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bending plastic

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  • Member since
    October, 2009
bending plastic
Posted by Steel77 on Saturday, February 13, 2010 12:53 AM

amateur model builder here. I got everything painted and glued together and was ready for that final step of attaching the sweet looking body to the undercarriage. thats when I noticed it. the undercarriage was some how arcing up in the middle making it impossible to join the two halves.

keeping in mind i am an amateur (having only build 4-5 models in my life) is there a way that a low bidget modeler like me can flatten out that curve? it still has the engine and tire assemblies on it.

  • Member since
    August, 2006
  • From: Neenah, WI
Posted by HawkeyeHobbies on Saturday, February 13, 2010 8:34 AM

You might have to cut it and remove it then reattach it after you take out the bend. Too late now for you to use hot water as it will cause other parts to bend as well.

Is there any way to make it work as is with a little trimming and reshaping.  If it won't be visible what harm will there be.

Gerald "Hawkeye" Voigt



"Its not the workbench that makes the model, it is the modeler at the workbench."

  • Member since
    October, 2009
Posted by Steel77 on Saturday, February 13, 2010 10:25 AM

its a very broad bend. so much so that it keeps both end from even touching the upper part by about half an inch on both sides. 

how hot would the water have to be?


  • Member since
    June, 2008
  • From: Iowa
Posted by Hans von Hammer on Saturday, February 13, 2010 10:39 AM

Too hot for bare hands...

  • Member since
    October, 2009
Posted by Steel77 on Sunday, February 14, 2010 10:34 PM

i can deal with taking the engine and wheel parts off to correct the bend, I just dont know how to go about it. how would you guys do it?

  • Member since
    February, 2010
  • From: Ontario, Canada
Posted by Bockscar on Monday, February 15, 2010 2:06 PM


Polystyrene melts to a liquid at about 460 Degrees F, begins to transition (soften) at about 203F.

Water boils at 212F, so hot water will begin to soften the plastic.

If you are out about 1/2" at either end it sounds like a large project. Sometimes because of the casting you may find some sections are more curved than others, so if that is your case, it is best to find those sections and focus on them.

First rule of reshaping warped plastic:

Do not try to reshape the item all in the first try. You may have to go through a number of evolutions to get it right, so make up your mind from the outset that you can commit to at least a few dozen evolutions.

If using near boiling water set the item so that you can pour the water over the piece without scalding yourself and allowing for two 'grabs' that will be cool enough to touch.

If you've never done this before be patient and start out with water at about the 190F range. 

Pour the water over the pieces for a few seconds and use the grabs to test rebending with the opposite curve, try to match the degree of warp in the opposite direction to see how the bend feels and reacts.

Another approach is to fill a pan with the hot water, bend the piece and dip the part you want reshaped into the water.

This is a learning process and every re-warp is unique, so you will have to test the process a few times.

Again, be patient. Some styrenes are brittle even when warmed they will literally explode into pieces if you bend them too far too fast.

As your confidence for the process builds try hotter water and slightly more aggressive bends.

Here's the trick: once the piece is heated and you have it in the new rebend poition, hold it there until the temperature drops to the point where it is below about 100F: you can feel it isn't too hot to handle.

You should notice that with each evolution the piece begins to approach the desired shape. You will get to a point where it may not be perfect but can be taped and glued, or you can press on to perfection.

Patience and safety are the key. 

Good luck with your project,



  • Member since
    October, 2009
Posted by Steel77 on Monday, February 15, 2010 6:22 PM

thanks, ill let you know how it goes. I'll try it this weekend.

  • Member since
    February, 2017
Posted by dgb on Sunday, March 12, 2017 1:00 PM

Hello Willie, I mean Bockscar. Joke.  My needs: I'm starting  a Renwal trident boat w/ interior. I want the unglued seam of the hull halves in as close an alignment as is practical (when closed of course). When I rubber band the two empty hulls together they fit well  after some adjustment. Do you think I can heat them slightly so they'll stay that way after cooling and unbanding?  Possibly not, but inquiring minds want to know.  How about immersing banded hulls in about 185 water for a few. Any suggestion for time. Thanks dgb


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