Engine size developement in jet aeroplanes !

Discussion in 'Hangar Flying' started by topspeed100, Mar 21, 2013.

Help Support HomeBuiltAirplanes Forum by donating:

Thread Status:
Not open for further replies.
  1. Mar 26, 2013 #21

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
  2. Mar 26, 2013 #22

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    Does this look any better now ?
     

    Attached Files:

  3. Mar 26, 2013 #23

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    Better than what?
     
  4. Mar 26, 2013 #24

    bmcj

    bmcj

    bmcj

    Well-Known Member HBA Supporter

    Joined:
    Apr 10, 2007
    Messages:
    13,075
    Likes Received:
    5,005
    Location:
    Fresno, California
  5. Mar 26, 2013 #25

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    The earlier sketch.

    The numbers for speed come from regular automotive drag equation.
     

    Attached Files:

  6. Mar 26, 2013 #26

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    Cars push on a solid surface with their power.
     
  7. Mar 27, 2013 #27

    highspeed

    highspeed

    highspeed

    Well-Known Member

    Joined:
    Apr 10, 2011
    Messages:
    275
    Likes Received:
    13
    Location:
    Spring, TX
    I don't think you're doing your drag buildup correctly. BTW, aircraft drag coefficients use the reference wing area.
     
  8. Mar 27, 2013 #28

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    That is correct I just wanted to see if the frontal area study with general drag coefficient gives any hint of the speed. I also compared the Folland Gnat fighter along with it ( frontal 1.76 m2 and 20.9 kN power ).
     
  9. Mar 27, 2013 #29

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    You can't use supersonic theory trans-sonic. At the compressibility front air turns to concrete.
     
  10. Mar 27, 2013 #30

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    I wasn't referring to that...I am just figuring that if I have 11% less frontal area, 20% more power and 30% more efficient sharper into supersonic reagion made plane ( with almost no interference drag ) I could keep the Gnat sized plane in supersonic region longer than a Gnat that just went into supersonic in a dive !

    The least steep angle in my design in 31 degs...and in Gnat the steepest is 43 degrees ! So Gecko is kinda like " ULTRALITE SR-71 " on steroids !
     

    Attached Files:

    Last edited: Mar 27, 2013
  11. Mar 27, 2013 #31

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    And it is that sort of over generalization that gets you in trouble every time. It just doesn't work like that but you don't have any interest in doing some basic research on the claims you make before you make them so no one can help you with that. 20% more of this, 30% more of that, 50% less of that... But wait, there's more, you also get our 6 steak knives for free if you just call with a credit card within the next hour.

    Everything in the world is not linear and especially not scaling of aircraft.
     
    ultralajt likes this.
  12. Mar 27, 2013 #32

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    Fancy words Jay Kempf !

    I call my approach just common sense and reasoning. I just wish I had money to buy an aerodynamist to prove it for you ( like Howard Hughes had ).
    I am talking about measurable facts..not steak knives.

    rgds,

    Juke
     
  13. Mar 27, 2013 #33

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    You want to design aircraft and make claims about performance but you don't want to learn anything about aircraft design? There are people here just like what Howard Hughes had on staff and they tell you to go learn to do some basic estimating but you would rather make claims and not have any foundational math to support them. When you start talking like you are marketing a new design that is supersonic, super cruise, and you have already made drag, speed, takeoff and landing distance, and other claims that are divergent from science you will get opinions, just like you would get from someone you were paying to give them to you.

    So which of your "facts" are measurable? That you drew a 2D plan view and calculated the area and so you now know the lift, drag, yadda.... or you drew a front view and you now know the CD of the airframe so you know how far past supersonic it will go given a thrust? Those are "facts" and measurable? This is where you always get yourself into trouble. You can think about these things all day long. You can sketch and calculate to your hearts content. No one cares. But when you share them with the intent of impressing people on this forum how good of a technologist you are you just make yourself look like a dolt. Your approach isn't common sense. It's like watching someone trying to do a Calculus proof without knowing Calculus. Three dimensions are linear in their representation in the world we live in. Past that almost nothing is linear except your "methods."

