Aluminum terms?

[mhorowit]

I'm removing corrosion form the trapizoidal shaped piece of aluminum sheet located at mid-aileron. The CD describes the aluminum sheet as ".016 3S Hd. Alum"

Anyone know what the "3S Hd." stands for and what the modern equivalent is? - Mike

[mulwyk]

Re: Aluminum terms?

Mike:
According to Brimm and Boggess (1940): The 3S alloy is pure aluminum with 1.25% Manganese added. The H (or Hd perhaps?) means it has been hardened. Specs are:

3S-H 29,000psi tensile strength, 4% elongation in 2"

You'll want to get a material that exceeds those specifications. May I suggest 2024T3 is a good all around aluminum alloy for aircraft repairs.

Bob Gustafson

[VictorBravo]

Re: Aluminum terms?

That's the old nomenclature... 24ST is now 2024 T-3 and so on. There is a little blurb in the Aircraft spruce catalog showing the conversions on page 67 (2006 -07 catalog)

3 S is the old 3003 alloy. I also have a drawing that shows Taylorcraft was using 3003 series aluminum in some non-structural parts in 1985.

However, I agree that in general, you can replace most structural al uminum parts in an aileron with 2024 T-3 and make your IA happy. There WILL be some palces where this is not true and you have to use a soft alloy, or a different alloy, but for the part you are talking about 2024 T-3 will not piss anyone off. You can always use the same thing that came out of it, and be legal, but a sharp IA might question why a weaker alloy is being used and force you to go off and justify it, get the factory drawings, etc. etc.

[OldBits2]

Re: Aluminum terms?

I'm removing corrosion form the trapizoidal shaped piece of aluminum sheet located at mid-aileron. The CD describes the aluminum sheet as ".016 3S Hd. Alum"

Anyone know what the "3S Hd." stands for and what the modern equivalent is? - Mike

3S is a precusor spec to 3003 per the aluminum standards committee translator/transition data (circa 1956).

Hardness was denoted as 1/4 hard, 1/2 hard, 3/4hard and Hard or Hd. 3003 was - is used in many cowls and othe non structural parts where shear strength was a minor issue and forming clean was more important. Good for farings and swept curves, easy to form for internal ribs and webs, but very malleable.

2024-T3 is a general structural repalcement in GA aircraft, and tensile exceeds that of 3003- an engineering evaluation should be done before making a wholesale change in anything structural, but a substitution for farings would be likely be OK. 2024 may crack where 3003 might not.

[Robert Lees]

Re: Aluminum terms?

I didn't bother cleaning the corrosion off for these parts...much simpler to make new from the same thickness 2024T3, and quicker too.

[Forrest Barber]

Re: Aluminum terms?

those ribs were "formed" on the old hydro press and of course the "hardness" changed during that process, they then went into an oven for a certain time & at a certain temperature. You can "repair" the rib but to replace it , I would use another rib ( a TAYLORCRAFT rib) , lots of them around .

[Mark Julicher]

Re: Aluminum terms?

3003 = weldable
2024 not weldable

It is not too often you have to do a weld, but if you know a decent sheetmetal man/woman a 3003 lower cowl can be welded.

Just a thought.

Otherwise, 2024 makes a fine rib.