PVC Pier?

[MrB (Simon)]

I have a 1M length of uPVC storm water pipe, 177mm (7") diameter with 10mm thick wall. It weighs a ton for it's size, maybe 10kg. (my digital scale tops out at 6.2kg)

So, is PVC okay as a pier material?
Can anyone provide reasons why it is NOT suitable?

Also, I'm planing to build a portable pier that I can lug to dark skies, so filling it with sand is not an option.
However, I was thinking of making it sealed so I can fill it with water on site, then dump the water when packing up to head home, does this sound realistic? (ignore the fact it needs 19L water to fill!)

Thanks.

[anj026]

It might work Simon. I guess it would depend on how the legs are attached and what kind of load it is supporting. It could possibly be stiffened by adding fiberglass sheathing at the expense of more weight.

I have heard of PVC being used for permanant piers by filling with concrete and having substantial extra length buried below ground level.

[Ian Robinson]

No .

Too flexible, not enough resistance to bending and twisting .

Fill it with concrete and maybe it might be OK.

[bmitchell82 (Brendan)]

geometrically, fine, material wise..... don't bother, your tripod will give you 100% better proformance. portable peirs are fine if you have a solid footing for it to setup on. if your setting up on dirt in the bush, its not good. my 2 cents worth

[MrB (Simon)]

Cheers guys, this is one hell of a solid tube so might give it a flex test, will support it each end and see what sort of flex it shows with a dial guage and a stack of weight.

Brendan... what tripod?
My dark sky site has a rarely used, dead-end road I can setup on... very solid.

[Ian Robinson]

Dig out your old structural design textbooks , and see if you can get a rigid stucture that supports your GEM, counterweights (cantevered) and your OTA with incorporating the uPVC tube as a pier.
The mechanical properties are here : http://www.boedeker.com/pvc_p.htm

You'll be looking for near zero flexure under load , and near zero bending too , if you hope to achieve good tracking performance from your GEM.

This is the reason why most go for solid concrete , steel reinforced concrete , or thick walled steel tubes as the basis for their piers. Steel being the best common metal.

[Nightskystargaz (Thomas)]

Simon,

You can give it a try.

But I think it might work.

,

Tom