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  • Epoxy or Bondo

    I wasn't going to finish test MDF cabinets. But after hearing the sound, I'd like to put some finishing effort in these. Current issues before veneering:

    - The butted joints are not flat
    - Small holes and seams here and there

    I did some wood glue + wood dust mix to fix holes and seams. But for the un-flat surface, that's too much work. I am thinking to try the following:

    - Bath room putty (When I install a new faucet)
    - Epoxy
    - Bondo

    Never used either epoxy or bondo. The idea is to create a thin layer to even out the surface and then sand it with a orbit sander. Is Epoxy the right stuff to use here? I know "West Marine" is expensive. Any "reasonable price" epoxy to recommend? I read in another thread that Epoxy could help with MDF seams as well. So I'm leaning toward it if it is not too difficult.

    For wood veneering, I have some maple veneer leftover. If I only want to do two coats of finish, what would these be? One has to be poly so only one left for something else. I can live with the original maple color. Perhaps Tung oil or something? I have honey amber transit dye, rosewood stain (this one will destroy the wood grain), high gloss and satin poly. The idea is quick, not-so-dirty, and resue what's leftover.

    :D

  • #2
    Re: Epoxy or Bondo

    I've used a polyester mix for finish work from NAPA (15270)
    It works nicer/smoother than the usual "Swiss" stuff
    "Not a Speaker Designer - Not even on the Internet"
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    • #3
      Re: Epoxy or Bondo

      don't use the bathroom plumbers putty stuff - it won't harden, and crumbles. Remember that anything you put on will need to be sanded flat. If you have medium size imperfections you can use bondo, but try to apply it as flat and thin as possible. I believe the stuff Sydney mentioned is a thin red glazing creme for bodywork that is designed to be used after bondo to fill in very thin imperfections before painting. I've used it, and it works good.

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      • #4
        Re: Epoxy or Bondo

        Marine epoxy is great stuff but without using fairing additives it will cure so much harder than the MDF that it's hard to get it flat. And it's expensive.

        Bondo is fine. I actually use spackling compound (drywall) to fair small areas. Dries fast and is easily sanded fair. I have veneered dozens of surfaces over this stuff and never had any print through problems. I do use backed veneer though.

        For a durable simple maple finish, use minwax conditioner, then pick a light stain (natural, pine, light oak) and finish with Poly. It's not a real interesting finish but it's bulletproof and will last.

        I tend to spend more time on finishing if I going to the effort to veneer - conditioner, dye, gel stain and then 3-5 coats of rubbed in waterlox.

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        • #5
          Re: Epoxy or Bondo

          If your talking about the seams showing the only method I found that they have not shown up in has been the trench method. My link below shows how I did it. Not easy but works well. If you decide to try it I would use body putty in the trench then skim the whole cabinet with finishing putty. Do this on the bare MDF. Once sanded out to 220 start priming. Here is a link that goes into depth on methods I used to try to hide the seam. I started with about 8 samples then made more. The only one I didn't try was the West Marine Epoxy method. Properly done I am sure it would work fine. I have become sensitized to epoxy from using it. So be careful if you go that route. I used only products that are easy to obtain from HD or an automotive store. As far as the putty goes I'm sure there are a lot that will work fine. I would just try to stick with the polyester. So far I have not seen the seams show up on the test boxes I did over a year ago. Dan N. is the only other one I know that used this method. He used it on the Blades so if your looking for a second opinion you could message him.
          Hope this helps
          Dave
          http://www.pellegreneacoustics.com/

          Trench Seam Method for MDF
          https://picasaweb.google.com/101632266659473725850

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          • #6
            Re: Epoxy or Bondo

            Originally posted by parodielin View Post
            - The butted joints are not flat
            - Small holes and seams here and there

            For wood veneering, I have some maple veneer leftover. If I only want to do two coats of finish, what would these be? One has to be poly so only one left for something else. I can live with the original maple color. Perhaps Tung oil or something? I have honey amber transit dye, rosewood stain (this one will destroy the wood grain), high gloss and satin poly. The idea is quick, not-so-dirty, and resue what's leftover.
            Under veneer, this is all I use: Durham's RockHard Water Putty. Cheap, easy, sands fine, no problem with adhesives. It doesn't take stain, and won't finish as glass smooth as Bondo, so I don't think paint guys would be all that happy. For substrates, IMO, it's a no-brainer.

