And just like that it was August (or will be by the time anyone reads this) Like usual I've been letting various projects sit and simmer in my brain for a while while I tackle something else. The Dumod has been simmering since January and my brain was ready to start making some progress again.
The motor/retract pods I drew up last time came together fine. They've been glued into the wing and the wiring routed through the center section. They are pretty flimsy torsionally, so I'll probably need to add some bracing to correct for that. The nacelles may actually stiffen them up enough by themselves, but if they don't, a repair will be harder.
With the motors and pods mounted I was able to solder up the battery connections and plug everything into the receiver.
Previously, I had built the retaining dowels etc for the leading edge of the wing. In this update I've installed the retaining mechanism for the trailing edge of the wing. It consists of two 1/16" plywood plates on the wing side, and a 1/8" plywood plate with two spruce blocks glued atop it on the fuselage side. These were through-drilled and tapped for a pair of #10-24 nylon bolts. Initially I was going to use only one bolt in the center to save weight and complexity, but I like the idea of putting any wing loads into the fuselage as close to the fuselage sides as I can for a more direct load-path. The bolts are way long, and will be cut down at a later date.
The tail surfaces have been covered with fiberglass and WBPU and the outer V-stabs have been glued in place. I'm holding off on attaching the tail to the fuselage because I'm sure I've forgotten something which will be easier to deal with without the tail on.
The Beech 18 swung 99" diameter Hamilton Standard props. Here's what that looks like.
You'll notice that the prop tip only just clears the fuselage because the nose tapers away at that point. Now recall that the Dumod stretched the Beech fuselage forward more than 6 feet. At 1/12 scale a 99" prop comes out to about 8.25" diameter. Here is what an 8" prop looks like mounted to the motor. There is less than 1/8" clearance there. (1.5" in full scale.) Now I realize why the Dumod switched to 3-blade props; it let them drop the diameter enough to get the fuselage clearance. I may have to do the same.
Side note, I used a label maker for the servo wires and love how tidy it looks.
I had run the numbers for an 8" prop through web-o-calc and prop-calc previously and figured I needed an 8x8 2 blade. Now I need to do it again to figure out if I can run a commercially available 3-blade or a smaller 2-blade and still make my performance numbers. Maybe I'll have to cut my 8x8s down a little. We'll see. Anyone with prop suggestions etc, I'm open to feedback.
And finally, a beauty shot with the tail set in place temporarily.
Things I know I have to do still:
-Bend up landing gear wire for the nose wheel
-Mount the nose gear retract
-Solder stop-washers to the inside of all landing gear wires.
-Decide how the nose will mount and mount it.
-Install spars
-Make braces and a spar carry-through for the motor mounts.
-Cut out ailerons and add balsa to aileron bays
-Line ailerons with balsa, then add control horns and hinges.
-Install aileron servos
-Run aileron servo wiring
-Cut out nacelles to fit around new motor pods
-Sand and glass fuselage
-Install horizontal tail
-Make dorsal strake, install central tail and glass together.
-Shape wingtips
-Fill, sand, and glass wings
-Battery tray/hold-downs
-Figure out a battery hatch if necessary
-Paint
-Practice (haven't flown anything in months)
-Preflight inspections/checks
-Maiden!