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Thread: Fire wall Ti?

  1. #1

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    Fire wall Ti?

    I have a homebuilt and am thinking of putting a titanium fire wall on. I am not sure what size or grade to use? Any help would be great thank you.

  2. #2

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    I'll bite. What is the engineering rationale for use Ti? The alternatives are easier to machine and lend themselves better to being shaped if you need a non-flat forewall.

    The FAA specs for farewalls dictate the thickness of material that you require. A firewall needs to be able to handle a 2000 degree heat source for several minutes. If you have seen a firewall burnt through due to a failure in an exhaust system (I have), you will believe the spec. So you have to calculate how thick your material needs to be to resist the high temperature erosion for that long. Look in FAR 23 and its derivatives for the exact spec.

    Best of luck,

    Wes
    N78PS

  3. #3

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    Titanium Firewall

    Titanium is a great choice for an airplane firewall, exept for the cost, of course. However you might be able to find some scrap material for around $200 that would be big enough to do a firewall. You need a thickness of .016 to .020 in. If you go any thicker you start losing the advantage of titanium's lighter weight. Commercial pure titanium is your best bet if you can find it. It has the lowest tensile strength, which is not really important, and is therefore easier to work with -- cut, make holes in ,etc.

    The 6AL-4V alloy seems to be much more readily available but it is twice as strong and thus harder to work with.

    When cutting or drilling titanium be sure to go slow and provide lots of lubrication for cooling. It tends to gum up tooling because of its poor heat transfer qualities. In fact it conducts heat about 10 times less efficiently than steel, which makes it great as a firewall material.

    A titanium firewall can save about 2 pounds as compared to stainless steel on the typical single-engine airplane.

  4. #4

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    What would a sheet of Ti say 42"w x 30"h cost?

    Regards,

    Wes
    N78PS

  5. #5

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    From Online Metals, Ti Grade 2 sheet, .028" thick, 48"x 36" runs about 400$ plus shipping. I don't know what they are calling grade 2 alloy wise, you would have to call. Stainless is going to be 1/5th or less in cost.

  6. #6

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    Big Grin Thanks

    Thank you all for your input. The reason Ii want Ti is to reduce weight I am rebuilding a Stitts SA3-B Playboy and I want it lite. Also a Ti fire wall will look so clean. I won't be forming it, so I only have to cut it to size and drill holes.

  7. #7

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    Titanium Sheet

    Here is a piece of .016 thick Titanium 6AL-4V that is 36" x 41" for $251.69 plus shipping.

    http://www.titaniumjoe.com/6al4v%20sheet.htm

    Titanium Joe always seems to have a good selection of sheet in this alloy, but seldom has anything very thin in com'l. pure for some reason.

    If someone can find a source of com'l pure titanium in thicknesses in the .016 to .020 range I would love to hear about it.

    Dave Prizio

  8. #8

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    Thermal conductivity of Ti is around 8 while stainless is around 12 so a more realistic value for heat conduction comparison is 50% less for Ti.
    You are paying mucho bucks for a relatively small benefit. Primary use of Ti is for hot structure around jet engines or special aircraft skins seeing high stagantion temps like an SR-71.
    It also has value for corrosion resistance in bad environments not containing chlorides which promote cracking.
    I'd vote for stainless on a cost-benefit comarison.

  9. #9
    steveinindy's Avatar
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    Thank you all for your input. The reason Ii want Ti is to reduce weight I am rebuilding a Stitts SA3-B Playboy and I want it lite.
    Rule #1 of homebuilding: Don't screw with the structural design unless you REALLY know what you're doing.

    Also a Ti fire wall will look so clean.
    As compared to what precisely?

    I'd vote for stainless on a cost-benefit comarison.
    But you're overlooking the "cool" factor of having titanium in your homebuilt!

  10. #10
    Matt Gonitzke's Avatar
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    Quote Originally Posted by Bob H View Post
    Thermal conductivity of Ti is around 8 while stainless is around 12 so a more realistic value for heat conduction comparison is 50% less for Ti.
    Assuming this site is accurate, you've got those numbers turned around.

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