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            • #7
              Re: Epoxy or Bondo

              Originally posted by LouC View Post
              Under veneer, this is all I use: Durham's RockHard Water Putty. Cheap, easy, sands fine, no problem with adhesives. It doesn't take stain, and won't finish as glass smooth as Bondo, so I don't think paint guys would be all that happy. For substrates, IMO, it's a no-brainer.

              I forgot about water putty; works well and dries really fast.

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              • #8
                Re: Epoxy or Bondo

                semi Off Topic but I've seen at the G&R research forums Durham's suggested to help seal kerf cuts in a mass production speaker. Does it add mass to the enclosure wall changing its resonate frequency or make a thin panel less resonate?

                Take it easy
                Jay
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                • #9
                  Re: Epoxy or Bondo

                  Originally posted by Brewski View Post
                  semi Off Topic but I've seen at the G&R research forums Durham's suggested to help seal kerf cuts in a mass production speaker. Does it add mass to the enclosure wall changing its resonate frequency or make a thin panel less resonate?

                  Take it easy
                  Jay
                  It's pretty low mass. I doubt it would have much effect on resonance. I would think something like vinyl floor mastic would have more effect.

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                  • #10
                    Re: Epoxy or Bondo

                    I would go with the water putty or the Bondo. Stay away from epoxy in my opinion just because it's hard to sand. If you try to sand where it sits proud of the rest of the wood, it's easy to remove too much wood and not enough of the epoxy unless you are very very careful. It doesn't sand well.

                    TomZ
                    *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
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                    • #11
                      Re: Epoxy or Bondo

                      Originally posted by tomzarbo View Post
                      I would go with the water putty or the Bondo. Stay away from epoxy in my opinion just because it's hard to sand. If you try to sand where it sits proud of the rest of the wood, it's easy to remove too much wood and not enough of the epoxy unless you are very very careful. It doesn't sand well.

                      TomZ
                      +1

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                      • #12
                        Re: Epoxy or Bondo

                        Originally posted by parodielin View Post
                        I I know "West Marine" is expensive. Any "reasonable price" epoxy to recommend?

                        :D
                        http://www.raka.com/
                        a bit cheaper if you decide to go epoxy route.
                        http://www.diy-ny.com/

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                        • #13
                          Re: Epoxy or Bondo

                          Originally posted by LouC View Post
                          Under veneer, this is all I use: Durham's RockHard Water Putty. Cheap, easy, sands fine, no problem with adhesives. It doesn't take stain, and won't finish as glass smooth as Bondo, so I don't think paint guys would be all that happy. For substrates, IMO, it's a no-brainer.

                          +1 - this stuff is great. Easy. No significant VOCs. Sandable.

                          I've found that you have to be a little careful in what you are trying to get to stick to it. Vaneer using the TBII method showed some areas of resisting adhesion. Rough it up slightly and apply a little extra heat and you're golden.

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                          • #14
                            Re: Epoxy or Bondo

                            Originally posted by tpremo55 View Post
                            +1 - this stuff is great. Easy. No significant VOCs. Sandable.

                            I've found that you have to be a little careful in what you are trying to get to stick to it. Vaneer using the TBII method showed some areas of resisting adhesion. Rough it up slightly and apply a little extra heat and you're golden.
                            I will use TB1. I have some extra putty and/or dry wall compound in my house so that's what I'll try first. They are test cabinets anyway.

                            Question on the epoxy, I found epoxy associated with boat and it looks like a "finishing". I guess I should be looking at "potting" or "encapsulating" epoxy - i.e., two parts that have to be mixed vs. 1 Ga of pour can. Not really know what epoxy is. ;)

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                            • #15
                              Re: Epoxy or Bondo

                              I've used Bondo, but I've also used drywall "mud" on another.

                              It's not as hard as bondo, and will not like to see water, but apart from that, it did the job fine for painting. Not sure about veneer though?

                              I have water putty and have used that to repair some wood window sashes (inside) and door frames (inside). I was just thinking about using this for speaker projects the other day.

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