SBD-5 Bu36175, coded B-22, rising out of Lake Michigan during its recovery in 1994. The aircraft ditched into Lake Michigan during wartime flight training activities on January 20, 1944, suffering considerable impact damage in the process as this image reveals. The entire engine section was torn away and the wing leading edges crushed. Pioneer Aero's engineers have had to refabricate much of this structure. (image via A&P Recovery)
SBD-5 Bu36175, coded B-22, rising out of Lake Michigan during its recovery in 1994. The aircraft ditched into Lake Michigan during wartime flight training activities on January 20, 1944, suffering considerable impact damage in the process as this image reveals. The entire engine section was torn away and the wing leading edges crushed. Pioneer Aero's engineers have had to refabricate much of this structure. (image via A&P Recovery)

Overview:

When Lieutenant Charles L. Ford III ditched B-22 into Lake Michigan while attempting to land aboard the training carrier, USS Wolverine, on January 20, 1944, the forward sections of the SBD's wing and nose suffered considerable impact damage, as the above image captured during the aircraft's 1994 recovery reveals. Note that the leading edge wing root fairings which blend the wing into the forward fuselage (Skins #8 and #9 on the illustration below) were virtually obliterated. As a result, the latter components required complete refabrication, a process which demanded significant skill and endeavor from Pioneer Aero's engineers, as this article will demonstrate.

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The Refabrication Process:

Given that surviving manufacturer's drawings for the SBD's leading edge wing root fairings lacked sufficient detail for their refabrication and that B-22's original examples were too damaged to serve as templates, Pioneer Aero's engineers (principally Craig Cunha) had to find an alternate pathway for building new fairings. As it happened, the surviving forward fuselage of the Museum's RA-24B Banshee, a former Wind Machine on Hollywood movie sets, still retained its own, undamaged set of these deceptively complex parts. (The RA-24B, as many will remember, was a variant of the SBD-5 which served with the US Army Air Forces.)

An image showing the intact lefthand upper leading edge wing root fairing still present on the Douglas RA-24B Banshee fuselage section belonging to the Museum. Pioneer Aero's engineers scanned this component to create an accurate 3D model of it, which they then used to machine a forming block to replicate the part. While the skin section may seem of simple construction, its areas of complex curvature make it a significant challenge to replicate. Note the reflective dots which Pioneer's engineers placed on the structure; these served as reference points during the 3D scanning process. (image via Pioneer Aero Ltd.)
An image showing the intact lefthand upper leading edge wing root fairing still present on the Douglas RA-24B Banshee fuselage section belonging to the Museum. Pioneer Aero's engineers scanned this component to create an accurate 3D model of it, which they then used to machine a forming block to replicate the part. While the skin section may seem of simple construction, its areas of complex curvature make it a significant challenge to replicate. Note the reflective dots which Pioneer's engineers placed on the structure; these served as reference points during the 3D scanning process. (image via Pioneer Aero Ltd.)

While Pioneer Aero could not simply remove, refurbish and reuse these fairings, since their existing rivet holes would not line up with those on B-22's underlying structure, it would be possible to use a 3D scanner to record their physical dimensions with the parts remaining in situ on the Banshee. This is precisely what occurred, with the resulting digitized 3D model being used to program a Computer Numerically Controlled (CNC) milling machine to scribe out forming blocks for shaping new parts over (see the video below).

Manufacturing the Forming Blocks:

To create a sufficiently large mass of material from which to machine a forming block, Pioneer glued together about a dozen sheets of MDF into a sizable stack. They used a CNC table router to first rough out the general shape from this stack, then made several passes with a finer bit to bring the forming block much closer to the desired dimensions, before a gentle hand sanding to produce the final result. A coat of epoxy resin was then added to harden the surface. They made the initial forming block for the lefthand upper leading edge fairing, then created its mirror image for the righthand example.

This image shows the stack of glued-together MDF boards on a table router part way through the rough cut. Pioneer’s Allen House is supervising the routing process, using a vacuum to suck away the fine dust. (image via Pioneer Aero Ltd.)
This image shows the stack of glued-together MDF boards on a table router part way through the rough cut. Pioneer’s Allen House is supervising the routing process, using a vacuum to suck away the fine dust. (image via Pioneer Aero Ltd.)
A closeup of the router in action showing the rough cut of the lefthand forming block in progress. (image via Pioneer Aero Ltd.)
A closeup of the router in action showing the rough cut of the lefthand forming block in progress. (image via Pioneer Aero Ltd.)
The finished forming block for the lefthand upper leading edge fairing after the application of epoxy resin to harden its surface. (image via Pioneer Aero Ltd.)
The finished forming block for the lefthand upper leading edge fairing after the application of epoxy resin to harden its surface. (image via Pioneer Aero Ltd.)

Aluminum Blanks:

Before cutting blanks for the new parts from a .051" thick sheet of soft 2024-T0 aluminum alloy, Pioneer dummied up a new part from orange masking tape using the Wind Machine as a template. This helped them plot out the replacement fairings in the aluminum blanks before shaping them over the forming block.

