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  1. R

    A Wind Turbine Design Application...looks neat!

    The problem I see is how do you maximize thrust while minimizing drag. Drag will reduce the efficiency of the "propeller".
  2. R

    Blended wing ACs are coming !

    All those surfaces are designed to deflect radar waves away from receivers. They were probably wondering if he got his ideas from them.
  3. R

    The Great FreeCAD Thread

    If you want a good viscous CFD solution, put a lot of points into the boundary layer.
  4. R

    Twin-VW engine Push-Pull design idea (The "Beetlemaster")

    Hi Pops, I thought I followed your JMR thread pretty closely, but I do not remember your discussion of airfoil selection. Please post a link to that thread or post an approximate date you were discussing the selection. Are you flying the JMR and have you thought about how your airfoil...
  5. R

    New airfoil website

    ... airfoils having a'Stratford pressure distribution, which has zero skin friction in the pressure recovery area. This pressure recovery represents an approximation to maximum pressure recovery without separation. ... report 19770020614.pdf from ntrs.nasa.gov. The report goes on to say the...
  6. R

    New airfoil website

    You should be aware the Stratford upper surface pressure distribution was meant to design the airfoil to be near stall at all positive angles of attack.
  7. R

    New airfoil website

    A better way to select an airfoil would be find and airfoil with a drag bucket* to include all the aircraft lift coefficients where you want to cruise efficiently. *drag bucket, range of lift coefficients with a large extent of laminar boundary layer Having said that your plot is misleading...
  8. R

    New airfoil website

    The largest problem with empirical codes like xfoil and eppler is prediction of the maximum lift coefficient. Do not use these codes to estimate maximum lift coefficient, they do not model the physics of the boundary layer accurately enough.
  9. R

    2023 final year for air racing at Reno

    Interesting How big will it be? Will it be horizontal or vertical axis? What are the other features you are working on? Doug
  10. R

    Around Airport Transportation

    How heavy is your onewheel? How long does it take to recharge? Have you had trouble finding an outlet? I watched someone trying to learn to drive(?) a onewheel, it is a lot harder than it looks. Doug
  11. R

    Wind turbines falling

    Could you share those numbers with us. My WAG is about Mach 0.1 to 0.2 Thanks, Doug
  12. R

    Euler problems

    I disagree. It has been my experience that all singularities in CFD are due to round off error or other problems with the CFD solution, probably because CFD doesn't include all real world physics.
  13. R

    Aerofoil layout

    If you want to "layout" a set of airfoil coordinates. That is create a 24" airfoil section, then you can scale the x and y coordinates by 24 (assuming the maximum x coordinate is 1.0) If you want to create a NACA 2418, you cannot scale up a 2412. You have to use the proper formulas to add 18%...
  14. R

    Achieving The Best Reflexed Airfoils for Flying Wing use in the Small Plane Categories

    There is no comparison between CFD and empirical methods like XFoil in this paper. Empirical methods cannot and should not be used to calculate maximum lift coefficient. The reason is that in empirical methods the boundary layer is assumed to be attached.
  15. R

    Spent the day at Duxford….not experimental, but worth the trip.

    I am adding my recommendation to visit Duxford if you have the chance. I visited during at VE day celebration. A very good day.
  16. R

    Airfoils

    A lot of people flying high performance gliders would disagree with you.
  17. R

    Systems Reliability - Need Component Failure Probability Estimates

    I am glad someone replied who knows something about statistical analysis. This a very complicated field.
  18. R

    EAA No Longer Has Free SolidWorks

    I didn't see anything about intellectual property in the link. But it seems they go out of their way to keep your info secure...
  19. R

    "SkyWing" hybrid wing body ultralight

    In general as the camber of an airfoil increases the negative pitching moment, nose down, increases. I assume bending the nose up, like reflexing the trailing edge up, would act to decrease the camber and decrease the negative pitching moment. But like a previous comment, it would be a good idea...
  20. R

    Airfoil Circumference and Area

    Hi rtfm, Do you know how the weight is calculated in the program? Also, how are the areas calculated, planform or surface? Thanks, Doug
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