberglassing aid, so I thought I'd list my resources upfront Thanks VERYmuch to these guys who I don't even know, but who's wisdom has helped me along, as it may withyou.
e-kittan.com
Chris' Tutorials
 
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fiberglass bonds VERY well to wood. no need to lay down some glass then put the wood down. i've seen people cut notches into the wood to help the resin adheare to it, but i dunno if it makes any difference.
 
no the resin will soak right into the mdf and if u try to break it chances are the wood will break before the resin/wood bond does. if your floor is flat go for the wood. if the floor is curved and has bumps i'd use fiberglass. fiberglass is strong in the curves and weak flat. with enough layers of fiberglass it will be allot stronger then wood. i mean just with around 4 layers of fiberglass on my kickpods i could stand on them without a problem 210lbs. if your concerned about the strength just add a few more layers then what u think it needs.
 
another thing as far as your wire terminal. don't use one, just drill a small hole and run a wire thru it. the less connections u have in your system the better it will be. and those terminals tend to leak over time.
 
Thanks alot guys, this is just what I wanted to hear! Makes life easy... Andyes, the floor is quite flat in this spot (the pass side rear corner of a P5) Hence my reasoning for putting wood there. I'm gonna see how it all lays out, an dlikely put some wood or atleast "ribs" throughout. I know it's strong stuff, but I also know my sub'll put a hurt on it. Asfor wire terminals, I've been debating this myself, but the tricky part isthat my amp is under my driver's seat, so it's got quite a distance to run. which has to be pulled through some tight spots, I'd rather be able to get at it easily form both ends.
 
if thats the case i'd personally put a connecter between the two wires on the outside of the box. i think most of those terminal things are junk. unless u go out and get a set that were made for like studio speakers.
 
sndsgood said:
if thats the case i'd personally put a connecter between the two wires on the outside of the box. i think most of those terminal things are junk. unless u go out and get a set that were made for like studio speakers.

yeah, the voltage drop on them can be rediculous. they add too much resistance, and don't transfer the power very well. i love seeing the 8 guage ones that have small tabs on the back side that i know aren't anywhere near the capabilities of 8 guage.
 
Y'kno what, I've always thought that, but just slapped 'em in anyway. I'm not really much of a box builder I s'pose. Hopefully that'll be coming around... Thanks for catching me guys. Guess I'll never stop learning...

As for the box, Dang these thigns take time... Guess I'm just sorta overly meticulous. Sofar I've got everything taped off (3hours, yikes!), and some of my MDF pieces layed out. There seems to be a shortage of fiberglass cloth in this town, I've been scrounging for eery chunk I can find... SO far I've simplified from my initial design, but it should actually just be smoother.

I'll get pics and possibly a write-up together as the pieces fall into place.
 
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yea building boxes is one hell of an undertaking, especially if your trying to get everything to fit perfectly. one thing thats for sure is the right tools make things go alot smoother and cleaner... im almost done building mine for the brahma and ive already put in about 20 hours!!! but then again im a perfectionist so itll all pay off in the end (dance)

PS: i ordered these wire terminals for my box http://www.sounddomain.com/sku/RTETBS4... i hope i wont have any issues pushin over 1K watts through them
 
i'm so slick that once i made a box with a circular saw... and everything fit, no leaks. looked like a q logic prefab. of course i used some silicon, but who doesn't. i'm talkin ruler straight cuts.
 
building boxes is fun, if its for your car or a friends, i would never build one for someone don't know. My latest creation was a juggarnaut box in a neon(in the trunk), what fun that was =), fortunately only took me a day(non-stop working all day basically) and it sounded awesome in the end.
 
This sh!t's quite consumig, After I make this I'm gonna drink a couplefew beers and passout happily for awhile... *L* actually, I might consider making up a few. I know as soon as my g/f gets her new car, she'll be hitting me up, and then I've got a couple other friends who are haning over me like vultures WAITING to see how it turns out. As soon as I get a circle cutter for the rotozip or some other method figured out, and rings start happening, hopefully things'll fall into place faster. This stuff is quite fun. Challanging enough to keep it interesting, and hopefully with a smooth end-product...

I haven't really accomplished much new today, but I did styrofoam peanut-test the area, looks like I'll be pushing over 1cubic foot without a problem and using ALOT less space than I'd previously thought!
 
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nice. i love fiberglass. its so fun, but messy and expensive too. i even got my wife to glass with me once=). anyways, as far as the circles go, i always use a jigsaw. pawn shop product for 10 bucks and its helped build countless boxes.
 
sam1 said:
nice. i love fiberglass. its so fun, but messy and expensive too. i even got my wife to glass with me once=). anyways, as far as the circles go, i always use a jigsaw. pawn shop product for 10 bucks and its helped build countless boxes.
I might wind up settling for that, but I was realy hoping to get ahold of a circle-cutterjig for my buddies rotozip. I've got an installer friend who builds alot of boxes, I'm about to go hit him up and see what happens.