    Here's a graph for you... I am sorry it isn't very linear:

    Transonic Drag Rise
     
  14. Mar 27, 2013 #34

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland
    I am a professional who designs 3D objects for living...I have ability think spatially...this is very rare among many people. This could be more common ability among aviation engineers and artists etc. Besides I have done millions small models as a kid and even pinched a hole on all my Airfix models wings and tied a fishing string there and started swinging them around at age 12 to find out how they all react to different angles of attack and elevator deflections adding weights etc. Then CL models and free flite and finally R/C at 16 when I got my first FUTABAs. My best ability lies there and really not in calculus...my problem actually is calculus...I never had an A in highschool in calculus...exept for the exams where I got my first and only A ( I had advanced calculus ). Enough to get me to study architecture. I would have never made it to study here aviation engineering...because it is all just god **** boring f****n calculus !

    But anyway...I liked the curve...since it seems that there is less drag after you have punched the hole in the sky !

    Thanks Jay !

    About the measurable facts...well I know that I have enough lift and right geometry to go supersonic..foil is nearly symmetrical thickest at 40% and 6 % thick.

    I use Helwan and Super Mystere as roadmap to see what kinda monsters in history have gone supersonic in level flight and which only reached there in a dive ( supposedly Dh 108 and Me 262 ...and of course Gnat, F-86 and Mig 15 ).

    PS: I really don't give a rats arse about what people thinks about my methods...I sure as hell know I am right about this.
     
    Last edited: Mar 27, 2013
  15. Mar 27, 2013 #35

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    3D linear thinking is a trap. If everything is 3D linear then it limits your realm of thinking. One can superimpose as many variable as one would like against a single reference such as time. It is not intuitive thinking but there are tools and methods for reconciling these sorts of diagrams such that one can visualize interrelationships between related factors in a calculation. This is what you are not willing to do.

    You looked at that graph and your conclusion was that there is less drag after you punch through the threshold of compressibillity. That is incorrect. What the graph shows is that the drag at compressibility spikes almost infinitely but not quite and then settles back to very high drag requiring tons of thrust to overcome as compared to below the compressibillity threshold. And that is exactly why your frontal area drag estimate and your linear scaling estimate is just plain wrong. With compressibillity you can't make assumptions like density is a constant. That's why solvers for flows are completely different for all these sorts of regimes of flight.

    But you "sure as hell know" you are "right about this." Which is one of the definitions of mental illness.

    How would Homer Simpson approach design?
     
  16. Mar 27, 2013 #36

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland

    Jay you seem to be qualified shrink as well !

    Well I just counted that BELL X-1 had 3.2 m2 frontal area ( more than double the amount in Gekko and Gnat ) and only 26.7 kN of thrust ! It also featured smaller but thicker wing.

    Guess what it went Mach 2.2+ and into 27 km altitude. It was also pretty heavy device.

    So since Gnat was capable of 1120 km/t at 6 km ( mach 0.984 -0.99 ). I am also inclined to think it would have gone mach 1+ with 26 kN.

    This is cold reasoning and not very academic I admit.

    Have a good day !

    Bell X-1 - Wikipedia, the free encyclopedia
     
  17. Mar 28, 2013 #37

    highspeed

    highspeed

    highspeed

    Well-Known Member

    Joined:
    Apr 10, 2011
    Messages:
    275
    Likes Received:
    13
    Location:
    Spring, TX
    I usually stay out of this sort of thing, but you're missing a critical concept of supersonic aerodynamics. Wave drag is a function of the distribution of the cross sectional area, not frontal area.

    Volume Wave Drag
     
  18. Mar 28, 2013 #38

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,734
    Likes Received:
    996
    Location:
    Warren, VT USA
    It is most likely pointless to try...

    "Don't confuse him with facts. He has made up his mind." (this quote I attribute to my mother, although she didn't make it up, she used it a lot.)
     
  19. Mar 28, 2013 #39

    topspeed100

    topspeed100

    topspeed100

    Banned

    Joined:
    May 4, 2009
    Messages:
    4,063
    Likes Received:
    63
    Location:
    Oulu/Finland

    Hello highspeed I do appreciate your concern, but....

    My entire concept is based on this....area ruling in english !

    All my slower prop designs feature the " POOR MANs AREA RULING " so I wouldn't miss the real thing on my jet...would I ?
     
    Last edited: Mar 28, 2013
  20. Mar 28, 2013 #40

    koha

    koha

    koha

    New Member

    Joined:
    Dec 19, 2010
    Messages:
    1
    Likes Received:
    0
    Location:
    Finland
Thread Status:
Not open for further replies.

Share This Page



arrow_white