Aluminium square tube -v- spruce or other woods

[Hargraves]

The problem with the best and strongest aluminiun alloys is that unlike the steel alloys they do not lend themselves to heat treatment in their extruded forms which with the exception of skins would be their main airframe use. Anyone that has worked with marine grade 5083 H34 tempered alloy plate would know how far structurally ahead it is of any of the other series sheet alloy and that the extrusions of 6000 series don,t even come close due to the very nature of the extrusion process itself. Theirs allways a caviate of course and that is any manufacturing processes involving heating reduces or invalidates the structual integrity of the tempered product, and forming or pressing beyond radius limits causes stress fracturing as well, If I were ever lucky enough to be in a position to scratch build an aircraft, the the spars would be based on that grade or an equivelant from the manufacturer, as previously mentioned theirs alluminium and theirs alluminium alloys and using basically the same tools as wood working thats my choice of stuff to use, cheers Hargraves

 

 

[bexrbetter]

The problem with the best and strongest aluminiun alloys is that unlike the steel alloys they do not lend themselves to heat treatment in their extruded forms

Eh? I have watched it being done personally.

 

They go from the extrusion line straight to the various aging processes etc, depending on temper required.

 

There is no "tempered" product per say, it is not part of the products makeup, the product's temper is created through a post process, eg; after welding, milling, casting, extruding etc, usually by a heating process, and can be repeated if the temper is lost.

 

Anyone that has worked with marine grade 5083 H34 tempered alloy plate would know how far structurally ahead it is of any of the other series sheet alloy and that the extrusions of 6000 series don,t even come close due to the very nature of the extrusion process itself.

Not sure where you get your information from, but the extrusion process changes nothing regarding the element structure of the aluminium alloy. A 6061 billet goes in, a 6061 extrusions comes out the other side. Zero temper or "T0" - which is then post extrusion tempered to as required.

 

When literally every small aircraft company in the world uses 6061 or 2024, it might be fair to say that 5083 quite obviously doesn't command the same confidence with them as you have with it for various reasons.

 

 

[facthunter]

Alloy heat treated steels are usually welded into a structure and lose some of their performance (strength) in the heat affected areas unless re heat treated. You can also get a "chill" line alongside a weld run where a crack will occur. This requires local tempering back to soft(er) The size of the component limit's this. Larger structures would most likely distort if fully heat treated. Heat treatment is used for stress relieving, hardening and tempering. (not all at once).

 

Rivetting is the most common process involving aluminium structures, though they can be bonded as well or bonded only with skins. Rivetting reduces the effective cross sectional area locally. Even doing it correctly only minimises the effect. Nev

 

 

[Hargraves]

Your quite right 5083 H34 tempered alluminium marine grade sheet canot be made from other grade sheets due to their alloy composition but tempering is not an ageing process normalizing (softening) is. 5083 H34 cannot be produced via extrusion due to its composition. I am retired and I may well be behind the times but i know of no tempered alluminium extrusions and i havent seen a temper listing in them.

 

 

[spacesailor]

The best alloy I've seen is/was Duralamin (spelling).

 

It was a propeller. what off I've no idea, but was very springy yet hard.

 

spacesailor

 

 

[Hargraves]

Duralium is the only allumininm alloy I,m aware of that can actually harden with age and flys in the face of all the others in this regard, its texture and feel could be described as being on a par with the difference between a cold rolled steel flat bar and the same size piece in high tensile steel ground stock, I think us in U/L flying are fairly insulated from it but due to its huge cost, cheers Hargraves

 

 

[facthunter]

It's a trade name for a particular aluminium alloy. Used to use it for model aircraft undercarriages etc. Nev

 

 

[old man emu]

Duralumin is an aluminium/copper alloy (4% copper). The article in the link lists the various grades and uses of Duralumin.

 

Duralumin - Wikipedia

 

 

[facthunter]

"Y" alloy is also a copper added alloy (usually cast) developed for the aircraft industry. Has probably been superceded by superior alloys since. Metallurgy made great strides in the late 20's. Nev

 

 

[spacesailor]

Duralumin

 

Has a corrosion problem, that all the samples I've seen were heavily painted.

 

"Although the addition of copper improves strength, it also makes these alloys susceptible to corrosion. For sheet products, corrosion resistance can be greatly enhanced by metallurgical bonding of a high-purity aluminium surface layer. These sheets are referred to as alclad, and are commonly used by the aircraft industry".

 

I didn't know that!. Thanks Wikipedia.

 

spacesailor

 

 

[Litespeed]

Alclad is awesome-it is the reason a beautiful polished aircraft can exist. It does not easily corrode and keeps its surface finish protected with a micro layer of Aluminium oxide. It can be polished beautifully and keeps its shine. Don't polish too hard though or you go through the pure metal on top.

 

When I finally build if the design is alloy- it will be skinned with the modern version and polished. Much lower cost than painting, weighs nothing. The ultimate finish, polished au naturale. Naturally it is a hanger job, not left to bird bomber runs acid etching the finish.

 

 

[Hargraves]

Thanks spacesailer I did,nt know of that either, I did know of the lack of inclusion of copper in marine grade alloy sheets though due to electrolysis arising from the dissimilar metals issue and lightspeed is correct regarding the thin (air oxidized) surface coating that takes place and is a very good anti- corrosion barrier and the reason painting alluminium tinnes and larger is a external cosmetic only opperation. I,m guessing that the necessity of excluding or greatly reducing copper content in marine grade may be a reason for its strength and temper abillity possibly. Hargravescheers

 

 

[bexrbetter]

Metallurgy made great strides in the late 20's. Nev

Actually the aluminium grades naming should have been upgraded, they are no where near the same strength as they were even just 50 years ago.

 

The literal makeup of the alloying elements are the same, no change there, but the refining purity and processing techniques of the sub elements to create the specific alloying has increased tremendously over the decades so that now a 5000 series today is as strong as a 7000 series was in the 1950's.

 

You could replicate a Cessna 150 built in a 2000 series 50 years ago in a cheaper 6000 series today, and retain the same strength (applicable to researching these facts of course), or just feel confident that you have a far stronger plane if you used a 2000 series again.

 

i saw a chart recently with this comparison, have a look for it later, if I didn't save it.

 

 

[spacesailor]

Litespeed

 

Even polished aircraft in hangars will oxidize, Mine is in the shed & covered but still needs that polish.

 

Hargraves

 

I dislike the use of pull rivets as it makes for three different metals, the aircraft's alloy, mild steel mandrill, & the metal that the rivet is made from, IE steel, stainless steel, nickel copper alloy (Monel), copper, and several grades of aluminum. If the mandrill head stay's in it can rust, if it comes out its not as strong & can leave a hole . there is a very expensive sealed rivet.

 

spacesailor

 

 

[Hargraves]

Spacesailer they were called, or at least were when I used them years ago, Imex sealed aluminium alloy rivets, and were, when first introduced many years ago the only pop rivet approved by the old department of labour and industrie for double staggered lapjointed riveted pressure vessels up to 100 psi. Which i found then and now amazing in its self. In marine applications the mandril hole was backfilled with sikaflex as was the joint and made for an extremely strong bond. Using any quantity required pneumatic guns or a heavy duty tong or lever riveter, the plier type requiring a gorilla if 3/16" or over is used due to their hard alloy composition. Cheers

 

 

[bexrbetter]

LitespeedI dislike the use of pull rivets as it makes for three different metals,

But the real world has proven for the last 100 years that, that, is a moot point, it just doesn't happen in the magnitude that warrants any concern, especially with some very simple preparation.

 

- not joking either, the blind pull rivet was patented in 1917!