The dummied up lefthand fairing, shaped from orange masking tape using the Wind Machine as a template is seen here arrayed over the forming block to verify its general fit. (image via Pioneer Aero Ltd.)
The dummied up lefthand fairing, shaped from orange masking tape using the Wind Machine as a template is seen here arrayed over the forming block to verify its general fit. (image via Pioneer Aero Ltd.)
The aluminum blank which would later be beaten over the forming block to create the replacement upper lefthand leading edge wing root fairing. The pen lines are an indication of where the fairing’s tightest curve and lower edge will sit; these were created using the flexible dummy part as a template. (image via Pioneer Aero Ltd.)
The aluminum blank which would later be beaten over the forming block to create the replacement upper lefthand leading edge wing root fairing. The pen lines are an indication of where the fairing’s tightest curve and lower edge will sit; these were created using the flexible dummy part as a template. (image via Pioneer Aero Ltd.)

Shaping the Aluminum Blanks:

With the forming blocks for the two fairings completed and the aluminum blanks for the new parts cut out and marked up, it was time to beat them into shape with rubber mallets over their individual forming blocks. The process continued by interchangeably beating the partially-formed parts against a sand bag and using an English wheel. This effort cycled repeatedly until the required shapes were achieved.

The partially formed replacement upper righthand leading edge wing root fairing. The initial curve has already been beaten in, with further shaping taking place with a nylon hammer drumming the blank against a sand bag, a process which moves the aluminum without stretching it. (image via Pioneer Aero Ltd.)
The partially formed replacement upper righthand leading edge wing root fairing. The initial curve has already been beaten in, with further shaping taking place with a nylon hammer drumming the blank against a sand bag, a process which moves the aluminum without stretching it. (image via Pioneer Aero Ltd.)
The replacement upper righthand leading edge wing root fairing during forming. The initial curve has been introduced with further shaping taking place by beating the part against the MDF form block. Using the MDF form block with the nylon hammer allows the aluminum to move and stretch towards its final shape. More shaping was carried out by again beating it against a sand bag and using an English wheel. This process cycled repeatedly until the required shaped was achieved. (image via Pioneer Aero Ltd.)
The replacement upper righthand leading edge wing root fairing during forming. The initial curve has been introduced with further shaping taking place by beating the part against the MDF form block. Using the MDF form block with the nylon hammer allows the aluminum to move and stretch towards its final shape. More shaping was carried out by again beating it against a sand bag and using an English wheel. This process cycled repeatedly until the required shaped was achieved. (image via Pioneer Aero Ltd.)

The partially-formed lefthand upper leading edge wing root fairing being checked and adjusted against the fuselage and wing center section to ensure a correct fit. This is close to the final shape. (image via Pioneer Aero Ltd.)

Another shot of the upper lefthand leading edge wing root fairing as it is checked and adjusted against the SBD’s fuselage and Wing Center Section to ensure a correct fit. It was close to its final shape at this point. (image via Pioneer Aero Ltd.)

Trial-Fitting:

After shaping the two leading edge wing root fairings close to their final shape, it was time to trial-fit them against the SBD's Wing Center Section. This involved offering the parts up against the intended underlying structure, fettling them until they blended perfectly against it, then drilling off the rivet holes so they matched those below. With that effort completed, it was time to trim the parts into their final dimensions. They were then ready for heat treating by a third party to increase the tensile strength and hardness of the 2024 aluminum alloy from its initial soft, T0 status to a far more robust T3 condition.

The lefthand leading edge wing root fairing (Skin #8) after its shape has been finalized; it is in the process of having its rivet holes drilled off against the associated structure. Note the row of black-painted clecos which secure the fairing’s upper edge beneath the lower edge of the fuselage skin just above it (Skin #6) to the lower engine mount stiffener behind them both. This indicates that the rivet holes have been drilled out to their final size (Ø5/32). The rows of silver-tinted clecos securing the fairing to Fuselage Frame #1 (at image left) and onto the upper surface of the wing (image bottom) indicate that, at the time the photograph was captured, these holes remained at their preliminary Ø3/32" size. Some of the holes had yet to be drilled in, but all of them would eventually be drilled out to their final diameter (Ø5/32) once all of the hole positions were plotted. (image via Pioneer Aero Ltd.)
The lefthand leading edge wing root fairing (Skin #8) after its shape has been finalized; it is in the process of having its rivet holes drilled off against the associated structure. Note the row of black-painted clecos which secure the fairing’s upper edge beneath the lower edge of the fuselage skin just above it (Skin #6) to the lower engine mount stiffener behind them both. This indicates that the rivet holes have been drilled out to their final size (Ø5/32). The rows of silver-tinted clecos securing the fairing to Fuselage Frame #1 (at image left) and onto the upper surface of the wing (image bottom) indicate that, at the time the photograph was captured, these holes remained at their preliminary Ø3/32" size. Some of the holes had yet to be drilled in, but all of them would eventually be drilled out to their final diameter (Ø5/32) once all of the hole positions were plotted. (image via Pioneer Aero Ltd.)

