Which is stronger?

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Bottom line- What is stronger and will have less deflection 1x2 11 gauge rectangular tubing or 1.5x1.5 11 gauge square tubing? )the rectangle would be used with it's widest section on the horizontal plane.I am building a 16' gate that is 48" high. The top rail is an arched piece I bought from King. It's 1x2 11 gauge rectangular . I figured I would build the sides and bottom out of the same  (1x2 11 gauge), however the pieces I picked up I guess I tied them down really tight and twisted them. Anyway, I got to thinking about it and was wondering if I made a mistake in my material selection. Since I have to buy more stock, I thought I would ask the question.Thanks in advance. I tried a search, but hit nothing.Last edited by dcs13; 07-05-2010 at 08:37 AM.Reason: clarification
Reply:The 1x2 is going to sustain more load in one direction and less at 90° than the 1.5x1.5 and also restrain less torque.16'x4' is a fair sized gate, gonna be a dandy to handle when you mount to the post.Matt
Reply:Very good question. In practical terms, the resistance to flex or bending will be greater on the square tube. The caveat is that it will be stronger in resisting one type of force; especially when it comes to rectangular tubing. Round tube is equally resistant in any direction, and that is why it is a favorite for many types of building flexible structures like chassis components. Also, bend stress is easy to deal with when using round tube; square tube can be bent and suffer great degradation of bend resistance, and if bent too far, it will fail appreciably faster.The real strength in a gate or wall like structure to resist sagging comes from a preloaded top tube (Arched) and from properly figuring how to set it up so it won't want to sag in the middle or tear itself apart. Usually, some kind of lateral strap, bar, or boxed section will add that rigidity. There are a lot of great project builders on this site to help you with any design questions you might have- post up some simple pics or ideas, and they will start to chime in. (Like it or not!!! LOL!!!!)And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Thanks.I have the arched piece for the top (2 actually). There will be vertical uprights 6" on center at the bottom to 6" high, then vertical uprights 1' on center to the top arched section. I will replace my "twisted" rectangle with 11 gauges square.I'm still mad I twisted those pieces. $36 each. Luckily in shorter lengths they will useful for some "other" yet to be dreamed of project.And for hanging the gate , after my welders, the best tool I have bought is a front end loader. I find more uses for that thing. I am sure it will nicely hold the gate while I secure it.   Thanks again
Reply:you can add a wheel on the unsupported end to take some stress for the hinge point . I used  a pneumatic tire from harbor freight on one i built , works great.