Program was written in Basic, specific to the Tandy Color Computer I had at the time.  On the next page is an Excel Spreadsheet.

30 REM SPAR LOAD CALCULATION

50 INPUT "ENTER  WING SPAN INCHES"; S

70 HS =S/2 'HS IS 1/2 SPAN

90 INPUT "ENTER SPAR DEPTH IN INCHES; SD

110 INPUT "ENTER SPAR WIDTH IN INCHES"; SW

130 INPUT "THICKNESS OF SPAR CAP"; CT

150 INPUT "WEIGHT OF AIRPLANE IN POUNDS"; W

170 INPUT "DESIGN LOAD FACTOR"; L

190 'HL=LOAD SUPPORTED BY ONE WING PANEL  (HALF TOTAL WEIGHT TIMES THE LOAD FACTOR)

210 HL=W/2*L

230 ' RS=LOAD AT WING ROOT

250 RS=HS*(HL/2)

270 REM J IS THE DISTANCE BETWEEN THE SPAR CAPS

290 J=SD-(2*CT)

310 ' C IS THE MOMENT OF INERTIA (THE ABILITY OF THE SPAR CROSS SECTION TO RESIST LOADS)

330 C=(SW*(SD^3-J^3)/12)

350 ' E IS THE DISTANCE FROM THE NEUTRAL AXIS (CENTERLINE BETWEEN THE SPAR CAPS FOR EQUAL CROSS SECTION CAPS)

370 E=SD/2

390 Z=RS/(C/E)

410 'Z IS THE MAXIMUM STRESS IN PSI SUSTAINED BY THE SPAR CAP

430 'LINE 450 ASSUMES 9000 PSI AS THE MODULUS OF RUPTURE OR MAXIMUM STRESS SPRUCE CAN SUSTAIN WITHOUT FRACTURING.  2500 PSI IS MY BEST GUESS FOR LIGHTWEIGHT BALSA, PERHAPS 4000 FOR VERY DENSE BALSA.

450 K=9000/Z*I00

470 CLS: PRINT"                      D0 YOU WANT THE RESULTS             ON THE SCREEN, AS A HARDCOPY              (S/H) OR ARE YOU DONE(D)?"

490 A$=INKEY$

510 IF A$="D" THEN 570

530 IF A$="S" THEN 590

550 IF A$="H" THEN 810 ELSE 490

570 CLS: END

590 CLS: PRINT "WING SPAN IS “ ;S

610 PRINT "SPAR DEPTH IS " :SD

630 PRINT "SPAR WIDTH IS " ; SW

650 PRINT “SPAR CAP THICKNESS IS " ;CT

670 PRINT "DESIGN WEIGHT OF AIRPLANE IS ";W

690 PRINT "STRESS AT WING ROOT IS "Z" PSI"

710 PRINT "DESIGN IS "K" % OF DESIGN REQUIREMENTS ASSUMING A LOAD FACTOR OF";L

730 PRINT "PRESS C TO CONTINUE”

750 B$=INKEY$

770 IF B$="C" THEN 790 ELSE 750

790 GOTO 470

810 CLS: PRINT#-2, "WING SPAN IS ";S

830 PRINT " PRINTING IN PROGRESS"

850 PRINT#-2, "SPAR DEPTH IS ":SD

870 PRINT#-2, “SPAR WIDTH IS ";SW

890 PRINT#-2, "SPAR CAP THICKNESS IS ":CT

910 PRINT#-2, "DESIGN WEIGHT OF AIRPLANE IS ";W

930 PRINT#-2, "STRESS AT WING ROOT IS "Z" PSI"

950 PRINT#-2, "DESIGN IS "K"  % OF DESIGN REQUIREMENTS ASSUMING A LOAD FACTOR OF ";L

970 CLS

990 GOTO 470

 
Sample Data:

WING SPAN IS 70.41   SPAR DEPTH IS .96875   SPAR WIDTH IS .375

SPAR CAP THICKNESS IS .125   DESIGN WEIGHT OF AIRPLANE IS 6 LBS

STRESS AT WING ROOT IS 9131.1191 PSI

DESIGN IS 98.5640414 % OF DESIGN REQUIREMENTS ASSUMING A LOAD FACTOR OF 6

Page 5 of article ____ Golden Era Model Service  Index ____ John Eaton Home Page