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NOBLNG

Curving narrow styrene strips

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Posted (edited)

I have on a few occasions tried to curve thin strip around a curve, eg: .020”x.030” strip as a chrome trim divider for a vinyl roof. If the curve is too sharp, the second I touch the extra thin cement to it, it will snap.  I have also recently tried curving a .020”x.125” strip around a 1/4” diameter circle. I managed this after about 10 attempts by wrapping it around a drill bit and carefully heating it with a lighter so it would retain the approximate shape before glueing. 
Any hints on this? CA may work better than the Tamiya cement since it wouldn’t “melt” the styrene, but I really hate the stuff.

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Edited by NOBLNG

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I have made moldings using different sizes and shapes from Plastruct. I have been using Tamiya Extra Thin Cement for gluing and like you I'm not 100 % on it either. The problems I run into is that it dries very fast and I do best gluing a section at a time. I get just enough to hold it in place and then tape it down. I then move to the next section and repeat until I get the desired molding laid out. I'll go back over the moldings while still taped in place and lightly apply additional glue with the brush. After it cures in about an hour I'll remove the tape and treat those sections. A light sanding around the edges and a light coat of primer will show if any additional attention is needed.    

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Try warming the pieces just a bit and wrapping it around a piece of tubing first, forming it with your fingers.  It will take the stress out of it so when you go to bend it around what you need it works easier.  The tubing best to use is either brass or aluminum.  As to the warming part, you can put it in some warm water first.

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7 hours ago, espo said:

I have made moldings using different sizes and shapes from Plastruct. I have been using Tamiya Extra Thin Cement for gluing and like you I'm not 100 % on it either. The problems I run into is that it dries very fast and I do best gluing a section at a time. I get just enough to hold it in place and then tape it down. I then move to the next section and repeat until I get the desired molding laid out. I'll go back over the moldings while still taped in place and lightly apply additional glue with the brush. After it cures in about an hour I'll remove the tape and treat those sections. A light sanding around the edges and a light coat of primer will show if any additional attention is needed.    

Plastruct is harder to find but is a better quality than Evergreen. It bends more without cracking.

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Sheat styrene does not react well to heat. It will shrink or curl up in weird ways.

Cold molding is what I would suggest, slow and over different size mandrels till

you get it where you want it. 

Also try using two thinner sheets layered to get the thickness preferred.

Wick in some thin cement like Tamiya and it should hold that curve your trying

to achieve.

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try rolling your strip around something small and round like a hobby knife handle to curl it, I find it works better to attach with super glue, start at one end and when it 's solid do another section. 

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Yet another route: apply some Tamiya Extra Thin to the plastic card part, and let it soak in. Do not use it (yet) to glue, it's just to make the part softer and more pliable. Wait a few minutes, then curve the part.

I used the same technique to wrap a piece of plastic strip around pullies. It kept breaking beforehand.

flathead-07.jpg


Rob

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2 hours ago, robdebie said:

Yet another route: apply some Tamiya Extra Thin to the plastic card part, and let it soak in. Do not use it (yet) to glue, it's just to make the part softer and more pliable. Wait a few minutes, then curve the part.

I used the same technique to wrap a piece of plastic strip around pullies. It kept breaking beforehand.

flathead-07.jpg


Rob

That's a great tip.

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On 5/6/2020 at 8:48 AM, stinkybritches said:

That's a great tip.

Ditto. Basically, just coat the strip with the liquid cement. The chemical will soften the plastic. You may need to sand the strip smooth after. Hopefully once it is on the model.

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Using a MEK based liquid cement, you can work your way around a little bit at a time.

Not exactly the same, but I used a similar technique for the intake hoses on my '68 442 project.

 

image.jpeg.d6223f6681fc1eca57866c47b8e48df5.jpeg

image.jpeg.42566883696b328e387c507b702aa9a0.jpeg

image.jpeg.3d56972a56420a943ed19ea8691c854e.jpeg

 

 

 

Of course it's a little more time consuming with thicker plastic, but it's absolutely do-able.

 

 

 

 

 

 

Steve

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7 hours ago, StevenGuthmiller said:

Using a MEK based liquid cement, you can work your way around a little bit at a time.

Not exactly the same, but I used a similar technique for the intake hoses on my '68 442 project.

 

image.jpeg.d6223f6681fc1eca57866c47b8e48df5.jpeg

image.jpeg.42566883696b328e387c507b702aa9a0.jpeg

image.jpeg.3d56972a56420a943ed19ea8691c854e.jpeg

 

 

 

Of course it's a little more time consuming with thicker plastic, but it's absolutely do-able.

 

 

 

 

 

 

Steve

Now that's a good idea. I'll have to remember this one. 

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Posted (edited)
On 5/5/2020 at 10:15 AM, NOBLNG said:

I have on a few occasions tried to curve thin strip around a curve, eg: .020”x.030” strip as a chrome trim divider for a vinyl roof. If the curve is too sharp, the second I touch the extra thin cement to it, it will snap.  I have also recently tried curving a .020”x.125” strip around a 1/4” diameter circle.

Interesting suggestions offered, Greg. However, applying liquid cement on multiple layers of styrene of the type used by Evergreen and Plastrruct has its own set of problems. The styrene used is a different formulation than "standard" kit material. It's softer. This styrene also tends to stay softer after applying liquid cement to bond multiple pieces of the same for a long time after bonding. Use plastic .020-.030" rod instead. Being that it's round, it possesses better ductility than square or flat strip. It can be conformed to fit on compound curves as found on and around a car roof. The rod also can be, if required, sanded flat after it is attached. As far as trying to wrap .020”x.125” styrene strip around a 1/4" inch dowel, my question is why? First of all. .020" thick strips are too thick to be bent around a round shape without breaking. Applying liquid cement or heating the strips isn't practical for the aforementioned reasons. The most logical approach would be to use styrene tube with an inner diameter slightly larger than the part you want to wrap. It can be cut to the proper height easily, doesn't leave a seam around its circumference and won't break. But hey, if you think that layering and bonding or bending work better for you, zei gezunt

Edited by SfanGoch

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I do a fair amount of scratch building using mostly polystyrene sheet and shapes. I typically will pre-bend strips around a similar shaped object to avoid breakage and always gradually attach using CA glue and apply kicker to be sure the parts don't come loose. When working on things like those strips on a vinyl top mentioned above I recommend drawing a nice straight line in pencil to help parts aligned correctly.

As an alternative to always using round styrene like the air intake tubes shown  earlier I would suggest using copper wire applied with CA. It achieves the texture you want and conforms well to curves.

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