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Posted (edited)

I do a lot of heavy re-styling, both on models and in full scale.

What I'd recommend for models is just about any 2-part POLYESTER automotive glazing putty (made for real cars).

It's basically a finer-grained "bondo", and is available at auto-body supply stores and many general car-parts places.

The best quality I've found so far is USC "Icing", but it comes in a tube that is too big for modeling...unless you do a LOT of custom work, and it's only available at bodyshop supply places.

A very good second choice that is available in modeler-friendly packaging is the Bondo brand 2-part "PROFESSIONAL" glazing putty. It's stocked at stores like Advance, Carquest, Napa, etc.

This custom body kit for a Datsun 240 Z is being built using these products.

Image result for ace-garageguy 240z            Image result for ace-garageguy 240z     

                                                                                  Image result for ace-garageguy 240z     Image result for ace-garageguy 240z

Image result for ace-garageguy 240z

Be absolutely certain you buy the "PROFESSIONAL" labeled product if you go with the Bondo brand. It has its own catalyst packaged with the tube. You do NOT want to use ordinary lacquer putties (like Squadron or Testors or the Bondo ONE-PART) for heavy fill work because they will take forever to dry, and tend to shrink and crack if piled on thick.

This is the good stuff in the Bondo brand...

Image result for bondo professional glazing putty

 

 

 

Edited by Ace-Garageguy
Posted

Bill, does that stuff dry quick and sand smooth fairly easy ?  I have been using the Tamiya putty for years and am pretty happy with that but always looking for something better.

Posted

One thing no one has mentioned so far is that the bulk of the bodywork should be done using plastic and cement. With flares for example, you need to build the basic structure out of plastic, then use the putty to cover the flaws. Most of the filler/putty should be sanded away, leaving what is required (a very thin layer) to fill seams and other flaws.

Don't build your body kit of filler alone so that there is 1/4" of putty and nothing else. The first time the body flexes, it will pop off.

 

Posted (edited)

One thing no one has mentioned so far is that the bulk of the bodywork should be done using plastic and cement. With flares for example, you need to build the basic structure out of plastic, then use the putty to cover the flaws. Most of the filler/putty should be sanded away, leaving what is required (a very thin layer) to fill seams and other flaws.

Don't build your body kit of filler alone so that there is 1/4" of putty and nothing else. The first time the body flexes, it will pop off.

 

Well...I've built an awful lot of custom stuff, and I'll have to elaborate. Thinner filler is always better in principle, but it takes a lot more time to do the fab work very close to final-contour in styrene.

If you look at the 1/12 scale Z-car model i posted above, you'll see the main lines were established with styrene, and the contours were filled in with a pretty fair amount of "bondo".

There's nowhere near enough "flexing" to pop the filler off, and the styrene was roughed up with 180 to help with adhesion anyway.

Another problem with very thick fender flares that are primarily bondo is that they'll be too thick to allow the tires to go up in the wheel wells to look right. You can grind the filler off the backside of a fender to remedy this, but you'll have to do some reinforcing as shown on the model below.

This is a 1/25 scale model I'm almost finished with. The shapes were again established with styrene, and contoured with "bondo". Actually, on this particular model, I ran into some minor problems because I let the filler get TOO thin on certain areas...and that's where "flexing" played merry hell with the stability of the substrate while sanding the primer.

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I had to reinforce the underside of the custom work with fiberglass to stabilize it in order to be able to block-sand it straight enough for paint. (It wasn't a long-term problem on this model, as the finished body is a plug for a set of molds, and it only has to function as a master, so the underside thickness isn't an issue.)

DSCN9881_zpsuwvur0ss.jpg

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Edited by Ace-Garageguy
Posted

Bill, does that stuff dry quick and sand smooth fairly easy ?  I have been using the Tamiya putty for years and am pretty happy with that but always looking for something better.

Ray, the Bondo 2-part stuff is fully kicked and ready to sand...even in very thick fills (like 1/4 inch) in 10 to 20 minutes, depending on how "hot" you mix it.

There is a little learning curve to get the mix ratios right every time, but once you have that dialed in, you can do a LOT of heavy sculpting very quickly. Mixing IS somewhat critical, because too little catalyst and it will NEVER harden, and too much and it won't harden right.

You can, in fact, sculpt the stuff if you hit it with sharp tools just as it begins to gel. Again, there's a learning curve. Hit it too soon, and it will ball up and the bond between the Bondo and the plastic will fail.

Wait a few minutes too long and it will be too hard to "sculpt", but that's not a problem, as it will still sand to shape very easily.

I can't compare it to Tamiya putty, as I've only been using Squadron Green (another one-part lacquer putty) for tiny surface imperfections. There's just no way I could do the kind of heavy custom work as shown above with a one-part putty.

 

Posted

Bill, does that stuff dry quick and sand smooth fairly easy ?  I have been using the Tamiya putty for years and am pretty happy with that but always looking for something better.

