Mount the Fiberglass Nacelle Covers
mounting the fiberglass nacelle covers the engine needs
to be removed so that the nacelle cover will fit over
the nacelle. Make sure the correct nacelle cover is
used, as there is a left and right cover. The easiest
way to tell the difference is the notch cut out for
the landing gear strut. To mark the mounting holes for
the nacelle cover I found it easier to use painter's
tape to hold the cover in place as I marked the mounting
hole. Use a Dead Center marking tool to mark the position
of the mounting holes on the wing. Remove the nacelle
covers and use a 3/32" drill bit to drill the mounting
holes. Use a 1/8" bit to enlarge the mounting holes
in the nacelle cover.
the #4 x 5/8" Phillips head screw to cut threads
in each of the drilled mounting holes and then use thin
CA to harden these threads. When the CA has cured use
#4 x 5/8" Phillips head screws, #4 lock washers,
and #4 flat washers to mount the nacelle cover to the
bottom of the wing. A long shaft screwdriver is essential
to mount the nacelle cover. I found the easiest way
to do this was to shine a flashlight on the mounting
screw from the landing gear bay, and then look through
the crack between the firewall and the nacelle cover
to place the screwdriver on the head of the screw.
Don't worry if it feels clumsy putting this nacelle
cover in place on the wing, because you're going to
get a lot of practice as the assembly of the plane continues.
The nacelle cover will be put on and removed several
times as we continue.
Mount the Main Landing Gear Doors
gear doors have always been a bit difficult to design
and implement, but Top Flite has done an outstanding
job of accomplishing this very task. Their design for
working gear doors is very well done and very sturdy.
first step to installing the gear doors is to remove
the nacelle cover from the wing. Locate the areas on
the inside of the gear doors where the hinges will mount.
Use a hobby knife to scrape away the black paint where
the hinges will mount to the gear doors.
tape to secure the gear doors in place on the nacelle
cover. At this point I found I had a problem with one
of the gear doors as it was pretty warped and would
not mount correctly on the nacelle cover. I was able
to correct this by running hot water over the gear door
to heat it up.
Then I twisted the gear door in the opposite direction
of the warp. A few minutes of doing this straightened
out the gear door so it fit flush on the nacelle cover.
Use a razor blade to cut off 1/8" from two nylon
ball links, then use a 5/64" drill bit to drill
out the inside of the ball link. These hinges will be
used for the rear of the gear doors. Now cut 1/6"
off of two ball links and construct two more hinges,
which will be for the front of the gear doors.
ball links are mounted to the door hinges using 2-56
x 3/8" screws, # 2 lock washers, and #2 flat washers.
The orientation of the hinges is very important so make
sure to refer to the instruction manual as they are
installed in the plane. Four nacelle hinges are constructed
by mounting 0-80 ball link ball in the bottom hole of
each hinge using a 0-80 nut and a drop of threadlock
to secure the nut in place. Be careful here as I had
one ball link shaft break off as I was tightening down
the nut, which caused me to be short at the end of the
assembly of the plane. Build two "A" hinges
and two "B" hinges, referring to the instructions
as a guide for doing this. Referring to the pictures
in the instruction manual use coarse sandpaper to roughen
the inside of the nacelle cover where the gear door
hinges will mount
30-minute epoxy mixed with microballons to glue each
hinge assembly to the gear doors where the paint was
scraped off earlier. After the epoxy has set repeat
this to glue the hinge bases to the inside of the nacelle
cover. After all of the epoxy has set remove the tape
from the outer doors and ensure that the gear doors
open and close freely. If any epoxy has "oozed"
out so that it interferes with the closing of the gear
door it will need to be removed.
If for any reason the gear doors need to be removed
it's important to NOT pop the ball links off of the
ball mounts. If the door needs to be removed unscrew
the door hinges at the ball link and remove the gear
door this way.
Hooking up the Main Landing gear
a 1/8" x 1/2" hardwood dowel into a lever
mount, with the end of the dowel should be flush with
the backside of the lever mount. Hold the lever mount
on the back side of the nacelle so that the outer edge
of the lever mount is flush with the side of the nacelle,
and the top flat portion of the lever mount is flush
with the top of the nacelle. Use a 1/16" drill
bit to drill a pilot hole for the mounting screw. Remove
the lever mount and use #2 x 3/8" button head Allen
screw to cut threads in the pilot hole and then harden
the threads with thin CA. When the CA has dried install
the lever mount in place using the button head Allen
screw. Use the second hole in the lever mount to drill
a pilot hole using a 3/32" drill bit; this hole
will be to mount the bell crank. Use a #4 screw to cut
threads in this hole and then harden the threads with
wooden bell crank that is made out of hardwood ply operates
the gear doors. While the original wood doors are very
durable some may find that repeated use over a long
period of time may wear out the wooden doors. With this
in mind one of our RCU members had made available a
set of aluminum bell cranks that can be used in place
of the stock wooden ones. They are available for a cost
of $10, which includes shipping. If you are interested
contact RCU member
doors may be found here) to get a set of these bell
cranks. I picked up a set so that I could show them
here in this review.
