Sheet Metal Mike

What do your local laws, codes, and regulations say?

That's interesting: calls for thicker galvanized than aluminum.

It's a weight thing. Metal is sold by the pound. From:

Sheet metal - Wikipedia, the free encyclopedia

Sheet metal thickness gauges for steel are based on the weight of steel, allowing more efficient calculation of the cost of material used. The weight of steel per square foot per inch of thickness is 41.82 lb (18.96 kg), this is known as the Manufacturers' Standard Gage for Sheet Steel.^[4] For other materials, such as aluminium and brass, the thicknesses will be different.

Gauge and Weight Chart for Sheet Steel, Galvanized Steel,Stainless ...

I appreciate the explanation.

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I am still fuzzy on how gauge standards being based on weights of steel can result in a less dense material, like aluminum, being thinner for a particular grade.

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It seems like whether it was just about weight per square foot, or if it were based on rigidity, the same gauge aluminum should be thicker, not thinner.

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Can you help me understand why basing it on weight would lead to aluminum gauges being thinner than the same numeric gauge of galvanized?

I think it has to do with how much sheet metal you can make with a pound of material.

This is different from wire gauge.

You're making me think way too hard here.

0.040 aluminum should work fine compared to 24-gauge steel. Do the same cross-bumping on large flats.

Mike, you need to think more about heat sink that metal thickness. Aluminum is a much better transformation metal and will transfer heat and cooling to the outside walls of the duct system. Galvanized sheet metal is not a very good conductor of heat and cold and that is the underlying reason for using it. If you want efficiency of your cooling and heating through ducts then aluminum would not be a very good material. If you wrap the sheet metal duct with insulation it will yield more cool air and warm air to the ends of the duct work. The best of the best would be a piece of PVC pipe large enough to serve the purpose and have it wrapped with fiberglass insulation. The reason is that plastic is a very poor conductor of heat and cold.

Good luck with your project.

Ahoy!

Heh.

seemed like the most appropriate response to #8

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Carry on, smartly.

Byron,

That's pretty far out. Totally wrong, too.

Asking this question this way is a bit like closing the stable door after the horse has run off:

• If 24 gauge galv is the standard, and a decision has already been made to use .040 aluminium instead, then there is nothing left in the question for the forum to answer.

After careful reflection, I have to agree with you 100%.

Hi, I was just wanting to make sure the .040 was the comparison to 24 ga galvanized

and maybe drop to a thiner gauge.

Did you consider mechanical properties? Everything else being equal, steel is stiffer and stronger than aluminum. What about vibration?

That's why the aluminum is thicker. (I.e., everything else is not equal.)

And thermal...