The B- 25 Sunday Punch sets in
the bones, ready for power and
Drew shows off his soldering skills by connecting an ESC to a Blue Wonder
Drew is at the sticks after a hand launch. Removing the plug-in
landing gear gives it a nicer look in the air and less drag.
For simplicity, our prototype used plug-in landing gear
mounted to plywood formers in the nacelles and fuselage
former F2. On a second build, the same formers were
modified to accept retracts without servos. Alternatively,
this Mitchell could be belly landed, but the belly and
nacelles should be planked in the contact areas for
The top half of the fuselage is built over the plans. Start
by pinning down the horizontal keel parts. Next, glue in
all of the T formers. Ensure that they are all perpendicular
to the board except F7—use the angle gauge on the plans
to tip F7 backward. F7 forms the back of the battery hatch
and the angle allows the hatch to easily lift off.
Slide in the battery tray (BATT) and glue it into place
along with the upper keel and wing pockets (WP) marked
side facing out. Add some stringers to stiffen the structure.
Alternating from left to right can minimize stress in the
assembly, as can dampening the stringers before installation.
After the upper fuselage is fully cured, unpin and flip it
over. Glue in all B formers perpendicular to the horizontal
keels. Assemble the servo tray and install the elevator servo,
then mount it to F7b. The wing bolt pad (WB) is part of the
servo tray, too.
Epoxy a nylon 10-32 nut to the WB and then seal it in
with all of those stringers. The battery is accessed from a
hatch above the wing. Knock out the airfoil marked on the
WPs. Slice through the upper keel and the stringers between
the pairs of upper formers at F5 and F7 down to the airfoil
opening. Carefully free the hatch.
Because the Mitchell had distinctive gull wings, the
wings are built as two inner and two outer panels. Each
is assembled over the plans in the typical manner. The
main spar consists of an upper and lower 1/8 x 3/32 balsa
or basswood spar joined with full laser-cut shear webs.
Pin down the TE, rear spar, and the lower main spar.
Glue in the ribs, the upper main spar, and then the shear
webs. Use the supplied angle gauge to tip ribs W1 and
W6 to obtain the correct dihedral. All other ribs should
be perpendicular to the board.
Fill in the aileron parts and the wingtips in the outer panels
as shown. Join the inner and outer panels with plywood
(BRACE2 and LE). Sheet the upper wing surface from the
main spar to the LE with 1/32 balsa. Sheet the top and bottom
between W1 and W2. Now glue a 3/8-inch soft balsa LE into
place and sand it to the correct shape. Join the two wings with
Slice through the TE where shown to free the ailerons. The
aileron servos are attached to a plywood door that seats into
a pocket between ribs W7 and W8. Add scrap wood to the
31 Model Aviation OC TOBER 2013 www.ModelAviation.com