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Continuum Speakers Using my Trench Method on the MDF Seams

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  • #16
    Re: Continuum Speakers Using my Trench Method on the MDF Seams

    Touche.

    Comment


    • #17
      Re: Continuum Speakers Using my Trench Method on the MDF Seams

      I drug out my test pieces from 3 years ago to look them over. Really no change. All but the trench method was showing a seam. The thinner trenches, 1/16" or less was showing a wave which at the time I said was not thick enough.




      What I did notice I found interesting is all the ones with a trench has a crack in the center of the piece b u tting against the other piece. All the other samples no mater what finish or method does not have this crack. Originally I thought the body putty was flexing over the seam enough to keep it hidden. Now I wonder if part of what is going on is the putty is stopping the moisture from coming through the surface but still allowing it to get in and out through the back side. So the shrinking and expansion is now in the middle of the piece. If you look at my samples above you can see I experimented with a slot cut an 1/8" below the surface. None of those attempts worked.

      These are the samples that have various depth of trenches and one without a trench but has a 1/16" layer of body putty over the whole piece.



      samples without trenches




      Just my theory anyway.

      Dave
      http://www.pellegreneacoustics.com/

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

      Comment


      • #18
        Re: Continuum Speakers Using my Trench Method on the MDF Seams

        I should mention when I quoted building these cabinets they wanted a painted cabinet. I priced them at a wide price range from just enhancing the seams with satin finish to hiding the seams and automotive paint. His exact words where " I want all the bells and whistles" so that to me was build the best cabinet I know how.

        Back to the progress.

        I hadn't realized I hadn't posted since the trenches.

        One coat in the trench and one coat over the whole panel. I found it is best to coat the whole panel. It is much easier then trying to feather in. Plus coating the MDF even a very thin coat seals it for primer really nice. I'll show that farther down.



        This is one thin coat put over the routed edge by hand. Left side is sanded right is not.



        Second coat sanded.



        Third coat on sides. This is the build up I think is worth the extra time to keep the panels flat.




        You can see the trench depth on the right side of the cabinets. See they really are only an 1/8" deep.




        Dave
        http://www.pellegreneacoustics.com/

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

        Comment


        • #19
          Re: Continuum Speakers Using my Trench Method on the MDF Seams

          Edges routed. I waited to do this until the panels where nice and flat. Having that sharp edge is much easier to get them flat. That top corner where the two trenches meat, on the side and top is the toughest part to get right.



          I filled the edges up heavy so I can skim the baffle in and have a nice coat over the corners.



          Sanded ready for primer.




          Dave
          http://www.pellegreneacoustics.com/

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

          Comment


          • #20
            Re: Continuum Speakers Using my Trench Method on the MDF Seams

            This is with two coats of primer. I used USC 2K Urethane primer. This has a hardener you add and it is very important to wear a carbon filter mask when spraying. The pic makes the sides look rough but they are very smooth. Must be my cellphone.




            Now some lessons learned. This is one of the posts all I did was wipe body putty into the round over. This is not my cellphone making it look bad. I figured the flats sanded to 180 would be fine. You can see how nice the round over is which should be the hard spot to cover. The primer soaked in on the flats and ended up with a lot of over spray on them. I think they will sand ok but I bet I'll have to spray them again because of pit marks. To me it would have been quicker and better to do a thin skim coat of body putty.




            Now here is the bone head move of the week! This is a fourth coat I applied using "Icing" which is great for a final coat. Problem is for some reason I was thinking it was a spot putty which is basically a thick primer. So, I apply the icing and it's going on great, nice and smooth. I get done and am standing there checking out my fine work and I'm thinking " wait a minute I can't put that on a 1/6" thick" I pick up the tube and read and sure enough I was suppose to put hardener in. If you know body putty well and know how sticky it is WITHOUT hardener you know what a mess I have on my hands! It took me about a half hour to scrape it all off and wipe the remaining film off with lacquer thinner. Luckily there was no damage to the boxes but what a feeling when I realize what I had done.

            Here is a pic of the mess.
            Looks really nice doesn't it?



            Dave
            http://www.pellegreneacoustics.com/

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

            Comment


            • #21
              Re: Continuum Speakers Using my Trench Method on the MDF Seams

              No John. It might be a good idea for the first coat. I just used regular putty.

