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total amateur here. I’m trying to figure out some options for building, essentially, a pipe with these attributes:

  • 3-inch walls (can be hollow)
  • inner diameter of about 3 feet
  • length of this tube/pipe/tunnel would be also 3 feet

I’m thinking that the end caps would be easy - basically cut out two donuts with a router.

What’s been challenging for me is figuring out the middle section without having to steam bend plywood to form the body of the tube.

Any suggestions besides steam bending?

For more context as to why I’m trying to build this, I run a soft play rental business for kids under 5. I have some of these foam and vinyl wrapped tubes that are supported by wood understructures. The bent plywood that was previously used was very thin and essentially got punched through. Replacement costs are too prohibitive to reimport from China so I’m trying to recreate the wooden structure so that I can rewrap in foam and vinyl.

Picture reference (it’s the blue tube in the foreground): It’s the blue tube in the foreground

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  • Other than using a lamination (not bent plywood exactly but ends up being similar) I think the only other option is what's called stave construction, which is how both barrels and buckets are made. But I have to warn you this isn't a project for a beginner. There's this saying, "There are no amateur barrel makers." which is a bit of an exaggeration but it gives an inkling of how challenging this is to do. – Graphus Dec 20 '18 at 14:20
  • You also don't say why you want to build such a thing. What is its purpose? This way, people can offer answers that solve the actual problem you have. – jdv Dec 20 '18 at 16:17
  • Just added more context and a picture for reference :) – Henry Ong Dec 20 '18 at 18:38
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Flexible plywood can be used for this. It typically has a bend radius of about 12", so your 3' diameter should be fine. Do note that flexible plywood is usually pretty thin, so to get the 3" wall thickness you'd need two layers of plywood with some solid wood spacers between them.

You would need some kind of form to bend the plywood and to construct the double layered wall.

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  • This is almost certainly the most appropriate answer. – jdv Dec 20 '18 at 19:20
  • I don't think that flexable ply would be strong enough for this application, as you'll be loading it (he expects kids to climb on it) in a way that will stress it in the same direction as the flex. – SaSSafraS1232 Dec 21 '18 at 17:03
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I think the best way would be to make multiple of those "donuts" out of a thicker plywood, and use them as bulkheads down the length of the pipe. Run stringers to link them together, then bend a thinner plywood around and either glue, nail, screw or a combination to the bulkheads. Or, if you think you can pull it off, figure out how many 1x4's it will take to go around the circumference, and cut the angles accordingly rip-style on a table saw.

How structurally strong does it have to be?

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  • That’s a good idea. Should be able to support up to a roughly 80-lb kid standing on the sides. – Henry Ong Dec 20 '18 at 18:40
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this is how barrels are made: You make it out of individual staves that are then compressed with a band to hold liquid.

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  • Can you flesh this out somewhat? – Graphus Dec 20 '18 at 14:26
  • for the purpose of the OP, i dont think it needs to be perfectly round or hooped... this application just needs beveled planks glued together in a way that approximates a cylinder. However, it is probably outside of the OP's skill level to do so - the edge joints required need to be well done and gap-free. – aaron Dec 20 '18 at 18:45
  • Graphus was asking if you could expand on your answer in the text to make it clear what you mean. Future readers may not be familiar enough with the what you are talking about to picture what you mean. Because what you suggest is actually very apropos. – jdv Dec 20 '18 at 19:19
  • I'll give it a shot ;) - the cylinder shape is assembled from individual narrow boards ("staves") which have beveled edges. When the edges are all placed side by side, they form a cylinder. To make a robust one, the ends need to be compressed - commonly with a metal band. – aaron Dec 20 '18 at 21:20
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Maybe not quite what you are looking for because you don't say why this needs to be solid wood, but you could re-purpose something like ABS or PVC pipe (or even those forms used to make smaller foundation pilings) and cover it in quality wood veneer.

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  • Thanks JDV. I added some more context and picture above. – Henry Ong Dec 20 '18 at 18:41
  • 36 inch corrugated drainage pipe would work too, light and durable. – Netduke Dec 21 '18 at 15:00

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