Equivalent Aluminium Grades

Rob Swain · Post by **Rob Swain** » Fri Jul 16, 2010 10:30 am

I'm doing some work on non-structural bits of an aircraft (aluminium panels that cover parts of a steel tube fuselage) and I've just checked on the price of 2024-T3 sheet and 6061-T6 angle - hideously expensive. This is mainly because of the expense of certification, paperwork and probably insurance liability issues.

Can anybody suggest other commercial grades of aluminium that will have similar (not necessarily exactly the same) hardness, temper, strength etc. but be more reasonably priced. An Alclad layer is not necessary as I'll be painting both sides of the panels. I just need the sheet to have the right characteristics to be workable, strong enough and with the right resistance to cracking, tearing etc.

I asked a metals supplier if they could suggest a suitable alternative but as soon as they heard it was for an aircraft they refused to co-operate, just quoting for the 2024 (they don't do 6061 and refuse to even speculate as to an alternative).

I'm not just being a cheapskate here, just prudent; £150 a sheet when I need around 3 sheets is no joke. Rest assured if I was repairing my RV I'd definitely use the precise grade of metal.

bertdeleporte · Post by **bertdeleporte** » Fri Jul 16, 2010 11:32 am

Hi,

I use aluminum at job, I fear you have no real choice in grade of material. We for instance use some 5083/5086 T1 to T3 grades, we work with classification societies (LR, BV, GL, DNV, ABS...), the mod of grade implies a thorough design AND process re-certification. Read between the lines: the cost of re-certification is dissuasive to change grade at each new project.

The other traps with aluminium are:
-condition of storage: dry place, flat storage compulsory
-duration of storage: maximum six months, the material is nearly alive, properties change a lot with time. Some short radius bending we manage to do on "fresh" material is impossible with a plate stored a few months.

You can find a lot of literature (real or on web) on the subject, for instance, comprehensive information on process and properties of aluminium P399 and following:

http://books.google.fr/books?id=9ohkDUr ... &q&f=false.

The two issues of the excellent "Light Aviation" a few mont ago dealing the subject were really very good, read them again, I think you will see why everybody is very cautious prior permuting aluminium grades. Mechanical caracteristics are not all, the chimical properties will impact corrosion behaviour, I am not sure you will find some substitutes exactly matching the originals.

The amount you mention is not stratospheric, I'll check in France and tell you.

Bertrand

Bill McCarthy · Post by **Bill McCarthy** » Fri Jul 16, 2010 2:52 pm

If you go to a lithographic printer and ask for some sheets they will be glad to give them away free. The aluminium is very high grade - it has to be, and comes in sheets about 2ft by 2ft. I could have taken away about half a ton of the stuff if I wanted but came away with about fifty of them for nought. One one side though, you will get the page of whatever was being printed. The sheets are about half a milimeter thick I would say.
How come this forum page is too wide for the screen ?

Ian Melville · Post by **Ian Melville** » Fri Jul 16, 2010 5:10 pm

Prob90 the url used by Bertrand

I'd better get cracking with my build if Alu age hardens that fast, or does that depend on the temper it was suppled at?

Bill McCarthy · Post by **Bill McCarthy** » Fri Jul 16, 2010 5:14 pm

Come on Ian, you've had those plans a while now - what are the "hard to do" bits in the Thatcher then. Give us a run down in the type section if you like.

Ian Melville · Post by **Ian Melville** » Fri Jul 16, 2010 6:17 pm

The hard bit is the approval

Oh, and too many distractions.

tnowak · Post by **tnowak** » Mon Jul 19, 2010 9:03 pm

Rob,

There is a good reference to different aluminium grades etc. in the back of the Aircraft Spruce catalogue (available on-line).

When I had a query about aluminium properties I contacted the Aluminium Federation who were very helpful. PM me if you would like the details.

Regards

Tony N

Rob Swain · Post by **Rob Swain** » Wed Jul 21, 2010 2:10 pm

Thanks for all the feedback - I'll get nosing around.

I re-checked the plans for the Starduster and discovered the material for the cowlings is specified as 2024-T3 so that ought to come from an approved source, but there's still the coaming, side and belly panels that are just generic 'aluminum' (not even a thickness) so can be 'something else'