Center Flap Progress:
Jayden Malloy is making solid progress rebuilding the SBD’s central wing flap, an effort which began back in February of this year. While he had to refabricate numerous new ribs for this key component, Molloy was able to save all of the doublers. The latter components rivet to each rib, adding strength over the spar cut outs. To ensure that each rib (with its doubler) matched up properly with the original spar, Jayden had to remanufacture the right angle attaching brackets. While these brackets may seem simple to construct, the addition of a joggle allowing the part to overlap the rib doubler made the process more complicated.
Stiffener Extrusions:
Jayden also cut, formed and installed new stiffeners. A series of these modified extrusions straddle the flap’s entire length adding strength to the structure. Thankfully, he was able to also refurbish a couple of original examples from the donor flap. These new components also required joggling at each end (in most cases) in order to overlap other components mounted to the flap’s perforated skin properly. As with the rib angles, this effort required the use of a specialized press die tool
A right angle bracket during the fabrication process. Each rib on the center flap uses one of these parts to secure it onto the component’s main spar. Note the ‘joggle’ pressed into the edge facing out of the image; this provides clearance for the step up from the rib to the doubler. (image via Pioneer Aero Ltd.)
Here we can see the center flap’s main spar, a reconditioned original salvaged from the donor flap, clecoed to the new skin. The bracket clecoed to the spar at image center is one of the newly-fabricated right angle brackets used to hold each rib to the spar. We saw this device part way through its remanufacture in the previous image. (image via Pioneer Aero Ltd.)
A section of extrusion having its end joggled via a specially fabricated press die set. A joggle essentially involves the addition of a small offset into a part to allow it a flush overlap flush with another component. This process was repeated for the end of each stringer section. (image via Pioneer Aero Ltd.)
The replacement stringer sections (with joggled ends) temporally fitted to the flap skin. Two of the afore-mentioned right angle brackets for attaching ribs to the flap’s spar are also visible. Note how the locations for each of the dive flap's characteristic perforations have been inked onto the skin. (image via Pioneer Aero Ltd.)
Perforations:
As noted previously, the SBD’s set of dive flaps is one of the type’s most distinctive features, with its numerous perforations being a prominent detail. After restoring or remanufacturing numerous parts for the dive bomber’s center flap, Jayden Malloy began cutting and shaping each of these perforations. This flap spans the entire 11’ width of the SBD’s wing center section, so Molloy had to repeat this process many times over - 81 in total!
Cutting & Flanging:
Molloy used a fly cutter to make sure each hole was placed at the correct location and with the appropriate diameter. A fly cutter is a tool which fits on a drill press. There is a drill bit at its center, to position the hole precisely, while a cutting blade is set on an arm at a specific radius extending from the center to set the hole size. Jayden used this technique to cut out half of the holes in a checkered pattern across the flap skin. He then de-burred the hole edges, followed by a light sanding, to prevent any crack propagation during the flanging process. By cutting a set of holes in a checkerboard pattern to begin with, Molloy ensured that the skin retained sufficient structural integrity when flanges were pressed into each of them (i.e. the aluminum would not pull away from adjacent holes, distorting the sheet). After forming flanges for each of the first set of holes, Molloy then cut and flanged each of the remaining holes to form the complete set.
Forming the Flap Trailing Edge:
The flap’s trailing edge has to be folded up. Because the aft two radii are close together, it was impossible to use a traditional sheet metal brake to place the second fold at the correct angle. As a result, Jayden had to manually adjust the flange with special pliers to ensure that both folds were placed at the correct angle relative to one another. This will ensure that when it is installed it will not buckle the skin, warping the flap.
Here we see a new flange about to be created. The steel plate sandwiched between the hydraulic and the tooling, spreads the loading over the entire die set, protecting the tooling. (Image via Pioneer Aero Ltd.)
After cutting and flanging half of the holes into the center flap’s skin, it was time to cut out and flange each of the remaining holes. Here we can see some of the first new set of holes to be cut from the skin. Note how the fly cutter has bored a hole in the center of the disc of metal cut from the skin; this is how the tool both centers the hole and keeps the cutting blade from chattering against the material as it bores into it. (Image via Pioneer Aero Ltd.)
