# My Mathematical Formula Spreadsheet by zbe36955

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```									Background Summary

As a scratch builder of the Zenith Zodiac CH601XL aircraft, I was faced with the challenge of making accurate
bending brake. From my online conversations with others, I learned I was not alone.

As an aside, the design for my bending brake came from Dave Clay, a Texas builder of the same type of airpla
brake provide a straight-forward and cost-effective means of making straight bends in metal in your own shop.
his website at http://www.daves601xl.com and look under "Tools." The only modification I made was to extend
decrease the pitch (spacing) between rivets to add strength for the longer hinging action.

After much trial and error, I picked up my copy of Tony Bingelis' excellent book "Sportplane Construction Tech
his section on "Making Fittings." This is where he goes into great detail to describe the mathematical process
sheet aluminum into a piece with a flat web and two flanges. This involves a 7-step process (shown on tab #4
quite time-intensive if done manually. I decided that this was the perfect place for an Excel spreadsheet.

The spreadsheet labeled "Bingelis DL Calculator" is the result of that effort. To the best of my knowledge it is

After going through that process, I then re-read the Construction Manual for my airplane. This is a Chris Heint
experience in aircraft engineering is evident throughout the plans and the final product. On page 12 of that ma

Starting with that much simpler formula, I then created the worksheet tab labeled "ZAC Single Bend DL Calcul
modifications I was able to produce the "ZAC Double Bend DL Calculator" worksheet. By comparing that work
Calculator" it is possible to see how incredibly close the Heintz approximation is to the more
whichever method works best for you.

A future addition I hope to make is additional tabs for triple and quadruple bends. On the 601XL there are sev
web, aileron stops, cross stiffeners and standard "z" angles). Two parts -- the gear channel and heel support
As time allows, I hope to modify the spreadsheets to accommodate those calculations. Any help from others in
appreciated. If you would like to share your findings, I'll be glad to incorporate them with credit.

Of course, as with all matters pertaining to experimental aircraft production, you are responsible for all decision
and the parts you make. I'm not an aeronautical engineer, so these formulas and worksheets may contain erro
For the sake of others, please report any errors you find and I'll be glad to make corrections.

Larry Winger
Larry Winger
Tustin, CA
larrywinger@gmail.com

2006-09-01
th the challenge of making accurate bends in sheet aluminum with a

xas builder of the same type of airplane. His plans for an 8' bending
ght bends in metal in your own shop. For a copy of his plans, visit
nly modification I made was to extend the length to 10 feet and to
hinging action.

describe the mathematical process needed to change a flat piece of
step process (shown on tab #4) that is very precise but also

t. To the best of my knowledge it is accurate and works as intended.

or my airplane. This is a Chris Heintz design and his long
final product. On page 12 of that manual he writes:

abeled "ZAC Single Bend DL Calculator." With only slight
worksheet. By comparing that worksheet with the "Bingelis DL
tion is to the more-complicated Bingelis formula. Feel free to use

bends. On the 601XL there are several triple bends (center spar
the gear channel and heel support -- require four straight bends.
calculations. Any help from others in this area would be
rate them with credit.

n, you are responsible for all decisions regarding the advice you take
las and worksheets may contain errors. Use at your own discretion.
make corrections.
Assumptions:
mm       inches
Length of Flange A                       18 mm
Length of Flange B                       18 mm

Degree of Bend                           90 degrees
Thickness                             0.063 inches

Results:                              32.81 dl in mm

16.41 Bend Line (sight line) in mm from A edge

Feel free to direct comments or questions to
larrywinger@gmail.com
Formula:

DL = A + B - (R/2 + T)

Bend Line = A - R/2
Assumptions:
mm       inches
Length of Flange A                       18 mm
Length of Flange B                       18 mm
Length of Web                            80 mm

Degree of Bend                           90 degrees
Thickness                             0.016 inches

Results:                            112.01 dl in mm

16.41 Bend Line (sight line) in mm from A or B edge

79.19 Distance between bend lines (in web)

Feel free to direct comments or questions to
larrywinger@gmail.com
Formula:

DL = A + B + C - (R + T*2)

Bend Line = A - R/2
Assumptions:
mm       inches
Length of Flange A                                    18 mm
Length of Flange B                                    18 mm
Width of Web C                                        80 mm

Degree of Bend                                        90   degrees
Thickness                                          0.016   inches
Setback                                            3.581   mm                  SB (Setback) = R (Radius) + T (T

Step 1:    Subtract Setback from Flange A                     14.42   mm
Step 2:    Add Bend Allowance                                  5.27   mm                  BA (Bend Allowance) = ((.01743*R
Step 3:    Subtract Setback from both sides of Web B          72.84   mm
Step 4:    Add Bend Allowance                                  5.27   mm
Step 5:    Subtract Setback from Flange C                     14.42   mm

