i was wondering,,,do i need to use the same thickness of plexi as the wood. i am debating on using plexi for the back wall of my sub box. it is going to be a blow thru, and i think it would be cool to make the backs of the subs visible. i even have some orange neon to stuff in there. the back wall measures 2x4'. would i need bracing in the middle. also i remember reading somewhere a while ago that you're not supposed to attach plexi directly to mdf, and must build a frame of some sort and attch it that way. is this right? it doesn't make sense to me,,what does the frame need to be made of?

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just put some sealing material around the edges of the plexi where it meets the mdf, should be the same. pleaxi is weak when it's thin. so double up on it if it seems weak?

I would not double up, just use 3/4 and you will be fine, a center brace is always a good idea.

As dwvw said use 3/4" , as for the frame use a router bit to sink the plexi flush with the mdf. This will require a thicker mdf then the plexi, then router down into the mdf 3/4" allowing for a groove for the mdf to recess into. Then apply foam tape to the mdf edge and compress the plexi onto the tape with the screws! Take note that screw heads should be countersunk into the plexi, also hand tighten the screws as too much pressure will crack you plexi piece.Now in order to hide the taped edge and screws,build a three eights panel, wrap in your choice of material and voila !

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i was thinking of just screwing the plexi to the back if the box like i would with a piece of MDF. also i was going to use urethane(the stuff we use to install winshields) as the seal between the two. would this not be ok?

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I like to use brass T-nuts....the type used to put furniture together with the large head approx 1 inch diameter and like a 3/8 or 1/4 bolt. Has a round head with a Hex so you can crank them on real tight with Allan keys. I also like to use a 1 inch wide drill bit with the small v tip to counterset the head of the bolt into the plexi, prevents the plexi from cracking and gives a nice mounting surface for the head of the bolt.

This technique requires approx 2 inch wide mounting lip inside the opening the plexi fits inside, the lip is positioned in such way that the plexi flushes with the edge of the opening.

The T-nut end goes on the inside of the lip so the plexi can be clamped to the lip with bolts, every 4 inches or so. If you get the threaded T- nuts they also get installed with an Allan key for a nice finish, and you don't have to worry about banging them in on the inside of the lip with a hammer and wrecking the lip.

[ February 07, 2004, 02:42 AM: Message edited by: islandphile ]

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I had similar ?? when I had buit mine. 3/4 plex worked ok, no chance of busting ( but I'm only runing 1 10" ) predrill and counter sink every 1 1/2 or so,take your time and hand screw together. Think about the inside of the box now that it will be very visible. I put a layer or 2 of resin then panted it! Some sort of suport...?? maybe it needs it maybe not your call. Clean clean clean I have a very small problem with a very few specs of ?? inside, just not worth taking it all out for that. Have fun!

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