Problem with Plastic Sheet Warping - Need Advice

[Waketrail]

I've been trying to do some scratch building details for some model kits using Evergreen plastics. But I've been having really bad luck. Everything I build seems to start warping out of shape after a week. I shouldn't say everything, just the parts involving sheets and thin strips acting as walls. For example, If I build a box with plastic sheet it seems to cave in on itself.

I've been using Tamiya super thin cement. Its been great for styrene model kits.
Should I be using something else?

Any suggestions are welcome.

 

[korben44]

How large of a project are we looking at?

 

[Analyzer]

I've encountered the same issue when assembling some buildings for my HO scale layout using Testors glue.

The more space between supports, and the thinner the sheets, the more likely it is to warp after bonding.

Gluing in "support beams" or bracing can greatly reduce the warping

the post by doctorwayne in the link below (about the 7th post down) demonstrates some internal support options you can use for various shapes
sheet styrene warping - Model Railroader Magazine - Model Railroading, Model Trains, Reviews, Track Plans, and Forums

 

[SofaKing01]

I would suggest using a thicker backer - acrylic or 1/16th MDF then cover with styrene?

 

[TazMan2000]

The Tamiya glue is a solvent, so it melts the plastic. Try using CA or as others have suggested a thicker plastic.

TazMan2000

 

[Duncanator]

If you are making an enclosed box, excess solvent glue can stay trapped inside. This can soften the plastic sheet from the inside as the solvent tries to evaporate through the plastic. I have intentionally left a pinhole for it to escape on some things I've made.

I love and prefer solvent glues, so this is not a knock against them - just something to be aware of.

 

[Waketrail]

Thanks for all the advice. I thought bonding through melting would be the best thing to do when working with plastics. Maybe I continue doing so but using less or only bonding a bit each day.
The pictures show the actual model kit warping (1/144 AAV-7A1 by Trumpeter). It only seems to happen when I use plastic strips for detailing. I guess I am using too much cement.