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Thread: CAD Program for Aircraft Design

  1. #16
    Registered User cavelamb's Avatar
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    Re: CAD Program for Aircraft Design

    Quote Originally Posted by loopy View Post
    G'Day all, I'm looking for a decent CAD program that I can use to model a few designs I have on paper. Ideally, the sort of program I'd like would be: a) Easy to use b) Cheap! c) Have the facility to accurately model airfoil sections d) Able to integrate with a CFD program to calculate lift, pressure and drag coefficients for a design e) Able to perform "aeronautical" calculations on a design, such as calculating wing area, wetted area, etc f) Able to save in a format compaitble with a CNC mill or lathe Any help would be greatly appreciated, Brad
    Drawing airfoils is dead easy with Design CAD. That's because DC uses a cubic spline for a curve. I don't know of many others that do that. Anyway, draw a horizontal line and dimension it to 100 units long. Then working from the table of ordinates for the airfoil you want to draw, set points at those locations (using point relative from the leading edge of the line). When all the points are there, just wrap a curve around the points and save the file. Then, to set the actual chord length, just scale that 100 unit drawing by the chord length you want (in inches) and save it as a new file. And you can add offsets for skin thickness with a the parallel line command. It take me about 10 minutes do do one these days. As for the calculations part, you are dreaming of something that none of us can afford! That's what spreadsheets and programming languages are for. CAD and Spread Sheet. Tools of creation. Richard

  2. #17
    Registered User Jay Kempf's Avatar
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    Re: CAD Program for Aircraft Design

    Quote Originally Posted by cavelamb View Post
    Drawing airfoils is dead easy with Design CAD. That's because DC uses a cubic spline for a curve. I don't know of many others that do that. Anyway, draw a horizontal line and dimension it to 100 units long. Then working from the table of ordinates for the airfoil you want to draw, set points at those locations (using point relative from the leading edge of the line). When all the points are there, just wrap a curve around the points and save the file. Then, to set the actual chord length, just scale that 100 unit drawing by the chord length you want (in inches) and save it as a new file. And you can add offsets for skin thickness with a the parallel line command. It take me about 10 minutes do do one these days. As for the calculations part, you are dreaming of something that none of us can afford! That's what spreadsheets and programming languages are for. CAD and Spread Sheet. Tools of creation. Richard
    Cubic splines are in almost every CAD package now, even tunable versions of different linear algebra for curve fitting. The highest end packages have the best tools of course. I was always really impressed with the design CAD kernel for the price. It has a little bit of a learning curve but it really is a capable engineering package for even a small company. For an Individual it is really good and shines above all the others sub $100. I think I paid ten times that for it more than a decade ago back when 3.5" floppy discs were an amazing new invention.
    Jay K.

    VT USA

  3. #18
    Registered User cavelamb's Avatar
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    Re: CAD Program for Aircraft Design

    On the subject of computer aided Design...

    This is a simple minded old BASIC program.
    I have the .exe file and it does run on a XP box -
    as Win95 compatible.
    If anyone wants the .EXE just ask.
    Or maybe use it as a guide for your own wing
    design spread sheet?

    It might offer a quick and dirty way to get wing
    parameters in the ball park quickly.

    And it's kind of fun to look at numbers for say -
    a Bowing 747. Or Gossamer Albatross.

    Solve wing questions for Lift Velocity Surface Clift.
    Assign values to 3 parameters and solve for the 4th.

    'Wing.BAS
    'This was developed on a Tandy pocket computer.
    'But this file is from the QuickBASIC 4.5 compiler,

    FF = 0
    TT = NOT FF
    doRun = TT

    KK$ = "LVSCQF?"

    'initial values:
    L = 555
    W = L
    A = 55
    V = A * 1.4666
    Cl = 1.2
    S = 125

    DataFile$ = "Wing.Txt"

    CLS
    PRINT
    PRINT " Finite Wing Theory: ---== R. Lamb 1983 ==---"; : PRINT
    PRINT " Data file is "; DataFile$
    PRINT

    WHILE doRun = TT

    PRINT " solve for Lift Velocity Surface Clift Quit File [LVSCQF?] ";
    Z$ = ""
    WHILE Z$ = ""
    Z$ = UCASE$(INKEY$):
    IF Z$ = CHR$(13) THEN Z$ = ""
    IF Z$ = CHR$(27) THEN Z$ = "Q"
    IF INSTR(KK$, Z$) = 0 THEN Z$ = ""
    WEND

    PRINT
    SELECT CASE UCASE$(Z$)

    CASE "L"
    PRINT " Calculate LIFT.............."
    GOSUB doLift

    CASE "V"
    PRINT " Calculate Velocity.........."
    GOSUB doVel

    CASE "S"
    PRINT " Calculate Wing Area........."
    GOSUB doSurf

    CASE "C"
    PRINT " Calculate Coef. of Lift....."
    GOSUB doCL

    CASE "?"
    'GOSUB doDump
    PRINT
    PRINT " Variable dump:---------------------------"
    PRINT " Lift / Weight "; L; " lbs"
    PRINT " Airspeed "; A; " mph = "; V; " fps"
    PRINT " Coefec of Lift "; Cl
    PRINT " Wing Area "; S; " sq ft"
    PRINT " -----------------------------------------"

