Clad 2024–T3 2024–T3 Clad 7075–T6 7075–T6 2024–T3 Clad 7075–T6 7075–T6 7075–T6 7075–T6 Clad 2024–T42 Clad 2024–T3 Clad 7075–T6 2024–T42 Sheet 0.016 to 0.125 Formed or Extruded Section  Initial Material Shape Replacement Material 1.00 1.00 1.00 1.00 1.00 1.00 1.28 1.08 1.00 1.10 1.00 1.00 1.00 1.00 1.00 1.28 1.18 1.00 1.83 1.76 1.10 1.00 1.00 1.00 2.00 1.83 1.00 1.20 1.13 1.00 1.00 1.00 1.00 1.86 1.75 1.00 1.20 1.13 1.00 1.00 1.00 1.00 1.50 1.41 1.00 1.24 1.16 1.03 1.03 1.00 1.00 1.96 1.81 1.00 1.84 1.76 1.14 1.00 1.14 1.00 1.98 1.81 1.00 1.78 1.71 1.10 1.00 1.00 1.00 1.90 1.75 1.00 1.78 1.70 1.00 1.00 1.00 1.00 1.90 1.75 1.00 1.30 1.22 1.09 1.00 1.00 1.00 1.63 1.52 1.00 7075–T6 Clad 7075–T6 2024–T3 Clad 2024–T3 2024–T42 Clad 2024–T42 7178–T6 Clad 7178–T6 5052–H34 Notes •  All dimensions are in inches, unless given differently. •  It is possible that more protection from corrosion  will be necessary when bare mineral is used to  replace Clad material. Refer to 51-10-2. •  It is possible for the material replacement factor  to be a lower value for a specific location on the  airplane. To get that value, contact Boeing for a  case by case analysis. •  Refer to Figure 3 for minimun bend radii. • Example: To refer 0.040 thick 7075–T6 with Clad 7075–T6,  multiply the gage by the material replacement factor  to get the replacement gage 0. 040 x 1.10 = 0.045.  These materials cannot be used as replacements for the  initial material in areas that are pressured. They also cannot be used in the wing interspar structure at  the wing center section structure.  Use the next thicker standard gage when you use a formed  section as a replacement for an extrusion. For all gages of flat sheet and formed sections. For flat sheet less than 0.071 thick. For flat sheet 0.071 thick and thicker, and for formed sections. 2024–T4 and 2024–T42 are equivalent. A compound to give protection from corrosion must be  applied to bare material that is used to replace 5052–H34. Sheet Material to be Replaced 7075–T6 2024–T3 Clad 7075–T6 Clad 2024–T3 2024–T4 2024–T42 Clad 2024–T4 Clad 2024–T42 Material Replacement Factor C C A A A A A A A A A A A A A A A A B B D D C H H H G G E E D E D E F F F F F D E Figure 4-168.  Material substitution. Aircraft structural joint design involves an attempt to find  the optimum strength relationship between being critical in  shear and critical in bearing. These are determined by the  failure mode affecting the joint. The joint is critical in shear  if less than the optimum number of fasteners of a given size  are installed. This means that the rivets will fail, and not  the sheet, if the joint fails. The joint is critical in bearing if  more than the optimum number of fasteners of a given size  are installed; the material may crack and tear between holes,  or fastener holes may distort and stretch while the fasteners  remain intact. 4-88 Shear Strength and Bearing Strength