              Dave

              Originally posted by jhollander View Post
              Dave are you using the fiber reinforced bondo?
              http://www.pellegreneacoustics.com/

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

              Comment


              • #22
                Re: Continuum Speakers Using my Trench Method on the MDF Seams

                Originally posted by bigfishe View Post
                Dave try the Nason ful-pox epoxy primer over the MDF
                Takes several coats to build up. Once you're there it has the best hide out capabilities
                I've found for wood or Bondo.
                I've been painting cars and speakers for 26 years!
                Is this similar to the 2K Urethane primer. As I mentioned I have to stay away from epoxy. This product may be ok as long as I use it with a carbon mask and wear gloves but I'm not sure it's worth it.

                Dave
                http://www.pellegreneacoustics.com/

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

                Comment


                • #23
                  Re: Continuum Speakers Using my Trench Method on the MDF Seams

                  It's nice to know that even you make mistakes.
                  They're going to look fantastic when done.

                  TomZ
                  *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                  *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                  *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                  Comment


                  • #24
                    Re: Continuum Speakers Using my Trench Method on the MDF Seams

                    It's simpler to hide those B U T T joints with a laminate like Formica. The cheapest sheets with the smooth base color are maybe $45 for 4x8 sheet at Lowes. Epoxy the Formica to the cabinet, trim the excess with a flush trim router, sand smooth, and apply the next sheet. Scuff the laminate at the end with some nice automotive sanding discs to remove the shiny surface of the Formica, and it's ready for primer/paint.
                    I've seen an acid etching primer you can use instead of sanding and primering. Saves a step. I believe Sherwin Williams sells it.

                    Comment


                    • #25
                      Re: Continuum Speakers Using my Trench Method on the MDF Seams

                      Originally posted by richard t View Post
                      I've seen an acid etching primer you can use instead of sanding and primering. Saves a step. I believe Sherwin Williams sells it.
                      Dupont also makes etching primer. We get it in spray cans at work. Nasty fumes ( do not breath ) but dries in about 1 min.

                      Comment


                      • #26
                        Re: Continuum Speakers Using my Trench Method on the MDF Seams

                        The Dupont self etching primer I am familiar with is for metal.

                        http://www.pc.dupont.com/dpc/en/US/h...19303_615S.pdf

                        Comment


                        • #27
                          Re: Continuum Speakers Using my Trench Method on the MDF Seams

                          I saw the SW brand used on glass. They rolled it on and weren't wearing any respirators. Neat stuff.

                          Comment


                          • #28
                            Re: Continuum Speakers Using my Trench Method on the MDF Seams

                            Can you give details on your paint setup? What do you use to spray the paint?

                            Comment


                            • #29
                              Re: Continuum Speakers Using my Trench Method on the MDF Seams

                              Originally posted by r-carpenter View Post
                              I don't really want to sound negative but I don't understand why Dave is inventing the wheel here. The reason seams show up if bu.tt joints are used is the difference in the expansion/contraction of MDF within it's thickness compare to it's plane. Adding filler to the mix means adding another variable component which will not expand and contract as MDF all together. It's not like the "trench method" is a quick thing. You need to rout the "trenches", fill them, sand and so on. A proper 45miter joint may initially take some time to set up on the router table or table saw but will resolve most of the issues. I have never seen a miter cut show ghosting the same way as a bu.tt joint.
                              The other way to work around it would be veneering. Commercially, there's a thick phenolic paper that available for exactly such purpose. So, instead of veneer, this paper is pressed on the cabinets using rigid adhesives.
                              I absolutely agree with you. Why make it so complicated to begin with?
                              I think we all endeavor to find a way that will work best for us, and when we do, we stick with it. Regardless of the difficulty.
                              Trenching seems silly especially since there are other ways to achieve the same results. But joints are already the worst as it is, both structurally and cosmetically. In the cabinet industry, it's all about production and making a fast buck, so they use simple but joints.

                              Comment


                              • #30
                                Re: Continuum Speakers Using my Trench Method on the MDF Seams

                                Originally posted by davepellegrene View Post
                                Man I hope this doesn't' turn into another MDF seam argument.
                                Dave
                                You mean like we seem to have a seam disagreement? Then why post it if you know there will be a disagreement?

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