1. ## Re: CAD Program for Aircraft Design

Originally Posted by loopy
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. ## Re: CAD Program for Aircraft Design

Originally Posted by cavelamb
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.

3. ## 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

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. ## Re: CAD Program for Aircraft Design

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

5. ## 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. ## 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. ## 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
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. ## 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.

Spar-Strut.zip

9. ## 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. ## Re: CAD Program for Aircraft Design

Originally Posted by Dana
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)