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Thread: Titanium fuselage

  1. #1

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    Titanium fuselage

    I know its expensive but its stronger and lighter than 4130 from what I can tell. Has anybody considered this material combined with some nascar roll cage technology for improving the cabin cage.

  2. #2
    Dave Calkins's Avatar
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    Bill M. of Mountain Goat fame says he saved "about" half the weight of a chome-moly frame by going ti.

    He said the Goat chro-mo. frame weighs 'about' what a Cub frame weighs.

    If we are conservative and say a Cub frame weighs 'about' 110 pounds, half of that would be 55 pounds. That would be an amazingly light structure for the size.

    Come to think of it, a Cub frame is an amazingly light structure even at 110 pounds!

    I'm not sure the compromises to build from ti are worth the complications and cost for a project savings of 55 pounds.

    Sure would be cool, though, and I'm all for weight-savings, but what about cost, shielding while welding, field repairs, tubing sourcing, keeping the gawker's slobber off your windows??

    ....now a set of Titanium lift struts, tailfeathers, and landing gear would REALLY be cool......and you could unbolt them off the a/c to take 'em in for a repair. oooooooooohhhhh, this is an idea. Thank you, 46-12.

    DAVE

  3. #3
    T.J.'s Avatar
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    Is ti an approved material for Cubs?

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    Pure titaniunm is relatively soft.

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    skukum12's Avatar
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    I personally stood on a scale with the Goat Ti fuselage. Roughly 64.5 lbs. No b.s. in this claim.

    As for Ti cubs, been pondered by many. Not the least of whom Dan's AC. When Ti prices were consided several years ago, at over 30 bucks a foot, the Ti idea priced itself right out of production. Of course you add parts and labor and watch that price per foot skyrocket.

    Plus, our good friends the Russians were cheapest source for Ti, but considering their production ways, how good is their quality control?
    "Always looking up"

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    My guess is that you want an alloy of titanium and vanadium for the cub, not pure titanium. As with any alloy, how the alloying was done will determine the strength of the final product. The stuff ain't magic. I have some broken, fatigue failed titanium on my desk.

  7. #7

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    Pure Titanium is also very reactive so it's typically alloyed with other metals/chemicals for various purposes. Here is a table of some "commonly" used aircraft titanium alloys. One of the larger suppliers to Boeing of Titanium Alloy parts used to be in Albany Oregon. Not sure if they are still they as they were bought out some years ago.


    Table 1. More widely used titanium alloys in aircraft applications.

    Alloy Attributes/Applications

    Ti6Al4V Workhorse, general purpose high strength alloy

    Ti6Al2Sn4Zr2Mo (6-2-4-2) Creep and oxidation resistant engine alloy

    Ti6Al2Sn4Zr6Mo (6-2-4-6) Creep and oxidation resistant engine alloy

    Ti3Al8V6Cr4Zr4Mo (Beta C) Beta alloy with established spring applications

    Ti10V2Fe3Al (10-2-3) Beta forging alloy used for 777 landing gear

    Ti15V3Cr3Sn3Al (15-3-3-3) High strength heat treatable beta sheet alloy

    Ti3Al2.5V Medium strength alloy used for hydraulic tubing

    Ti4Al4Mo2Sn (550) Higher strength heat treatable airframe and engine alloy

    Ti5.5Al3.5Sn3Zr1Nb (829) Advanced engine alloy, creep and oxidation resistant

    Ti5.8Al4Sn3.5Zr0.7Nb (834) Advanced engine alloy, creep and oxidation resistant

    Ti5Al2Sn4Mo2Zr4Cr (Ti17) Advanced engine alloy, creep and oxidation resistant

    Ti15Mo3Nb3Al0.2Si (21S) Oxidation and corrosion resistant beta sheet alloy


    Table 2. Titanium alloys of increasing importance in aircraft applications.

    Alloy Attributes/Applications

    Ti6Al2Zr2Sn2Mo2Cr0.25Si (6.22.22) Airframe alloy for F22 and JSF projects

    Ti4.5Al4Mo4Sn0.5Si (SP 700) Competitor for Ti6Al4V for SPF and general use


    Table 3. Less widely used titanium alloys in aircraft applications, but alloys that may be critical in their application to specific fully validated components.

