metals, and filler rod is added for roundness and strength.  If a higher stress is to be placed on the corner, the inside is  reinforced with another weld bead.  [Figure 5-44C] The lap joint is seldom used in aircraft structures when  welding with oxy-acetylene, but is commonly used and joined  by spot welding. The single lap joint has very little resistance  to bending, and cannot withstand the shearing stress to which  the weld may be subjected under tension or compression  loads. The double lap joint offers more strength, but requires  twice the amount of welding required on the simpler, more  efficient butt weld.  [Figure 5-45] Dents at a cluster weld can be repaired by welding a formed  steel patch plate over the dented area and surrounding  tubes. Remove any existing finish on the damaged area and  thoroughly clean prior to welding. To prepare the patch plate, cut a section from a steel sheet of  the same material and thickness as the heaviest tube damaged.  Fashion the reinforcement plate so that the fingers extend  over the tubes a minimum of 1½ times the respective tube  diameter. The plate may be cut and formed prior to welding  or cut and tack welded to the cluster, then heated and formed  around the joint to produce a snug smooth contour. Apply  sufficient heat to the plate while forming so there is a gap of  no more than  1 ⁄ 16 -inch from the contour of the joint to the plate.  In this operation, avoid unnecessary heating and exercise care  to prevent damage at the point of the angle formed by any  two adjacent fingers of the plate. After the plate is formed  and tack welded to the joint, weld all the plate edges to the  cluster joint.  [Figure 5-46] A damaged tubular section can be repaired using welded  split sleeve reinforcement. The damaged member should be  carefully straightened and should be stop drilled at the ends  of any cracks with a No. 40 drill bit. Select a length of steel tube of the same material and at  least the same wall thickness having an inside diameter  approximately equal to the outside diameter of the  damaged tube.  Diagonally cut the selected piece at a 30° angle on both ends  so the minimum distance of the sleeve from the edge of the  crack or dent is not less than 1½ times the diameter of the  damaged tube. Then, cut through the entire length of the  sleeve and separate the half sections as shown in  Figure 5-47 .  Clamp the two sleeve sections in the proper position on the  Dents Between Clusters Repair of Steel Tubing Aircraft Structure  by Welding Dents at a Cluster Weld Lap Joints Figure 5-46.  Repair of tubing dented at a cluster. A 1 1 /2 A 1 /2 B B Thickness of patch plate same as  longeron thickness Longeron dented at a station Patch plate before forming and welding Patch plate formed and welded to tubes 5-32 Single lap Double lap Figure 5-45.  Single and double lap joints.