Overview:

Pioneer Aero has been working diligently on our SBD Dauntless for a little over two years now, and their progress in that time has been remarkable. The dive-bomber's Wing Center Section is naturally at the heart of this effort, and is presently deep within the trial-fitting process, where newly-made and/or refurbished original subassemblies are offered up to one another on the jig and drilled-off against adjacent components before being taken apart again for primer-painting and another round of trial-fitting. However, with this article we can now report that structural subassemblies have recently received their first layer of topcoat paint—this being the interior spaces within the left and righthand leading edges. It is an auspicious milestone for this project! are now in their final color, ''!an auspicious milestone in the project. T

A view of the SBD’s righthand leading edge subassembly drying in the spray booth at Pioneer Aero after having received a layer of non-specular Insignia White in the exposed sections of the undercarriage bay. Furthermore, the internal areas now sport a coat of dark green paint mimicking the zinc chromate used during the aircraft's original manufacture. (image via Pioneer Aero Ltd.)
A view of the SBD’s righthand leading edge subassembly drying in the spray booth at Pioneer Aero after having received a layer of non-specular Insignia White in the exposed sections of the undercarriage bay. Furthermore, the internal areas now sport a coat of dark green paint mimicking the zinc chromate used during the aircraft's original manufacture. (image via Pioneer Aero Ltd.)

Painting (and Riveting) the Leading Edges:

Trial-fitting the leading edges to the SBD's Wing Center Section jig, as covered in Update No.88, permitted the restoration team to back-drill the final rivet holes linking the nose spar and stiffener plates to the overall leading edge structure. Finalizing the locations for these holes then allowed the individual components to receive a layer of topcoat, courtesy of Pioneer's Jason Harris, thus ensuring complete paint coverage of each surface prior to the next step. With the paint dried, Craig Cunha permanently riveted the nose spar and stiffener plates to the leading edge ribs and skins. The images below show this process for the righthand inner wing leading edge; Cunha followed the same procedure for the lefthand example too.

Craig Cunha in the process of riveting on the stiffener plate forward of the nose spar in the wheel bay. Note that blue masking tape has been applied in some areas. This protects the fresh paint during riveting, as working in a confined space such as this with the rivet gun in one hand and the bucking bar in the other requires intense concentration. Note that bucking bars are referred to as dollies in New Zealand. (image via Pioneer Aero Ltd.)

The inner righthand leading edge after being riveted together. This effort involved riveting in the nose spar, the stiffener plate forward of the Nose Spar in the wheel bay, the doubler around the empty shell case chute openings, and the ribs which sit between the Nose Spar and Spar #1. (image via Pioneer Aero Ltd.)

Another shot of the inner righthand leading edge (albeit from a different angle) after being riveted together–looking outboard from the wheel bay. The view through the two lightening holes in the stiffener plate forward of the nose spar should explain why painting this particular area prior to assembly allows each surface to receive complete paint coverage. The same situation applies when peering through the openings into the outer end of the leading edge. The decision regarding when to apply the final coat of paint is one of the many details to consider during the final assembly process. (image via Pioneer Aero Ltd.)

A third view of the inner righthand leading edge after riveting completion, this time looking inboard down the length of the undercarriage leg bay. The order in which the various components are riveted together is a critical consideration during final assembly. If a component is fastened in place too early, it may limit, or even deny proper access to the rivets on another interlinked component. Conversely, riveting a component in place too late may also prevent access to all of the rivets. (image via Pioneer Aero Ltd.)

Trial Fitting (Again):

With the inboard leading edges each now riveted together as essentially complete subassemblies, Pioneer's engineers could temporarily remount them back onto the Wing Center Section jig. This allowed the team to begin fabricating interconnecting parts for the central bomb and wing root fairings, along with other structure linking the main Wing Center Section subassembly to Fuselage Frame #1. The images below show Pioneer personnel in the process of re-attaching the leading edges to the jig, with the captions also providing details about some of the various components on view.

Craig Cunha, Doug Brown (just visible behind Craig) and Rod Hansen (in blue overalls) in the process of trial-fitting the assembled and internally painted lefthand leading edge onto the SBD’s Wing Center Section jig. (image via Pioneer Aero Ltd.)

Another view of Rod Hansen, Doug Brown and Craig Cunha in the process of trial-fitting the lefthand leading edge onto the Wing Center Section jig. (image via Pioneer Aero Ltd.)

Just visible on the far side of the wing, Craig Cunha is finishing up the process of trial-fitting the lefthand leading edge onto the Wing Center Section jig. (image via Pioneer Aero Ltd.)

A view of the SBD’s lefthand wing leading edge in place on the Wing Center Section jig. This will allow neighboring parts to be positioned and drilled off. (image via Pioneer Aero Ltd.)

