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Sono-tube for Obsrvatory

Started by Barlow, 07/04/2003 03:49PM
Posted 07/04/2003 03:49PM Opening Post
I have a square legnth of aluminum tubing 6" x 6" x 5-ish feet. I intend to sink a 10" Sono-Tube in the grownd with a couple-three feet above and sink the aluminum tube in the center with a couple-three feet exposed to put the mount on to. (tubing is drilled and tapped for the mount already).

After pouring the concrete in the Sono-Tube, setting the tubing in, and letting it set/dry... Do I take the Sono-Tube off by unwinding it, do I lift it off, do I cut at grownd level and lift the top part off, or do I leave it as is?

If I leave any or all of it in the grownd I imagine it'll start to break down(?). If that does happen, as it's happening, does the dirt slowly fill in the missing paper or does it leave a gap?

I'm hoping to get the hole dug this next week and star filling it with concrete near the weekend.
Posted 07/05/2003 06:55AM #1
Michael,
You didn't say what size of scope will be mounted on your new pier. The 10in. concrete pier might be on the small side if your planning on putting anything of size on it, especially if you ever want to do any astrophotography. While the 10in. pier will stand okay, it probably will not have enough mass for good vibration dampening. The aluminum tubing also while being a very good choice from an appearence and corrosion stand point is also lacking in the material rigidity area. I would highly recommend increasing the pier diameter to at least a 12in. or larger if your scope weighs more than a few pounds. I would also suggest using steel tubing at least 6in., preferabelly 8in. in diameter with .25in. side wall thickness.

Getting back to the sonotube question. I would only use the sonotube for the above ground portion of your pier. If you use it below ground level, you will have a difficult time getting the hole the exact size needed to allow the sonotube to fit without being oversized. If you have any air gaps between the undisturbed ground and the sonotube you will be losing some of the rigidity that you are trying to achieve. Just make sure and leave the hole realatively smooth so that the frost went cause the pier to heave. Eugene also gives good advice on the vibrator. Nothing makes a concrete project look bad like the alligators. I would also suggest to remove the sonotube while the concrete is still green( few days after pouring). If you wait to long the sonotube will have tendency to stick when you go to peel it off. You can make a cement wash to spruce up any scars or imperfections when you remove the sonotube. You can cut the sonotube but it is an awful lot of work. Unwrapping is usually much easier.

Good luck on your project.