The first image below shows the assorted bucking bars I acquired for this project. The second image shows one of the small bars which I modifed for use reaching inside skins to buck the rivets on the horizontal and vertical stab spars. The third image shows another bar with more mass modified to perform the same function.
When beginning this project, I never seemed to have the perfect bucking bar. However, I have found that it is relatively easy to modify various bars to make them more useful. The small bar in the second image has two additional working surfaces added. The two polished surfaces shown were not on the bar as purchased. A few minutes with a bench grinder, file and scotchbrite wheel, however, created two 1/2" wide surfaces which work well when bucking the tail spar rivets. The polished 1/2" end shown in the third image was accomplished in the same manner. This bar has a bit more mass and can also fit in some tight spaces.
