Decalage angle

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

Help Support HomeBuiltAirplanes Forum by donating:

  1. May 30, 2019 #941

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,824
    Likes Received:
    2,242
    Location:
    Port Townsend WA
    I think the engine above the wing (like that and Seamax) is less drag.
     
    Eugene likes this.
  2. May 30, 2019 #942

    AdvenJack

    AdvenJack

    AdvenJack

    Active Member

    Joined:
    May 11, 2019
    Messages:
    36
    Likes Received:
    21
    Location:
    Florida - Between St. Pete & Weeki Wachee
    SALUTE TO EUGENE'S RUSSIAN Experimental Thinking!!!
    Russian Philosophy On Fighter Jets -
    TOUGH, MANEUVERABLE, PRACTICAL!!!
    Certainly Worth Factoring Into Anyone's Thinking !!!

     
    Eugene likes this.
  3. May 31, 2019 #943

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    I was thinking about making nose sharper, but they tell me that this would be waste of time.

    fullsizeoutput_145c.jpeg fullsizeoutput_1463.jpeg fullsizeoutput_1596.jpeg fullsizeoutput_1468.jpeg fullsizeoutput_1467.jpeg
     
  4. May 31, 2019 #944

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,824
    Likes Received:
    2,242
    Location:
    Port Townsend WA
    Sharper won't help.
    Looking at that first photo (front view) the armpit area of the gear legs looks like a choke point for airflow.
    Angles less than 90° are not good. That's not a normal design feature and unique to that design.
    Could fill those armpits maybe to make it 90° to the fuselage. It is faired some but maybe not enough.
     
    Eugene likes this.
  5. May 31, 2019 #945

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    Here is another stupid question -

    - in level flight we are moving draggy object through the air. Drag of this object have center. We should try to install our engine inline with this center. If we don't = we will have moment arm = balancing drag.

    So, moment arm has nothing to do with CG, when we are talking about drag? Were CG is located vertical is irrelevant.
     
  6. May 31, 2019 #946

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    Its what I would call center of drag but since almost everything is below the thrust line then yes, there is a moment to consider. I said CG because most people understand that term better. When I design RC planes this is always something I consider.

    If you had a small turbine mounted behind the cockpit pushing through the center of drag/mass then this thread wouldn't exist. Well, maybe for the turbulence/stability issues
     
    Eugene likes this.
  7. May 31, 2019 #947

    Doggzilla

    Doggzilla

    Doggzilla

    Well-Known Member

    Joined:
    Jun 2, 2013
    Messages:
    1,793
    Likes Received:
    354
    Location:
    Everywhere USA
    Yes, CG has no effect on the moment arm of drag. They just use similar calculations, turned 90 degrees from one another. But are completely unrelated otherwise.
     
    Eugene likes this.
  8. May 31, 2019 #948

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    From Peter Garrison -
    "3. The flow over the aft portion of the fuselage is separated. This has the effect of immersing the stabilizer in a turbulent wake and reduces its effectiveness.
    The model I created does not include the boom, landing gear, vertical fin, or engine, whose effects on lift and pitching moment are small."

    So, nothing is black and white in aircraft design like I was thinking 3 years ago. Some very smart people still disagree on simple fundamentals. Like landing gear has small effect on pitching moment.
     
  9. May 31, 2019 #949

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    Thats why I suggested VGs earlier as it would allow for better flow.
     
    Eugene likes this.
  10. May 31, 2019 #950

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
  11. May 31, 2019 #951

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    Yes, but you may create a different trim condition so you may need to abort if it feels weird. Just a heads up.
     
    Eugene likes this.
  12. May 31, 2019 #952

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,518
    Likes Received:
    3,224
    Location:
    Memphis, TN
    One row of vgs will not help much. The whole back section should look like a windmill farm. VGs don’t stop the swirling as much as they suck it in , making the dead spot smaller. Or you could have little wings like German Touring Car Racing
     
  13. May 31, 2019 #953

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,824
    Likes Received:
    2,242
    Location:
    Port Townsend WA
  14. Jun 1, 2019 #954

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    My designer doesn't like vortex generators at all. Sure there is time and place for them. In his mind they always producing more drag than doing good. VGs can be used as temporary band-aide. If you need to use them = you made some kind of mistake. Correctly designed aircraft normally should not need them at all.

    I think by now we all agree that rear cowling on Skyboy was probably ok for 65 mph Quicksilver competitor with enclosed cabin. But for 100 mph aircraft I need to shape it differently.

    What I am trying to say, is that most likely rear cowling eventually will be completely or partially rebuild in to different shape in the future. So why couldn't I drill some holes to find out pressure drop. I really like that Idea. I can also build up using foam different shapes and test fly to find out pressure drop changes.

    Worst that can happened, that I will to fly to Oshkosh this year with 100 little holes in my airplane. So what! I can cut round 1" pieces of white tape to cover all holes. It will look cool! Nobody will ever know what is it. There is white tape on my airplane already everywhere you look!
     
    poormansairforce likes this.
  15. Jun 1, 2019 #955

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    Eugene, you are the definition of experimental aviation. We are all living vicariously through you. But you don't need that many holes!:)
     
    birdus, akwrencher and Eugene like this.
  16. Jun 1, 2019 #956

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    Screen Shot 2019-06-01 at 06.17.03.png Screen Shot 2019-06-01 at 06.15.37.png

    Can one of this bolts be used as test ports? I think test tube will go right over the threads on the inside.
     
  17. Jun 1, 2019 #957

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    They are button head so will give a higher reading if there is good flow over the surface because they will expand the air over the head. If the flow is stagnant then its good. But you don't know that yet.

    A hole that the tube itself can be squeezed into would work. It shouldn't protrude higher than the surface.
     
  18. Jun 1, 2019 #958

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,486
    Likes Received:
    6,241
    Location:
    97FL, Florida, USA
    Static ports that have proven to be accurate on several airplanes are made with a hole in the center of a disc about 1 1/2” in diameter that is raised about 1/8” above the fuselage surface.


    BJC
     
    poormansairforce likes this.
  19. Jun 1, 2019 #959

    Eugene

    Eugene

    Eugene

    Well-Known Member HBA Supporter

    Joined:
    May 26, 2017
    Messages:
    719
    Likes Received:
    131
    Location:
    Merrill, Wisconsin, USA
    Got it! Thank you! I will think about something, without spending $1000.
     
  20. Jun 1, 2019 #960

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    598
    Likes Received:
    130
    Location:
    Just an Ohioan
    Yeah, just like the ones I put on the Max. Thats why they are 1.5" diameter so the flow is straight across the hole. Well, as straight as can be on a small disk.;)

    If we make the air do work by flowing around a curve then it changes the air pressure. The button heads will do that. That was for general info since I know you know that.
     

Share This Page

arrow_white