Another view of the SBD’s lefthand leading edge during trial-fitting onto the Wing Center Section jig. Looking carefully inside the leading edge, just forward of the nose spar, we can see the tube that forms part of the duct which supplies cold air to the cockpit; its intake is just visible in the leading edge skin immediately to the left of the steel pole nearest the camera. (image via Pioneer Aero Ltd.)

Another view of the lefthand leading edge interior. Note the two curved rectangular openings in the skin at the inboard end; the case ejection chute for the lefthand, forward-firing machine gun passes through these holes, allowing empty .50 caliber shells to fall free of the airframe safely when the pilot operates his guns. This shot also provides a nice view of the pilot's cold air tube snaking through the wheel well interior too. (image via Pioneer Aero Ltd.)

Here we see the SBD’s righthand leading edge during trial-fitting onto the Wing Center Section jig. (image via Pioneer Aero Ltd.)

Another view of the righthand leading edge during trial-fitting onto the SBD’s Wing Center Section jig, albeit from a different angle to the previous image. (image via Pioneer Aero Ltd.)

A closeup showing the upper side of both leading edges temporarily fitted onto the Wing Center Section jig. This image reveals the relationship between the leading edges, the Bomb Displacement Gear support ribs and the lower half of Fuselage Frame #1. Note the white tube protruding from the inboard end rib for the lefthand leading edge (at image right); this is part of the pilot’s cold air duct which funnels exterior air from an opening on the wing leading edge into the cockpit. While more difficult to see in this image, there are also steel tubes extending between each inboard end rib and the Bomb Displacement Gear support ribs either side of them; these are the mounts for the brake master cylinders which also tie into the rudder pedal tips. (image via Pioneer Aero Ltd.)
A closeup showing the upper side of both leading edges temporarily fitted onto the Wing Center Section jig. This image reveals the relationship between the leading edges, the Bomb Displacement Gear support ribs and the lower half of Fuselage Frame #1. Note the white tube protruding from the inboard end rib for the lefthand leading edge (at image right); this is part of the pilot’s cold air duct which funnels exterior air from an opening on the wing leading edge into the cockpit. While more difficult to see in this image, there are also steel tubes extending between each inboard end rib and the Bomb Displacement Gear support ribs either side of them; these are the mounts for the brake master cylinders which also tie into the rudder pedal tips. (image via Pioneer Aero Ltd.)
A view of both inboard wing leading edges temporarily remounted to the Wing Center Section jig. With these attached, along with the intersecting internal structure between Fuselage Frame #1 and Spar #1, the skins for the central bomb fairing and wing root fairings can now be remanufactured. (image via Pioneer Aero Ltd.)
A view of both inboard wing leading edges temporarily remounted to the Wing Center Section jig. With these attached, along with the intersecting internal structure between Fuselage Frame #1 and Spar #1, the skins for the central bomb fairing and wing root fairings can now be remanufactured. (image via Pioneer Aero Ltd.)

Wheel Well Surround Channels & Wing Root Fairings:

The sheet metal panels for both the forward wing root fairings and the channel sections surrounding the wheel wells each feature aspects with significantly complex curvature (i.e. bends occur in multiple directions) making them a challenge to reproduce. Since our SBD suffered significant damage in this part of the airframe during its wartime crash, many of the original components from that area did not survive in sufficient condition to be refurbished for airworthy use. This did not mean the damaged parts weren't useful in helping recreate their replacements, however, as the following sections will reveal...

An image of our Dauntless (Bu.36175/B-22) as it was raised out of Lake Michigan following recovery from its wartime crash site back in September 1994. Note how badly crushed its leading edges appeared to be. Despite this damage, Pioneer Aero's engineers were able to untangle much of it so the parts could serve as patterns. (image via A&T Recovery)
An image of our Dauntless (Bu.36175/B-22) as it was raised out of Lake Michigan following recovery from its wartime crash site back in September 1994. Note how badly crushed its leading edges appeared to be. Despite this damage, Pioneer Aero's engineers were able to untangle much of it so the parts could serve as patterns. (image via A&T Recovery)

Channels:

Pioneer's engineers were able to unfold several crumpled pieces from the SBD's wing leading edges into their original configuration, making them useful as patterns for refabricating replacements. Given the complicated shapes involved, forming blocks were the only practical way of creating the new parts, since working freehand would have involved far more effort. Pioneer’s Craig Cunha produced the set of forming blocks to help refabricate the forward wheel well surround channels (left and right) using B-22's original example and factory drawings as a guide. He then trial-fitted the new parts into the wheel wells and trimmed them to the correct dimensions.

The wheel well surround channels curve in several different directions, making them difficult to remanufacture without the use of forming blocks. As a result, Pioneer’s Craig Cunha created a set of male and female forming blocks for each of the channels by laminating several MDF sheets together than routing the required shape into the block before applying epoxy resin to provide a harder surface to work on. This image shows the female forming block (with its male counterpart immediately to its rear) for the lefthand forward wheel well surround channel. Note the numerous MDF laminations involved. (image via Pioneer Aero Ltd.)