install the bell crank first glue a plastic washer to
each side of the bell crank using thin CA. Now fit a
brass bushing into the bell crank and install it in
the lever mount using a #4 x 5/8" screw. Tighten
the screw tight enough to hold the bell crank in place,
but it still needs to be able to move freely. Bend a
hook in each end of the provided spring approximately
3/8" from the coils of the spring. One end of the
spring is hooked through the hole in the bell crank,
and the other end is hooked into one of the notches
in the lever mount. Start in the middle notch, but this
can be adjusted if needed for better operation of the
gear door. Test the operation of the landing gear in
that it moves freely and does not bind. If needed trim
the bell crank in order to provide free movement of
the landing gear strut. Cut a 4" pushrod so there
is 3/8" of thread remaining and then a total length
of 2-1/2". Bend the pushrod to match the diagram
provided in the instructions.
this point I was a bit perplexed in constructing the
other gear door pushrod. The instructions do not mention
what to use to build this. I finally a found small piece
of threaded rod that is used for this in the bag that
contained all of the screws, but it took me some time
searching to find this. Once the pushrods are constructed
use epoxy mixed with microballons to glue control horns
to the inside of the gear doors, attach the pushrods
to the bell crank and use this as a guide in placing
the control horns.
each gear door and work the retracts to adjust the length
of the pushrods so that the gear door completely closes
without binding. I found it easier to disconnect one
door to adjust the pushrod of the other door. With both
doors adjusted use a can of compressed air to cycle
the landing gear and make sure that the gear doors completely
close without binding.
pictures can be used as reference for the workings of
the landing gear and gear doors.
Mount The Cowl
again, the nacelle cover needs to be removed for these
next steps. Use 5/32" drill bit to drill holes
through the firewall at the 8 precut marks for the cowl
mounting tabs. As you can see in the picture place something
solid behind the firewall when drilling the holes to
prevent accidentally drilling holes in the fuel tank.
Use a 4-40 x 3/8" Phillips screw and 2 #4 washers
to pull the blind nuts in place in each of the holes
that were just drilled. Use thick CA to secure the blind
nuts in place, making sure to not get any glue in the
threads of the blind nuts. There are two different sizes
of cowl mounting tabs: the long ones are marked "A"
and the short ones are marked "B". One of
the "A" tabs will have a larger hole in the
top of it. Press a 4-40 blind nut into the larger hole
and use thick CA to secure it.
threadlock on the screws to install the cowl mounting
tabs and install each mounting tab with 2 each 4-40
x 3/8" Phillips screws, #4 lock washers, and #4
flat washers. When installing the tabs the "A"
tab with the blind nut in it is installed at the top
of the firewall, with the blind nut to the rear. Install
the remaining tabs so that the blind nuts are to the
front of the nacelle. In the cowl ring there are 3 larger
holes pre-drilled and one smaller pre-drilled hole.
Install 3 4-40 blind nuts in the 3 larger holes.
When installing the 4-40 socket head screws that mount
the cowl it's important to remember that when the plane
is assembled it's going to be rough to get into the cowl
when removing it, and therefore could lead to the screw
falling out and being lost. I will admit that this is
not my idea and that I picked it up from the thread
about this plane here on RCU, but use fuel tubing to
retain the screw in place. Insert the 4-40 x 1/2" socket
head screw, #4 lock washer, and #4 flat washer through
the mounting tabs (and through the cowl ring for the tab
at the top of the cowl) and then slide a small piece of
fuel tubing over the screw. Now when the cowl is removed
the fuel tubing will keep the screw from falling on the
ground and being lost. As you can see it is about
impossible to get an Allen wrench straight on to the
cowl mounting screws, so a ball end wrench is mandatory
for this plane. The ball end will allow the screws to be
turned from an angle so that the cowl can be removed.
And as you'll see later a long shaft wrench is needed as
well in order to access the one screw at the top of the
cowl ring. Great Planes makes a set
of ball drivers that are perfect for this application,
the part number for these can b found in the instruction
As can be seen above, the cowl ring is mounted on the
the cowl ring in place cut the ring so the engine muffler
can be installed on the engine. The cowl now needs to
be rough-cut in order to allow it to slip over the head
of the engine. Use a cutting wheel on a rotary tool
to rough cut this hole. The hole will be cleaned up
later on as we finish up the installation of the cowl.