I might be a bit anal here but 2-part putties do not "dry" - they harden by chemical reaction.  That is a very desired property (since there is no shrinking or long-time out-gassing).  The 1-part putties have solvent in them which evaporates to make them hard. So those putties "dry".   Since the solvent was taking up some volume in those putties, once it evaporates the putty shrinks. If the putty layer is thick enough the solvent gets trapped deep inside the layer of putty and it will not fully evaporate for a very long time.  That is also undesired properly.

Posted (edited)

Excellent point, Peter, and important to remember when choosing a material. 

The ratio of filler to catalyst IS important to maintain within a relatively narrow window, and most problems arising from using catalyzed filler are due to improper mixing.

One-part putties still have their place for filling very minor surface imperfections, but they're entirely obsolete for heavy fill work.

Edited by Ace-Garageguy
Posted

Bill, I have a two questions for you.

Do you have issues with the heat from the two part bondo and has it caused any warping issues for you and do you every use MEK and make your own liquid plastic? 

I have always wanted to use the two part stuff but the heat has been a concern.

Posted

Bill, I have a two questions for you.

Do you have issues with the heat from the two part bondo and has it caused any warping issues for you and do you every use MEK and make your own liquid plastic? 

I have always wanted to use the two part stuff but the heat has been a concern.

The heat has never been a concern. If you don't over-catalyze, the stuff doesn't ever get more than a few degrees over room temp.

On a hot day, with the amount of material you'd use on a REAL car, you CAN get some excess heat, and the stuff will sometimes kick before you've been able to get it all on the car.

But for MODEL work, you'll be using very small amounts, and again, if you get the right amount of catalyst, you'll have several minutes to work it, and no significant heat from exotherm.

For the second part of your question, yes, I have used MEK and styrene shavings to make a slurry for filling things like panel edges where any kind of putty just won't stick well enough.

BUT...since I started using Loctite "toughened" gel for edge filling, I haven't needed to go to all the bother of making up MEK / styrene goop.

 

 

Posted

Thanks for the clarification on the 2prt. I normally use CA and baking soda for filler. Just recently mixed up some MEK liquid plastic, so far not a fan of it. Dries out too fast and is just gummie. 

Appreciate the info Bill. 

Sorry for the hi-Jack Suzier, thought my questions could be relevant and might add to your inquiry. 

Posted

Bill, I have a two questions for you.

Do you have issues with the heat from the two part bondo and has it caused any warping issues for you and do you every use MEK and make your own liquid plastic? 

I have always wanted to use the two part stuff but the heat has been a concern.

I've used 2-part polyester body putty many times over the years to create shapes, even a complete body shell on occasion.  I've never had any problem with the heat coming from the curing process--even though as Bill and others have said, the more catalyst used the more heat is generated as the putty cures.

This is a still-stalled restyling project, using the OOP AMT/Ertl "Black Force" custom car snap kit from the late 1990's/early 2000's.  Called a "1941 Duesenberg Model J, all the bodywork you see was done with USC Icing, the same product Bill mentions above.  I tend to over-catalyze the stuff a bit, as I needed it to begin setting up fairly quickly--probably used about double the recommended proportion of catalyst to putty--yes, those fender extensions did get warm, but not nearly enough to even be uncomfortably hot to the touch.  To ensure absolute adhesion of the putty to the styrene plastic, I drilled a number of small holes in the styrene plastic surfaces onto which I was going to apply the putty--those holes, once filled with the putty, act like built-in rivets--this in addition to roughing up the surface of the plastic as well.  You will note that the Icing has a bit of a mottled look--that's because I used two different colors of catalyst, red and blue.  This was so that as I shaped the raw puttywork, I could see where more putty was needed, so a contrasting color of putty helped me in that regard as well.

Once I get back on this project, wnen I have the polyester putty work as smooth as I can get it, I'll shoot some red oxide primer on it, then lightly sand that, to find any surface imperfections, which will get filled with ordinary lacquer-based spot & glaze putty.

This is a system for bodywork that  I've used, off and on, since about 1969-70--it's never failed me yet!

Art

41Duesenberg2.jpg

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41Duesenberg3.jpg

Posted

Thanks very much Art for taking the time to provide this in depth information, much appreciated. I like that you use different colour kicker to help you. Now that I know you guys have great succes with this stuff I will give it a go.

Nice looking work btw, it will look pretty slick once your done with it. 

  • 2 years later...
Posted

Can someone address how Tamiya Polyester Putty compares to Bondo Professional?  I have used Tamiya Polyester Putty several times and have found the mix ratio to be very forgiving.  There have been no setting problems despite my inability to have a consistent mix ratio. (In my estimation).

 I have not had good results previously, using automotive polyester putties on real cars (not models). I tend to mix the stuff wrong and it kicks way too early. No such problems have appeared with the Tamiya putty on plastic and resin models.

 How do these products compare in mix ratio latitude? I generally mix batches the size of a pencil eraser, as an indicator of my usage.

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