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  • Users: cludwig
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  1. cludwig

    Aerobatic Airfoils Design Considerations?

    You're spot on about the flat sides not meeting the ellipse at the point of max thickness. They meet slightly further aft at the point where the slope of the ellipse matches the slope of the line. That is what I meant by tangent point. The flat plates will either meet in a point at the...
  2. cludwig

    Aerobatic Airfoils Design Considerations?

    These airfoils of the type on the Edge and Extra were first proposed by Dr. Eppler. (at least that is the oldest reference to the design that I can find, correct me if I am wrong, I'd love to see read more on the subject) Eppler proposed an airfoil with an elliptic nose and flat plate top and...
  3. cludwig

    Aerobatic Airfoils Design Considerations?

    TractorPilot, Please click on the link below and call or email me. I'd like to discuss this with you offline. Regards, Chris. http://directory.utk.edu/search.jsp?query=Chris+ludwig
  4. cludwig

    Question on studying aeronautics.

    South Africa will offer a world class engineering education with much lower cost of living.
  5. cludwig

    Aerobatic Airfoils Design Considerations?

    to btrueblood: The symmetric airfoil is so you can fly clean inverted figures. For an example, go fly a 2 point hesitation roll in a Citabra. Then fly it in an Extra. You will see the difference. An unsymmetrical airfoil requires much, much higher alpha to generate the lift required for...
  6. cludwig

    Aerobatic Airfoils Design Considerations?

    Hell No! Negative G hurts!! I don't like much over 3 or 4 G negeative. Designing for -6G would be enough from an operational standpoint.
  7. cludwig

    Aerobatic Airfoils Design Considerations?

    The twist is not geometric, it is aerodynamic. The wing is identical right side up as upside down, it is perfectly straight. Root arifoils are selected that stall prior to the tip airfoils. 5 degrees difference in critical angle of attack is about the biggests difference you can get using...
  8. cludwig

    Aerobatic Airfoils Design Considerations?

    I can't copy a Pitts airfoil. The top (and forward) wing is a laminar airfoil. The lower (and rearword) wing is not a liminar flow wing. The laminar wing stalls at a slightly lower angle of attack than the other. When the laminar wing stalls (forward wing), the nose of the plane drops. This...
  9. cludwig

    Aerobatic Airfoils Design Considerations?

    Hello all, I've got B.S. in Aerospace Engineering and I am trying to design my own personal homebuilt aircraft. It will be two place aerobatic, designed for about 8G solo, 6G dual, fully inverted systems, etc, etc. Wing will have no twist, 1 degree or less dihedral, zero sweep about the...
  10. cludwig

    Testable ASME Ring Joint flange?

    Thanks for the suggestions. I was finally able to source the seals from Karmsund Maritine, Norway (http://www.kamos.no) The are very expensive, with each seal costing at least several hundred dollars. But this is perfect for intervention work when you need to break containment on a pipeline...
  11. cludwig

    Testable ASME Ring Joint flange?

    I am looking for a testable seal ring for ASME B16.5 6", 8", 10" and 12" 1500# flanges with a ring joint (grooved flanges and metal ring gasket). I would need to test the joint after the connections are assembled to verify the pressure integrity. A hydrostatic (or any other fluid) pressure...
  12. cludwig

    Analog to HART converters?

    I need this to be a rail mount design so it will fit in my flameproof junction box. Adaptions using full transmitters won't work for me.
  13. cludwig

    Analog to HART converters?

    I have user HART tri-loop to Analog converters supplied by Rosemount before with great success, but I now need to acquire 4-20 mA signals with a HART modem-only acquisition system. The acquisition system is capable of acquiring only the digital portion of the HART signal, not analog signals...
  14. cludwig

    EEx d to EEx ia interface?

    All, Sorry, to post two threads in a row... Is there a ready built and certified interface box for connecting an EEx d (flameproof) certified HART system to a EEx ia (intrinsically safe) system? I would either need a box with 4 zener barriers, or maybe just 1. (4 sensors on 1 loop or 4...
  15. cludwig

    flameproof HART connectors

    Thanks Controlnovice... I guess I wasn't too clear on the certification. Offshore installations are divided into 3 zones, clean, zone 1 and zone 2. Zone 2 requires IS, purged, or explosionproof... Zones are more of an industry definition of hazard than a level of certification. For the...
  16. cludwig

    flameproof HART connectors

    Hello Everyone, We currently have a flameproof acquisition system operating in a hazardous area (zone 2, offshore). I need to interface the current flameproof system with an external Intrinsically Safe HART network of cabling and sensors. I can't modify the current system in any way...
  17. cludwig

    Low torque 4" ball valves?

    Triple offset butterfly valves won't work for us as they are torque sealed. A geared mechanism normally provides the torque to create the seal. We need a level operated valve so we can operate it by hand quickly. We'd prefer not to use air actuators as most of our manifolds are used in a...
  18. cludwig

    Low torque 4" ball valves?

    Hello, I am searching for 4" 1/4 turn 600lb flanged (1440 psi) ball valve that can be opened and closed by hand. We have used Balon ball valves with great success for our 2" and 3" applications, but the torque on a 4" Balon is too much for one person to operate with one hand. Handle...

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