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Technical question on Fillers /Bondo

Discussion in 'Traditional Hot Rods' started by blazedogs, Dec 6, 2014.

  1. Rage gold over reinforced waterproof filler on seams or welds works everytime..........never use allmetal filler it cracks and shrinks and has zero flexibility
     
  2. Bib Overalls
    Joined: Aug 3, 2001
    Posts: 4,068

    Bib Overalls
    ALLIANCE MEMBER

    Not a painter/body man but I have talented friends. Just so happens that after a week of prep work we are painting my Model A coupe body tomorrow. We used Master Pro light weight filler and a shot of Evercoat "honey". It improves the filler's "spreadability." A shot of fiberglass resin will do the same but makes the filler harder to sand.

    [​IMG]05BodyWork093 by Bib Overalls, on Flickr
     
  3. uc4me
    Joined: Feb 3, 2006
    Posts: 516

    uc4me
    Member

    I have had good luck with USC Pro Gold, sands nice and seems to hold up well (no problems with shrinkage :)).
     
  4. 30dodge
    Joined: Jan 3, 2007
    Posts: 423

    30dodge
    Member

    I try not to use any filer and never a skim coat.
    The tip on mixing a bit of fiber glass resin in with the filler reduces the pin holes, makes it spread nicer and makes it harder to sand , but gives a nice workable surface.
     
  5. Devin
    Joined: Dec 28, 2004
    Posts: 2,352

    Devin
    Member
    from Napa, CA

    Just out if curiosity; assuming your weld are sound and well executed, why is fiberglass filler considered necessary over weld seams as opposed to regular filler?


    Posted using the Full Custom H.A.M.B. App!
     
  6. Torkwrench
    Joined: Jan 28, 2005
    Posts: 2,430

    Torkwrench
    Member

    :D:D:D Black Knight??? :D:D:D
     
  7. G. Anderson
    Joined: Oct 7, 2010
    Posts: 41

    G. Anderson
    Member
    from MN.usa

    Blazedogs;
    I am at 167th and Cedar in Apple Valley/Lakeville.
    Retired body and paint guy.
    Give me a shout, and I can guide you through the process.

    Gary Anderson
    952-212-1118

    Your Pal, Gary
     
  8. Ulu
    Joined: Feb 26, 2014
    Posts: 1,732

    Ulu
    Member
    from CenCal

    If I can't get the shop warm (like 65 at least) I just don't want to paint. Then again I don't paint for a living. And I live in the desert.

    Small things (bikes & my MG midget) I have done in a plastic tent inside a rather cold drafty shop, using several heat lamps to warm the area and metal gently for many hours before painting. I like to cure the primer a loooong time before painting, especially if it's cold. The thing is, if you use a fan for ventilation while you're in the tent painting (& you really must!) it blows in cold air. I put electric heaters at the fan, but it still was too cold for my taste.

    Now that I'm old and patient, I'll just wait for spring if necessary.
     
  9. Ulu
    Joined: Feb 26, 2014
    Posts: 1,732

    Ulu
    Member
    from CenCal

    Oh, yeah...

    You're going to have thermal problems sometimes when you put heavy filler over welded seams. Metal grows and shrinks with temperature. A 1964 Cadillac will grow almost 1/8" longer if you take it from 0F to 120F.

    Now where there's a heavy seam, the metal is restrained, forcing some expansion/contraction to deform the thinner (and therefore more rapidly heated) metal at the edges of the seam.

    This localized deformation along a seam can pop filler loose like a little zipper.

    Gorilla Hair or Kitty Hair, or any catalyzed preparation with reinforcing strands in it will bridge this area & help prevent failure from thermal movement.
     
  10. Well it's hard to explain and define except when looking at the extremes, but someplace in the middle is where most welds are.

    On one end the extreme is a undetectable weld that is perfect. That wouldn't need filler on the back side. The thickness of the metal would be uniform and the back side is just as nice.

    The other extreme is a weld that has been put in and there are pin holes, porosity, and inconsistent amounts of welds, the dot dot dot welding has places where the dots didn't knit fully together. Those have a sound panel but it's no where near perfect. The waterproof fiberglass on the backside is to protect the pretty side from failure caused by moisture getting thru.

    Now let's say the weld really looks nice some sections of it are perfect but not the entire think. The smallest spot can eventually lead to a finish popping off just the same.

    If it's a lap weld, not only is there a direct path into the seam, but you also have the problems ULU described with the caddy example. Some guys claim no problems but I can spot a lap weld under the paint in many cars.
     
    Last edited: Dec 15, 2014
  11. Ulu
    Joined: Feb 26, 2014
    Posts: 1,732

    Ulu
    Member
    from CenCal



    It's often quite easy if you take it from a dark garage out into the summer sun. Not so much with lead as bondo though.

    The lead doesn't give as much and thermal movement is much closer to steel than plastic fillers. That's because lead is a great conductor like steel, while plastic is a good insulator.

    Insulators generally don't grow or shrink much with temperature.
     