the next step the inboard portion of the wing with the
nacelle needs to be mounted on the fuselage. Slip the
three wing tubes through the fuselage and slide the
inboard wing section in place. I placed a small board
across the wing tubes on the other side of the fuselage
and placed some weight bags on the boards to counter
the weight of the wing section. This let the fuselage
sit level. Position the fiberglass carburetor intake
in place on top of the wing and mark the position of
the mounting holes. Use a 1/16" wrench to drill
mounting holes, cut threads in each hole with the #2
x 3/8" Allen Head Button screw, and then harden
the threads using thin CA. When the CA has cured install
the carburetor intake using #2 x 3/8" Allen head
Now slide the cowl into position on the nacelle. As you
can see in the picture above there is quite a bit of
down thrust built into the engine mounts. Because of
this the user will need to make a compromise between
centering the propeller in the cowl and aligning the
cowl with the nacelle cover. The user needs to position
the cowls so that they look "about right". Looking at
the cowl from different angles while doing this will
help to get it positioned correctly. When satisfied with
the position use thin or medium CA to tack the cowl to
the cowl ring.
breaking the cowl ring free from the cowl carefully
remove the cowl. Use 30-minute epoxy mixed with microballons
or milled fiber to build a fillet all the way around
the cowl ring on both sides of the ring. When dried
remount the cowl and cut an access hole in the top of
the cowl that will be used to insert a ball driver to
access the mounting screw. With the cowl mounted now
cut the cowl in order to allow the muffler to be mounted.
Also clean up the hole cut for the engine, ensuring
to add a hole for the glow diver to be attached to the
this is a 3-line fuel system a mount in the cowl is
needed for the fill line. Included with the plane is
an end for the fill line, so we need to build a mount
in the cowl. This is actually very easy to do with a
scrap piece of balsa and 9/32" brass tube. Cut
the scrap balsa to approximately 1" square and
shape one side to fit the curve on the inside of the
cowl. Drill a 9/32" hole in the middle of the block
and insert the brass tube. The tube needs to be cut
so that it just extends to the outside of the cowl.
This is then epoxied into the plane inside the cowl.
To mount the replica engine first sand the side of the
replica to remove the paint from the plastic.
out two of the cylinders from the replica. This is to
allow air flow through the replica to the "real"
engine inside of the cowl. On the remaining cylinders
us a small drill bit, or the tip of a hobby knife, to
make small holes for the replica pushrods. Each cylinder
has 2 pushrods on it. Insert the replica pushrods and
put a drop of medium CA on the inside of the replica
engine to hold the pushrods in place. Next mount the
replica engine inside of the cowl so that it sit evenly
in the cowl. Use thin CA to secure it in place. If needed,
enlarge the hole around the center of the replica engine
in order for the "real" engine to sit without
rubbing or vibrating against the replica.
last bit for installing the cowl is to install a needle
valve extension. As you can see in the pictures I had
to have my needle extension exit at the bottom of the
cowl. I really didn't want to do it this way, but because
I couldn't reverse the carb on the FL-70 engines I didn't
have much choice. I used a tried and true technique
for installing items such as this. First tape a strip
cut from a file folder to the nacelle behind the cowl.
Position the needle extension and make a hole in the
file folder. Without moving the strip of folder install
the cowl into position and then transfer the hole to
the cowl. Drill the cowl to install the needle valve
Hook up Flaps and Ailerons
you can see in the picture above there are a lot of
servos in the wing (in fact there are two more servos
for the throttles as well, for a total 8!). The flaps
and ailerons all use standard servos. The mounts for
the servos are all pre-constructed with the wood mounting
rails already glued to the hatches. I did find a couple
of the glue joints to be a bit loose, so it would be
a good idea to run a bead of medium CA around the base
of each servo rail just to make sure it's secure. One
mistake I see a lot in mounting servos is that many
times they will be mounted directly to the wood in installations
such as this. This is not a good idea because that contact
with the wood will directly transfer vibrations to the
internals of the servo. If direct contact such as this
occurs it bypasses the benefits that the servo grommets
give. To avoid this contact I will place a small metal
ruler between the servo and the hatch when marking the
mounting holes. This gives enough separation to keep
vibrations out of the servo. Mark the holes with a Dead
Center marking tool and drill the mounting holes with
a 1/16" drill bit. I like to use #2 servo mounting
screws from www.microfasteners.com
for mounting servos, as the socket heads in these screws
aren't prone to stripping like regular screws are. After
using a screw to cut threads in the mounting hole the
threads are then hardened with thin CA.
servo is then mounted to the hatch. The hatches are
mounted into the wing using #2 x 3/8" Allen head
button screws. As with all other screws in wood the
threads are hardened with thin CA prior to mounting
the screw in the hole. For each aileron a 6" servo
extension is added to the servo wire. Heat shrink tubing
is provided with the plane and should be used on all
connections such as this to prevent the joint from pulling
apart. Simply slide the heat shrink over the joint and
heat it with a heat gun to shrink the material. Although
the instructions say to use a heat gun or lighter to
shrink it I would advise against using the lighter.
