"Closing up the Wing"

Adding wingtips, anti-stall slots and bottom sheeting

OK, after thouroughly checking to make sure I had everything done "inside" the wing, and the wing was ready to be closed up, I had our trusty QC inspector go over it. With his approval, I proceeded to sheet the bottom of the wing with 3/32" balsa sheeting.
The Dauntless uses 3 anti-stall slots (affectionately called "mailbox slots" during WW2) at the end of each wing. You build the slots "offline" as a box with 2 dividers in each box, then cut the sheeting and ribs out at an angle to slide the anti-stall box into the wing. Once glued in, you sand the boxes down flush with the top and bottom wing surfaces.

The wingtips themselves are built by sandwiching multiple layers of 3/8" balsa sheeting over a 1/16" aircraft ply core. The finished "sandwich" provides a solid balsa wingtip that you further whittle and sand down to the finished wing tip shape. You get the shape close "offline" then glue it onto the wing and further sand it to the final shape. Messy job, no fun, but the end result is well worth the effort and very strong.

Access hatches

To sheet up to and around the servo hatches, I used the following techniques. First off, I had already made the 3/32" plywood hatches that had the aileron, flap and brake servos mounted on them. So I removed those hatches, sheeted over the area, then cut a small hole in the servo area of the sheeting. I could then stick a pin up through the screw holes from the inside of the wing, out through the sheeting to line up my hatches. I screwed the hatches back down in position over top of the sheeting, then used a razor knife to cut the sheeting out around the edges of the hatch. This gave me a perfectly fitting plywood servo hatch in the bottom sheeting.

Retract hatches

For the access hatch to get into the retract mechanism, I did it a little differently. These hatches were only for "access" and did not actually have servos mounted to them. Also, they were not just "flat" panels, they had to conform to the compound curves of the wing and dihedral joint.

First I ironed a small piece of Monokote over the entire retract area. Next I began building layers of heavyweight glass over the Monokote. Next, I cut 2 small pieces of 1/32" aircraft ply to act as stiffeners. I pre-warped them to the approximate shape they would need to fit. I used two because I needed to have an angle change at the dihedral joint. I epoxied them down and used masking tape to hold them to proper shape until the epoxy was good and hard. With the ply plates epoxied down, I added another layer of glass and let it cure overnight.

Now I was able to remove the laminated assembly by pulling the Monokote loose from the sheeting, and set it aside. I then cut out a "reduced" hole for the wheelwell and hatch, making sure I was a good half inch or so from my final desired hole. Now that I could see up inside of the wing, I was able to pencil my exact hatch and wheelwell lines onto the sheeting. I transferred the dimensions onto the laminate hatch, and cut it to shape.

Like the servo hatch technique above, I was now able to lay the hatch down onto the wing and use a razor knife to cut the sheeting out around the hatch for a perfect fit. I then marked and cut the strut cover out of the laminated hatch, giving me a perfectly fitting strut cover that also conformed to the contour of the wing. I haven't yet worked out exactly how I'll attach the strut covers to the retract struts, but will cover that later.