I am building a Bachmann CityScenes Variety Store. It is made entirely of styrene plastic. A canopy, measuring 11" long by 1" wide, runs across the front of the store.
Trouble is, it is warped. About 7" of the canopy are flat, but then 4" at the end of the canopy are warped, sorta twisted. I weighted it down in a pan of scalding water, but to no avail. It is too thick for hot water to have any real effect.
I have considered using a heat gun or a hair dryer, but I worry that it could soften the plastic too much or even melt it.
Another thought is to glue a thick strip of styrene to the underside of the canopy to force it straight. Not sure, though, if that would work.
How is it fastened to the wall – you may be able to glue a strip of basswood along the edge to straighten it out – maybe even both edges if the strip can be made to look like part of the canopy.
The back of the canopy gets glued to the front wall of the structure, and a series of six tiny tabs fit into small holes in the front wall. The canopy is approximately 1/8" thick.
Years ago, Fine Scale Modeler had an article on straightening a model car chassis that was warped (from factory or heat). The idea is to get a heat lamp- one of those small bullet-shaped desk lamps with a 60 watt standard light bulb (maximum wattage allowed) would work (you can get them at Walmart, I believe).
Place the warped piece on a true flat surface, such as a piece of plywood or MDF and locate the lamp close to the part. Let the heat from the bulb relax the styrene, but monitor it regularly, until the part is straight again. This process may take a few hours or so, but is less abusive to the part than using a heat gun.
I wonder if the approach used for a bendable stone wall I bought could work. I bought some Ultimate Scenery System “Master Casting” stone wall where the instructions have you place the piece in a warm (250F) oven for 2-3 minutes, then put it in place, bending to the desired shape and it cools and holds its shape. The concept might be borrowed but the different materials (the stone wall seems like a hard foam but I don’t know what it is) would call for different time & temp, plus affect the working time before it re-sets. I’d consider starting at 225F (even 200F), warm it a bit and place it on a flat surface with a flat weight atop as it cools. If not achieved, increase temp and/or heating time in small stages until it works.
EDIT: With some google searching I see that poystyrene has a “glass transition temperature” of 100C, 212F) below which it is fairly inflexible and above which it is “rubbery” (soft and flexible, not the higher temp where it would “melt”; i.e., REALLY soften). Thus, I’d start the experiment at, say, 190F and go from there, hoping the flexibility occurred by 200-215F or slightly above. I don’t know if our “styrene” models are pure polystyrene or have co-polymers which would complicate the temperature characteristics for a specific product. Perhaps experiment with an expendible piece of the same material.
I can’t imagine that would hurt anything if addressed gradually, starting with a low temp/time. My guess it that would work better (more controllable) than with a heat gun.
I have some 1/8" thick birch plywood from Midwest products which is very stiff and non-bending. I trimmed a strip to fit on the underside of the canopy, and it is pretty much concealed from view. So, I will pick up a small tube of WeldBond at Michaels today and clamp the canopy to the birch to hopefully straighten it. My plan is to rough up the surface of the canopy to maximize the bonding surface.
And the variation I remember reading about was to place the item between two sheets of glass, perhaps plate glass, and have the heat lamp above the glass – but again, with careful and constant monitoring so it does not go “too far”
When placing ao a flat surface prior to heating, you may have to “shim” and set weights to exert “over” bending. The plastic will still have a tendancy to spring out of shape even on a flat surface once cooled.
Actually, I did the heat lamp thing with an old 1/32 scale Revell (or was it Monogram) Firebird chassis many years ago.
One thing, as has been mentioned above, is that I have no idea about the type of styrene used to make the model. Certainly it was harder than, say, Plastruct sheet styrene material I buy at Hobbytown- if the canopy (clear?) part is of a particular styrene type, then perhaps different techniques may be required.
I used WeldBond to glue the styrene to the birch plywood strip about 10 AM this morning, and I have a series of clamps holding it tightly together. The instructions say to wait 24 hours before unclamping to ensure maximum holding power. So, I will know sometime tomorrow morning if it worked.