BTW, I noticed, you're in couer d'alene. That's close enough to here. Would you bychance be willing to let me know if you see any P5's or sale near you? My gf's looking for one now, and pickings are kinda slim. She's hoping to get into one for under 13ish...
 
sure can. i actually see so many mazdas around here it rediculous. i bet you could get into a P5 for pretty cheap. esp preowned ones. when i took a road trip down to Portland i didnt see one single Protege or P5. but you come back up here and youre lucky if you dont see one. i guess we just have taste or something up here. =) but anyways, im sure you could get into a used one for maybe under 12. i got mine brand new for 13500, but its a dx.
 
DZnutz said:
yea building boxes is one hell of an undertaking, especially if your trying to get everything to fit perfectly. one thing thats for sure is the right tools make things go alot smoother and cleaner... im almost done building mine for the brahma and ive already put in about 20 hours!!! but then again im a perfectionist so itll all pay off in the end (dance)

PS: i ordered these wire terminals for my box http://www.sounddomain.com/sku/RTETBS4... i hope i wont have any issues pushin over 1K watts through them

i spent 20 hours just designing a box for my brahma 10(dunno) then another 20 to build it, but it was 2 layers of 3/4" MDF on all the walls, so it took some extra time to get everything perfect.

post a pic of the backside of those terminals. the front side looks good, but if the back isn't up to par, it's worthless. if it is up to par, then it'd be a worthwhile investment, since it has the bridging bars.



AFaceInTheCrowd said:
i'm so slick that once i made a box with a circular saw... and everything fit, no leaks. looked like a q logic prefab. of course i used some silicon, but who doesn't. i'm talkin ruler straight cuts.
build one with just a jig saw and no screws and we'll talk(freak) i just wanted to see if i could, and it worked. it looked like ass, but it was air tight (that required setting the pieces together and putting a cinder block on it to get the glue to dry without shifting) and sounded pretty good.
 
actually if you go to the sounddomain link and click on the picture of the terminal itll show you a backside shot. when designing my box i wanted it to be as rigid as possible and still be fairly light so i decided to use 3/4" mdf for the bottom, top, sides and back but 1.5" (two 3/4" glued together) mdf for the front baffle... i also used 2 braces inside that connect the front, top, bottom and back together. so far it looks kickass and its definately pretty sturdy... too bad its still about 50 lbs (dunno)

right now im siliconing all the inside seams... although there are absolutely no gaps (band2)

PS: the inside volume is 1.25 F3 taking the braces and driver into account.... i assume that thisll give me some good SQL with 1K watts... right???
 
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Y'kno I've never quite been able to figure out what SQL meant.. ;)

Anyway, hey, so things are falling into place much better lately. Looks like I'll be ghetto-rotozipping my rings (well not SUPER ghetto, I've got a technique in mind....) SOfar, here's the cardboard mock-ups that I'll cutout of 3/4" MDF tomorrow. Nowthen, anyone have any thoughts on putting a top-piece on? is this gonna make me hate life as much as it seems like there's a possibility for? is it possible to fiberglass upside-down? As far as joining the wood to the fiberglass, I've prettymuch concluded that I'm gonna do the top-side, and then see how it seems to be holding, if I feel it needs more, I'll just fiberglass the backside of it as well. Which means I'll likely be doing that anywhich way...

To explain the pics better. the pile of peanuts is the amount it took to fill my old 1.2cuf box. If it's actually held into place, it prettymuch just fills the wheel-well area there. (meaning there's LOTS of space to be found if you fiberglass) You may notice that my planned area is going to be quite a bit bigger, This is to compensate for me angle-mounting my sub in it. I plan for it to be about 45deg from vertical, and basically pointing directly at you if you open the hatch. (Or roughly about 45deg from inline with the rear wheels) This will accomplish 2 things. 1. Provide some passive protection for my precious. sort of "tucking" it out of harms way, especially with the upper Chunk of MDF which should create a sort of "cave" kind of effect when fleeced. and 2. well, mostly I think it'll look cool...

Oh, yes, and BTW, word to the wise, when you're working in your hatch, and you decide to shut it to see where you'll be able to fiberglass up to, it's a good idea to have checked in advance that A. your alarm isn't set to auto-arm after all doors are shut. B. your keys were not left inside your house. C. Your back seat is NOT filled with a pile of such thigns as your old sub box, packing peanuts, cardboard, assorted pieces of wood, amidst other thigns. D. It is NOT 4am. (freak) Ahh, my neighbors LOVE me...
 

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well on my sub box i problaby had around 20 hours just in sanding the fiberglass.

u can see pics of it here since i can'r remote host from that site, http://www.j-body.org/members/sndsgood/cars/1/

your off to a good start me personally i'd lay down more tape or ate least plastic on the floor where youlle be working, one drop of resin on your carpet and youlle have a hard plastic blob there forever. as for the top. you can always leave that till last, get the back and sides and front done, then pulle the box out flip it upside down and do the top. if u want a certain shape, use wood to make a frame of sorts think of like your ribs. just thin pieces cut the shape u want spaced out every 4-5" to get the shape right. if it's flat u can just use mdf.
 
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