  12. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,549

    49ratfink
    Member
    from California

    if you have done your patches right there will be no difference between mudding a welded seam and mudding a light dent.

    I can't think of any auto body project where any of the magic fiberglass fillers would do any good.
     
  13. G. Anderson
    Joined: Oct 7, 2010
    Posts: 41

    G. Anderson
    Member
    from MN.usa

    If you need, or THINK you need any of that fiberglass filler,
    or are having cracking or shrinkage problems,
    YOU HAVE DONE THE BODYWORK on the METAL WRONG!!!!
    NEVER, NEVER, NEVER should you have MORE than
    1/8" of ANY filler on the metal work!!!
    AT ALL....EVER!!!

    The REAL work in doing bodywork to prep for
    paint is doing the metal work correctly!

    By rights, you should be able to use a
    VERY THIN SKIM COAT of plastic glaze.

    And MOST of that will end up on the floor, sanded off!

    Your Pal, Gary
     
    49ratfink likes this.
  14. image.jpg

    You're absolutely right G, and no one can say otherwise.

    Now for the rest of us who aren't as perfect, well there are things to talk about.
    As far as perfect metal work goes, not many men have been able to stand there.
     
    Last edited: Dec 15, 2014
  15. Here's another example of not to use fiberglass. Remember the days when we used to fiberglass hood scoops on steel hoods. It didn't last long. Why? Fiberglass and steel make a bad bond in the long run. Better of to glue that scoop on with bondo. Have you ever tried to feather edge fiberglass on a steel panel it will break away like a bad paint job. It just flakes off the edges. Who's got room for a layer of fiberglass anyway. Barely enough room for a skim coat of bondo.
    here's a full length butt weld on a 70 torino 1/4. thin layer of bondo, a little glaze....done over 10 yrs ago
     

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  16. Slopok
    Joined: Jan 30, 2012
    Posts: 2,432

    Slopok
    Member

    I know you're makin fun of it but if they would've paved our highways with that stuff we wouldn't have as much road construction goin on.;)
     
  17. Torkwrench
    Joined: Jan 28, 2005
    Posts: 2,430

    Torkwrench
    Member

    You're right. Actually the body work that I did on my 55, with Black Knight lasted for almost 20 years. This was without any cracks, or further rusting. The other spots where I used Bondo, had to be redone a couple of times, between 1977 and 1997.
     
  18. Olmon
    Joined: Apr 21, 2011
    Posts: 7

    Olmon
    Member

    One thing no-one mentioned, not even the other 'bodymen' is to NEVER put catalyzed body filler over bare metal. The Hardener is an oxidizer & can, in time, cause rust. Always spray at least a light coat of self-etching primer over the bare metal before using any plastic filler. That is more important than the 'kind' of filler you use. On painted areas where the paint is sound & adhering well, just rough up the paint for adhesion & put the filler over the paint to kep the oxidation isolated from the metal. I-Car started stressing that back in the 90s. Other than that, the advice all the other guys gave appeared good to me.
    (I am retired now, but was I-Car certified in all areas of auto body & Frame/Unibody repair + being Michigan state certified for Auto Body Mechanical & Structural Repair and Steering, Suspension & Braking systems for cars & light trucks)
     
  19. Slopok
    Joined: Jan 30, 2012
    Posts: 2,432

    Slopok
    Member

    The reason I know about its strength is I put one of those backwards tear drop bubble scoops on a 63 Ford I had and bonded it only with the Black Knight. Didn't have a rivet gun or any other means to affix it. When I sold the car to my friend he didn't want the bubble hood and traded it to another friend who had a 63 Convertible and wanted the bubble hood. Shortly thereafter the convertible hit a tree very hard dead center and the bond between the hood and bubble never even so much as cracked, it just followed the contours of the dents. Wish I had photos.
     
  20. Slopok
    Joined: Jan 30, 2012
    Posts: 2,432

    Slopok
    Member

    Not only did I go over bare metal but my frenched headlites, rounded hood corners, shaved door handles & moulding holes were brazed which is another no no. No access to a Mig Welder back in 1982. Roughed up the metal with a 36 grit disc and applied bondo. Not saying it was right but that's what I did. Granted my car doesn't see daily use but in 32 years it has held up very well. Just regular lacquer primer & paint with clear lacquer only on the flames.
     
    Last edited: Dec 15, 2014
  21. Short Straw
    Joined: Dec 8, 2014
    Posts: 30

    Short Straw

    Gene is the man, but I disagree with the stranded fillers usage,not flexible enough. A quality filler (rage gold) over properly prepped metal works fine.
    Blazedogs: The surface temperature of the vehicle is the most important,if you can get the surface you are working on warm,the air temp can be pretty cool. I always end up using heat lamps and such for small areas in the winter,and if I'm working or painting a large area I wait till later in the day until the car itself has warmed up.
     
  22. creepjohnny
    Joined: Dec 1, 2007
    Posts: 867

    creepjohnny
    Member
    from Sunland,CA

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