I want to form a 36" long 1/2" diameter pvc pipe into square pvc tubing. How would I distribute even heating to form the pipe into shape?

What are you using to make the form?

A square piece of iron rounded down at the end and heated might work well enough to form if you push the pipe over it. Of course, this assumes you are trying to make a square pipe that is about 1/2" or larger across.

After this article ran we received the following suggestion from another Paddling.net reader:

Instead of using 90 degree pvc pieces I suggest bending the length of pvc pipe itself. This would allow a more customized fit and cleaner look.

It is done by placing caps on both sides of pipe(these are sold along side with the pipe and other various fittings). Remove one of the caps. Place enough clean sand in the pipe to fill it to the top. Now pour the sand in a pan and heat it on the stove or a hotplate. Once the sand is hot place it back in the pipe and put the second cap back on. Wait a few seconds and then the pipe will bend like cooked spagetti. It will not kink. When it is to the desired shape quickly cool it using a hose.

This is something that you will want to do outdoors and a metal funnel and ovenmitts or heavy leather gloves help as well.

Using this method opens up a lot of possibilities: kayak cradles for one....

- John P. Hay


Never tried this, but seems plausible. Found it a while back on this kayak camera cradle thing. I'd try doing 90° bends first just to see how soft the pvc really gets, and if it's really like a wet noodle just push it down into a U-brace with a piece of wood. Or get three 3/4" ply strips, 36" long [OD of your tube is about 3/4" right?], then place two strips 3/4" apart on top of another. So you get a 3/4" square slot with 3 sides. Then drop the heated pipe in [it'll probably have to be heated a lot more than you would for bends], and clamp a 36" 2X4 on top. Let cool.

I almost want to try this just for kicks, I'll let you know if I do I got everything I need besides sand sitting in my basement.

I've heard Navy gus use that method to bend metal pipes as well. I'd use that to bend exhaust pipes when I get to need it, unless prebent mandrel stuff is almost as expensive.

I don't think AP2k's idea would work too well since PVC doesn't conduct heat very well and the key is going to be evenly heating the pipe through the entire wall thickness. It would take a while and you'd have to be applying constant heat to the iron the whole time but not too much so you won't start to melt or burn the surface of the pipe.

For the sand idea, remember that since the area of a square is about 79% of the area of a circle with the same length perimeter, the pipe is either going to have to be stretched or you'll have to dump some of the sand out as you're bending it, sand isn't just gonna squeeze out.

How long is it?
I'd maybe try putting it in an oven set to the lowest temp that the PVC becomes pliable at, if you can find out what temp that is.

I'm not too sure about the sand idea. The grains might melt into the pipe and be hard to scrape out. Argon's idea might work. I have a 24" forge so I can get a good amount of steel heated.

sand isn't just gonna squeeze out.

....the pipe stretches...

the pipe is either going to have to be stretched or you'll have to dump some of the sand out as you're bending it, sand isn't just gonna squeeze out.
.....

I'm not too sure about the sand idea. The grains might melt into the pipe and be hard to scrape out. Argon's idea might work. I have a 24" forge so I can get a good amount of steel heated.
Use something like salt,then you can flush it out with water:p

Well, I can't tell you about square pvc, but when you enlarge PVC for rod holders down here, you heat a beer bottle with a blowtorch and push that into the pipe. Should work just as well if you had a square mold.
http://lh4.ggpht.com/_Dhw5qz8iScc/RTJRXkifABI/AAAAAAAAAQc/y2n4lbER7kU/DSC01350a.jpg < similar to that

Well, I can't tell you about square pvc, but when you enlarge PVC for rod holders down here, you heat a beer bottle with a blowtorch and push that into the pipe. Should work just as well if you had a square mold.
http://lh4.ggpht.com/_Dhw5qz8iScc/RTJRXkifABI/AAAAAAAAAQc/y2n4lbER7kU/DSC01350a.jpg < similar to that

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File not found?

Tinypic'd
http://i36.tinypic.com/xba450.jpg

I've heard Navy gus use that method to bend metal pipes as well. I'd use that to bend exhaust pipes when I get to need it, unless prebent mandrel stuff is almost as expensive.

Yeah, this is how my dad taught me to bend pipe, he was a coppersmith and fitter and turner for the navy for 20 or so years, so he probably knows what he is talking about.