    Alloy Attributes/Applications

    Ti2Cu Heat treatable sheet alloy

    Ti4Al4Mo4Sno.5Si (551) High strength airframe alloy, very limited availability

    Ti8Al1Mo1V Early alloy now mainly used for spares and replacements

    Ti-6-6-2 High strength alloy with specific earlier applications

    Ti11Sn5Zr2.5Al1Mo0.2Si (679) Earlier engine alloy rarely specified in new programs

    Ti6Al5Zr0.5MoO.25Si (685) Engine alloy now mainly for spares and replacements

  8. #8

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    A lot of good points, I was primarly thinking about this in terms of experimental. Probably correct about the added hassle of field repairs, attatching different metals and so on. When just running with less gas makes up the difference doesn't seem worth the trouble. Seams like it would be the ultimate though.

  9. #9
    SJ's Avatar
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    Maybe more important is the cost. One of our members told me the titanium gear legs he bought for his 180 for $6000 are now worth $12000 or something crazy like that.

    But I guess if I lived in Florida and money were no object....

    sj
    "Often Mistaken, but Never in Doubt"
    ------------------------------------------

  10. #10
    behindpropellers's Avatar
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    So does Titanium Corrode? I think the idea of building the smaller sub-assemblys out of TI is a good idea.

  11. #11
    supilot's Avatar
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    it is used in alot of military aircraft now. its pretty cool cause as soon as it comes in contact with oxygen an oxide film forms making it impossible to corrode, at least on earth. if it gets damaged and new titanium is exposed, it just forms a new oxide film and its good to go.

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    Christina Young's Avatar
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    Hard to work with and brittle. I had some of my specialty dive gear made out of titanium by a friend who is a welder. Very light weight and doesn't corrode, though! Some of the structural stuff I had cracked under stress, and had to be re-welded.

    Also, don't expose to high oxygen environment, titanium will spontaneously combust.

  13. #13
    behindpropellers's Avatar
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    Quote Originally Posted by Christina Young
    Hard to work with and brittle. I had some of my specialty dive gear made out of titanium by a friend who is a welder. Very light weight and doesn't corrode, though! Some of the structural stuff I had cracked under stress, and had to be re-welded.

    Also, don't expose to high oxygen environment, titanium will spontaneously combust.
    What alloy were you working with? Was your welder trained on how to weld it? There are a lot of factors, but selecting the right alloy along with the correct process should make it possible to use for most applications.

  14. #14

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    Pure titanium is highly reactive. Titanium alloys have been chemically altered by combination (taking advantage of the highly reactive property) with other metals so they are less reactive otherwise they would be unusable. Welding with titanium alloys requires use of gas shield (using Helium or Argon) so molten metal is not expose to atmosphere. If exposed to atmosphere above 260C will typically recombine with oxygen, nitrogen and carbon in atmosphere to form brittle inclusions. Gas shield must be used until weld puddle has cooled below annealing temperature. All edges of areas to be welded need to be cleaned thoroughly to remove all contaminates (particularly if the metal surfaces were cut with a gas torch). If not cleaned then remaining carbon etc. will react with molten titanium to again form brittle inclusions in the finished weld. Big reason for lousy finished titanium weld is poor environment and prep. Next reason is lousy equipment.

  15. #15
    supilot's Avatar
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    interesting

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    Dave Calkins's Avatar
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    I'm sure Fortysix12 meant 'a suitable titanium alloy' when he said "titanium". We could argue alloys all day, some of you guys would like that??

    A suitable alloy would make a fine fuselage structure if we ensured all the proper construction conditions.

    I've heard people claim ti is brittle. I'll not dispute that some alloys of ti are brittle.

    We've kind of already had this discussion a while back, but I guess here we go again. It IS interesting.

    Many high-end bicycle frames are built of titanium tube sets. If there is a field requiring high strength to weight ratios near or surpassing that of aviation, the cycling world is it........and there is no cost spared in this world either.

    I'll go across the street to my neighbor and get a photo of a titanium-framed bicycle with front and rear supension that has 5 inches of rear wheel travel, but no mechanical pivot point. What? Yes, the thing is designed to flex in the middle and even has a shock-absorber, but no pivot for the rear suspension....be right back.....



    So anyway, what alloy of titanium do we want?

  17. #17
    behindpropellers's Avatar
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  18. #18
    supilot's Avatar
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    what do you think a TI fuse for a supercub would cost?

  19. #19
    behindpropellers's Avatar
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    Quote Originally Posted by supilot
    what do you think a TI fuse for a supercub would cost?
    To put it in perspective:

    Square foot (not in bulk) of .063 Ti grade 2 is 92.50 while a square foot of .063 4130 is 12.66(not in bulk).

    Source: Mcmaster-Carr.

  20. #20

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    Here are two good reads. This is what I read that got me thinking about the whole thing.

    http://www.ing.unitn.it/~colombo/tel..._titanio.htm#1



    http://www.thefabricator.com/TubePip...icle.cfm?ID=22

    This is fairly interesting as well.

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