I have used them in the past and it's possible to melt
and distort the servo connections if too much heat is
applied. This is why I prefer to use the heat gun. As
with the throttle wires, make sure each wire is properly
all the servo hatches in place the pushrods for the
ailerons and flaps need to be installed. The TF B-25
includes solder clevises for all the pushrods, which
I really liked to see. To install the control horns
first use a ruler to mark their location on the control
surface. When mounting the control horns the ailerons
are mounted 3/16" from the edge of the aileron
and the horn on the flaps is 3/8" from the edge.
One thing I do want to point out is that even though
backs for the control horns are provided they are not
used to mount the control horns. The horns are mounted
by directly screwing in #2 x 3/8" Phillips head
screws into the control surface. I like to use a couple
of craft sticks and two clamps to center a control surface
such as this when I am setting up the pushrods.
the servo into the receiver and turn it on in order
to center the servo and then measure the pushrod for
the proper length. Use proper soldering techniques to
solder the clevis on the pushrod at the length that
was previously marked. Install the pushrod on the control
Assemble the Tail
the tail starts with installing the rudders on the vertical
stabilizers. These are mounted with the same smaller
hinge points as the ailerons use, and are installed
in the same manner. While the epoxy is setting on the
rudder hinges move on to the elevator. The TF B-25 has
a split elevator that is connected with an elevator joiner
wire. Use a piece of sandpaper to rough up the torque
arm portion of the elevator joiner wire so that the
epoxy will get a better grip. Slide 2 plywood elevator
joiner mounts onto each side of the elevator joiner
wire. Once the mounts are on the wire use thin CA to
glue the two mounts together.
installing the elevator mounts to the trailing edge
of the horizontal stabilizer it's very important to
make sure that it is straight. Slide each elevator half
onto the joiner wire and place on a flat surface to
see if the wire is straight. If both sides don't sit
flat then bend the joiner wire until both sides do sit
flat. Cut away the covering on the trailing edge of
the stab and epoxy the elevator joiner mounts to the
stab. While the epoxy is mixed use a little bit to install
the stabilizer dowel in the hole in the front of the
the elevator hinge points in the same way as all others
already installed. When installing each elevator halve
also put a bit of epoxy into the hole for the elevator
joiner wire. Install both elevator halves and set aside
until the epoxy sets. While the epoxy is setting install
the rudder servos into each servo hatch in the same
manner as the aileron and flap servos were installed.
the elevators are set install the rudder servos into
each hatch using #2 x 3/8" Allen head button screws.
Use the string that is installed in the stabilizer to
pull the rudder servo wires to the middle hole. Use
heat shrink on the connectors and connect each rudder
wire to each side of a Y-harness, and then connect the
Y-harness to a 24" extension that will run to the
front of the fuselage. The vertical stabilizers are
installed using 2 4-40 x 3/8" socket head screws
on each stabilizer. Use a bit of threadlock on each
screw before installing them. Next install the rudder
control horns on each rudder; this is done in the same
manner as the ailerons were done.
rudder pushrods are built from threaded rod with a metal
clevis on the servo end and a nylon clevis on the rudder
side. Connect the rudder servos and center them before
installing the rudder pushrods. The elevator servo is
the only high torque servo used on this plane, and is
installed in the precut servo mount in the horizontal
stabilizer. Mark, drill, thread, and harden the mounting
holes the same way as the rest during this installation.
The pushrod is soldered together in the same manner
as the aileron pushrods.
tube is provided to run the servo wires to the front
of the airplane. However, I had a hard time getting
the wires all the to way the end of this tube, so I
ran the wire inside of the fuselage instead. The tail
assembly is installed by inserting the front dowel pin
into the hole in the fuselage. The tail assembly is
secured using 4-40 x 1-1/2" socket head screws,
#4 lock washers, and #4 flat washers. I put a bit of
threadlock on these bolts as well as a little added
insurance to keep the tail securely attached to the
Mount the Nose Gear
nose gear is controlled by a separate servo mounted
in the bottom of the fuselage behind the cockpit. The
nose wheel is connected to the servo by two steel cables
that steer the nose wheel. The steel cables are connected
to a brass coupler, which will be screwed into a metal
clevis that will connect to the servo arm. To assemble
the wire first slide a copper swage over the wire, through
the brass coupler, and then back through the swage.
Use pliers to crimp the swage and secure it on the steel wire loop. I found the swage to be very
small and I had a very hard time getting the second
wire into it.
the steering servo into the mount at the bottom of the
fuselage. The steering wires are routed to the nose
wheel bay through two plastic guide tubes.
the nose gear strut and file a flat spot on the rod
to help the setscrew hold tightly. Reassemble the nose
gear and set the retract mechanism into the gear bay.
