fg and mdf

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ths_system

Member - Posts: 1

Joined: May 15, 2007

Posted: May 15, 2007 at 6:42 PM / IP Logged

when you guys make a box out of fg and mdf how do you guys join them?

just wondering i was thinking of makeing a coustom fg bottom for my truck.

bellsracer

Silver - Posts: 703

Joined: January 14, 2006

Location: United States

Posted: May 16, 2007 at 2:34 AM / IP Logged

Welcome to 12v first off. Now down to business. There are several ways to join them. Here are a few ways that I frequently use... Times where I use them will vary and there is no exact situation, it is a matter of experience mostly. Ok here you go:

1) Rabbet cut the edge of the wood where it meets the FG 1/8" in and 1/4" high. Staple the fleece to the wood using 5/32" staples (if available). If you are like most people though, 1/4" staples will work too. Add your resin and cure. Next use duraglass to blend the joint area and proceed to bondo and finish.

2) Tape off the non-FG surface of the MDF with 3 layers of masking tape. Let the tape overhang the edge just a little bit. Then hit the edges of the wood with 80 grit sandpaper just to the point where the tape is trimmed off. Try not to sand into the wood. Stretch your fleece all the way around and staple at least 1/2" in on the side with the tape. Trim the fleece an additional inch in from the staples. Apply your resin covering all the fleece including the side where the staples are. Let cure. Using a die grinder with 80 grit sandpaper on it or a 4" grinder with a flapwheel attached, grind down where the edge of the wood is but ONLY to where you hit the tape. Try not to hit the wood (you will have to repair it later if you do). Using a flathead screwdriver, pry off the excess fleece/resin. As the excess is removed, it will pull the staples with it.

There are other ways, of course, but I find these techniques to be the strongest. I hope this helps out though.

Ganbatte ne!

Never send your ducks to eagle school.

The difference between ordinary and extraordinary is that little extra.

The 3Ls of life: Learn from the Past, Live for the Present, Look to the Future.

quadraphonic

Member - Posts: 8

Joined: May 20, 2007

Posted: May 21, 2007 at 11:45 PM / IP Logged

This was actually a question I was going to ask. I was going to make a trunk enclosure (left side of the trunk in my 2003 Toyota Echo. Based on the design I'm going with right now, I was going to FG the back, sides and bottom of the enclosure. I know that I'm using MDF for the mounting surface, and thought I'd use it for the top of the enclosure as well, since I want it flat, and thought that would be fairly easy to do. A few questions based on your response above..

1. The rabbet edge seems most appropriate for the front of the enclosure (and maybe even the top). You mentioned stapling fleece to the wood, did you mean FG? If not, can you explain more about the FG, MDF, fleece joint?

2. Should my box top be MDF, or should I use fleece?

bellsracer

Silver - Posts: 703

Joined: January 14, 2006

Location: United States

Posted: May 22, 2007 at 11:17 AM / IP Logged

1) Fleece is easy to form for a more form fitting curve, then you would apply FG mat on it for strength. Whether it is on the inside or outside is dependent on the project. There is some debate on this part, but being that it is polyester with a low melting point, fleece will have a chemical bond when you apply your mat to the fleece and resin to it. Now you could use FG for this as well, I never said you couldn't. It is just a lot easier to use the fleece for shape, FG for strength, and MDF for flats & frame.

2) That would be all up to you on what you want your project to be. Either choice is fine really. If you plan on using MDF for your top, consider applying a thin coat of carpenter's glue on the back after you attach it to the FG. It'll fill in the pores and shrink them as it dries giving you a better seal.

I hope this helps. Any other questions? ^-^

Oh yes, I almost forgot, Welcome to the12volt!

Ganbatte ne!

Never send your ducks to eagle school.

The difference between ordinary and extraordinary is that little extra.

The 3Ls of life: Learn from the Past, Live for the Present, Look to the Future.

quadraphonic

Member - Posts: 8

Joined: May 20, 2007

Posted: May 22, 2007 at 6:12 PM / IP Logged

Thanks fo the welcome! I've got what I consider to be enough base knowledge to do a simple enclosure form browsing other forums, but only recently came upon this forum. There's a significant amount of very helpful information.

