Need an 8 foot super rigid tube that needs to beak down into 2 foot sections

Hi --

I need to create a tube that is as small diameter as reasonable, relatively lightweight, and very stiff. It will be supported only on the extreme ends (thus the need for stiffness). There will be a comparatively light load, equally distributed over the entire length of the tube when in use. 

The thing needs to build up to 8' overall, HOWEVER, no single section can be longer than ~2' when broken down.

My first thought was 1" PVC - it's NEARLY stiff enough, but a trifle bulky, and it does droop in the center by about 1.5". 3/4 EMT tube is great, and stiff over a 10' span (when in one piece). Problem is how to connect the sections together. Typical off-the-shelf EMT junctions tend sag just trying to support the tube with no load. I have a number of ideas that are likely overly complex and stupid, but was wondering if y'all might have a something that I have not thought about.

Thanks!

Ted

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ilpug2 months ago

Carbon fiber tube? you can get it cut into 2 foot sections and then use some aluminum rod to make a plug connection at the ends of the pieces.

Toga_Dan2 months ago

if u find tubing. That fits snugly over another size tubing, that's an option for diy couplings. A 2 inch long coupling won't be as stiff as a 2 foot one.

kelseymh2 months ago

The EMT is a good option, but it'll be fairly heavy. In addition to the four 2' section and joints, get some approximately 6" to 1' sections of either more EMT or PVC, with an OD that matches as closely as possible the ID of your EMT. Slip those in at each joint, secure inside with, for example, museum wax or earthquake putty, then close the joints.

caitlinsdad2 months ago

Get a longer saddle clamp or a long piece of pipe section that fits on the tube to splice the joint. That will keep the joint from flexing. The EMT fitting is meant to just connect two pieces.

Downunder35m2 months ago

Take some wire and pretension the tube ;)

morgan834 (author)  Downunder35m2 months ago

Yeah, I thought of that, but I would still need something on the ends of the tube to hold the thing in alignment while applying the tension....