Mark the location for the mounting holes, then drill
and cut threads in the same way as the main landing
gear was done. Use #6 x 1/2" Phillips screws to
mount the nose gear in place.
in the picture is the 0-80 ball link that broke earlier
as I was installing the main gear doors. Because of
this breaking I was short one ball link. According to
the instructions two ball links are installed on each
side of the nose gear strut and the steering wire is
then looped over it to steer the gear. I had to do it
a bit differently because I was one ball link short.
What I did was to simply loop the wire through the holes
on each side of the nose gear strut. Also, as this area
was really tight I didn't feel that I could get the
brass swage threaded with both wires. I cut two 1/16"
diameter brass tubing and used that to crimp on the
steering wire. The axle for the nose wheel will need
to be cut off with a cut-off wheel on a rotary tool.
not absolutely necessary, the hinge wells for the front
gear door can be painted grey to match the color of
the covering. I used paint intended for plastic models,
as this is what I had on hand to do the job. The hinges
for the front gear door are spring-loaded and should
spring to the "open" position for the door.
This is because it's actually the spring action that
opens this gear door and not the motion of the landing
gear. The gear strut will engage a wooden lever which
will pull the door shut as the gear retract. The lever
is constructed with a 2-56 ball link bolted in place
in the pre-drilled hole and a 4-40 x 1" socket
head screw used as a pivot point. The socket head screw
is inserted through a brass bushing before it is put
through the lever.
epoxy to glue the front gear door in place. Place epoxy
on each side of the spring loaded hinge and install
the gear door to the fuselage. While the epoxy is setting
up tape the gear door in place. Use something to insert
into the gap between the fuselage and the gear door.
Here I used two nail files that I had on hand, as they
were the perfect thickness. Once the epoxy has set use
medium CA to glue a control horn on the inside of the
gear door. This will attach with a pushrod to the gear
door lever. Retract the landing gear and then use a
long shank ball driver to adjust the linkage. Cycle
the front gear to ensure the proper movement of the
landing gear and gear doors, and make any necessary
Assemble the Cockpit
In the initial run of kits for this plane there was a
misprint on the needed air tank if Robart retracts are
being use. While the plane was originally designed to
use a small air tank, the stock number listed in the
instruction manual is for the large air tank available
from Robart. Actually, it may be better to use the
larger air tank as it will give more retract cycles than
the smaller air tank will. The plane was designed to
have the small air tank installed just forward of the
cockpit, but the larger tank will not fit into this
location. If using the large air tank the area directly
behind the cockpit is the perfect location to place this
tank. Top Flite has a template for making mounts on
cockpit is assembled by first gluing two 3/16"
x 3/16" x 5" balsa sticks to each side of
the cockpit, just slightly above the edge of the front
shelf in the cockpit. Using the cockpit floor as a guide
drill 4 1/16" pilot holes in the balsa rails. Use
Allen head button screws to mount the cockpit floor.
Use black paint to paint the parts of the cockpit that
will be visible when the plane is assembled.
instrument panel is made from the two instrument decals,
the plastic instrument panel back piece, and the wooden
instrument. Use spray adhesive to attach the decal with
the instrument dials to the front of the black plastic
panel back piece. Trim off any excess around the edges
of the panel. Now glue the wooden piece on top of the
panel decal. Finally, place the last decal over the
top of the wooden panel middle, lining up the holes
in the instrument panel with the dials below. The pilot
figures are simply profiles of a pilot. Cut the appropriate
decals and attach them to the wooden pilot profiles.
Glue the 2 full size pilots to the cockpit floor by
CA'ing them into the provided slots. Complete the cockpit
by adding the seat backs and the control yokes to the
cockpit. At this point the cockpit floor will be removed
until the plane is put back together for final assembly.
The mount for the retract air control valve is made from
the supplied ply parts. Assemble the mount and secure
the air control valve. Install a 0-80 ball link ball on
the control shaft of the valve. Mount the retract servo
and the air control valve beneath the cockpit on the
right side of the fuselage. The retract servo
needs to be adjusted so that it has no more movement
than 1/4" of travel.
are two ply mounts that will serve to hold the receiver
in place beneath the cockpit floor. Install these with
medium CA. There are 4 slots in the floor to glue these
mounts in, so you can tailor it to fit your specific
radio gear. Use the supplied parts to build the air
fill valve mount. Mount the fill valve in the mount
and adjust it so that the end of the fill valve is 7/32"
from the top of the ply side rails. With this build
install this in the plane on the left side of the fuselage
in the pre-cut mount hole. The air fill valve should
be installed so that it sits flush with the outside
of the fuselage side.
epoxy to glue the air fill valve in place. Included
are several wire management "loops" that can
be used to tame down all of the wires and air lines
that will run in the fuselage of this big bird. One
of these guides is glued in place behind the retract
servo, but the other guides can be placed as needed.
