Overview:

During the same period when Pioneer Aero's Craig Cunha began building up and trial-fitting a new set of upper leading edge wing root fairings for the SBD's Wing Center Section (see Update No.108), he was also working on the lower leading edge wing root fairings (see Update No.94), the Wheel Well surround channels (see Update No.94) and the central bomb fairings (see Update No.84). This article will cover his efforts to complete these components.

Aft Wheel Well Surround Channel Fabrication:

As with his effort to remanufacture the forward wheel well surround channels, described towards the conclusion of Update No.94, Craig Cunha first had to build a set of forming blocks to make the new components from an aluminum blank. With dimensional data derived from surviving non-airworthy parts salvaged from B-22 and original factory drawings, Cunha was able to create a digital model of the aft wheel well surround channels using 3D CAD software. With that model, he could then design a CAD model for milling a forming block on a routing table for shaping the replacement parts.

A view of the forming block for shaping the lefthand wheel well’s aft inboard surround channel; the manufacturer’s drawing for the part is visible in the background. Pioneer created this tool by first laminating several MDF sheets together and then routing out the required shape from that material. They then hardened the tool’s working surface by coating it with epoxy resin. (image via Pioneer Aero, Ltd.)
A view of the forming block for shaping the lefthand wheel well’s aft inboard surround channel; the manufacturer’s drawing for the part is visible in the background. Pioneer created this tool by first laminating several MDF sheets together and then routing out the required shape from that material. They then hardened the tool’s working surface by coating it with epoxy resin. (image via Pioneer Aero, Ltd.)

This image shows the blank for the new surround channel (cut from aluminum sheet) in front of the forming block. Interestingly, the manufacturer’s drawing (seen in the background) specifies what size of blank to start with (5 1/2” x 24” in this case). This is true for almost all aircraft manufacturer’s drawings for the time period as it helped reduce the amount of waste material which would have occurred if the blank was cut too large or too small. (image via Pioneer Aero, Ltd.)

A view of the replacement lefthand, aft inboard surround channel (after completion of the shaping process) sitting next to the heavily corroded original part from B-22. The new part still required trial-fitting and trimming to its final dimensions at the time this image was captured. (image via Pioneer Aero, Ltd.)

Here is a view of the aluminum blank for the replacement lefthand, aft inboard surround channel after it has been worked over the forming block for a while. Stretching and/or shrinking tools will also have been used in between sessions of beating the aluminum over the forming block to help relieve material stresses which can build up in certain areas when creating a part featuring significant compound curvature, as this one does, for example, in its rolled over edge. (image via Pioneer Aero, Ltd.)

Trial-fitting the replacement aft inboard surround channel in the SBD’s lefthand wheel well. (image via Pioneer Aero, Ltd.)

The aft surround channels sitting in the SBD’s lefthand wheel well. The replacement inboard channel (at right in the image) is in the process of being trial-fitted, whilst the outboard channel is an airworthy original B-22 component. (image via Pioneer Aero, Ltd.)

Another view of the SBD’s lefthand wheel well, this time with an overall depiction of the aft surround channels. The replacement inboard channel (shiny aluminum) was undergoing trial-fitting at the time. (image via Pioneer Aero, Ltd.)

A view of the SBD’s righthand wheel well, with its replacement aft outboard surround channel undergoing trial-fitting. (image via Pioneer Aero, Ltd.)
A view of the SBD’s righthand wheel well, with its replacement aft outboard surround channel undergoing trial-fitting. (image via Pioneer Aero, Ltd.)

Righthand Wing Root and Bomb Rack Fairings

With the righthand wheel well surround channels positioned the replacement righthand bomb rack fairing skin could then be fabricated and trial-fitted to the SBD's Wing Center Section. Its inboard edge has a significant joggle, which was pressed into it, with the curves added to match the underlying structure. With trial-fitting completed, Cunha trimmed the part's forward edge to match the forward lower wing root fairing. The stainless steel chute feeding spent shells from the righthand forward machine gun was then positioned, with its lower fitting drilled off against the fairings. With those efforts completed, it was then possible to trim the fairings and wheel well surround channel dimensions so they each lined up properly with each other.