Results:
Step 6:    Add all figures to obtain developed length       112.21 dl in mm
Step 7:    Draw Brake or Sight Line                          16.51 bend line (sight line) from edge of flange in mm
Distance between bend lines (in web)              79.19

* Based on the process described by Tony Bingelis in "Sportplane Construction Techniques" (EAA, Fourth Printing 19
in the section on "Making Fittings" (pp. 38-47)

Feel free to direct comments or questions to
larrywinger@gmail.com
SB (Setback) = R (Radius) + T (Thickness)

BA (Bend Allowance) = ((.01743*R)+(.0078*T))*degrees of bend

) from edge of flange in mm

echniques" (EAA, Fourth Printing 1998)
Bend Allowance Table
Gage                1/32        1/16       3/32        1/8        5/32       3/16
0.016           0.060       0.109      0.158       0.207      0.256      0.305
0.00067     0.00121    0.00176     0.00230    0.00285    0.00339
0.025         0.067       0.116      0.165       0.214      0.263      0.312
0.00074     0.00128    0.00183     0.00237    0.00292    0.00346
0.032         0.071       0.121      0.170       0.219      0.268      0.317
0.00079     0.00134    0.00188     0.00243    0.00297    0.00352
0.040         0.077       0.126      0.175       0.224      0.273      0.322
0.00086     0.00140    0.00195     0.00249    0.00304    0.00358
0.051                     0.134      0.183       0.232      0.281      0.330
0.00149    0.00203     0.00258    0.00312    0.00367
0.063                     0.142      0.191       0.240      0.289      0.338
0.00158    0.00213     0.00267    0.00321    0.00376
0.072                                0.198       0.247      0.296      0.345
0.00220     0.00274    0.00329    0.00383
0.081                                0.204       0.253      0.302      0.351
0.00227     0.00281    0.00336    0.00390
0.090                                0.210       0.259      0.308      0.357
0.00234     0.00288    0.00343    0.00397
0.125                                            0.284      0.333      0.382
0.00315    0.00370    0.00424
0.188                                                                  0.426
0.00473
0.250

Thickness Multiplier        0.0078

Legend:
x.xxx      Light yellow = Bend allowance for 90 degree bend
x.xxxxx    Light green = Bend allowance per degree of bend

* Based on the formulas described by Tony Bingelis in "Sportplane Construction Techniques" (EAA, Fourth Printing 1
in the section on "Making Fittings" (pp. 38-47)
7/32       1/4            9/32       5/16      11/32       3/8        7/16       1/2
0.354      0.403          0.452      0.501      0.550      0.599      0.698      0.796
0.00394    0.00448        0.00503    0.00557    0.00612    0.00666    0.00775    0.00884
0.361      0.410          0.459      0.508      0.557      0.606      0.704      0.802
0.00401    0.00455        0.00510    0.00564    0.00619    0.00673    0.00782    0.00891
0.366      0.415          0.464      0.513      0.562      0.611      0.709      0.807
0.00406    0.00461        0.00515    0.00570    0.00624    0.00679    0.00788    0.00896
0.371      0.420          0.469      0.518      0.567      0.616      0.714      0.812
0.00412    0.00467        0.00521    0.00576    0.00630    0.00685    0.00794    0.00903
0.379      0.428          0.477      0.526      0.575      0.624      0.722      0.820
0.00421    0.00476        0.00530    0.00584    0.00639    0.00693    0.00802    0.00911
0.387      0.436          0.485      0.534      0.583      0.632      0.731      0.829
0.00430    0.00485        0.00539    0.00594    0.00648    0.00703    0.00812    0.00921
0.394      0.443          0.492      0.541      0.590      0.639      0.737      0.835
0.00437    0.00492        0.00546    0.00601    0.00655    0.00710    0.00819    0.00928
0.400      0.449          0.498      0.547      0.596      0.645      0.743      0.841
0.00444    0.00499        0.00553    0.00608    0.00662    0.00717    0.00826    0.00935
0.406      0.455          0.504      0.553      0.602      0.651      0.749      0.848
0.00451    0.00506        0.00560    0.00615    0.00669    0.00724    0.00833    0.00942
0.431      0.480          0.529      0.578      0.627      0.676      0.774      0.872
0.00479    0.00533        0.00588    0.00642    0.00697    0.00751    0.00860    0.00969
0.475      0.524          0.573      0.622      0.671      0.720      0.818      0.916
0.00528    0.00582        0.00637    0.00691    0.00746    0.00800    0.00909    0.01018
0.568          0.617      0.666      0.715      0.764      0.862      0.960
0.00631        0.00685    0.00740    0.00794    0.00849    0.00958    0.01067

chniques" (EAA, Fourth Printing 1998)

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