One thing I found that really helps keep down the clutter
is to join each set of retract lines together. I do
this by using small pieces of fuel tubing slipped over
the lines to hold them together.
receiver is wrapped in foam rubber and then mounted
in the cockpit area. Air lines for the main gear are
run back through the fuselage and then a "T"
fitting is used to branch out to each main landing gear.
Quick disconnects are provided with the plane to facilitate
removal of the wings if needed. Here you can see the
completed cockpit area.
the review of the Top Flite B-25J Mitchell
I had the opportunity to try a new product
that I have not seen before. These are new
power systems from Duralite batteries. These
systems are unique as they are Lithium chemistry
batteries that are regulated down to the
voltage of the receiver that is being used.
Because of this there is a constant voltage
available to the receiver even when the
battery drained. These batteries also have
the advantage for being able to handle large
current draws from the servos and flight
system in today's modern planes.
setup of these batteries is a bit different
than some people may be used to. The battery
itself is a 2-cell Lithium-Manganese battery
that has 2 wire sets coming out of it. The
heavy gauge wire is the power tap and this
is plugged into the voltage regulator. The
second wire is the charge lead which will
be used to recharge the battery. The second
component is the voltage regulator. This
is plugged into the power tap from the battery.
The regulator has it's own power switch
that is used to turn on power to the system.
There is a jack attached to this switch
which is used to check the voltage level
of the battery. Duralite has an adapter
available that will go from the voltage
regulator into your radio system. All power
connections in these systems utilize Deans
connectors to handle the higher voltage
loads on the system.
Lithium-Manganese Receiver Batteries
flammable if punctured or overcharged
Discharge - 20c continuous with 40c
low temperature toleranace
charge rates up to 10c
Balance circuit built into pack - no
need for external balancing
life cycles than li-polymers
lead system - choice of power output
leads/connectors, plus charging lead
mah - 2 cell Li-MN -7.4 volt
Flight weight: 5.8oz (165
Size: .5 x 1.75 x 5.5in (T/W/L)
Discharge Amperage: 44Amp (20C)
Charge Rate: 1AMP
Current Regulator The High Current
version of the DURALITE regulator uses 16
gauge wire and the Ultra Deans connectors
to reduce resistance in the wiring and the
connectors which improves the regulators
overall efficiency. We have found that the
minimum voltage is significantly higher
when the HC-wiring is used. We hope to have
another graph of this same situation that
will show as soon as the weather co-operates
mounted electronic components.
RF filter in and out delivers highest
at 7.5 amps with 10 amp spikes
Hybrid Pulsing Design
for 6 - 8.4 volts
designed for use with the DURALITE PLUSTM
Battery but also works well with other
battery chemistry types
Voltage Regulator with
Fail Safe Switch, 7.5 amp w/standard
22ga wire, 6.0 volt
If the switch were to fail regulator stays
in the on state until you unplug it from
the battery. Not suitable for ignition applications
due to fail safe feature.
in all of the servo leads to the receiver. Labeling
each wire will help to keep them all straight
is a tube provided to run the receiver antenna
through. Use a strain relief to keep the wire
from pulling out of the receiver if any pressure
is placed on the antenna wire.
antenna wire isn't long enough to extend all the
way to the tail of the plane. Tie a piece of string
to the antenna wire and pull back to the tail
and tie off the string. This will keep the antenna
from working it's way back up the antenna tube.
on/off switch is mounted on the left side of the
fuselage directly below the cockpit. The Duralite
power system provides a jack used to check the
power level of the battery. This jack is mounted
here with the switch.
battery installed where small air tank should
power regulator. Zip ties used to secure regulator
behind front landing gear bay.
installation completed. All components in place.
Power lead from battery is routed back underneath
cockpit to the voltage regulator located behind
the landing gear bay. The charge jack for the
battery is tied off in the landing gear bay and
can simply be pulled out to charge the battery.
Mount the Inboard Wing Panels
design of the Top Flite B-25J Mitchell leaves the end
user with several options as to how to transport the
plane to the field. The wing is actually made up of
2 sections; the outboard wing section and the inboard
wing section that has the engine nacelles on it. If
transportation space is limited it's possible to leave
both sections off and assemble the entire wing at the
field. I chose to instead install the inboard wing sections
on the fuselage and transport to the field assembled
30 x 440 mm main wing tube and 2 10 x 305 m wing tubes
support the wing sections. The smaller wing tubes are
secured with 4-40 socket head screws, which also secure
the wing sections to the fuselage. These tubes come
with one end already tapped to accept the socket head
screw. Slide these sections into the wing section and
install the 4-40 x 1" socket head screw through
the wing section into the wing tubes. Slide these wing
tubes into the fuselage section and connect all of the
wiring and air connectors. Because I plan to leave these
assembled I used heat shrink on all of the connectors
to ensure that they remain secure. With all the connectors
in place slide the wing section all the way tight against
the fuselage around and slide the other wing section
onto the wing tubes. Once again secure all the wires
and air connections and slide the wing section tightly
against the fuselage. Ensure that both wing sections
are tight against the fuselage. Use brass tubing to
make a small drilling jig to drill pilot holes in the
wing tubes. First place a 1/8" piece of tubing
into the screw hole in the wing. Then place a 1/16"
piece of tubing inside of the first brass tube. Now
use a 1/16" drill bit to drill a pilot hole in
the wing tube using the guide to keep the drill straight.
