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View Full Version : Mounting Plexiglass to MDF, How???



profoundwill
04-07-2006, 11:08 AM
I am going to make a box out of MDF, but I want the complete top of the box to be plexi not just a window the whole top. Anyway, what would be the best way to mount the plexiglass to the MDF that will also create a seal as well as not come apart?

tRiGgEr
04-07-2006, 11:15 AM
I am going to make a box out of MDF, but I want the complete top of the box to be plexi not just a window the whole top. Anyway, what would be the best way to mount the plexiglass to the MDF that will also create a seal as well as not come apart?

Use a weather seal strip. And screws:)

profoundwill
04-07-2006, 11:18 AM
Will the srews be strong enough to keep the glass from eventually getting loose?

tRiGgEr
04-07-2006, 11:21 AM
How could the plexi come loose? Screws don't just come loose;)

profoundwill
04-07-2006, 11:24 AM
Okay, I just thought it would be something more difficult, like some special kind of glue or something. I know they make different types of weather stripping which one do I need?

bjfish11
04-07-2006, 12:24 PM
how thick is your plexi going to be? I bet it will flex if you dont go real thick, like around 3/4 or so, since your going with the whole top.

nVRuckus
04-07-2006, 12:50 PM
yeah you will need 3/4" plexi so plan on paying alot of money. Its not cheap at all, thats why you dont see it all the time. and make sure you take your time on predrilling the hole, dont let the bit get hot and dont go too fast your you will make an expensive crack.

Expy2K
04-07-2006, 12:57 PM
What are the demisions of your box dude..

I got some plexi and lexan in my garage in 3/4


:0

bumpin_blazer
04-07-2006, 01:07 PM
everyone says you need 3/4" right away but if he's only running a small amount of power or the box isn't huge, he'd be fine with 1/2" which is MUCH cheaper and easier to come by. what ruckus said is right though go slow, even start with a small hole and work your way up. i learned my lesson on a 250 dollar piece of lexan i used for a customer's box once, got to quick and cracked it, no bueno. good thing i made like 800 off that install so the 250 i paid to replace it wasn't horrible lol.

profoundwill
04-07-2006, 01:24 PM
The piece I need is 21x16. I will be using a DD9512 with two Us Amps DE1000's. I was planning on getting a 3/4 piece, think that will be enough or do I need it to be thicker.

bumpin_blazer
04-07-2006, 01:25 PM
The piece I need is 21x16. I will be using a DD9512 with two Us Amps DE1000's. I was planning on getting a 3/4 piece, think that will be enough or do I need it to be thicker.

LOL 2kw on a 9515 at that size, 3/4" will flex like arnold used to. i'd say with that power and size of a sheet, you'll need doule that thickness.

profoundwill
04-07-2006, 01:28 PM
I thought plexi was stronger than MDF?

Expy2K
04-07-2006, 01:29 PM
Dude you should def rethink it.. or make a smal 10x7 window or something..

Lexan is gonna run you *** some big $$$



:)

bumpin_blazer
04-07-2006, 01:32 PM
i'd say listen to me or expy but people seem to think me stupid. me no don't why no though.:D

Fate710
04-07-2006, 01:36 PM
yea I would listen to them. Plexi is exactly like MDF in flexing properties from what I've seen. If you would need double thickness on MDF most likely you will need it on plexi too.

Thats why alot of people just make windows. I'm make a front window(not where subs mount) for my box and I'm making windows for my amps in their amp rack.

profoundwill
04-07-2006, 01:39 PM
How much money are we talking, just a ballpark amount, for the glass?? How do I go about making a window?

2loud4u
04-07-2006, 01:39 PM
Go to your local hockey rink and see if they have some plexiglass.
some times a corner breaks and they have to replace it.
So they will just give it to you cause they are going to throw it out.

Just a thought cause that is where i got mine for free. I got 4 sheets of it.

profoundwill
04-07-2006, 01:41 PM
we don't have a local hockey rink

bumpin_blazer
04-07-2006, 01:43 PM
typically a sheet that size will cost you about 250 bucks in that thickness. i'd say you'll need almost 1.5" in plexi or lexan.

thatkidbob
04-07-2006, 01:43 PM
use 3/4 and brace it in the center

use a thick hardwood dowel.

also, lexan flexes MORE than plexi, which is part of the reason it's stronger.

Expy2K
04-07-2006, 01:47 PM
You don't want plexiglass

You need a polycarbonate material. It is much much stronger.. Plexiglass is a basically an acrylic, if you want that goto a place where they build fish tankes..

