Reshaping plastic

KariFS wrote:How about heating it more while it is still clamped? Maybe you need to ”over-bend” it slightly to compensate the ”bounce-back” of the plastic  

This is an interesting topic for me too, since the fin of my P-40 is bent, probably because of being stored upside down and/or under a pile of stuff.

I tried that Kari heating with it clamped.  Tried the "over bend" too but because I don't have a third arm it went nowhere.  

Heat "probably" caused the distortion in the first place softening the plastic and causing the molecules to expand.  But, wouldn't heating it again cause the same expansion multiplying the problem and resulting in even more distortion. The theory is more heat with applied pressure compresses the molecules back into place.  

But, if heat causes expansion and cold causes contraction.....I'm about to clamp the thing on a flat board and pop it into the freezer.  

Someone here. I think it's Jim or maybe Roddie is proficient in molding plastic canopies over a mold, maybe they know the secret of how to get them back into place.

Bob

If you can get the wing into boiling water for a good 30 seconds or longer, it heat soaks the area better. It makes it pliable and it can be shaped by holding with a rag until it cools. It certainly lessens the chances of breaking or shrinking from high concentrated heat.

I will be watching this carefully as well. Tried a few things on the Cox dragster I recently picked up with no luck as of yet.

its always a hit or miss reshaping plastic, i like (tea kettle) concentrated steam (wearing gloves) hold to shape or slightly opposite twist, hold firm and quickly stick under running sink cold water to set plastic.

NEW222 wrote:I will be watching this carefully as well. Tried a few things on the Cox dragster I recently picked up with no luck as of yet.

There is a nice straight flat frame up for bid on ebay:
https://www.ebay.com/itm/Cox-Funny-Car-Chassis/123912038190?hash=item1cd9bba72e:g:N8gAAOSwIDhde~89

Bob,

I was in a dilemma on how to remove plastic handle bar grips from a set of 1969 Ski Doo handle bars without destroying the original plastic. They would NOT come off period. Heating the handle bar risked melting the plastic grips. The solution was to boil water in a big enough kettle to fit one grip in. Left it in for approximately 1 minute. No go. Back in for two minutes. Off it came pliable yet not altered. The goal was to incorporate heated handle bar grips that appeared factory installed without the telltale sign of customization. After the bar was wired, then the grip went back into boiling water for approximately 2 minutes and then slipped back onto the handle bar coaxed with a little Windex as a lubricant that eventually dries out.

As mentioned by Ken, try the same thing with the distorted wing and then mount it to a flat surface. Air cool or if impatient, spray with some compressed air to evaluate the straightening process. Let us know your progress.

Best of luck. You'll straighten it out.

Thanks everybody. When all else fails I will try the steam/hot water route.

It's presently clamped on a flat board, checked it this afternoon and it seems to be coming out. At the very least, it's a whole lot better.

Thinking all-over olive drab and proper decals.




Bob

Bob, if you have a large crock pot or a large pot to boil water in, this may work using the dip and shape method. Dip a little twist a little until you get the proper shape. Or you could use a heat gun but be careful this thing will burn the house down if used improperly. If you use the heat gun you'll have to practice before using, much like spray painting. Not too close and keep it moving. You can rent the heat gun from a local tool rental, or I could loan you mine. Let me know, would be more than happy to help!!! Mark

Problem with a heat gun is it can get too hot and the plastic will suddenly melt without any indication, its a small window, lol, i know...

Mark Boesen wrote:Problem with a heat gun is it can get too hot and the plastic will suddenly melt without any indication, its a small window, lol, i know...

I agree, and that's my fear not just with this $7.99 (went back and checked the actual ebay price) Testors P-51 but with my Aurora models too @ $100+.  Large chance to make it worse than it already is.  

I have a couple of dual range heat guns and use them very carefully.  Problem is, they spread the heat out over a large area when I need concentrated heat in a small area for a short period of time.  I have a butane torch that does that, but imagine the consequences of using it on plastic.  

Balsa is so much easier to work with.  

I had a difficult time removing the side decals.  Testors did a good job with them.  The side decals had three layers, a base of metal foil, the decal and a clear plastic cover.   Simple Green removed most of the silver paint on the model but getting it out of the highly detailed (simulated rivets) areas was a pain.  

I had some paint remover, directions say "Do not use on plastic" so naturally I had to try it.  It took off the paint and seemed to do the plastic no harm.  Same for the decals but it took a lot longer.  Later my son reminded me that I could have used Easy-Off oven cleaner which does not harm plastic.  I did rinse it well right after using the paint remover.  

That is nice and clean , Since wee have alot of guessing what has worked before let me have a go at it Have no idea what kind of plastic was used but i would say from what i have looked at 225-250F degree oven for about 8-10 min. should make it more limber to work with or maybe ? it will straighten it self ?! https://www.google.com/search?rlz=1C1SQJL_enUS817US817&sxsrf=ACYBGNRWWSNYRuUOYwE3a1WbElVkTPJXoA%3A1569583304095&ei=yPCNXaqnBeHD_QbelpfACQ&q=plastic+melting+temps&oq=plastic+melting+t&gs_l=psy-ab.1.1.0l3j0i10l3j0j0i10l3.4546435.4554863..4558416...2.0..0.99.1334.18......0....1..gws-wiz.....10..35i362i39j0i67j0i131i67j35i39j0i131j0i13j0i13i10.HAwSkd9TWUc#iqh=resin

On mine, I had some of the original paint on it, along with some type of blue paint the original owner had painted it with. What worked decent for me was brake fluid. I had read about it online and had to try it. But yours is looking great as well!

Thanks Chancey, Brake fluid works but it takes awhile.  I have lots of experience with non-synthetics eating away at the paint around my MG and others master brake cylinders.    Does a great job at that.

Eric It seems to me that the plastic used in these model cars and airplanes is some sort of high density polyethylene with melting temperatures of around 250 to 350 degrees F.  I wouldn't think it was acrylic.  No way would I heat it that high.  

Heat gun moderately applied then clamped over and over is showing promise.