Ensure that you drill all the way through the wing tube.
the wing section and re-drill the holes in the wing
tube using a #43 drill bit. Use a 4-40 tap to cut threads
into the wing tube. After tapping the tube use a file
to remove any metal burrs that may be left around the
hole. Reinstall the wing section and secure in place
using a 4-40 x 1" socket head screw. Use a drop
of threadlock on the screw to secure it in place on
the wing tube.
Mount the Outboard Wing Panels
outer wing panels are installed in a similar manner
to the inner wing panels. Wing tubes are used to support
the wing using a socket head screw at the rear wing
tube to secure the wing to the tube. The difference
here is that a nylon bolt is used at the front of the
wing to secure it. This bolt is installed at an angle
along the front of the wing panel and is hidden from
view by the molded plastic oil cooler. The instructions
call for determining which oil cooler went on each wing,
but as I looked at them I found both oil coolers to
be identical. The oil cooler is placed in position on
the wing and then use a marker to outline the oil cooler.
Use a hobby knife to cut through the covering 1/16"
inside of the line. Remove the covering from this area,
leaving the black covering in place over the air scoop.
Use medium CA to glue the air scoop in place on the
the 2" nylon bolt in the front of the wing panel
and tighten it down against the inboard wing panel.
Use the same method to drill and tap the wing tube as
we did for the inboard wing panel. Use a 4-40 x 3/4"
socket head screw to secure the wing panel in place.
medium CA to glue the plywood rubber band hooks on the
inside of the nose-gunner window. To prepare the parts
of the nose section to be joined first use medium grit
sandpaper to scuff the edge of the bottom piece as well
as the edges of the nose canopy. Align the parts and
use tape to hold the nose canopy and bottom section
The nose canopy and bottom section are joined using thin
CA. Maybe it's just me, but I never have any luck using
CA around clear pieces on a plane. No matter how careful
I try to be CA always seems to wind up in the clear
portions. I would rather use different method than had
been used to construct the nose portion of the plane. I
followed the instructions and use thin CA for gluing the
nose canopy parts together, and tried to be very careful
as I did this. However I still had CA run where I didn't
want to, which resulted with CA in the clear window
portions of nose canopy. When I tried to remove it with
CA debonder it clouded the canopy. I was able to "clean"
this up by "painting" that portion of the nose canopy
with clear fingernail polish which did a pretty good job
of filling in the clouded portion of the canopy. But
it's still not perfect and if looked at close enough
brush strokes can be seen where the nail polish was
brushed on. It looks ok as long as you don't look too
closely at it. If I were to do this again, or had to
recommend and alternative method, I would use Formula
560 Canopy adhesive to join these parts together.
When the nose section is complete use rubber bands to
secure the nose gun into position. Glue the supports to
the bottom of the nose gunner cabin platform. Also, this
platform can be used to secure the battery if needed.
Parts are provided to assemble a platform that glues to
the underside of this section. Unfortunately I could not
use this because the Duralite battery that I used was
too long to fit under the platform. This is the reason
why I needed to move the battery to the cockpit area of
the cabin platform into position on the plane. If Top
Flite missed on anything big in this plane I would have
to say it was the paint used on the scale parts. While
I compliment TF for putting the parts in the plane,
the colors were all off. What should have been a
interior green turned out to be an almost neon green, and
the leather of the nose gunner seat turned out orange.
Hopefully they can correct this in later editions of
this plane as I feel that correct colors would add a
lot to this great warbird. Use the provided Allen head
button screws to secure the cabin back wall to the structure
of the plane. I made sure to install these so that I
could access them later on so I could remove the back
wall if any servicing is needed of parts behind the
wall. Use medium CA to glue the cabin floor to the platform.
the tops of ammo boxes on the ammo boxes and then glue
the boxes to the ammo tray. Then glue the ammo tray
to the cabin floor as shown. I would recommend using
epoxy to glue the ammo cans to the ammo tray. I initially
used medium CA for this and while I was breaking-in
the engines the vibrations caused them all to break
loose. I reattached them using epoxy and so far that
seems to be holding. Glue the kneeling pad to the post
on the floor of the cabin. Position the canopy on the
plane and use Allen head button screws to secure the
canopy in place. Unfortunately I did not have enough
of these to complete this. As I state in my summary
below I had a problem with these screws "stripping"
out as I installed them, even though I used several
different wrenches. I used #2 socket head screws from
to install the canopy in place.
scale features for the tail gunner are installed in
the same manner as the nose section. Scrape the paint
away from plastic parts before gluing them together.
all the plastic scale parts in place including the tail
gunner profile figure. I used Formula 560 Canopy Glue
to install the tail gunner canopy in place. I had another
issue with the tail section similar to the nose section.
