Overview:

Over the past several months, Pioneer Aero’s Hadon Smith has made great strides restoring the leading edges for the SBD’s Wing Center Section. He started with the righthand side, bringing that subassembly close to completion before, more recently, initiating work on the lefthand side. The latter endeavor is now well advanced, as this report will reveal. 

The SBD's lefthand leading edge undergoing trial fitting in its jig, as viewed from the inboard rib at Station #10. At the time this image was captured, each of the ribs had been positioned and drilled against the leading edge skin. (Image via Pioneer Aero Ltd.)
The SBD's lefthand leading edge undergoing trial fitting in its jig, as viewed from the inboard rib at Station #10. At the time this image was captured, each of the ribs had been positioned and drilled against the leading edge skin. (Image via Pioneer Aero Ltd.)

Moving Forwards:

Smith’s last report saw the lefthand nose spar essentially complete, with the opening stages of the leading edge reassembly process underway. With the leading edge skin located accurately in the jig, Smith positioned the nose ribs against it. He then drilled mounting holes along each rib’s forward flange and through the skin, temporarily securing the components in position with clecoes. This allowed the nose spar to be drilled into positioned and secured (again with clecoes) against the rear flange of each nose rib.

Another view of the lefthand leading edge during trial-fitting. The semicircular skin cutout to the left gives clearance for the wheel during gear retraction (once the cutout is trimmed to its final shape). The curved inner contours in the adjacent ribs form the wheel well. Note: the stringer which runs along the leading edge has also been positioned and drilled against the skin. (Image via Pioneer Aero Ltd.)
Another view of the lefthand leading edge during trial-fitting. The semicircular skin cutout to the left gives clearance for the wheel during gear retraction (once the cutout is trimmed to its final shape). The curved inner contours in the adjacent ribs form the wheel well. Note: the stringer which runs along the leading edge has also been positioned and drilled against the skin. (Image via Pioneer Aero Ltd.)
A view of the lefthand leading edge showing the nose spar during trial fitting; it has been positioned and drilled against the rear flange of each nose rib. The noticeable cutout in this spar also helps form the wheel well. (Image via Pioneer Aero Ltd.)
A view of the lefthand leading edge showing the nose spar during trial fitting; it has been positioned and drilled against the rear flange of each nose rib. The noticeable cutout in this spar also helps form the wheel well. (Image via Pioneer Aero Ltd.)

Wheel Cutout and Remaining Stringers

Smith was then able to position and drill the fore-most stringer against the leading edge skin. With the locations for the nose ribs and nose spar now firmly established (by drilling them against the skin), Smith could then calculate the precise position and orientation for the wheel axle. Using this information, he rigged up a cardboard template outlining the wheel clearance so he could trim away excess leading edge skin to properly define the wheel cutout. He then carefully shaped the remaining leading edge stringers to align perfectly with the skin contours and secured them in place.

Another view of the lefthand leading edge during trial-fitting. The large cardboard disc represents the necessary clearance for the left wheel to retract into the wing. The black rod running from its center marks the precise location for its axle, a detail made possible by drilling the leading edge ribs and nose spar into position. This allowed excess leading edge skin to be trimmed, using the cardboard disc as a guide. (Image via Pioneer Aero Ltd.)
Another view of the lefthand leading edge during trial-fitting. The large cardboard disc represents the necessary clearance for the left wheel to retract into the wing. The black rod running from its center marks the precise location for its axle, a detail made possible by drilling the leading edge ribs and nose spar into position. This allowed excess leading edge skin to be trimmed, using the cardboard disc as a guide. (Image via Pioneer Aero Ltd.)

Primer Painting And Reassembly

After drilling the nose ribs and stringers to the leading edge skin to formalize their positions, it was time to take the temporarily-assembled structure apart to coat each component in primer paint. With the paint set, Hadon Smith then re-clecoed the parts back in place for the next stage, forming the fresh air ductwork.

Some of the parts for the lefthand inboard wing leading edge following the application of primer paint. Hadon Smith soon reassembled them with clecoes to allow manufacture of a new fresh air duct. (Image via Pioneer Aero Ltd.)
Some of the parts for the lefthand inboard wing leading edge following the application of primer paint. Hadon Smith soon reassembled them with clecoes to allow manufacture of a new fresh air duct. (Image via Pioneer Aero Ltd.)
The lefthand leading edge skin, nose ribs and central stringer clecoed back together after primer painting each part. Note: this view is looking towards the outboard bulkhead. (Image via Pioneer Aero Ltd.)
The lefthand leading edge skin, nose ribs and central stringer clecoed back together after primer painting each part. Note: this view is looking towards the outboard bulkhead. (Image via Pioneer Aero Ltd.)