Lexan is what you need if you are set on this..


:)

req
04-07-2006, 02:02 PM
unless you want to be spending like $400 on your box, i would not even consider it. if it was like a pair of 10" CVR's or something, sure go for a 3\4" piece. but a 9512 and 2kw will flex a single baffle MDF piece.

i strongly suggest 2 pieces of MDF for the baffle of your box and possibly braces all around. easy way to do braces in a large box is cut a piece of MDF that would fit inside and cut a big circle out of it so you brace all the sides at once :)

unless you are rich as hell, i wouldnt do the plexi thing. maybe just do a window or something.

QtrHorse
04-07-2006, 02:05 PM
Lexan/ polycarbonate will flex much more than plexi. Lexan/ polycarbonate is a much softer material but has more strength when it comes to shattering, that's basically the only difference. I don't see how a 3/4 pc of plexi will flex in the size he stated. I have been in the sign industry for the past 10 years and have worked w/ both of these materials. I now sell sign supplies and am very familiar w/ both of the items being discussed.

The plexi will be more rigid than MDF in that thickness and size. I would personally get some good 3M double sided tape (3M part number 4910 = water clear tape or 4929 = black tape) and use that to mount it to the top of the box. Both of the part numbers that I listed are very high bond tapes that will not dry rot. You do not want to use a basic foam tape, because it will get brittle over time. These tapes will also form a air tight seal, if applied correctly. You would then to drill a lot of holes and use screws. As stated already, make sure you use a sharp bit and be carefull when exiting the plexi, that's when it will crack or splinter.

Just to give you an idea, A 4x8x.750 sheet of clear plexi will cost you roughly $475. That's what the company I work for sells a full sheet for. You may be able to find a sign supply company that will cut a pc for you but you will pay much more for it.

req
04-07-2006, 02:11 PM
thanks for the great info horse, but the problem is, when you drill alot of holes around the plexi into the MDF, the mdf will split and the integrity of the box is then comprimised. if he spends like $150 on a single piece of cut plexi for the top and then it comes loose from the box, not via the plexi breaking or anything, but the MDF letting go (2kw is alot of power lol).

i just think that it would be more economical for him to make a window on the side of the box, and make a double-thick side panel, and insert it from the inside of the box (for a nice flush look) and silicone it into place. eaither the sub faces up and the window is on the side, you can see the motor real well, or the sub faces forward\back and the windows on the top and its the same thing :)

but thats just what i would do.

its your box man, its your decision. IMO - its too expensive, but we all have different tastes and budgets.

profoundwill
04-07-2006, 02:11 PM
So Qtrhorse you are saying I will be fine using a 3/4 piece of plexi that is 21x16 on a box with around 2k watts rms???

PatFitz9
04-07-2006, 02:12 PM
Go to your local hockey rink and see if they have some plexiglass.

only in Canada... :P

profoundwill
04-07-2006, 02:16 PM
If I did a 12x12 wnidow or something like that, how thick does the glass need to be?

QtrHorse
04-07-2006, 02:43 PM
req;

You are correct, I would not want to drill a bunch of holes either and it would be much cheaper just making a window, even w/ the extra pc of MDF that will be needed. For cosmetic reasons alone, this would be better. You will be able to see the caulking or double sided tape though the plex if you make one whole side out of the plex, unless you put some type of ring/ frame around the outside edges.

To answer your question profound; the 3/4in plex will be just as strong or stronger than the 3/4in MDF in the sizes that you stated. If you made a small 12inx12in window, I would think that 1/2in plex would be just fine. You will be able to get the 1/2in material much cheaper, it is more common than the 3/4in. I bet I could get ahold of a 12inx12in PC but the shipping cost would probably kill the deal.

Look up sign supply businesses in your area and ask them if they cut acrylic to size.

profoundwill
04-07-2006, 02:52 PM
What type or screws should I use to secure the plexi to the MDF. I usually build the boxes out drywall screws, will those be okay for the glass or should I use something else. As far cosmetic reasons I can use a ring or something to cover the caulk and what not, I just want to be sure that 3/4 or 1in glass is strong enough to cover the entire box, because if it isn't I will just go with a window.

bjfish11
04-07-2006, 03:31 PM
i wouldnt even attempt it. Its too expensive to risk for ME. However, if you do do it, please post a vid of the first time you put your subs in and crank it up.

tRiGgEr
04-07-2006, 03:56 PM
Buy a pre-fab bandpass box!

NeverEnuffBass
04-07-2006, 03:57 PM
IMO, a window makes a much cleaner looking install over a whole side being plexi or lexan.