Advice Needed - Wood for Roll off Observatory
Posted 23 November 2012 - 12:51 PM
I intend on build a roll off observatory. It will be a fairly small thing at ~6x8. I live in Texas and the summers are bordering on brutal. In addition to this, a single day here can show temperature variation of sometimes up to 30 degrees (not always, but it happens).
While fairly handy, I don't have a great deal of construction experience, especially for outdoor projects. I am concerned about the type(s) of wood selected and I am unsure about warping. There are certain parts of the observatory that can warp a bit without much worry, but there are also certain parts that need to remain as straight as the day the were installed (like the roof track supports). Pressure treated pine is very popular here in Texas... it's abundant and cheap. That said, I can't really find a lot of information about its suitability for projects like this.
Has anyone done this with all pine before? Skyshed plans call for spruce for certain parts (like track supports), but that wood is not really available here in the south.
Thanks for your help.
Posted 23 November 2012 - 02:56 PM
I assume you are concerned about the rails. If it is going to keep you up at night then make your beams out of laminated plywood.
There are a few important things you should be worried about at this point. Heat, dust, unwanted guests etc. These could cause problems that will plague you for the life of your observatory. If one of your rails warps 1/4 of an inch you won't ever notice it. Set you mind to worrying about something worth worrying about.
A 30 deg change in temperature can happen anywhere in the central plains. You won't be the first one to have to deal with those conditions. I did very successfully. As for warping and shifting, I dealt with that as well.
Take a look at the archives of this forum and a few others. See what sort of problems people have with their observatories. That's how I started. Then I designed my building to avoid those problems. Much of what I did and why I did it is documented in my website.
Posted 23 November 2012 - 03:28 PM
The biggest problem with PT lumber is that t is normally pretty wet - it has a high internal moisture content - and as it dries out, it is nearly guaranteed to warp, a condition helped by being thoroughly nailed down, but not cured.....
I'd suggest going to a local-type lumber dealer (not a big-box) and ask them what they have available that is warp-resistant. You're not the first with that request.
Often, it's safe to build with the bottom framework board PT, and the rest regular lumber. Regular framing lumber is delivered dryer than PT, but not Texas-dry, so even it'll move around some. The daily temp fluctuations won't matter, most attics go through way more than 30 degrees daily, and survive. Another idea might be to use sturdy steel or aluminum angle or square tubing for the rails.
Posted 23 November 2012 - 06:02 PM
Posted 23 November 2012 - 06:34 PM
I used a triple 2x4 top plate to support the roof track in my ROR observatory and have never had a problem with warping.
Posted 23 November 2012 - 06:38 PM
I built the base with 2X8 treated lumber for the outside frame and the floor joists are treated 2X4s. The walls are outdoor sheets. The inner framework is made of standard 2X4s as are the roof joists. The roof is nothing more than roofing paper with metal roofing on top. I used that silver coated bubble insulation under the roof. The roof is made light so I don't have any problem rolling it.
The runouts are treated 4X4s and the uprights are 4X4 with a 2X8 treated end plate. The uprights are cemented into the ground. It's survived 3 hurricanes. And I can tell you with confidence that I have rudimentary carpentry skills. The one tool I recommend is one of these. This thing will save you a lot of time. Good luck!
Posted 23 November 2012 - 09:13 PM
I would love to build 8x8, but I'm dealing with fairly tight clearances. I'll see if I can get away with it though.
Posted 24 November 2012 - 11:04 AM
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Posted 24 November 2012 - 06:35 PM
Hope this helps stimulate the ideas
Posted 24 November 2012 - 06:42 PM
(BTW, the cable is wound in the wrong direction in the picture.. I did wind it the proper direction after I took the pic.. LOL)
Posted 24 November 2012 - 06:50 PM
Posted 24 November 2012 - 06:54 PM
Posted 25 November 2012 - 09:12 PM
Thanks for all the pics! Unfortunately I don't have any direct access to welding equipment. Nonetheless, I appreciate all the effort you put into relaying your experience.