Your explanation helps a bit, though I'm still having trouble visualizing how everything comes together. I made a terrible drawing in Paint, showing how I see it, perhaps we can take it from there Right now I envision the FG fitting in the rabbit edge with fleece being attached to both the FG and MDF to finish the seam. How would you attach the fleece to the FG, just spray adhesive?

Here's my artist rendering. Is it close to what you're describing? FYI.. this is a very rough idea of what my enclosure would look like looking through the rear of the car forward. The second image is a photo of the actual location.

fg and mdf -- posted image.

bellsracer

Silver - Posts: 703

Joined: January 14, 2006

Location: United States

Posted: May 23, 2007 at 12:21 AM / IP Logged

LOL... silly rabbit. First off don't worry about the pain image... those mad art skills are enough for us t ounderstand what you are after.

Now to business:

The fleece covers the entire area that you want ot put glass. In other words, where you have just the FG, it's all fleece with resin. after that has cured, you go back ofer the fleece (in your case on the inside of the enclosure and apply FG to it. The fleece is the base, then you apply FG to that to make it strong.

The green spots are where you apply duraglass to reinforce the area that meets the MDF. not 100% needed but really helps out a LOT!

Any other questions?

Ganbatte ne!

Never send your ducks to eagle school.

The difference between ordinary and extraordinary is that little extra.

The 3Ls of life: Learn from the Past, Live for the Present, Look to the Future.

quadraphonic

Member - Posts: 8

Joined: May 20, 2007

Posted: May 23, 2007 at 12:30 AM / IP Logged

I got you.. makes sense. The reason I misunderstood was that I thought it would be easier to simply tape off the area I wanted to glass for the back and sides and go the FG route. I do have another question now, How do I form the fleece to the car? I imagine I still need to tape everything off and keep it protected. Would I use some type of adhesive to hold the fleece in place at that point then? It still seems easier to go pure FG, though I suppose having the fleece base with built up layers of FG on the inside would give me a stronger enclosure.

bellsracer

Silver - Posts: 703

Joined: January 14, 2006

Location: United States

Posted: May 23, 2007 at 3:52 PM / IP Logged

You could do that. You'll just have to figure a way to get the FG to attach to the MDF then. FG mat does not tend to hold well when stapling to MDF before resin, so yeah...

Instead of fleece you can get a hold of some cheap auto carpet and stretch sections of it to take the shape of the area of the car. I'm sure there are other alternatices I just can't think of them right now (kinda in a rush dear) You could use spray adhesive to hold the fleece temporarily.

Ganbatte ne!

Never send your ducks to eagle school.

The difference between ordinary and extraordinary is that little extra.

The 3Ls of life: Learn from the Past, Live for the Present, Look to the Future.

e36rok

Member - Posts: 18

Joined: May 23, 2007

Location: Canada

Posted: May 23, 2007 at 10:44 PM / IP Logged

^^^ About the second diagram there, I have a question:

I don't have any fleece on mine, i just have the mold of a corner in my trunk (taped it off and fiberglassed). I want to attatch mdf now for the front, would I still have to stretch fleece OVER that? It fits pretty snug now I don't know about more layers over the outside.

I was thinking attach the mdf with glue or anything temporary (mdf to mdf I'll use screws) and once it's in place fiberglass the inside through my speaker hole where the edges of mdf and fiberglass meet. Around the outside maybe one small strip of fiberglass just so it doesn't look so rough? Then sand the edges down?

quadraphonic

Member - Posts: 8

Joined: May 20, 2007

Posted: May 23, 2007 at 10:48 PM / IP Logged

e36rok wrote:

^^^ About the second diagram there, I have a question:

That's what I was thinking too.. or perhaps rough up the mounting edge of the MDF and use resin to mount it, then FG and duraglass the seam. It seems like it would be too hard to start with fleece for the enclosure back.

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