"Class B" Scratch builder's instructions
1.
On one trailing edge
(1”x32”x1/16”) mark the rib positions as follows.
1.1.
Find the exact center and mark it.
1.2.
Space the motor mount ribs equal distant from the center
3/8” apart (inside to inside).
1.3.
Mark the radio compartment ribs equal distant from the center
8” apart (inside to inside).
1.4.
From the radio compartment ribs mark the inboard ribs 4”
and 8”.
1.5.
The wing tip ribs should be aligned flush with the end of the
trailing edge.
1.6.
Copy those marks to the 1/4 by 1/4 spars and
leading edge.
2. Glue the 2 motor mount beams to the rear motor mount spacer. Be sure to align the v-groove in the front and the notches on the beams. Use a rib for the dimensions.
3.
Put some weights temporarily
on the spar and trailing edge during construction to keep it warp free against
your flat building table.
4.
Assemble, but do not glue the ribs to the lower
trailing edge, top, and bottom spars.
4.1.
For proper alignment, build on a flat surface and prop up the
lower wing spar with 3/8x3/8 spacers.
4.2.
Place the Motor mount between the 2 center ribs but do not
glue yet.
4.3.
When everything is lined up and square, the trailing edge of
the ribs should be 1/16” forward
of the rear edge of the trailing edge.
4.4.
Glue the ribs to the trailing edge.
4.5.
DO NOT GLUE MOTOR MOUNT OR RIBS TO SPARS YET.
5.
Line up ribs to leading edge and glue in place.
5.1.
Make sure the ribs and spars are still lined up and glue to
spars.
5.2.
The motor mount will align itself straight if it is lined up
between the spars and the leading edge.
5.3.
Now glue the motor mount in place.
5.4.
Glue the front motor mount filler block in place.
6.
Glue the top trailing edge in place.
7.
Glue the top leading edge sheeting(s) in place.
7.1.
Hint: it is easier to glue ithe sheeting to the spar first,
letting it dry before trying to
wrap it around the front leading edge.
7.2.
Keep the sheeting fit tight to the motor mount for maximum
motor mount strength.
7.3.
Make sure the building weights keep the structure flat during
this operation.
7.4.
Don't waste a lot of glue here, we will do that later.
8.
Glue the 2” x 9” x 1/16” top rear center sheeting. Butt
it tight against the trailing edge. It overhangs ½” on each side f the radio
compartment ribs.
9.
Turn the wing upside down and glue the bottom leading edge
sheets on as per step 7.
10.
Glue the two 3-3/8” x 9” x 1/16” center sheeting to the
center section starting at the trailing edge. They overhang ½” on each side f
the radio compartment ribs also.
11.
With the bat still upside down, glue on the bottom ¼” x
6-5/8” x1/16” cap strips.
11.1.
The outside strips should be flush with the outside of the
tip rib.
12.
Now pick up the bat and generously glue the internal joints
of the wing sheeting, ribs, leading edge, and trailing edge.
13.
Put the bat back on the building board right side up (be sure
to put the 3/1” x 3/8” spacers under the spar) and weight it down again.
14.
Glue the two ½” x 4-5/8” x 1/16” cap strips on the
radio compartment ribs, keeping the flush with the inside opening (not centered
on the rib).
15.
Glue 1-5/8” x 3” x 1/16” shear webs to the top and
bottom spars.
16.
Glue the remaining ¼” x 6-5/8” x1/16”
top cap strips per step 11.
17.
Cut notches 1/16” deep by ½” wide in the two center ribs
to allow the 1/2x8 hatch mount strips to be recessed just slightly more than the
thickness of the hatch.
17.1.
Allow the rear mount strip to slide under the rear center
section a 1/16 for added strength.
17.2.
Glue the hatch mount strips securely.
17.3.
Glue a ½” x ½” x ¼” support block to the sides of
the ribs under the hatch mounts.
18.
Glue the wing tips and triangle gussets to your liking.
18.1.
The left wing tip rib requires an antenna hole.
18.2.
Glue a 1” piece of plastic tube (scrap nyrod) or straw on
the left tip to run the antenna through.
19.
Cut the ailerons to fit.
20.
Sand the wing leading edge to a nice blunt aifoil radius.
This will allow the bat to turn sharply without stalling out.
21.
Mark locations on servo hatch to mount
servos, switch, and charge jack (template supplied).
21.1.
Cut these locations out but do not mount radio yet.
22.
If you spent more than 2-1/2 hours your making it too nice to
risk in combat!
23.
Cover the wing , servo hatch, ailerons, and fins (still
unattached) with your favorite covering.
24.
Cut away the covering on the servo hatch to allow gluing the
vertical fins on
24.1.
Glue some scrap balsa triangle at the base of the fin.
24.2.
Cover the exposed areas.
25.
Attach the ailerons using the same covering material as on
the rest of the BAT.
25.1.
Be sure to have the aileron BEVEL SIDE ON THE BOTTOM.
25.2.
Cut 4 strips of covering the length of the ailerons by ¾”
wide.
25.3.
Hold the aileron to the wing as it should normally be, then
fold the aileron completely back on over onto the top side of the wing as if it
was on a hinge. HINT: hold in place with a couple of small masking tapes.
25.4.
Center the ¾” covering strip (hinge) and Iron it on
keeping the gap as tight as possible.
25.5.
Remove the masking tapes and deflect the aileron 30-45
DEGREES DOWN.
25.6.
Center the ¾” covering strip (hinge) and Iron it on
keeping the gap as tight as possible.
25.7.
When done correctly you will have a smooth, no-binding,
gap-less hinge that will outlast the Bat itself.
26.
This completes the assembly.
26.1.
Assemble a 2oz. Dubro rectangular tank and insert into right
wing leading edge cavity so that the clunk hangs toward the rear. Use a chunk
foam rubber to keep it from sliding.
26.2.
Put the battery pack and receiver in the left leading edge
cavity.
26.3.
Run the antenna through the left wing panel holes near the
spars.
26.4.
Mount the servos of your choice directly to the servo board.
26.5.
Mount the control horns so that the push rods run straight
from the outside of the servo to the horn. Two 2-56 all-thread works great for
the push rods.
26.6.
Drill a ¼” hole in the center of the trailing edge to tie
the streamer.
26.7.
Mount a .10 - .15 engine with #4 x 3/4” socket head bolts
and blind nuts.
26.8.
Use your favorite props. Master Airscrew 7-4 works fine for
the .10 and 7-6 for the .15.
26.9.
Use a 1-3/4” spinner.
26.10.
Drill 1/16” pilot holes and mount the servo board to the
wing with six 2/56” screws as marked.
27.
If you spent more than 5 hours total, stomp on the bat and go
fly scale!!
28.
The airframe ready to cover should weigh 5 to 6 ounces. Ready
to fly it will weigh 22 to 26 oz, depending on your radio and covering.
Using a 270ma battery verses a 550ma saves about an ounce. New micro
servos can provide similar weight savings although more costly. Remember that
the lighter the better, and that 1 oz is about 5% of the total weight. Shave a
couple of ounces and it has the same effect as adding a bigger motor.
29.
Good Luck......
Rev B