C channel vs square tubing

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Re: C channel vs square tubing

Postby saltydawg » Wed Mar 10, 2021 8:26 pm

QueticoBill wrote:Just for bending strength, a channel will be stronger than a square tube that weighs the same per foot. Consider a C3 x 4.1 is a 3" channel weighing 4.1 plf and has a moment of inertia - the property that determines bending in the X axis - of 1.66. A TS 2x2x3/16 weighs more at 4.32 plf but has a moment of inertia of 0.64 - less than half.

My opinion is there are advantages and disadvantages of each that are far more important to consider than just the bending strength per pound of steel, especially for the relatively short spans in tiny trailers.

On galvanized, I believe nasty to weld and you still have to protect the welded area, but I'm old and there may be newer ways to solve that than were available when I learned welding - in 1969-1970.


Now look up 2x3 .085, its 3.7 pounds a foot, and is stronger than 2x2 3/16.

C channel is strong enough until its not and it fails dramatically. Watch the video posted above by Mick.
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Re: C channel vs square tubing

Postby QueticoBill » Thu Mar 11, 2021 7:56 am

I was considering rolled structural sections, not formed sheet metal or plate as in the youtube. Also, I was using simple bending as just one measure of "strength". As I tried to note, its far from the only criteria for selecting material for a trailer frame.
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Re: C channel vs square tubing

Postby iconicflux » Thu Mar 11, 2021 9:41 pm

I ended up deciding on a combination of channel and rectangular tubing. Mostly because the rectangular tubing is easier to weld channel onto than channel onto channel. I'm good at coping wood but I don't know that I want to spend the time coping steel channel.
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Re: C channel vs square tubing

Postby Ottsville » Fri Mar 12, 2021 8:51 am

QueticoBill wrote:I was considering rolled structural sections, not formed sheet metal or plate as in the youtube. Also, I was using simple bending as just one measure of "strength". As I tried to note, its far from the only criteria for selecting material for a trailer frame.


It's easy to find data for structural steel C, not so much for formed steel C like harbor freight style trailers, but obviously it can be strong enough to build a trailer on, especially for the teardrop trailers.
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Re: C channel vs square tubing

Postby Ottsville » Fri Mar 12, 2021 8:53 am

iconicflux wrote:I ended up deciding on a combination of channel and rectangular tubing. Mostly because the rectangular tubing is easier to weld channel onto than channel onto channel. I'm good at coping wood but I don't know that I want to spend the time coping steel channel.


As my dad, who was a welder and ran a trailer shop would say: I prefer metal because if you cut it wrong, you can always weld another piece on.
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Re: C channel vs square tubing

Postby Ottsville » Fri Mar 12, 2021 8:53 am

iconicflux wrote:I ended up deciding on a combination of channel and rectangular tubing. Mostly because the rectangular tubing is easier to weld channel onto than channel onto channel. I'm good at coping wood but I don't know that I want to spend the time coping steel channel.


As my dad, who was a welder and ran a trailer shop would say: I prefer metal because if you cut it wrong, you can always weld another piece on.
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Re: C channel vs square tubing

Postby PCO6 » Fri Mar 12, 2021 9:02 am

Ottsville wrote:As my dad, who was a welder and ran a trailer shop would say: I prefer metal because if you cut it wrong, you can always weld another piece on.


LOL - I tell my Brother, who is an excellent wood worker, that all the time.
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Re: C channel vs square tubing

Postby QueticoBill » Fri Mar 12, 2021 11:20 am

Ottsville wrote:
QueticoBill wrote:I was considering rolled structural sections, not formed sheet metal or plate as in the youtube. Also, I was using simple bending as just one measure of "strength". As I tried to note, its far from the only criteria for selecting material for a trailer frame.


It's easy to find data for structural steel C, not so much for formed steel C like harbor freight style trailers, but obviously it can be strong enough to build a trailer on, especially for the teardrop trailers.


Exactly. Also, the youtube referenced does not account for the lateral support of a deck.
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Re: C channel vs square tubing

Postby Tom&Shelly » Fri Mar 12, 2021 11:26 am

Ottsville wrote:
iconicflux wrote:I ended up deciding on a combination of channel and rectangular tubing. Mostly because the rectangular tubing is easier to weld channel onto than channel onto channel. I'm good at coping wood but I don't know that I want to spend the time coping steel channel.


As my dad, who was a welder and ran a trailer shop would say: I prefer metal because if you cut it wrong, you can always weld another piece on.


True enough, but as an amateur woodworker, I heat the cabin with my mistakes! :D

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