Decalage angle

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

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  1. Jun 26, 2019 #1121

    plncraze

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    Try to park into the wind. There are videos online of people in the wind tunnel with a smoke wand. It will be interesting if it works and what it looks like behind the cabin.
     
  2. Jun 26, 2019 #1122

    Hephaestus

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    I'm personally curious about interference drag around the LG/fuse because essentially it looks like you have 2 separate areas of interference drag. Basically like a biplane. I know people say high wing it matters less but then wittmans tailwind is revered for how he's handled it...
     
  3. Jun 26, 2019 #1123

    Eugene

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    Wondering, if I should fly into the wind instead of just parking, for better results ?
     
  4. Jun 26, 2019 #1124

    plncraze

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    Remember you only have so much smoke and it might be hard to get a good picture in flight
     
  5. Jun 26, 2019 #1125

    Eugene

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    It is easy to do experiment, it’s not like I will blow up $5000 doing it
     
  6. Jul 2, 2019 #1126

    Eugene

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    5F526F6D-2DD5-42B7-A8A7-15DF917377F2.jpeg 164326F3-3621-4114-A2BF-1C867F85C063.jpeg
    Looking at this numbers, I am making conclusion that my horizontal tail should be two times bigger !!!
     
  7. Jul 2, 2019 #1127

    Eugene

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    Nesmith Cougar is more or less same as Tailwind. Why does it need Vh 0.48? Maybe that is why decalage is only 1°
     
  8. Jul 2, 2019 #1128

    Eugene

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    fullsizeoutput_1751.jpeg
    Here is my smoke test from this morning.

    Looks like I need to find 100 stronger smoke generator.
     
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  9. Jul 3, 2019 #1129

    Doggzilla

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    Yes, they are not very powerful. Most are used in low light with a spotlight of some sort.
     
  10. Jul 3, 2019 #1130

    Eugene

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    fullsizeoutput_1754.jpeg

    For 101-st time I am trying to replay in my head relationship between this three points on standard Skyboy in level flight at 85 MPH.

    So, all this points - A, B and C in harmony in cruise and aircraft is moving through the air with 4.5° AOA.

    What can I change? I can reduce pressure on point A and we all know what will happen. Speed will go down, AOA will get larger, pressure on point B will go down, point C will need smaller AOA to match new smaller moment between A and B.

    What else can I do? Can I increase pressure on point A ??? No, I don't have money for bigger engine! And I don't think this will be very good idea anyway.

    I can also with aerodynamic clean up reduce drag and pressure on point B. What will happened after I do that - not so clear to me:
    - so, we abruptly reduced pressure on point B by 10%
    - speed will go up and AOA will get smaller
    - smaller AOA will give us wing drag reduction
    - speed will stop moving up after pressure at point B will match pressure at point A
    - horizontal tail is moving up an 2 things is happening at the same time: #1 - stabilizer is getting larger AOA and #2 - airflow velocity increased. So we will need to change trim setting.

    So, if I am correct in my thinking, if I find the way to reduce drag and aircraft will move a little faster. At new higher speed my stabilizer and elevator will be inline again!

    So, maybe Peter Garrison is correct - all I need is to reduce drag. That simple!
     
  11. Jul 3, 2019 #1131

    BBerson

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    In post 1128, it looks like your stabilizer is even with the horizon, not -5.7° (maybe even + 2°)
     
  12. Jul 3, 2019 #1132

    Eugene

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    Yes that is correct. My decalage now is 6° vs 10.2°on standard Skyboy. But my elevator needed to help stabilizer in level flight. You can see it on my pictures. I was just wondering if I ever will get a little faster as a result of drag reduction. Maybe elevator will get inline with stabilizer?
     
  13. Jul 3, 2019 #1133

    Hephaestus

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    Well, my .02
    wing incidence is set to make lift needed at speed X.
    You either need to make the wing create more loftso it needs less incidence to make that lift at X...
    Or you need to drop weight... So it needs to make less lift at X.

    What do your ailerons/flaps look like? Possibility to add reflex? Not exactly a minor change...

    If your tail surfaces are big enough you could eyeball an electric jackscrew to tweak the angle of the horizontal see if you can trim it out and how it's affected by speed changes.

    Not even close to reasonable solutions to the normal mortal man... But normal mortal men fly Cessnas
     
  14. Jul 3, 2019 #1134

    Eugene

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    Why doesn’t anybody ever understanding what I am trying to ask? Not even my own wife ?

    Let’s try this one more time in Russian.

    Picture of my horizontal tail in flight suggests that tail is undersized or doesn’t have sufficient angle of incidence.

    If I can find magic way to clean up total drag on my airplane, speed will go up with same engine power. Moment between point A and point B will be the same, because engine power did not changed. But we will have a situation with higher speed and smaller angle of attack on the wing. That part is clear to me and I don’t have any questions here.

    Question is about horizontal tail. It will need to deal with exactly same moment generated buy points A and B, but will be doing that with increased air velocity. Stronger airflow over the tail might be sufficient enough for stabilizer generate enough down pressure without help from elevator at the same angle of incidence.

    In addition to that increased air velocity, as angle of attack on the wing is getting smaller, angle of attack on horizontal tail is getting larger by same amount. This change on angle of attack might be sufficient by its self to generate more down pressure even at the same speed.
     
  15. Jul 3, 2019 #1135

    poormansairforce

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    I understand what your asking and we have been talking about it for several pages. But crazy russian doesn't do anything about it!:D
     
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  16. Jul 3, 2019 #1136

    Eugene

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    All I want you to tell me, that my logic is correct.
     
  17. Jul 3, 2019 #1137

    BBerson

    BBerson

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    Yes, it will require magic to make it go faster.
     
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  18. Jul 3, 2019 #1138

    poormansairforce

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    I do agree with you but as others point out it is hard to get the last bits of it.
     
  19. Jul 3, 2019 #1139

    Eugene

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    Thank you! That made my day! I will be walking around for rest of the day with my nose pretty high!!! And I will tell my wife that I am not so stupid after all!!!

    As far as how to get there .......?

    I am sure in a few weeks I will find many smart people at Oshkosh, who will teach me what to do.
     
  20. Jul 3, 2019 #1140

    poormansairforce

    poormansairforce

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    Well, see now, if your using my brain as a measuring stick then your wife may be right!:D
     
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