Fresh Air Ductwork

With the nose ribs, stringers and leading edge skin clecoed together, Smith could then begin forming components for the fresh air duct to match the leading edge structure. The duct snakes its way from a port in the SBD’s lefthand leading edge through the ribs into the cockpit, providing fresh air to the pilot. This duct comprises several sections of 2” diameter aluminum pipe, flared at each end to allow adjoining sections to slip together during installation. 

Smith began the process of making this duct by creating the necessary bends in a single piece of pipe. Due to the nature of the machine used to bend the pipe, however, it was not possible to produce consecutive bends with the required length of straight pipe between them (i.e. the straight sections were too long). As a result, Smith cut away these excess lengths of straight pipe and welded the bends together to form the appropriately sized part.

The duct has multiple bends, enabling it to pass through the nose ribs and around other obstacles. This image shows a length of 2” diameter aluminum pipe with all of the required bends installed. Note, however, the lengthy sections of straight pipe between bends. This resulted from the pipe-bending machine being unable to induce consecutive bends without a minimal length of straight pipe between them - a length which proved excessive to the part's needs. Therefore, after this image was captured, the excess straight sections were cut out. The remaining bends were then welded together with appropriately-sized straight sections to create the proper pipe contours. The pieces seen in this image with expanded ends were welded in place to form the joints. (Image via Pioneer Aero Ltd.)
The duct has multiple bends, enabling it to pass through the nose ribs and around other obstacles. This image shows a length of 2” diameter aluminum pipe with all of the required bends installed. Note, however, the lengthy sections of straight pipe between bends. This resulted from the pipe-bending machine being unable to induce consecutive bends without a minimal length of straight pipe between them - a length which proved excessive to the part's needs. Therefore, after this image was captured, the excess straight sections were cut out. The remaining bends were then welded together with appropriately-sized straight sections to create the proper pipe contours. The pieces seen in this image with expanded ends were welded in place to form the joints. (Image via Pioneer Aero Ltd.)
Here is part of the fresh air duct during its fabrication. Although they are hard to see, there is a slip joint at each end of the long, straight section of pipe. The sheet of paper at image center is the factory drawing for the complete duct, while the cardboard beneath it has the full-sized drawing of the bends inked onto it. The latter helped to ensure complete bend accuracy. (Image via Pioneer Aero Ltd.)
Here is part of the fresh air duct during its fabrication. Although they are hard to see, there is a slip joint at each end of the long, straight section of pipe. The sheet of paper at image center is the factory drawing for the complete duct, while the cardboard beneath it has the full-sized drawing of the bends inked onto it. The latter helped to ensure complete bend accuracy. (Image via Pioneer Aero Ltd.)

For the duct’s interface with the leading edge, Smith had to weld an appropriately curved flange to the section of pipe which attaches to the interior face of the skin. He then fashioned a matching exterior flange for riveting the duct to the leading edge skin, rolling its inner edge to provide a smooth transition for the air entering the duct. Smith then trial-fitted the duct to the leading edge, and fabricated specialized clamps for holding each section of ductwork together or to the nose ribs they passed through.

Riveting

After forming the fresh air duct, its parts went into the paint booth for a coat of primer. It was then time to rivet together the leading edge structure comprising the skin, nose ribs and stringers. The video below shows Hadon Smith on the rivet gun (closest to camera) working with Craig Cunha on the bucking bar to form up the rivets which hold one of the nose ribs to the skin. Listen in to the call and response between these two engineers; it really reveals how well an experienced rivet team collaborates.

Final-Fitting the Nose Spar

It was now time to final-fit the nose spar into the leading edge structure. Hadon Smith had already drilled off this subassembly against the rear flanges of each nose rib. Smith had permanently riveted these ribs in place against the leading edge skin, so he could now drill off the spar against the skin too.

A view of the lefthand leading edge when the nose spar was being final-fitted against the adjacent structure. The ribs are clecoed in place against the spar to hold it firmly in place while Hadon Smith works along the length, drilling holes for attaching it to the skin. (image via Pioneer Aero Ltd.)
A view of the lefthand leading edge when the nose spar was being final-fitted against the adjacent structure. The ribs are clecoed in place against the spar to hold it firmly in place while Hadon Smith works along the length, drilling holes for attaching it to the skin. (image via Pioneer Aero Ltd.)

Trial-Fitting the Inter-spar Ribs:

Now that the nose spar had been drilled off against the leading edge ribs, Smith could begin using these holes to trial-fit the inter-spar ribs linking the nose spar to Spar #1. He had formed the basic shapes for each of these ribs some time earlier, but Smith used this opportunity to trim and fit each of them into the correct position against the nose spar. With that work completed, these interspar ribs were ready for the paint booth and primer painting!