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  1. davefried

    Putting a tapered wing on an RV

    oops, here is the polar...
  2. davefried

    Putting a tapered wing on an RV

    This is the polar comparing the original wing and the tapered. Original wing: Min Drag 136.6 lb @ 92.4 ktcas L/D max = 12.08 Flat plate area 2.359 ft^2 Tapered wing: Min Drag 123.9 lb @ 89.7 ktcas L/D max = 13.31 Flat plate area 2.273 ft^2
  3. davefried

    Putting a tapered wing on an RV

    Something to compare to... The CAFE Foundation did an APR on an RV-6A. The aircraft was instrumented and carefully tested. Having nothing else, and for the sake of the discussion I will use it to illustrate what I did. http://cafe.foundation/v2/pdf_cafe_apr/RV-6A%20Final%20APR.pdf The...
  4. davefried

    Putting a tapered wing on an RV

    I'm sure that there are differences but since all I have is the modified condition there is nothing to compare. Subjectively it is an RV-6, I can use the math to talk about the differences. If I had a before and after I would need some carefully controlled conditions to be objective as you said.
  5. davefried

    Putting a tapered wing on an RV

    I wasn't offended only surprised that you maintain a simple aero cleanup would produce performance gains in excess of a planform change. Do they have to compete? I would love to see an RV pulled from a close tolerance mold with all of the tweaks to the surfaces, gaps and cooling flow that you...
  6. davefried

    Putting a tapered wing on an RV

    The comment about details/fit/finish/etc. typically making more of difference to performance than wing planform is a bit of a stretch. I am sure that there is some variation between different versions of the same aircraft due to fit, finish and other installation choices, that's typical...
  7. davefried

    Putting a tapered wing on an RV

    No spins thanks. Remember the posts about the change in fin size going from RV-6 to 7?
  8. davefried

    Putting a tapered wing on an RV

    Here is a wing planform where Schrenk will predict zero lift at the tip. Not the best way to increase effective aspect ratio as the tip vortex is looking for an edge out at the tip to attach to. This one will attach somewhere between the tip and the aileron edge.
  9. davefried

    Putting a tapered wing on an RV

    You certainly have given this some thought. How does Schrenk compare quantitatively with the method you referenced in TOWS? Just saying... If the planform analysed with Schrenk happened to have rounded tips, the resulting lift distribution would go to zero at the tips. A wing with an...
  10. davefried

    Putting a tapered wing on an RV

    I didn't think I was the only one who thought that way. Sometimes you just want to do something different. Best of luck with your project.
  11. davefried

    Putting a tapered wing on an RV

    Where has the passion gone? Lost in a sea of sameness.😉
  12. davefried

    Putting a tapered wing on an RV

    I have had no problems with the way it handles. The taper is moderate and the resulting spanwise location of Clmax is at 40% span... it behaves. Perhaps there are corners to the flight envelope yet unexplored that might might reveal something interesting. The basic design has good bones, lots...
  13. davefried

    Putting a tapered wing on an RV

    What does your lift distribution look like and how does taper change it? Do you have a reference for your model?
  14. davefried

    Putting a tapered wing on an RV

    From the numbers you posted, this is the wing planform I came up with... Cr @centre 59.74 in Cfus @ y=12 in 58.00 in Ctip 38.00 in Cbar 48.87 in Taper Ratio 0.64 S...
  15. davefried

    Putting a tapered wing on an RV

    Fenix: Your wing is very close to mine. If you could post the following numbers I will run them through my Schrenk spreadsheet and post the result. Chord at fuselage side Spanwise location of above Tip chord Span Twist The Schrenk "approximation" is here and is easy to recreate. I have added...
  16. davefried

    Putting a tapered wing on an RV

    Stall speeds I used Schrenk to determine the speed at which the wing would reach the airfoil’s maximum section Cl somewhere along the span. This is just the wing only and lift may continue to increase for a bit before the stall completely develops. There is a component of lift generated by the...
  17. davefried

    Putting a tapered wing on an RV

    Looks like they slip onto a metal stub spar and are held with two pins. Rear spar fitting still to come?
  18. davefried

    Putting a tapered wing on an RV

    On the original wing, flaps start at Y = 20 and extend to 78 in. Ailerons extend from there to 126 in, 12 in from the tip. Percentage of wing area ahead of flaps is 42.0 and 34.8 for ailerons. On the tapered wing, flaps start at Y = 20 and extend to 90 in. Ailerons extend from there to 140 in...
  19. davefried

    Putting a tapered wing on an RV

    Different wing on the RV-7, 25 foot span and 121 ft^2 wing area.
  20. davefried

    Putting a tapered wing on an RV

    Directional stability I did a static stability analysis to determine if the vertical stabilizer remained suitable. The big driver is the tail contribution and that has a volume coefficient impacted by the change in wing planform. VT volume = (Sv/Sw)*(lv/bw) The original planform...
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