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Thread: Epoxy or Bondo

  1. #1

    Default 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.


  2. #2
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    Default 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

  3. #3
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    Default 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.

  4. #4
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    Default 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.

  5. #5
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    Mar 2008
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    Malvern, Ohio
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    Default 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

  6. #6

    Default Re: Epoxy or Bondo

    Quote 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.

    Lou's Speaker Site [speakers.lonesaguaro.com]
    "Different" is objective, "better" is subjective. Taste is not a provable fact.
    Where are you John Galt? I may not be worthy, but I'm ready.

  7. #7
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    Default Re: Epoxy or Bondo

    Quote 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.

  8. #8
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    Default 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
    "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

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  9. #9
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    Default Re: Epoxy or Bondo

    Quote 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.

  10. #10

    Default 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

  11. #11
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    Default Re: Epoxy or Bondo

    Quote 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

  12. #12
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    Default Re: Epoxy or Bondo

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

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

  13. #13
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    Default Re: Epoxy or Bondo

    Quote 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.

  14. #14

    Default Re: Epoxy or Bondo

    Quote 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.

  15. #15
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    Default 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.

  16. #16
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    Default Re: Epoxy or Bondo

    Man, all this talk of seams is starting to dissuade me from even attempting mdf. Would switching to a (proper braced, of course) ply enclosure make finishing easier? Ie, will the seams still tend to show as much?

    Have people found an inexpensive paintable veneer-like material? I think I saw wallpaper mentioned at some point...If we can just cover up the issue, that would certainly make the whole process easier!

  17. #17
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    Default Re: Epoxy or Bondo

    Man, all this talk of seams is starting to dissuade me from even attempting mdf...
    It sounds worse than it is in reality; the HiFi speaker industry uses a lot of MDF after-all. It depends on what is the final surface is; with a laminate - this touch up of surface is not critical; for a painted final surface it is.
    Plywood is often chosen for PA, because of durability required from road abuse.
    Plywood can have chip out at the seams however, so ( again in a PA ) the cab edges and corners are often covered with edging.
    Touch up with fillers can be reduced by using construction methods that assemble with internal fastening - no external screws/brads.
    The seam issues are minimized with precise setup and sharp blades ( off course )

  18. #18
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    Default Re: Epoxy or Bondo

    Haaaah....I suppose the right answer is to start using my small table saw's mitering capabilities and avoid the but t joint entirely...But that means I'll need to be all precise with my cuts! Grumble.

  19. #19

    Default Re: Epoxy or Bondo

    Quote Originally Posted by Starkiller4299 View Post
    Man, all this talk of seams is starting to dissuade me from even attempting mdf. Would switching to a (proper braced, of course) ply enclosure make finishing easier? Ie, will the seams still tend to show as much?

    Have people found an inexpensive paintable veneer-like material? I think I saw wallpaper mentioned at some point...If we can just cover up the issue, that would certainly make the whole process easier!
    With plywood, you still need to fill grain (end and face).

    If you can find it, MDO plywood stock has a paper/resin cover and is routinely used for sign building.

    By the time you do all the prep work, I think veneer is cheaper, easier and faster than paint. (especially rattle can) Heck, buy some cheap white ash veneer, and paint that!
    Lou's Speaker Site [speakers.lonesaguaro.com]
    "Different" is objective, "better" is subjective. Taste is not a provable fact.
    Where are you John Galt? I may not be worthy, but I'm ready.

  20. #20
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    Default Re: Epoxy or Bondo

    Quote Originally Posted by Starkiller4299 View Post
    Haaaah....I suppose the right answer is to start using my small table saw's mitering capabilities and avoid the but t joint entirely...But that means I'll need to be all precise with my cuts! Grumble.
    I hear your frustration - I just got a nice table saw so I can make precise 90 degree cuts, then realized that I really couldn't miter the edges with it - I'd never be able to setup a precise 45 degree angle for the edges. As far as I know, you need a sliding chop saw for that.

    I'm definitely not a woodworking expert, but I've seen many projects where peeps used plywood or mdf b u t t joints and veneered over that with good results.

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