    CASE "Q"
    doRun = FF

    CASE "F"

    OPEN DataFile$ FOR APPEND AS #1

    PRINT #1, ""

    PRINT #1, "W=";
    PRINT #1, USING "#,###,###"; W;

    PRINT #1, TAB(15); "L=";
    PRINT #1, USING "#,###,###"; L;

    PRINT #1, TAB(30); "C=";
    PRINT #1, USING "#.###"; Cl;

    PRINT #1, TAB(40); "S=";
    PRINT #1, USING "####"; S;


    PRINT #1, TAB(50); "V=";
    PRINT #1, USING "####"; A

    CLOSE 1

    END SELECT

    PRINT

    WEND
    END


    doLift:
    GOSUB GetSurf
    GOSUB GetVel
    GOSUB GetCL
    L = .001188 * Cl * V * V * S
    PRINT " Lift = ";
    print using "#,###,###";L
    RETURN

    doVel:
    GOSUB GetSurf
    GOSUB GetCL
    GOSUB GetWgt
    V = SQR(L / (.001188 * Cl * S))
    A = V * .681
    PRINT " Velocity = ";
    PRINT USING "#,###.#"; A;
    PRINT " MPH = ";
    PRINT USING "#,###.#"; V;
    PRINT " FPS"
    RETURN

    doSurf:
    GOSUB GetCL
    GOSUB GetWgt
    GOSUB GetVel
    S = L / (.001188 * Cl * V * V)
    PRINT " Surface = ";
    print using "#,###";S
    RETURN

    doCL:
    GOSUB GetWgt
    GOSUB GetVel
    GOSUB GetSurf
    Cl = L / (.001188 * S * V * V)
    PRINT using " Coeff. Lift = #.###"; Cl
    RETURN

    GetSurf:
    PRINT " Wing Area (sq ft) ["; S; "]";
    INPUT ""; X
    IF X <> 0 THEN S = X
    RETURN

    GetVel:
    PRINT " Airspeed (mph) ["; A; "]";
    INPUT ""; X
    IF X <> 0 THEN
    A = X
    V = X * 1.467
    END IF
    RETURN

    GetCL:
    PRINT " Coeff. Lift (#.##) [";
    print using "#.###"; Cl;
    print "]";

    INPUT ""; X
    IF X <> 0 THEN Cl = X
    RETURN

    GetWgt:
    PRINT " Gross Weight (lbs) ["; L; "}";
    INPUT ""; X
    IF X <> 0 THEN
    W = X ' steady state W = L
    L = X
    END IF
    RETURN

  4. #19
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    Re: CAD Program for Aircraft Design

    Alibre 3d $99, has a CAM module also.
    Rich

  5. #20
    Registered User BoeveP51's Avatar
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    Re: CAD Program for Aircraft Design

    Realize this is an old thread but just found a reference to some CAD software called "SpaceClaim". Does anyone have some experience with this software?????

    SpaceClaim|3D Direct Modeling Software for Engineering, Manufacturing and CAE

    Merle

  6. #21
    Registered User cavelamb's Avatar
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    Re: CAD Program for Aircraft Design

    I've heard from a few folks who would like to play with these programs,
    but don't have the programming background (in ancient languages).
    So I've recompiled them using FreeBASIC to run on a windows machine.
    The zip file contains both the source code and executable files.

    WingX (listed up-thread) does simple wing parameter calculations;
    Area, Coefficient of Lift, velocity, and lift (weight).
    It assumes sea level standard day conditions.
    It was originally designed to run on a Tandy Pocket Computer.

    WingX.zip

  7. #22
    Registered User cavelamb's Avatar
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    Re: CAD Program for Aircraft Design

    This is the other program I posted a while back.
    It is a bit more ambitious - to design cantilever wing spars.

    It took a bit of rewrite to get it to compile, since FreeBASIC
    doesn't allow low level access to the underlying machine like
    QuickBASIC 4.5 did. And it doesn't like the dot notation I
    used back then (precursor to object oriented properties).

    I don't have all the resources that I did when I wrote this.
    But it still seems to be running right.
    Wouldn't hurt to give it a reality check or two.
    If you run into any problems with it, please let me know.

    SparX.zip

  8. #23
    Registered User cavelamb's Avatar
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    Re: CAD Program for Aircraft Design

    Another old program - calculates stresses in strut based spars.
    Not my code, so I can't offer the source.
    But might be helpful...

    Spar-Strut.zip

  9. #24
    Moderator Dana's Avatar
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    Re: CAD Program for Aircraft Design

    CATIA and Pro/E are far from cheap. And Autocad is quite obsolete.

    Dana

    If ignorance is bliss, why aren't there more happy people?

  10. #25
    Registered User Jay Kempf's Avatar
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    Re: CAD Program for Aircraft Design

    Quote Originally Posted by Dana View Post
    CATIA and Pro/E are far from cheap. And Autocad is quite obsolete.

    Dana

    If ignorance is bliss, why aren't there more happy people?
    They are cheap if you buy them from a street vendor in India or Taiwan (sorry in advance)
    Jay K.

    VT USA

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