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Bob,
Do you have a solution to a problem where the exhaust gasses exit the cowling area and have "chared " the epoxy airframe. I've seen this on a couple of LN-2's I've worked on, some others only just have discoloration of the paint in this area.
Obviously, a solution was to move the exhault pipes down away from the fulislage, by either cutting and rewelding the tips, or shimming the system.
Would a Carbon/Carbon or other high end "patch" etc be effective ?? Would appreciate your comments. Don Skeele A&P
-------------- Original message from "bob mackey" <n103md@yahoo.com>: --------------
> > I think I missed something.
> > What is carbon/carbon and what are the temp characteristics?
>
> Craig:
> I'm glad you asked. Most of the previous replies on this subject
> have been misinformed.
>
> Carbon (graphite fiber) retains its strength and stiffness well
> up to about 2000 C. Yes... that's about 3600 degrees Fahrenheit.
> It does start to oxidize at about 600 C (~1100 F) in air though,
> so it is difficult to test to its full temperature range.
>
> Some have mentioned that "carbon composites" lose strength at
> 120 F or some other low temperatures. Actually, the EPOXY softens
> at temperatures varying with the type of epoxy. There is a wide
> range, but typical values o
f Tg (glass transition temperature)
> http://www.siliconfareast.com/tg.htm
> are around 135 C. There are higher temperature resins like
> phenolic or bis-maleimide with Tg of 200 C or more.
> One of these days I'll rebuild my engine baffles with
> carbon-bismaleimide composite instead of repairing the
> cracked aluminum.
>
>
> The highest temperature "resin" in common use is carbon itself.
> Hence "carbon-carbon composite". That's carbon fibers with carbon resin,
> forming a composite matrix.
> http://www.composites-by-design.com/carbon-carbon.htm
> The carbon resin can be pitch that is infiltrated into the carbon fiber
> preform then fired to drive off the hydrogen. The pitch shrinks
> leaving voids, so the process is repeated a few times. Other methods
> use gas-phase carbon sources to carry the carbon into the matrix.
> Because of the shrinkage, a final machinin
g operation is often used
> to make the net shape part.
>
> The end result is lighter and stronger than steel, and suitable for
> use at extreme temperatures except for oxidizing flames.
> Space shuttle re-entry tiles and many rocket engine nozzles are
> made of C-C.
> http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_sys.html
>
> If you want it to look metallic AND be made of lightweight
> carbon-carbon, you could nickel-plate the carbon-carbon exhaust tunnels. :-)
>
> -bob mackey
>
>
>
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