Decalage angle

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Eugene, May 29, 2017.

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  1. Jan 13, 2020 at 6:24 PM #1541

    photocopter

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    Hey Eugene,

    I measured my total horizontal stabilizer (includes elevator) surface area and it is 19.33 square feet or 1.8 square meter.
    Hope this helps
     
  2. Jan 13, 2020 at 7:38 PM #1542

    Doggzilla

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    Yes, but why only in turns? During a turn the effective angle of attack would decrease because it’s inverted.

    Anyways, adding some foam to the bottom then sanding it into a wedge will eliminate that.
     
  3. Jan 13, 2020 at 7:58 PM #1543

    Aerowerx

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    Because the angle of the air flow is different on each side when in a turn??

    And the velocity of the air is more on the outside of the turn than the inside?
     
  4. Jan 13, 2020 at 9:48 PM #1544

    Doggzilla

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    That would affect the wing far more than anything attached to the fuselage, since it has both larger area and a much better moment arm.

    Its most likely that its changed the vortexes.

    The old design the vortexes would have come off wide near the landing gear. With this design they come off closer to the centerline near the new "beaver tail".

    As the angle of attack increases these vortexes will move from below the elevator to above them, as the flow bends and the tail lowers into in incoming flow.
     
  5. Jan 13, 2020 at 10:51 PM #1545

    Eugene

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    Thank you. My total horizontal tail is 21.2 sq.ft. with 10.5 feet arm to 25% of 60" chord on 138 sq. ft. wing. Unfortunately we need to know more to make statement about horizontal tail volume.

    Screen Shot 2019-03-02 at 22.27.52.png
     
  6. Jan 13, 2020 at 10:51 PM #1546

    Aerowerx

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    Which is covered by both of my statements, isn't it?

    Change the velocity or angle of the airflow and the vortexes would change.
     
  7. Jan 13, 2020 at 11:01 PM #1547

    Eugene

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    As aircraft parked level ground, I am holding digital level to the bottom of the wing (NACA 4412) and I see 2.2°vs 4.5° on original Skyboy. Doing same thing to flat stabilizer I have 3.5° vs 5.7° original.
     
  8. Jan 13, 2020 at 11:06 PM #1548

    Eugene

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    So, should I make conclusion that preferable shape of my fuselage must be as round as possible? So, it doesn't change airflow over the tail?
     
  9. Jan 13, 2020 at 11:10 PM #1549

    Eugene

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    Turning final at about 75-80 MPH - 4500-4700 RPM
     
  10. Jan 13, 2020 at 11:14 PM #1550

    Eugene

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    Eugene,

    I assume you will replace the ribbons with yarn.

    This will have to be rechecked with yarn tufts, but the disturbance aft of the prop suggests to me that you might as well get rid of that part of the fairing. Also, it strike me that the fairing is quite thick until near its trailing edge and then converges rather quickly. Shouldn't the fairing taper more gradually?

    If you got a 5-7 mph speed gain, that's good news. If it's at the same rpm as previous tests, then the power must be the same; it's not just due to the temperature.

    Peter
    [​IMG]
     
  11. Jan 14, 2020 at 1:28 AM #1551

    TFF

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    If you are measuring from the bottom of the airfoil, you are probably another +2 degrees from what you think. You need to build a rig board and that will be parallel to the cord line like this. I lifted it from the biplane forum.
     

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  12. Jan 14, 2020 at 2:06 AM #1552

    Eugene

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    Yes, I determined that long time ago that actual measurement will be at least 2°bigger than reading to the bottom of the wing. So, my actual wing incidence is 2+2=4°

    6CC60079-4BAE-4542-8A89-5EB823DEC0E6_4_5005_c.jpeg 354A2E8E-F917-4A5E-9FF9-7FEC77F168C5_4_5005_c.jpeg
     
  13. Jan 14, 2020 at 2:22 AM #1553

    Eugene

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    14260A79-2448-497E-A271-FBD28D580EFA.jpeg

    As with everything else on this project I am getting all kinds of different recommendations. So, I created a little picture to make sure that we are talking about the same thing. Some people suggest that area A should be eliminated. Some, like Peter believing that area C not needed at all. And some think that this whole thing should be shorter and area B should go away. I will not do anything too quick at this point. You always can cut things easier then put them back on.
     
  14. Jan 14, 2020 at 3:46 AM #1554

    Doggzilla

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    During high angles of attack vortexes will come off the sides. The tail is likely hitting those vortexes.

    This is caused by the air pouring off the sides during high angle of attack.

    Two things can be done. Add sheet metal to the rear to make it a "sword tip", because reverse sweep tends to pull air inward instead of towards the tips. But this alone will do little.

    What is more important is to add small fences to the belly to keep the air from rolling out from under it at high angle of attack.

    Fences are just strips of metal that interrupt flow from side to side. They run with the airflow and add very little drag.
     
  15. Jan 14, 2020 at 4:27 AM #1555

    Eugene

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    Pretty cool explanation. It is turned out to be pretty large area or pretty large wing. I need to sit down and try to put it on paper. So I can see how rolling out vortexes hitting horizontal and vertical tails.

    0F74C996-C6AC-4D65-8482-D39441319C61_1_201_a.jpeg
     
  16. Jan 14, 2020 at 12:07 PM #1556

    Eugene

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    Peter Garrison
    Jan 13, 2020, 10:40 PM (7 hours ago)
    [​IMG]
    [​IMG]
    to me
    [​IMG]

    It does look as if you could dispense with C and blend B into the boom with a sharp trailing edge. Air appears to be flowing up around the edge of A, so maybe you could taper it inward (as you have shown) and make it more rounded. It would also be interesting to put a camera on one of the wheel pants to see what flow looks like on the bottom.

    CBE73D82-B34D-43A0-9961-837DDFB08BCB_1_201_a.jpeg
     
  17. Jan 14, 2020 at 12:11 PM #1557

    Eugene

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    Maybe it will look like this picture. ? They need to land on water, so its different

    B4956BB4-835D-46E9-9842-3677AEA5500D.jpeg
     
  18. Jan 14, 2020 at 2:03 PM #1558

    Eugene

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    453E511F-26F2-47E6-B305-3989E3711227.jpeg

    Hopefully I understand message from Peter correctly. We will see
     
  19. Jan 14, 2020 at 3:19 PM #1559

    photocopter

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    Now I understand what you need. As soon as the weather gets better i will measure all the data for you
     
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  20. Jan 14, 2020 at 3:21 PM #1560

    Aerowerx

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    Why not go from the leading point of "A" back to the trailing point of "C", avoiding any sharp corners and trailing edges. Make everything a smooth transition.
     
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