Overview:

While many SBD restoration reports in recent months have focused upon the aircraft’s Wing Center Section, Pioneer Aero has also continued to make significant progress with the upper fuselage. Last November, Will Lowen placed the upper longerons in the jig for trial-fitting alongside the forward skins. As regular readers will remember, these longerons were newly-manufactured replacements which came with the cache of parts the Museum purchased subsequent to B-22's acquisition, but they required a little fettling to get them into the correct shape.

An illustration itemizing the various skin panels (plates) on the upper fuselage. The callout numbers 01 & 02 correspond to skin plates #10 & $11, whilst 16 & 17 refer to plates #88 & #89. Note that the odd-numbered skin panels fit to the lefthand side of the airframe, whilst the even-numbered panels are their mirrors on the righthand side. (image from page 17 of the A-24 Illustrated Parts Manual)
An illustration itemizing the various skin panels (plates) on the upper fuselage. The callout numbers 01 & 02 correspond to skin plates #10 & $11, whilst 16 & 17 refer to plates #88 & #89. Note that the odd-numbered skin panels fit to the lefthand side of the airframe, whilst the even-numbered panels are their mirrors on the righthand side. (image from page 17 of the A-24 Illustrated Parts Manual)

Upper Longerons and Forward Skins:

After checking their alignment to ensure they were level and correctly positioned, Lowen drilled off the longerons to match the engine mounts and all of the fuselage frames in the cockpit area. This then allowed him to continue trial-fitting and drilling off the replacement skins (plates) which run between Fuselage Frames #1 and #7 on either side of the fuselage, these being plates #10 & #88 on the left, and plates #11 & #89 on the right. These skins are now drilled off against the upper longerons and all of the associated original stringers too.

A view of the righthand side of the SBD’s upper fuselage showing the replacement skins in the process of being drilled off. Each skin (plate) has its own number. Skin #89 lies laterally between Fuselage Frames #1 & #3 and vertically between the righthand upper longeron and Stringer row #6. Meanwhile, Skin #11 lies laterally between Fuselage Frames #3 & #7, and vertically between the righthand upper longeron and Stringer row #6. With the upper longeron position confirmed, the rivet hole pattern could then be drawn and drilled, using the original skin and drawings as references–however, it was impossible to use the original skin here as a drilling pattern due to distortion caused by B-22’s wartime accident. (image via Pioneer Aero, Ltd.)
A view of the righthand side of the SBD’s upper fuselage showing the replacement skins in the process of being drilled off. Each skin (plate) has its own number. Skin #89 lies laterally between Fuselage Frames #1 & #3 and vertically between the righthand upper longeron and Stringer row #6. Meanwhile, Skin #11 lies laterally between Fuselage Frames #3 & #7, and vertically between the righthand upper longeron and Stringer row #6. With the upper longeron position confirmed, the rivet hole pattern could then be drawn and drilled, using the original skin and drawings as references–however, it was impossible to use the original skin here as a drilling pattern due to distortion caused by B-22’s wartime accident. (image via Pioneer Aero, Ltd.)
Another view of the righthand side of upper fuselage, with the replacement skins in the process of being drilled. The longeron rivet holes were all drawn, then drilled. The frame and stringer rivet holes, however, were transferred directly from the original skins where possible or drawn on as required. Note that the canopy rails attach to the top sides of the upper longerons, another reason why they have to be perfectly level! (image via Pioneer Aero, Ltd.)
Another view of the righthand side of upper fuselage, with the replacement skins in the process of being drilled. The longeron rivet holes were all drawn, then drilled. The frame and stringer rivet holes, however, were transferred directly from the original skins where possible or drawn on as required. Note that the canopy rails attach to the top sides of the upper longerons, another reason why they have to be perfectly level! (image via Pioneer Aero, Ltd.)
A view of the lefthand side of upper fuselage, with the replacement skins (plates) in the process of being drilled in. As with the righthand side, each skin has its own number. Skin #88 (not fitted in this image) lies laterally between Fuselage Frames #1 & #3, and vertically between the upper longeron and Stringer row #6. Meanwhile, skin #10 lies laterally between Fuselage Frames #3 & #7, and vertically between the upper longeron and Stringer row #6. A close look at the longeron flange (the bit hanging down from the top surface) shows the rows of rivet holes drilled into it. Fabricating a replacement skin requires multiple fitment/removal cycles as the numerous details are confirmed, drilled, and then checked. Note that the original, damaged upper longeron is sitting across the row of clecos holding skin #10 to the its replacement. It was serving as a reference for marking the positions for some of the rivet holes. (image via Pioneer Aero, Ltd.)
A view of the lefthand side of upper fuselage, with the replacement skins (plates) in the process of being drilled in. As with the righthand side, each skin has its own number. Skin #88 (not fitted in this image) lies laterally between Fuselage Frames #1 & #3, and vertically between the upper longeron and Stringer row #6. Meanwhile, skin #10 lies laterally between Fuselage Frames #3 & #7, and vertically between the upper longeron and Stringer row #6. A close look at the longeron flange (the bit hanging down from the top surface) shows the rows of rivet holes drilled into it. Fabricating a replacement skin requires multiple fitment/removal cycles as the numerous details are confirmed, drilled, and then checked. Note that the original, damaged upper longeron is sitting across the row of clecos holding skin #10 to the its replacement. It was serving as a reference for marking the positions for some of the rivet holes. (image via Pioneer Aero, Ltd.)
Another view of the lefthand side of upper fuselage with the replacement skins in the process of being drilled in, this time showing the full length of Skin #10. Note the circular hole in this skin just behind the vertical steel jig structure; this is the port which the SBD’s rear crew member could use to fire their flare pistol through. (image via Pioneer Aero, Ltd.)
Another view of the lefthand side of upper fuselage with the replacement skins in the process of being drilled in, this time showing the full length of Skin #10. Note the circular hole in this skin just behind the vertical steel jig structure; this is the port which the SBD’s rear crew member could use to fire their flare pistol through. (image via Pioneer Aero, Ltd.)