The bare aluminum skin on view in this image belongs to a fairing for the righthand side of the central bomb rack. At the time this image was captured, Pioneer Aero were part way through the process of shaping it to fit snugly against the underlying structure in SBD’s Wing Center Section. Longitudinally, the part extends from Fuselage Frame #1 until the forward edge of Spar #2. Laterally, it runs from the wheel well’s inner edge up to the bomb aiming window and the opening for the bomb trapeze. At the time this image was captured, the part’s joggled inboard edge had been formed, with curvature added to match internal structure. (image via Pioneer Aero, Ltd.)
The bare aluminum skin on view in this image belongs to a fairing for the righthand side of the central bomb rack. At the time this image was captured, Pioneer Aero were part way through the process of shaping it to fit snugly against the underlying structure in SBD’s Wing Center Section. Longitudinally, the part extends from Fuselage Frame #1 until the forward edge of Spar #2. Laterally, it runs from the wheel well’s inner edge up to the bomb aiming window and the opening for the bomb trapeze. At the time this image was captured, the part’s joggled inboard edge had been formed, with curvature added to match internal structure. (image via Pioneer Aero, Ltd.)

Another view of the part described in the previous image. Note that, at the time this image was captured, both the aft and outer edges of the parts have been drilled to match the underlying structure. The outer edge has also been drilled to match the replacement forward surround channel. Furthermore, the front edge has been trimmed to match the lower forward wing root fairing. (image via Pioneer Aero, Ltd.)

A further view, albeit from a different angle, showing the skin for the righthand bomb rack fairing during its trial-fitting to the SBD’s Wing Center Section. Looking carefully, you will see an original, unrestored component (the aft inboard surround channel) from B-22. While corroded beyond airworthy repair, it did help position the bomb fairing accurately, and was later replicated and replaced. (image via Pioneer Aero, Ltd.)

A closeup showing the righthand bomb rack fairing’s forward edge during trial-fitting; a line of blue tape runs along the outer flange of Fuselage Frame #1 (image bottom) to protect it during this process. Roughly at image center, we can see a rectangular stainless steel fitting in the process of being attached to the fairing’s interior surface. This fitting will connect to a chute from the forward righthand .50 calibre machine gun so that spent cartridges from the weapon can exit the airframe easily when it fires. (image via Pioneer Aero, Ltd.)

This image shows the righthand forward wing root fairing and associated bomb rack fairing skins after they have been trimmed to their final dimensions (the spent shell casings port has also been completed). These two fairings, along with the forward surround channel, define the wheel well’s edge. (image via Pioneer Aero, Ltd.)

Here we can see the previously-refabricated forward wing root fairing in the process of being match-drilled against the righthand bomb rack fairing. Completing these two fairings provides this area of the airframe with its final external shape! (image via Pioneer Aero, Ltd.)

A slightly different angle of the structure shown in the previous image. Note the spent machine gun cartridge exit port. (image via Pioneer Aero, Ltd.)

An overall view of the righthand, forward wing root and bomb rack fairings after they have been trimmed to their dimensions. Also positioned are the three sections (and joiners) which comprise the wheel well surround channel. (image via Pioneer Aero, Ltd.)
An overall view of the righthand, forward wing root and bomb rack fairings after they have been trimmed to their dimensions. Also positioned are the three sections (and joiners) which comprise the wheel well surround channel. (image via Pioneer Aero, Ltd.)

What's Next?

The components covered in this article were amongst the last items which Pioneer Aero needed to complete before they could begin final-painting, then riveting together the major subassemblies comprising the dive bomber's Wing Center Section. We will begin covering that process in the near future!