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  1. S

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

    Ok, I just wanted to make sure that's what you meant!
  2. S

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

    Actually I would prefer the answer coming from Addaon on what he meant by -15% SM, i.e. did he mean a naturally stable condition with a static margin of 15% MAC, which would be a positive value.
  3. S

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

    Did you mean to say a POSITIVE 15% SM? That would imply a statically stable dCm/dCL slope of -0.15.
  4. S

    Is there any proportion rule for aileron and flap chord proportions?

    A small amount can help, but not the amount that was added to the BC. A while back I did a roll analysis of the BC with the tips using the vortex lattice code AVL, and as I suspected, the roll performance was not that great. I can't remember if I also did the no tip version of the BC, but I...
  5. S

    Is there any proportion rule for aileron and flap chord proportions?

    I'm pretty sure that I asked Earl Luce years ago at Oshkosh about the aileron effectiveness of his Buttercup replica. My recollection is that he indicated that they weren't that effective. Perhaps someone on this forum has flown one and could comment directly. The Buttercup had closer to...
  6. S

    Is there any proportion rule for aileron and flap chord proportions?

    Rule of thumb statements can be too general and ignore other major factors. In Walter Diehl's excellent book "Engineering Aerodynamics, revised edition" he shows the effect of varying aileron span/wing span ratio and aileron chord/wing chord ratio. This is shown in the first figure, and his...
  7. S

    Is there any proportion rule for aileron and flap chord proportions?

    The units need to be consistent. For those of us who are metrically challenged, b is in feet and V in feet/s. P is in radians/sec. I mentioned that wing planform is a factor, which includes the effects of aspect ratio and taper ratio. The effect of ailerons stopping short of the tip can be...
  8. S

    Is there any proportion rule for aileron and flap chord proportions?

    How large the aileron chord needs to be, in percent of the total chord, depends on the desired maximum steady roll rate, total aileron span/total wing span, type of aileron ( Friese, sealed, or slotted), wing flexibility, total aileron deflection and wing planform. NACA in their report TR-715...
  9. S

    Wing spar sizing

    For production, a company will take it to ultimate load; not necessarily failure. In over 32 years of working in the industry, I remember only one time when a structure was taken to failure. That was at the end of a multiple life fatigue test for a version that was used by the military. Lots...
  10. S

    diffuser design info

    My experience with "Kuchemann" trumpet shaped diffusers has been good. Many years ago when we were developing the oil cooler installation on the Cessna T206H, we used more than one shape on the oil cooler diffuser and found that one following the Kuchemann approach provided the highest duct...
  11. S

    EAA - For better or worse

    Yes. It is cheaper to join ASTM and then gain access to the standards that you want then buying the standards individually.
  12. S

    EAA - For better or worse

    They were one of the founding committee members and they were very instrumental in getting the initial standards written and released. Earl Lawrence was the EAA government relations guy when it got started. He was the F37 Chairman when I joined to represent Cessna in 2006, and I took over as...
  13. S

    EAA - For better or worse

    No. LSA's are designed under ASTM consensus standards. For current production LSA's they need to meet the appropriate ASTM standard revision levels that are recognized by the FAA>
  14. S

    Sold Plans: Ritz Standard A Serial #181

    I sent payment for them yesterday.
  15. S

    Rethinking Propellers?

    That seems like a rather unfair assessment. Of course there are some other good propeller manufacturers outside of the US. The comments about the US manufacturers was based on comparative propeller data.
  16. S

    Sold Plans: Ritz Standard A Serial #181

    message sent
  17. S

    Rethinking Propellers?

    When designing a propeller, you need to decide what lift coefficient the propeller blade is going to be operating at for the design condition; particularly if fixed pitch. It can be constant along the blade, or vary if their are other design constraints affecting the blade design. Often it is...
  18. S

    Rethinking Propellers?

    I have not looked at the theory of a toroidal propeller, but my speculation is that there could be some incremental benefit for static and perhaps low speed thrust; similar to a ducted fan. The toroidal shape could be helping to mimic disk area flow profile of a ducted fan. IMO, you really...
  19. S

    Rethinking Propellers?

    According to the Sport Aviation article, yes. Here's a screen grab stating what Van provided the prop makers.
  20. S

    Rethinking Propellers?

    But that's not what you said in your quote that I referenced, repeated below: "Instead of pitch, props should be compared by equal blade angles at 75% diameter and tip. Assuming flat bottom. And equal blade area and diameter." There is no reason that to limit a comparison to diameter. It is...
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