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Will PVC piping bend under a wire tension? Answered

I'm looking to make a hot wire foam cutter, and have most of the setup all outlined. However, the 'bow' still need to be made, and I plan to use PVC. Reason being is I would like to be able to stick some four/three way bends on one ended as to allow me to stick the bow on a stand of sorts to make a band-saw style hot wire.

But, question at hand: if I were to make a frame out of PCB piping for a hotwire, would the tension of the hotwire cause the frame to warp? And if so, what would be an equally cheap option for the frame?





Best Answer 4 years ago

I used wood for my hot wire bow to cut foam wings for RC planes, a pine cross piece 20mm x 34mm x 800mm and the 2 vertical sections were 20mm meranti (hard wood) dowels 400mm long, tensioning is via a wire and spring on the top, very much like a traditional bow saw.

I use uncoated stainless steel single strand fishing leader wire, nothing else, no multistand or guitar string nonsense.

I have seen pvc bows on the net but they dont seem to have a tensioning means.


I've thought wood as well, but I'm unsure how to make the base for it (as I would like to make a base that can hold the bow in such a way that the wire is 90 degress to a board).

However, that link you posted is pretty close to the idea I have! The only difrence is I would be sticking springs inside the back two PVC pips (to pull the ends together) and stick a turnbuckle on a threaded road between the two to push them apart for tension.

I used the spring turnbuckle method too, I see that the SS wire has rusted off the bottom , I spose 15 years will do that sort of thing.
I made the broomstick verticals swivelling on the cross member with a wire joint to account for tension needs. I had a concern that the cross member might split so I wrapped the ends with string soaked in CA glue and of course it never did.

foam hot bow.JPG

If you stand the bow on end and then make one of the broomsticks a flat board, it could work. It doesnt need to be as long as mine which was used to cut 800mm long foam wings.

I might take a look into that. But I had an idea running off my first one. Going off the first link you had (with the PCB bow) I think I will make that (with the springs *inside* the rear pipes, and the turnbuckle between the two rear pipes) but replace the arms that will be under tension with wooden dowels. Think that would work? The reason I'm so hellbent on this design is due to the fact that I can keep the wire *perfectly* (or very close) perpendicular to both ends of the bow, and therefore, be perpendicular to a board.

Yip, sounds good, just need some sort swivelling clearance on the center cross piece and you're good to go.

Yip, sounds good, just need some sort swivelling clearance on the center cross piece and you're good to go.

PVC pipes will wrap or bend if its too long and for short pieces i think its ok..its better to use an aluminum frame with a higher Gauge thickenes

The pieces are looking to be about 8 inches long, maybe longer. Kinda had a brainfart as far as the aluminum goes, though. That might work out. Thanks!