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Wooden Helicopter blades?

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  • #31
    But isn't carbon fiber superior in almost all categories, except for fatigue life?
    Carbon fibre composite is wonderful, until it isn't. It has a nasty tendency of failing catastrophically with no detectable or inspectable warning. That is why the FAA requires a 2 times design safety margin for carbon composite and only 1.5 for wood and aluminum. That negates most of the weight advantage of carbon composite.

    If anybody can come up with a reasonable way to reliably inspect carbon composites on site and in situ they will make a billion dollars.
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    • #32
      A bit more here though:



      Phil

      Originally posted by The Artful Bodger
      Doesnt seem to be much bending stress here!

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      • #33
        If those blades are built the same as the Huey they have a high alloy full height steel spar at the 1/3 chord point. It is very springy and also acts as a bullet firewall to help prevent catastrophic damage from firearms and trees. There is a cockpit video online of a military pilot flying some type of military helicopter and he hits a tree. It vibrates like crazy but still stays together until he manages to land.
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        • #34
          Lazlo; I'm not aware of any aircraft propellers made for certificated aircraft, manufactured of carbon fiber. Doesn't mean they aren't in the pipeline, just that the certification rules, continuing airworthiness programs, and cost competitiveness in the marketplace haven't come together.

          Regarding the venerable Bell ne Scott 47, I understand there is a composite blade coming to market for it.

          I got a chance to look at an ex Soviet bloc Mi-24 "Hind" at the heli-Expo this spring, up close, hands on. I was amazed at the combination of crude bodge & watchmaker-like workmanship, in the same package.

          I also noted, the Horizontal stabilizer, which appeared to be trimmable, was of "dope & fabric" construction. Like a damn Piper Cub! A very formidable Gunship.

          And to think Rambo shot one down with a Bow & Arrow!!

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          • #35
            Originally posted by J Tiers
            Still "guv'mint" interference...... it it was viable, it would stand on its own with no university nonsense.....
            Slave labor Jerry
            I just need one more tool,just one!

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            • #36
              Intresting strobe effect in this video-

              I just need one more tool,just one!

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              • #37
                Originally posted by philbur
                A bit more here though:



                Phil

                still pictures usually aren't the best gauge as the craft can be taking off at a great rate or in a big decent therefore not loading the blades as much,

                but that one speaks volumes - the smoke streamers and the bending of the aft blades way more than the fore ones ensures that that bird is moving forward at a good clip,

                when this is happening the rear blades are going through double time - for there not only responsible for the majority of lift of the craft but also the propulsion --- all controlled by the swash plate and blade angles...

                Multiple blades can help share the load and therefore the deflection making it less --- but this is a catch 22 as in many cases multiple blades are required to rotate at lower speeds - this of course means more deflection due to less centrifugal force... it's basically all up to the math of the materials, RPM's, loading and number of blades which will have the least...

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                • #38
                  Are those rigid, semi rigid or articulated rotor blades?

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                  • #39
                    "Rigid" is really a misnomer.

                    Here's a "Hingeless" main rotor. No lead-lag or flapping hinges. The rotor head is one big chunk of Titanium, as are the blade grips. A damn fine machine. MBB (now Eurocopter) Bo-105. The blades are composite.




                    The Hind has a fully articulated main rotor system.

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                    • #40
                      Originally posted by Evan
                      If anybody can come up with a reasonable way to reliably inspect carbon composites on site and in situ they will make a billion dollars.
                      Wouldn't Ultrasonic inspection work? It works wonders on Fiberglass boat hulls.
                      I just need one more tool,just one!

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                      • #41
                        Nice picture,,, that's indeed a piece of work...

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                        • #42
                          Originally posted by wierdscience
                          Wouldn't Ultrasonic inspection work? It works wonders on Fiberglass boat hulls.
                          There must be some way that mainstream commercial and military helicopter rotors, most of which are composite, are inspected. Ultrasound would be an obvious candidate.

                          Nice picture,,, that's indeed a piece of work...
                          +1. Machine art.
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                          • #43
                            Wouldn't Ultrasonic inspection work? It works wonders on Fiberglass boat hulls.
                            I was discussing this recently with an engineer that is studying the problem. The problem is at a level where ultrasound doesn't have sufficient resolution. It seems that it may involve randomly distributed cracking of individual filament strands throughout the material. This isn't like gradual delamination although that can also happen. How to see this microscopic damage is the main problem.
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                            • #44
                              Originally posted by Evan
                              I was discussing this recently with an engineer that is studying the problem. The problem is at a level where ultrasound doesn't have sufficient resolution. It seems that it may involve randomly distributed cracking of individual filament strands throughout the material. This isn't like gradual delamination although that can also happen. How to see this microscopic damage is the main problem.
                              I've made calibration samples for scanning various materials.Simple items like heat exchangers are just samples with various degrees of "pitting" machined in.

                              Some of the Fiberglass samples were lay ups that were then stressed to varying degrees producing varying degrees of damage.

                              Those were used with a healthy sample as a comparative tool.Given that Carbon Fiber lay ups are much more precise than Fiberglass it might be possible.

                              It probably wouldn't be a tool used by a freelance service,but a manufacturer such as Airbus or Boeing might be able to use it if they produced calibration standards matching the areas of interest.
                              I just need one more tool,just one!

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                              • #45
                                If you can find a solution Airbus would probably like to speak with you.

                                This is from an A310. The rudder fell off in normal flight. The flight control system compensated so well that the pilots didn't know it happened until the system notified them of a problem. The rudder wasn't being used for any large inputs, just normal autopilot commanded flight conditions.This isn't the only one either. At least two others have failed in the same manner.

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