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  1. Norman

    How does a scale up affect airfoil center of lift?

    I'm saying that it's not a terribly sensitive airfoil but as you can see in the polars that Wingitis posted small deviations from the nominal shape can degrade performance or even turn a marginal airfoil into a dangerous one.
  2. Norman

    How does a scale up affect airfoil center of lift?

    It looks like Mr Spratt modified the 23112 ordinates to get rid of the leading edge cusp by decreasing the camber until it disappeared. Several designers (eg Marske Monarch, Schweizer 1-26, Corby Starlet) modified the 43012 similarly to produce the 43012a but they simply filled in the cusp...
  3. Norman

    How does a scale up affect airfoil center of lift?

    Guys as long as the leading edge pressure distribution is reasonably smooth at some small positive AoA and Cm0 matches the Cm0 of the airfoil described in NACA report 537 it's close enough. Any error caused by misinterpreting the fuzzy numbers on your plans can be smoothed over with inverse...
  4. Norman

    How does a scale up affect airfoil center of lift?

    Man, that was 10 years ago, I can hardly remember breakfast. I do remember that I didn't change the file name so searched with that. "NACAG" stood for something but I don't remember what. Something to do with hang gliders I think. Anyway that group appears to be gone. The BTB version should...
  5. Norman

    How does a scale up affect airfoil center of lift?

    The NACA-23112 has come up on HBA several times before, usually associated either with the Pou-du-Ciel or Spratt Control Wing. The coordinates in the NACA report that Wingitis posted are pretty coarse. They're good enough for hand drafting but if you're going to draw your rib templates in CAD...
  6. Norman

    How does a scale up affect airfoil center of lift?

    What you're asking about is called the pitching moment (identified as Cm (for moment coefficient) on polar diagrams) and, no, scale does not affect it. As long as you plot your airfoil from an accurate set of coordinates and use the same percentage for the hinge the control forces will be...
  7. Norman

    Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 series

    The Clark YH is a very early and rather crude helicopter airfoil. It's not a good choice for a fixed wing aircraft!
  8. Norman

    Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 series

    That's the main element of a slotted STOL airfoil. Cruise performance will be crap! Junkers flaps produce more force than plain control surfaces of the same dimensions with a fairly small drag penalty in cruise so can be a good choice but there's also a structural weight cost so the design...
  9. Norman

    ACHIEVING THE BEST REFLEXED AIRFOILS FOR FLYING WING USE IN THE SMALL PLANE CATEGORIES

    If your CAD program has a function to list the points on a spline you can copy that to a text file and use search and replace to get rid of the CAD specific parts. Back in the stone age I did it that way several times. IIRC the command in ACAD is <inquire> under the tools menu.
  10. Norman

    ACHIEVING THE BEST REFLEXED AIRFOILS FOR FLYING WING USE IN THE SMALL PLANE CATEGORIES

    I brought the loss of resolution problem up to the administrator a few months ago but got no help. Basically he just told me that it's my fault. OK I've been working on a real oddball problem off and on for a while. It's a drop-in replacement airfoil for the Mitchell U-2. The spar is right...
  11. Norman

    ACHIEVING THE BEST REFLEXED AIRFOILS FOR FLYING WING USE IN THE SMALL PLANE CATEGORIES

    You can use a .DAT file as the base to create a script file for your CAD program. I only know how to do this in Autocad but other programs also have a scripting language for automating repetitive tasks. I haven't done it in quite a while but here's what I recall: This can be done in any text...
  12. Norman

    Minimum clearance from air scoop to fuselage

    No corners on the inside either. You can have flat walls that diverge from the free stream by 7 degrees but any more than that and there will probably be separation from the walls with recirculation (drag and loss of cooling) near the walls. If you want to get really anal about internal drag...
  13. Norman

    Directly Downwind Faster Than The Wind

    Who do you suppose lost?
  14. Norman

    Minimum clearance from air scoop to fuselage

    The boundary layer gutter (the space between the fuselage and splitter plate) needs to be equal to or slightly greater than the thickness of the fuselage boundary layer. I'm not sure it's necessary unless you're flying fast enough to benefit from ram pressure. They did it on the latter model...
  15. Norman

    ideal aerofoil

    Was there an actual question? I thought it was a test. Or troll, to use the vernacular of the cool kids.
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