Construction Manual
www.oldschoolmodels.com
Page 17
German
Sunday Fighter
Heinschmitt
Step 126 - Top wing test fit (center cabanes)
With the main gear attached, re-attach the bottom wing. Now it’s
time to test fit the top wing. You’ll need the 4 outer struts, the
twelve 4-40x1/2 bolts and the twelve 4-40 t-nuts.
First position the top wing on the center cabanes. The metal lugs in
the top wing should be on the outside edges of each cabane, where
you sanded bevels earlier. Push a 4-40x1/2 bolt through each of the
4 mounting lugs and through the pre-cut holes in the cabanes.
Then thread 4-40 t-nuts on to each of these bolts. Slowly tighten
the bolts and seat each of the t-nuts teeth into the cabane. They
are properly seated when the flat of the t-nut is up-against the
wood of the cabane. Do not over-tighten as you can crush the
wood or strip the t-nut(s).
Step 127 - Top wing test fit (outer struts)
With the wing attached to the center cabanes, now install the
outer struts, keeping in mind the rounded struts are forward and
the more squared-off struts are aft. Again use 4-40x1/2 bolts and
t-nuts to secure the struts to the bottom, then top of the wings. You
might need to use a slight bit of pressure to align the mounting
holes, but only slight. If you need to use excessive force it means
that you might have built a warp into the wing and/or not aligned
the root ribs properly when building the wings.
We’ve found that attaching the struts to the lower wing first works
best. These struts should be positioned on the outside of the metal
straps, with the bolt running though the strap first, then into the
strut, and finally the t-nut.
The top wings should have the struts on the inside of the metal
straps.
When satisfied with the fit and you’re sure the t-nuts are all seated
properly, remove both wings and all the struts. Use a touch of glue
around the perimeter of the back of each t-nut to hold it in place.
Make sure not to get any glue into the threads.
Step 128 - Tailwheel mounting
Mount your choice of tailwheel to the bottom of the fuselage. It
should mount to the bottom of the plywood TW assembly, already
installed.
We chose to use a simple wire tailwheel that mounts into the
rudder. If going this route, make sure it’s in place before hinging
and mounting the rudder to the fuselage.
Ailerons
The ailerons are on BP2. The
longer AIL1 are for the upper
wing, the shorter AIL2 are for
the lower wing.
Your Sunday Fighter can be
built with either 3 (throttle,
rudder & elevator) control, or
4 channel (adding ailerons).
We prefer ailerons as it gives
another level of control in the rolling axis, but the purists out there
might prefer otherwise.
We find that the Sunday Fighter works just fine with ailerons only
on the lower wing. But, at this point you also have the option to use
ailerons on both upper and lower wings.
If you choose lower ailerons only, you’ll need to glue one AIL1 strip
to the trailing edge of the top wing as shown, on each side. The
flat edge should rest against the wing tip.
Make sure these are securely glued and properly aligned along
their entire length.
If you choose to use upper ailerons as well, you’ll need to get a few
things at your local hobby shop as we don’t include them. You’ll
need another set of aileron hinges for each top aileron, four control
horns, two 1/16” rods that are a minimum of 8 inches long with a
threads cut into one end, and a couple of clevises.
The control horns will mount to the top of the lower ailerons and
the bottom of the upper ailerons, in line vertically. They should also
be roughly mid-way along the aileron’s span.
Then mount the pushrods and clevises to link both ailerons
together. Use the threaded end for the bottom and bend a z-bend
for the top.
Now it’s time to think about radio and engine installation.
These next steps of covering, hinging, radio and power installation
are not in any particular order. Some modelers like to cover
everything first, then outfit the rest. Others like to hinge and
pre-install the components, working out the installation before
covering. Use the method that works best for you.
We prefer to pre-install many of the components to make sure
there are no surprises in the way things fit or might have to be
modified for after market items. We find it much easier to fix these
problems now, before covering, as there’s nothing worse than
ruining a good covering job by having to hack a hole or provide
clearance for something.
Aileron servo hatches
If you choose to use ailerons,
locate the servo hatches and
note the etched arrows in
each. This arrow signifies the
leading edge of the wing.
Note that the left hatch is a
mirror image of the right hatch.
Position your aileron servo on the inside of the aileron hatch so the
servo arm output shaft is centered in the opening.
From leftover basswood strip, cut and stack pieces to create servo
posts. Make a mounting post by laminating two or three pieces
together. Make 3 additional posts from the remaining pieces,
sanding the ends of all 4 posts flat.
On the inside of each aileron hatch, glue one post on each side of
the servo as shown in the previous photo.
Now attach the servos by drilling 1/16” holes through the servos
mounting lugs, then using the servos mounting hardware to attach
them to the hatches.
Aileron wire holes for servo wires
On the plans you’ll see callouts where the two holes should be
cut in the bottom wing’s center sheeting. These holes are only on
the top side and allow the aileron servo wires to pass through the
wing and into the fuselage. Mark and cut these holes with a sharp
hobby knife.
Pushrods (rudder & elevator)
In F7 and F8 we’ve made provisions to help you run flexible
pushrods back through the fuselage. You’ll see a pair of pre-cut