While breaking-in the engines the vibrations broke loose
the gunner figure. To fix this I drilled through the
cabin floor and used small screws to secure the figure
in place in the cabin.
The top turret gun is assembled from two machine gun
barrels and the gun unit. Included in the kit is a
circular piece of steel grey MonoKote that should be ironed down
where the top turret will be mounted.
back edge of the top turret guns should be placed 5"
behind the back of the cockpit. Mark and cut the MonoKote
where the guns will be mounted and glue the guns in
place. I used the Formula 560 adhesive again to glue
the top turret in place on the top of the fuselage.
I did have to trim the gun slots of the canopy a bit
in order to get the turret to fit properly over the
machine gun barrels into each waist gun window assembles
the waist gun windows. Place the waist gun window on
the side of the fuselage and mark it's position. Make
sure to get the windows on the proper side of the plane.
It was impossible to get them wrong on my plane as the
invasion strips on both the fuselage and the windows
would only line up one way. Use epoxy to glue the waist
gunner windows in place on the fuselage.
side gun packs are assembled by gluing the gun barrels
into each gun pack. The instructions called for the
bottom gun to extend 3-1/2" from the pack, but
I was unable to do this, as there just wasn't enough
gun to extend that far. I glued the gun in as far out
as it would go and then matched the other gun in the
pack with it so that they were even. The side gun packs
are molded to fit the curve of the fuselage so they
need to be mated to the sides of the plane. In addition,
the painting of the gun packs should also match up with
the covering of the fuselage. I would like to compliment
Top Flite here as I can't think of any other plane that
I've ever seen where painted parts matched the covering
scheme as well as they did here on the B-25. They definitely
did a great job here. When positioning the parts attention
needs to be paid to any switches, charging jacks, the
air fill valve, and anything else installed on the sides
of the plane. I used tape to hold the side guns in place
while I traced them.
the outline of the side pack guns traced out use a hobby
knife to cut the covering away, cutting approximately
1/16" inside of the line that was traced. After
cutting the covering away use a paper towel with alcohol
on it to remove the traced lines. Go back over the covering
with a covering iron to seal down the edges around the
cut away area. Use thin CA to glue the side pack guns
in place. I found that it helps to glue one part of
the gun at a time. I started with the bottom of each
pack and then when the CA was dried I would then do
the top pack.
homework that Top Flite put into this plane really shows
in parts as simple as the ADF "Football" antenna
mounted on the bottom of the fuselage. This part would
be very vulnerable to be broken off while transporting
or storing the plane. To prevent this Top Flite has
designed this part so that it mounts with strong magnets.
This allows the antenna to be removed for transportation
or storage, and if the antenna is accidentally "bumped"
it will simply come off and can easily be reattached
because it's mounted with the magnets. Included in the
ply parts is a template for cutting the holes for mounting
the magnets in the fuselage. I used a sharpened piece
of brass tubing to cut the holes for these magnets.
Once the holes are cut use thick CA to mount the magnets
in the fuselage.
the magnets are mounted it's very easy to install and
remove the ADF "Football" antenna.
Flite has included a very good set of decals to duplicate
the paint scheme of the "Executive Sweet",
which the plane is based on. While the decals are sticky
backed the instructions recommend an alternate way of
installing them. They call for using water with a mild
detergent for installing the decals, but I prefer to
use Windex for this. Spray Windex on the area where
the decal will be installed. Cut the decal away from
the decal sheet and place it down on the area with the
Windex. The Windex will allow the decal to be moved
into position without the adhesive on the back of the
decal "grabbing" hold. When the decal is in
place use a paper towel to push all the Windex out from
under the decal. Also use a scrap piece of balsa to
burnish the decal into place on the plane. Use the illustrations
in the manual, as well as the box art, to indicate where
to place all the decals on this plane.
instructions call for the B-25 to be balanced at a point
5" behind the leading edge of the wing, measured
at the fuselage side. The instructions also specify
to balance the plane with the landing gear in the down
position. I must admit that I was a bit worried about
the balance of the plane. The plane already weighed
over 19 pounds and I was afraid I might need to add
more weight to get it to balance properly. Once I had
the plane up on the balance stand I was pleasantly surprised,
as the plane only needed 2 ounces to come to a perfect
level. As you can see in my last picture, I used very
"precise" weights to add to the plane! With
the plane balanced the final dry weight was 19 pounds
*Note: 1/4" (6m) of down elevator
should be mixed in with the full flap deflection
to control "pitch-up" when flaps are extended