Aluminum 101

Great post from user Xanadu on Rcgroups.com


I owned a company that specialized in building all aluminum trailers, and here is the scoop in a nutshell.

There is 2 general basic aluminum alloys that are sold on the end consumer market. I mean at local home hardware stores, etc.

Yes, you can always get "aircraft alloy" but it is very expensive, and harder to get. You need to go to a specialty metal store.
There are indeed numerous alloys available, but 99% of everyone only has general access to only 2.

The 2 listed below are readily available to anyone at most home reno and hardware stores.

Structural aluminum, which is usually a harder alloy, deemed as 6061-T6, and is usually marked right on the piece as such.
Most extrusions such as pipe, tubing, flat bar, angles, come in this alloy and temper.
Does not like to bend, tends to crack at the bend due to the hard temper imposed, but is very strong............

Utility grade aluminum, quite softer, easy to bend, comes in sheets, flats, and sometimes smaller tubing, etc.
But prone to bending under stress as it hold less strength due to the low temper and alloy used. Obviously much softer than structural version.

If you want a aluminum to use for strength, such as spars, wing joiners, landing gear struts, etc, use a 6061-T6 designation. You can bend flat bars of it, just do not make a "sharp" radius at the bend point. It requires a larger radius bend so it does not crack.
Bend it too tight a radius, and IT WILL CRACK........


But if you want to be able to form it easily, like as a cowling, wing fairings, etc, use the utility grade.
You can bend sharp corners, very mailable, easy to work, but is no where near as strong as the one listed above. Its more for cosmetic if anything.
Same grade of aluminum as what they use on your eave troughs, window flashing, siding, etc, and it comes in numerous thickness and shapes.


There is no need to heat aluminum to bend it, and when you do you tend to change the temper, weakening it.

One quick way to tell them apart is the shine/gleam off them.
A utility grade is quite shiny, almost a light polished shine sometimes.
A structural one, such as 6061-T6, has a dull, mill finish, almost unpolished look to it.

Aluminum is a magic metal when used properly. Lightweight, strong, yet can be made to look polished, chrome like.

Structural, once you bend it one way, its done.......it will not readily lend itself to being bent back, and reformed. Tends to weaken and crack. So make sure that is the bend you really want the first time.

Utility is a bit more forgiving, as it will let you bend it several times before cracking.

Just a quick review.......

6060-T6, structural, dull, mill finish look, for if you want strength.
Utility grade, shiny, and bright, if you want forming abilities for cowlings, fairings, etc.

Any questions..........?
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I thought this would be helpful to share

I'm not trying to dispute you, but some of the info in that article isn't quite accurate.

First off "aircraft aluminum" doesn't really mean much. There are quite a few alloys in common use on aircraft (7075, 6061, 6063, 2024, 5052 and so on). The term is more often related with 7075, but like a lot of things, it isn't correct, and will often lead to misunderstandings.

Along with 6061, you'll see a lot of 6063, particularly in tube.

The "utility grade" (that phrase doesn't mean jack either), is likely 3003, based upon your description of it. It isn't very strong, but has decent bending properties, yet not the best corrosion resistance.

5052 is the one most of the tin boat guys should be most familiar with. It bends almost as well as 3003 (doesn't need near the bend radius that 6061-T6 does), as it only needs an inside bend radius of 1t (1 times the thickness - in other words, the knife edge die used in the brakes of many steel shops use would bend it to tight, and microcrack the outside corner). It is also a good bit stronger than 3003, and more corrosion resistant. Most of the freshwater aluminum boats on the market are 5052. Saltwater aluminum boats (I'm speaking of heavier boats with 3/16 - 1/4" hull thicknesses) generally are made from 5086, which does require a slightly greater bend radius, as it is stiffer, and is also more corrosion resistant.
I use 5052 even for non boat related items, as it does work nicely - welds very well - once radius's are understood, it bends well, and it is relatively strong.

The 7075 you mentioned doesn't have much value on a boat. Not the greatest corrosion resistance, nor is it easily weldable. It is more for strength alone, which is advantageous for machined parts which are fastened with mechanical fasteners (ie, tools).

There are BUNCHES of other alloys, and other varieties of alloys. But generally, for any boat work, stay within the 5000 series for plate/sheet, and the 6000 series for extrusions.

Thanks bassboy, I think your explanation is much more informative. It's a great help