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Released DG-100 Update #6

Discussion in 'Air' started by Phil--king, Mar 23, 2019.

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  1. cgjunk

    cgjunk
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    Thanks for the info! I’m going to make a couple of requests....any chance a yaw string would actually work, for real? I’ve noticed a tiny bit of uncoordinated flight totally spoils lift.

    Also, It seems this one doesnt have trim. Do gliders in general usually have trim, or are they set up naturally for best glide?
     
  2. Phil--king

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    Indeed a yaw string would be awesome. but atm i have absolutly no idea how to implement it.

    As far as I can remember gliders only have a trim for pitch, due to changing weight distribution front-back.
     
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  3. default0.0player

    default0.0player
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    The handling is a bit weird, when I aileron right it seems rudder left by itself.
    Also the thermal indicator is pointing left when the aircraft is too far left, should be pointing right
     
  4. cgjunk

    cgjunk
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    The weird handling is what makes it so realistic! What you are describing is called adverse yaw. It’s mostly caused by the higher amounts of drag the high side wing is making (because it’s the wing making most lift). Using only ailerons to change direction causes this yaw, and would be known as an uncoordinated turn. You need to lead turns with a touch of rudder, then roll, in order to have a coordinated turn.

    Most airplanes have an instrument called a “slip ball” that you use to help keep your turns coordinated (ball centered). Gliders usually have a piece of string taped to the canopy that serves the same purpose (keep the string straight down the length of the craft.)
     
  5. default0.0player

    default0.0player
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    Well, reailism does not mean difficult flying. I do fly RC model aircraft IRL, from powered glider to racing drone, and I do experience adverse yaw. However this mod adverse yaw is somewhat exaggerated.(see picture) BeamNGdrive-015067990-RELEASE-x642019_4_213_39_32.png
    I understand nothing is perfect, some real-world pilot said that Microsoft Flight Simulator exaggerate P-factor.

    Is that any way to "tune" an airplane? such as increase yaw stabiity.

    UPdate: I found the problem. It's the lift vactor tilted. Adverse yaw is caused by lift-induced drag, down aileron produce more drag than up aileron. BUT when you roll the airplane the lift vector is no longer stright up, but tilted forward, thus yaw the plane much more than adverse yaw itself.
     
    #45 default0.0player, Apr 2, 2019
    Last edited: Apr 2, 2019
  6. Phil--king

    Phil--king
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    Reducing the adverse yaw is not a big deal . I just have to reduce the drag of the aileron .

    But sth. else: Does somebody know how to move a vehicle with lua script (not the engine lua) ?

    Edit: Forget about the lua script move stuff. I actually found solution but this leads to a fight between the game engines physics and the vehicle lua script. I'll trying to find a cheaty solution again :D
     
    #46 Phil--king, Apr 2, 2019
    Last edited: Apr 2, 2019
  7. cgjunk

    cgjunk
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    Well, Im definitely not an aeronautical engineer, so Im not sure if lift vectors would change with aileron input, but it stands to reason that it may; since the shape of the effective airfoil is changing with aileron input, maybe even the effective angle of attack changes too. Not sure about it though, who knows, maybe it should tilt back?

    In any case, it seems Phil-king said the drag is tunable. So it may come down to taste. The last time I flew was in my youth some 29 years ago. But the Cessna 172s and and various Piper rentals I flew around were definitely not “feet on the floor” airplanes. Aileron only input, especially larger deflections, would have the nose swinging noticeably opposite roll. The slower you went, the more noticeable. In fact, in maneuvering flight near the ground (ie pattern work), you needed to be diligent about rudder use. It was constantly drilled into students, that uncoordinated flight near the ground was tempting a stall/spin situation. By the way, Pfactor was also very noticeable at high AOA on the C172, especially on the model I used, which had 20 extra horsepower (doesnt sound like much, but that really woke the plane up :) ). Full power while maintaining speed a little bit above stall speed needed almost full rudder from what I recall.

    A glider, due to the high lift, slow speeds, and leverage the wingspan can generate, would only add to the adverse yaw potential. Im sure IRL, significant aero magic goes into reducing the tendency, but Im sure constant rudder input is necessary. But in the end, in a sim it comes down to “taste”, preferably the “taste” of someone with experience in a similar type aircraft. I’d like to be that guy, but I need to lose at least 40lbs to get myself wedged into one of these gliders ;)

    This is a sim, which cant really replicate all the feelings of flight, but I didnt get the sense the the adverse yaw was out of hand, at least compared to a shorter wingspan c172. Ill fly it around
    some more just to get a better sense though.
     
  8. default0.0player

    default0.0player
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    Thanks for the reply, opinion form a pilot is nice.
    About flight simulators, did you know that in MSFS Pfactor was also very noticeable at low AOA on the C172, when level cruising at speed some rudder is still needed. Some one created a Fw-190 mod for MSFS and in the discussion thread some people(including real-world Fw-190 pilot) said p-factor is noticeable at cruise. Also in MSFS some people noticed that when flying inverted the adverse yaw becomes "proverse yaw" i.e the flight model feels "scripted".

    About adverse yaw in BeamNG.
    The picture is #45 showed that the yaw is mostly caused by the tilt of the lift force. In other words, even the author adjust the aileron have zero drag there's still noticeable yaw to the opposite during a roll. Even you use rockets/thrusters to roll the aircraft there still opposite yaw. The yaw is only partially caused by aileron deflection/induced-drag. Of course high adverse yaw on glider is realistic but this is still an approximation.

