Attaching the Empennage
When it came time to attach the empennage to the
discovered some minor issues at almost every step. Here's how
resolved them. Hopefully this information will save you some
horizontal stab. Take
your time here and
ensure all the measurements are accurate.
Any errors you leave here will result in lost
speed. You may not
be able to see
it, but your plane
will be slipping through the air with the control surfaces not fully in
trail position. This
slowing you down.
I found an easy way to
check that the
horizontal stab was
level front to back was to insert a drill bit into each tooling hole. Make sure you use bits
that just barely fit,
so they stick straight out on their own.
Then I placed the level on them.
attachment process, I only had trouble at one spot on the
horizontal stab. My
best guess is that the clamps slipped,
because somehow one of the outboard holes I drilled to attach the
line back up when I went to insert the bolts again.
The hole was nicely centered on the stab, but
it wasn’t centered in the F-887. When
lined up the other three front holes, this last one didn’t match. How did that happen? But more importantly, what
do I do about it?
I countersunk from the
top and bottom
of the F-877, and
bucked an AN426–5 rivet until the shop head filled the lower
countersink. If you
have to do this, don’t worry if you
use too large a rivet. Once
countersink is filled, stop bucking, and get the grinder out. Grind and sand the
leftover rivet until it is
smooth. This leaves
both the top and
bottom of the F-877 smooth and the erroneous hole filled in.
Then I clamped the
back on, and inserted
temporary bolts in all the other holes.
This time when I drilled, the hole was true. I still don’t know how it
next step in
attaching the empennage is the fitting of the vertical stabilizer.
Locating the new match drilled
vertical stab is a lot easier
than the older one. I
had to figure out
the actual height of the vertical stab that is now determined by the
hole that goes into the F-812B angle.
started at the bottom of the vertical stab by setting the VS-803 main
spar to a
height that would allow the bottom two bolts in the VS-410 to go
WD-409 with enough edge distance.
have the match drilled tail, make sure the marks you make to drill the
holes in “View A-A”, DWG 73 will have the required edge distance when
adjusted the front
vertical stab and F-681
(now the F-884) attachment plate until they were in the proper position. I dropped a plumb line
through the hinge
brackets to ensure the vertical stab was true and the hinges were in
line. The front of
my vertical stab was too close
to the turtle deck skin, so I had to trim the bottom of the vertical
and flange to get the required clearance.
You may not have installed your turtle deck
skin yet, just
be ready for
this when you finally do. You
want to put a big scratch or dent in the skin because you didn’t check
ensure there was clearance.
To continue with the
empennage, it's time to attach the elevators. Once you
determine the required
washers or spacers for the
elevator horns, make a little drawing.
Set the washers and the drawing aside together. It may be a while before
you finally install
the elevators, and you don’t want to have to spend the time to figure
required spacers again.
When you are drilling the
pushrod hole in the elevator
horns, make sure you use some sort of guide block.
I used a hardwood block just like the
directions, but I have seen others use a metal guide.
The material you use isn’t that important,
but the fact that you use something is.
There is too much play between the horns if
you don’t. If the
holes in both horns
don’t match, your
elevators will not be even, and the plane won’t fly straight.
Two parts left to the
empennage: the elevator and rudder.
The plans have you make
and fit all
the control pushrods for
the elevators at this time. Don’t
install them however. Just
fit them and
then remove them. You
will want access
to the inside of the tail while installing wiring and other components,
when riveting the top skin. Then
go back and final install the control system.
wanted to ensure I had
bellcrank in the neutral
position to adjust the lengths of the pushrods.
So I measured 3 1/16 from the F-808 bulkhead
per the plans
by clamping a
piece of angle across the back of the bulkhead, then measuring from it
center of the top hole in the F-635.
also made a little “jig” using some washers that filled the access hole
F-818 ribs and left a small center hole that I could align with the
in the F-635.
The front stop was easy
to adjust. I had
not yet riveted it
in place, so I
removed it, filed some metal off, reinstalled and checked it. I tried to file the rear
stops with the
elevators still installed, but there just wasn’t room.
That meant I had to file a little off the
stop, then reinstall the elevator and check.
If you have already
fiberglass tips, now is a
good time to balance the elevators.
Disconnect the pushrod from the elevator horns
free. Spray some
WD-40 or LPS on the
hinges, so they move easily. Now
have a perfect horizontal platform for balancing the elevators. I plan on test flying my
painting, so I left them a little front heavy until after I finish
painting. Then they
will have to be
Finish the empennage
fitting by adding the
rudder stops. Take
it slow and remove a
little metal at a time. Remember
you can always take more off, but you can’t put it back.
A few more
Vertical Stabilizer attachment photos
Forward vertical stabilizer bolts
Lower aft vertical stabilizer bolts
Vertical stabilizer rear attachment
from Attaching the
Empennage to Fuselage
Return from Attaching the Empennage
to Kit Plane Advice Home