Warped truck bed

[Kit Basher]

I'm working on the AMT Payhauler 350. The dump bed is badly warped. I've attached most of the bracing to it, holding it in the proper shape while doing so. I had hoped the bracing might correct the warp. No such luck.

Is there any way to permanently correct the warp? I've heard about using hot water, but I have no idea about temperature or duration. Any advice would be greatly appreciated.

I'm adding some photos to show my problem. Originally, the bed floor was humped up. By clamping the floor flat as I added the bottom braces, I was able to pretty much fix that problem, although those bottom braces are still under some stress. The result of flattening the bottom was to pull the sides in, as you can see in the photos. The side braces did not correct that problem. The side braces are not 100% glued, and with clamping and gluing might help to straighten the sides, but those braces would also be under some stress. I am hoping to remove that stress.

Edited July 6, 2020 by Kit Basher

[gman]

With the hot water technique, you want to use water that is just hot enough to change the plastic's warp, but not hot enough to cause it to lose its shape, i.e. cooler than boiling.

Water out of the tap may be hot enough, depending on how hot your water tank is set- allow the hot water to run, stick the parts in the stream long enough to slowly bend it back into shape (and then some). As the plastic has a memory, you'll want to bend it beyond straight and hold it that way. Once it it close to where you want it, set the shape with cold water while you hold the part in that position, so it (hopefully) doesn't return to being warped. It may take a few attempts, and using less pressure to correct the warp is better than too much, where the plastic becomes stressed.

If the water out of the tap isn't hot enough, you can warm some up in a pot on the stove, but you'll want to ensure the water isn't heated enough to burn your hands while you hold the part in its desired shape. Again, you can set the corrected shape by holding it in the desired position under cold running water.

[Kit Basher]

3 hours ago, gman said:

With the hot water technique, you want to use water that is just hot enough to change the plastic's warp, but not hot enough to cause it to lose its shape, i.e. cooler than boiling.

Water out of the tap may be hot enough, depending on how hot your water tank is set- allow the hot water to run, stick the parts in the stream long enough to slowly bend it back into shape (and then some). As the plastic has a memory, you'll want to bend it beyond straight and hold it that way. Once it it close to where you want it, set the shape with cold water while you hold the part in that position, so it (hopefully) doesn't return to being warped. It may take a few attempts, and using less pressure to correct the warp is better than too much, where the plastic becomes stressed.

If the water out of the tap isn't hot enough, you can warm some up in a pot on the stove, but you'll want to ensure the water isn't heated enough to burn your hands while you hold the part in its desired shape. Again, you can set the corrected shape by holding it in the desired position under cold running water.

Thanks for your reply. My tap water is about 114 F. Is that hot enough? The truck bed is too large (about 5" x 7" x 4") to hold in place with my hands. I can see making a wooden buck to fit inside the bed to hold it in shape while it's heated. Is there some temperature/ duration where the plastic will lose its memory and accept its new shape?

[gman]

It isn't an exact science, but worth a shot. You'll have to bend it beyond true, hold it for a while. The idea is to heat it to the point it takes the stresses and warp out of the plastic, and hold it there until it cools enough to hold its new and improved shape. 

Most kit parts warp because they have been taken out of the mold and packed too soon (with some kit contents virtually being crammed into the box)- when they cool, rather than taking the shape they were molded in, their shape becomes distorted. There is a good chance only a portion of the part has taken on a warp, and that is exactly the area you'll want to concentrate on with hot water and reshaping.

Posting some pictures may illustrate the magnitude of the problem with your parts.

[doorsovdoon]

If it's flat you could try sandwiching it between two pieces board under the grill for a minute. I did it with a piece of plastic dash trim on my car (real car) it flattened it out fine. It's risk though!

[Kit Basher]

4 hours ago, gman said:

It isn't an exact science, but worth a shot. You'll have to bend it beyond true, hold it for a while. The idea is to heat it to the point it takes the stresses and warp out of the plastic, and hold it there until it cools enough to hold its new and improved shape. 

Most kit parts warp because they have been taken out of the mold and packed too soon (with some kit contents virtually being crammed into the box)- when they cool, rather than taking the shape they were molded in, their shape becomes distorted. There is a good chance only a portion of the part has taken on a warp, and that is exactly the area you'll want to concentrate on with hot water and reshaping.

Posting some pictures may illustrate the magnitude of the problem with your parts.

I've added some photos to my original post to show what I'm up against.

I think you are right about the cause of the warp. One of the sprues is also badly warped, but the parts are still usable.

[Rodent]

I see 1:1s on the freeway all the time that look worse than that. If your straightening effort is a bust, you can always beat it up and weather it.

Good luck sir!

[Deuces ll]

I say put some weight on it on a flat surface and hit it with a hair dryer..... 

[gman]

Heat up the worst of the warped area, plus a good margin on either side. Apply pressure to the area marked by the arrow, pushing it outward at least the same distance as the warp is inwards. Hold it in that position for a while until it cools, or speed it up by running cold water over it while you hold it beyond the desired position. That looks like something that can be corrected, though it may take a few tries. 

If the plastic lightens while you push the warped area outwards, that is a sign it isn't hot enough to make the plastic malleable enough to be un-warped. A hair dryer is another method (as mentioned), but a heat gun would probably be too much.

[Kit Basher]

Thanks for the suggestions, guys. I'm a little hesitant to just wing it. I've already put a lot of time and effort into this kit. Still, I will probably do some experiments, I'll let you know how it goes.

[James Maynard]

You could also try heating it lightly with a cigarette lighter. Then holding it in place. Just be careful and not get it to hot. If you're going to paint it the don't worry about it turning black where you put the flame. This is Risky but it does work. I've done it before many times.

[Oldcarfan27]

Why not just cement some wire inside it, and then bend it where you want it?

[Kit Basher]

21 hours ago, Oldcarfan27 said:

Why not just cement some wire inside it, and then bend it where you want it?

Doh! I didn't even think of that .It would have been a great idea earlier on. I don't want to leave exposed wires on the bed, but the braces on the bed are hollow, and I could have put wires inside them before I glued on the side braces. Thanks for the suggestion, I'll keep that in mind if I have future problems.

Edited July 16, 2020 by Kit Basher

[Oldcarfan27]

It's not too late, drill a hole in the end, slip the wire and glue into the hole, let dry and seal the hole.

Done and done.