    I'm not asking the author to adjust the flight model to fit "taste". I'm just explaining that adverse yaw in beamNG is somewhat different compeared to real-life counterpart. So you cannot tune BeamNG flight characteristic according to real-life knowledge.
    --- Post updated ---
    Gamergull is a professional of moving vehicle via LUA, ask him.
     
  9. cgjunk

    cgjunk
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    MSFS is what got flying into my brain way back in middle school, running on color Apple II E. My math teacher let me play it whenever I was done with my assignments, and I loved the guy for it. I was still an avid simmer when I got my private pilot license back in the mid 90s, and as a matter of fact, made my training go a lot quicker. I stayed with MSFS until it died it's slow agonizing death. All throughout that time, I tried not to mind that it felt totally scripted. Because, yeah... it was scripted. :p My favorite was being able to stall helicopters if you tried to slow down to a complete hover.:confused: Ahh, those were the days....completely infuriating. They improved that in later years, but it still felt you were flying around a hacked variation of the C172 flight model. Xplane made me feel better, but the eye candy that MSFS had was sooo much better. My experience with scripted type modeling led to feelings of awe when physics-based sims like ROR and BeamNG started coming out.

    Now I'm not sure if I understood you correctly, and I'm not sure I'm interpreting your picture correctly. Are you saying the "down aileron" wing has a forward vector to it's lift? Is the forward lift vector symmetrical on both wings in level flight, and does the forward vector increase asymmetrically during aileron input (more on the high lift wing)? Wouldn't that have the effect of pulling the wing forward, and thus reducing the adverse yaw? Also, how did you get that picture, and does it work "live".... that's pretty cool :)

    Agree, it seems to me that there is some hackiness to the variables in BeamNG with regard to flight. I'm not blaming the developers, since it's not supposed to be a flight sim. But I agree with you that you cannot tune BeamNG models as if this were a finite-element analysis type sim, where you put in variables like surface area, weight, camber, chord, etc, then hit "calculate". But, from what I've seen others do, you can tune variables in a predictable manner to simulate things like drag, lift, etc. I got a chance to offer feedback on Darren9's helicopter "SuperGnat" while he was developing it, and was impressed with what he could approximate with just a little verbal feedback. Things like blade drag had to be simulated with fake invisible spoilers to get it to autorotate in a half believable fashion, but it flew in a believable fashion. I can't vouch that it's a perfect representation of a light heli, but holy cow did that machine give the feeling of rotary flight. That is what I mean by "tuning to taste" or until it feels right. Perhaps Xplane is capable of simulating flight with just measurements and numbers because of how the program simulates flight, but that won't work for Beam.....yet :)
     
  10. default0.0player

    default0.0player
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    I can barely explain that due to my poor English, sorry. I'm saying the "down aileron" wing has a backward vector to it's lift, exaggerating the adverse yaw.

    Please let me explain this again.
    You bank the aircraft via aileron input. IRL The adverse yaw is most significant when you initiating the roll. For example banking right you apply right joystick, left aileron down and right aileron up, at this time left lift is bigger than right lift force, so do the induced drag. This is where you experience the most significant adverse yaw. However when the roll rate stabilize, both the joystick aileron input and the angular velocity stabilize the left wing lift and the right wing lift are nearly the same, because the AOA difference between left and right is cancelling out aileron input. At that time the adverse yaw is significantly less compare to the time you had just initiated the roll.
    In BeamNG you get this high adverse yaw during the entire roll, not just during the start of the roll.
     
  11. fufsgfen

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    There is no turbulence, also every coltris sees the wind, so there is nothing to block the wind, those alone make things rather different from reality.

    Connected coltris are averaged though, but those that are isolated are not affecting any other coltris.

    So one have to find a way how to get decent behavior with fairly largely simplified means.

    Lift comes from angle coltris faces movement of air, not from shape of the wing, so naturally all values and structures need to be tuned to deliver desired result and everything realworld data offers is a goal to aim for, means to get there are completely free from chains of reality.
     
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  12. Phil--king

    Phil--king
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    Just a few sentences to the new update.

    The thermals increases their size and force with increasing altitude but they decrease if you are to high.
    Furthermore the downwards moving air has now it's own spot. Just like an anti thermal.

    The aircraft breaks if you pull the elevator to the limit and you airspeed is in the yellow range.
    I reduced the advers yaw a bit.
     
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  13. Bluedevil

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    Hey phil--king, I just wanted to say that i don't understand why your thermal lift is like this ?
    It's a strange shape for a thermal lift, to me a thermal lift have a shape more like a spring or a vortex or a vertical cylinder like this :
    https://en.wikipedia.org/wiki/Lift_(soaring)#/media/File:Thermal_column.svg
    And yeah I saw that you had an idea to do a trailer for this glider and this is a superb idea ! Maybe also if you want to do a jet powered glider or a winch to launch the glider, the more realistic option is the second one because the DG 100 didn't had a jet engine or motor.
    By the way I looove your work. Keep going.
     

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  14. Phil--king

    Phil--king
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    My graph of the thermal doesn't show it's shape. I know it's a bit missleading, but the x-axis (red) is set as the horizontal distance from the center of the thermal spot to the aircraft. The y-axis (green) is the vertical distance between the aircraft and the "vertical center" of the thermal and the passed time - because it moves updwards. The blue z-axis displays the resulting lift of the thermal. Now if you draw its shape in a 3D-Space it would looke like a tube with a constant radian. It fades in at the top and fades out at the end. But with the Update #6 I changed the shape of the thermal to a better matching Approximation, which should almost look like the one in your picture. ;)
     
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