The lefthand forward wheel well surround channel from B-22 is shown here sitting atop the female forming block (with the male behind) to show that it fits properly. This original part had to be uncrumpled into its original shape, and also received a repair along its lower edge. This was added to hold the part in place for 3D scanning, which Pioneer pursued to derive critical data missing from the manufacturing drawings. (image via Pioneer Aero Ltd.)

The replacement lefthand forward wheel well surround channel seen here atop the forming block part way through the manufacturing process. To create the required shape, an aluminum sheet metal blank is beaten, stretched and/or shrunk as required so that it conforms with the forming block’s surface. Most of the forming is done directly via the block, but other processes, like shrinking, are performed using other tools—the block being used to validate the results. (image via Pioneer Aero Ltd.)

Another view of the components shown in the previous image, only this time from the opposite face. (image via Pioneer Aero Ltd.)

The original lefthand forward wheel well surround channel from B-22 is seen here sitting beside the replacement part, which still needs trimming to size. These are the inside (wheel side) faces of the channels. (image via Pioneer Aero Ltd.)

Craig Cunha is seen here in the process of trial-fitting the replacement forward surround channel in the SBD’s righthand wheel well. All shapes like this require adjustment and then trimming to get them to sit exactly where required. (image via Pioneer Aero Ltd.)
Craig Cunha is seen here in the process of trial-fitting the replacement forward surround channel in the SBD’s righthand wheel well. All shapes like this require adjustment and then trimming to get them to sit exactly where required. (image via Pioneer Aero Ltd.)

A view inside the SBD’s righthand wheel well showing the damaged original aft channel surround section from B-22 aiding the trial-fitting (and trimming) of the replacement forward section. Note how the aft channel starts outside the wing skin, then passes through a notch to lie inside of the wing skin. The forward channel has been located to ensure its smooth transition to the lower fuselage skin. (image via Pioneer Aero Ltd.)

This image allows a close-in view of the components featured in the previous image showing how the aft lower corner of the forward channel (seen at the upper left in this image) will form a continuous curve with Bomb Displacement Gear support rib just to the left. (image via Pioneer Aero Ltd.)

Fairings:

Cunha followed a similar process to begin remaking the lower leading edge wing root fairings, starting with the righthand example. These fairings create a smooth transition between the wheel well surround channels, Fuselage Frame #1 and the Wing Center Section leading edges. They also each feature an opening for the earlier-mention chutes which direct spent ammunition casings from the machine guns out of the airframe too. The following images show the fairing work in progress...

The topmost item in this image is the original, non-airworthy lower, righthand leading edge wing root fairing from B-22. Its replacement lies beneath it, part way through fabrication, while the forming block Pioneer is using to shape the new piece sitting below that. (image via Pioneer Aero Ltd.)

Another view of the original lower, righthand leading edge wing root fairing sitting beside its partially-formed replacement. Close examination of the new metal reveals the material code “2024 O” inked upon the surface, meanings that this aluminum sheet is in its “soft”, more ductile state. This makes easier for Pioneer to deform the metal into the desired profile without overworking or cracking. Once the part is in the correct shape—which was fast approaching at the time this image was captured—it will undergo heat treating to bring it up to the correct temper/hardness. Only then will Pioneer’s engineers cut the rectangular opening into the skin (as seen on the original part). This will reduce the chances that the heat treating process will warp the new part to severely—which is a distinct possibility with thin lengths of skin. (image via Pioneer Aero Ltd.)

A view of the replacement lower righthand, leading edge wing root fairing during trial-fitting. This piece will blend elements of the wheel well surround channel, Fuselage Frame #1 and wing leading edge into one contiguous surface. The part is midway through the fabrication process, and still requires final shaping, trimming, and additional rivet holes drilled in before it’s ready for heat treating and final-fitting. (image via Pioneer Aero Ltd.)
A view of the replacement lower righthand, leading edge wing root fairing during trial-fitting. This piece will blend elements of the wheel well surround channel, Fuselage Frame #1 and wing leading edge into one contiguous surface. The part is midway through the fabrication process, and still requires final shaping, trimming, and additional rivet holes drilled in before it’s ready for heat treating and final-fitting. (image via Pioneer Aero Ltd.)

Another view of the same components depicted in the previous image; it provides a clear demonstration of how the curve of Fuselage Frame #1 blends into the leading edge profile. (image via Pioneer Aero Ltd.)

A third view of the replacement lower, righthand, leading edge wing root fairing, with this image describing how the lower fuselage shape is created between the Bomb Displacement Gear support rib and the wheel well surround. (image via Pioneer Aero Ltd.)