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How should I mend my fiberglass and MDF?


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90xjadam 
Member - Posts: 5
Member spacespace
Joined: May 16, 2006
Location: United States
Posted: May 16, 2006 at 7:39 PM / IP Logged  

Ok, so I've been kind of following along with how to do this whole fiberglass thing for a while now...and here comes time to where I'm going to mend my fiberglass that was molded to my panel and the MDF face.  Note that this is my first box and fiberglassing ever.

I think that the best way to mend the two is to cut the sides off the glass and make MDF sidewalls then fiberglass over the back so it will all still fit in.  Another way I'm contemplating is screwing it w/ some rubber in between the screw and the glass and sealing it with some sort of caulking or what not.  Any insight? Ideas?

Here are some pictures to help:

Here is the Fiberglass:

How should I mend my fiberglass and MDF? -- posted image.

Here is the MDF front and back.

How should I mend my fiberglass and MDF? -- posted image.

This is the best picture I have of the back.  Just take off that small block of wood and thats really it.

How should I mend my fiberglass and MDF? -- posted image.

xclusivecustoms 
Member - Posts: 24
Member spacespace
Joined: February 13, 2005
Location: United States
Posted: May 17, 2006 at 7:50 AM / IP Logged  
For your first box it looks amazing. Don't use mechanical fasteners on fiberglass, they will just crack the material and eventually rattle loose. Mix polyester resin with cabosil and let it sit until it becomes a thick paste. Rough up your MDF, mix in catalist, and use the paste to adhere the pieces together. Large gaps will have to be reinforced.
xclusivecustomsinc.com
Velocity Motors 
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Moderator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Fabrication. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member has been recognized as an authority in Mobile Security and Convenience. Click here for more info.spacespace
Joined: March 08, 2002
Location: Manitoba, Canada
Posted: May 17, 2006 at 10:26 AM / IP Logged  
How is the enclosure going to be attached to the vehicle ? Also, what I would do is start fiberglassing MDF peices to the outside edge of the fiberglass so that the MDF cutout you have for the sub can have something to attach to.
Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
primal impulse 
Member - Posts: 20
Member spacespace
Joined: May 16, 2006
Location: United States
Posted: May 17, 2006 at 4:08 PM / IP Logged  
how come you didnt just make a ring for your sub, glue it to the fiberglass back, and then glass over the whole thing? I dont see a point in having that whole mdf panel for the front...but to each their own....excellent job either way.
Hustle, Loyalty, Respect
Aruman 
Silver - Posts: 363
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Joined: July 27, 2005
Location: Aruba
Posted: May 17, 2006 at 4:23 PM / IP Logged  
primal impulse wrote:
how come you didnt just make a ring for your sub, glue it to the fiberglass back, and then glass over the whole thing?
primal impulse has a point there, but it's looks ver nice for the first time btw.
Shaking The Neighborhood
crazyoldcougar 
Copper - Posts: 185
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Joined: March 03, 2006
Location: Canada
Posted: May 17, 2006 at 9:19 PM / IP Logged  

wow that looks like a boat load of work for the baffle...nice job though...

as for joining them i would use either of the above methods...

Fiberglass Guru.
killer sonata 
Silver - Posts: 718
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Joined: May 17, 2006
Posted: May 17, 2006 at 10:44 PM / IP Logged  
thats looks great. much better than my first FG project. I completely understand why you used MDF as the front face. Its much cleaner and takes a lot less sanding. To join the wood to the fiberglass I would use a hot glue gun as a temporary hold to join them together how you want since it looks like one piece fits over the other. Then apply fiberglass matte (the hair kind that you can rip, not the woven stuff) on the creases on the inside of the box and apply resin. When that cures, mix yourself some pepto (or watermung) which is a 1:1 ratio of bondo and resin. Pour the pepto inside the box and let it cover the entire inside. Make sure you mix enough to coat the entire box. Doing this serves 2 puposes. 1:to make sure the box is completely sealed with no air leaks. and 2: it makes the box more solid which will help the sub produce a much cleaner sound.
90xjadam 
Member - Posts: 5
Member spacespace
Joined: May 16, 2006
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Posted: May 18, 2006 at 12:35 AM / IP Logged  

Thanks for all of your comments.

Here is a link to ALL of the pics I have of my project so far: http://community.webshots.com/myphotos?action=viewAllPhotos&albumID=549810254&security=AjdCVl

If you don't have webshots, try this: http://www.pnwjeep.com/phpBB2/viewtopic.php?t=5580

This is the site I've really been following and wondering if this is how I should mend the two: http://web.njit.edu/~cas1383/proj/focus_trunk/index.htm

I'm just worried that if I screw it and even put some kind of rubber between the screw and glass that the glass will crack.  But if I just do it like the guy on his site I'm afraid that the fiberglass won't hold to the MDF over time and will break apart.

Is the 'pepto' the same thing that xclusivecustoms was talking about?

The way its going to be attached is still a little in the works, but I think I'm going to put one bolt through on the hump under the pull out cover.  Then try to fit two bolts from the inside through the floorboard.  Do you think that will be enough?  If not I was thinking of also adding some type of hook for the top end, then doing the bolts. 

The reason I went with MDF rather than just glassing the whole thing is that I'm going for an OEM look.  I'll be finishing it by covering it with a 1/8th inch foam and matching interior vinyl.  So it will have something like a dashboard feel.  And I wanted it to have a flat surface rather than a fluid one.  Although I think i'm also going to make one completely out of FG also to see how I like it.

It will be hard to seal the inside because there will only be about a 1.5 inches of space inside the box so most sealing will be done from the outside.

I have one more question since I'm on a roll here.  Should I use a terminal?  And If I do, where the heck would I put it?

Oh, and one more.  I'm going to be making another ring to go around the edge of my sub since it won't be flush mounted.  With this ring I was planning on making it look smooth so that the raised surface trasitions into the flat lower surface.  will the MDF ring be too brittle to do this?

Sorry for the long post.  Thanks for reading.

How should I mend my fiberglass and MDF? -- posted image.

killer sonata 
Silver - Posts: 718
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Joined: May 17, 2006
Posted: May 18, 2006 at 12:58 AM / IP Logged  

Loos a little nicer with the sub in there. The pepto is not the same thing that xclusivecustoms  mentioned. Pepto will not adhere the surfaces together, only seal the leaks and made the box completely solid. You dont need to paint it on or anything. Once the mdf is attached to the FG, pour the pepto in and roll the box around with your hands so the pepto coats the entire inside concetrating most on the edges and corners.

A MDF ring will not be too brittle. If MDF was brittle, it wouldnt be used to make speaker boxes.

I never recommend using a terminal. Whats the point of making a good solid box just to cut a big hole in it and put in a weak plastic piece. Drill a hole just large enough to slide your speaer wire in and seal it with hot glue. Then FG over that so there is no air leak at all. on the speaker wire on the outside of the box you can use quick disconnects. I personnaly like the bullet style but you can use whatever works for you.

90xjadam 
Member - Posts: 5
Member spacespace
Joined: May 16, 2006
Location: United States
Posted: May 18, 2006 at 1:06 AM / IP Logged  

Well, I'm going to be sanding down the ring to a fine point so I wasn't sure if it would be.  I guess I'll just have to be careful with it and find out, just as everything else I've done so far!

Thats what I was thinking with the terminal.  What exactly is the bullet style?

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