A wider angle view of the structure shown in the previous image—the front of the aircraft being towards the bottom of the image. The fairing’s shape had yet to be finalized at the time this image was captured and the rivet holes were in the process of being drilled off (the fairing's edges were trimmed to their final dimensions after each of the rivet holes were drilled to their final size). Note that the forward edge of the adjacent wing root fairing (Skin #48) was also in the process of being shaped to match the aft edge of the leading edge fairing (Skin #8). Note. (image via Pioneer Aero Ltd.)

The lefthand leading edge wing root fairing (Skin #8) after its shape has been finalized; it is in the process of having its rivet holes drilled off against the associated structure. Note the row of black-painted clecos which secure the fairing’s upper edge beneath the lower edge of the fuselage skin just above it (Skin #6) to the lower engine mount stiffener behind them both. This indicates that the rivet holes have been drilled out to their final size (Ø5/32). The rows of silver-tinted clecos securing the fairing to Fuselage Frame #1 (at image left) and onto the upper surface of the wing (image bottom) indicate that, at the time the photograph was captured, these holes remained at their preliminary Ø3/32" size. Some of the holes had yet to be drilled in, but all of them would eventually be drilled out to their final diameter (Ø5/32) once all of the hole positions were plotted. (image via Pioneer Aero Ltd.)

This unusual perspective reveals the way in which Pioneer Aero’s engineer Craig Cunha saw the SBD’s Wing Center Section structure when lying on the hangar floor to work on the lefthand leading edge wing root fairing during trial-fitting. The edges of the fairing still needed to be trimmed to their final dimensions at the time this image was captured. To better comprehend what is on view, the wing’s leading edge runs diagonally, from where the fairing joins it and past the lefthand wheel well (top left corner). The forward face of Fuselage Frame #1 lies at image right, with the fuselage running back to its rear. Note that the workshop’s ceiling is visible in the bottom left corner. (image via Pioneer Aero Ltd.)

A slightly different view of the lefthand leading edge wing root fairing following the completion of its forming — note how each of the clecos is black now, revealing that each of the rivet holes has been drilled off to its final size. The complex nature of the part’s curves should be evident, a fact which made the part a significant challenge to shape. (image via Pioneer Aero Ltd.)
A slightly different view of the lefthand leading edge wing root fairing following the completion of its forming — note how each of the clecos is black now, revealing that each of the rivet holes has been drilled off to its final size. The complex nature of the part’s curves should be evident, a fact which made the part a significant challenge to shape. (image via Pioneer Aero Ltd.)
The righthand leading edge wing root fairing during the last stages of its fabrication. Its shape has been finalized but the rivet holes are in the process of being drilled. A number of the clecos holding it to the underlying structure are silver, indicating that some of the rivet holes have yet to be widened from their initial Ø3/32” diameter to their final diameter (Ø5/32”). The row of rivets which eventually attach the fairing to Fuselage Frame #1 had yet to be plotted and drilled at the time this image was captured. Note how the fairing’s upper edge has been tucked into position beneath the lower edge of fuselage Skin #7, its overlapping, as-yet undersized rivet holes serving as a guide to drill off matching holes in the fairing. (image via Pioneer Aero Ltd.)
The righthand leading edge wing root fairing during the last stages of its fabrication. Its shape has been finalized but the rivet holes are in the process of being drilled. A number of the clecos holding it to the underlying structure are silver, indicating that some of the rivet holes have yet to be widened from their initial Ø3/32” diameter to their final diameter (Ø5/32”). The row of rivets which eventually attach the fairing to Fuselage Frame #1 had yet to be plotted and drilled at the time this image was captured. Note how the fairing’s upper edge has been tucked into position beneath the lower edge of fuselage Skin #7, its overlapping, as-yet undersized rivet holes serving as a guide to drill off matching holes in the fairing. (image via Pioneer Aero Ltd.)

Another view of the righthand leading edge wing root fairing during trial-fitting. Note the primer-painted, wing root fairing immediately behind it at the top of the image. This is an original, restored component (Skin #49) from B-22; its forward edge sits atop the aft edge of the new part. As an aside, the circular, green-painted component in Skin #81 at the top right of the image serves as an access panel for replenishing fluid in the hydraulic tank. (image via Pioneer Aero Ltd.)

This is another perspective of the righthand leading edge wing root fairing during trial-fitting. It looks aft from Fuselage Frame #1 (at image right) and demonstrates how well the fairing’s curvature matches that of the underlying wing surface. Note the semi-circular, black-painted fitting at image right; this is part of the steel Wing Center Section jig, bolted to the lower righthand engine mount. (image via Pioneer Aero Ltd.)

The righthand leading edge wing root fairing after trial-fitting has concluded. The part’s shape has been finalized, its rivet holes all drilled to their final size and the edges have been trimmed to their final dimensions. (image via Pioneer Aero Ltd.)
The righthand leading edge wing root fairing after trial-fitting has concluded. The part’s shape has been finalized, its rivet holes all drilled to their final size and the edges have been trimmed to their final dimensions. (image via Pioneer Aero Ltd.)