ready to mount the tail on the fuselage, I have work to do on both the
main fuse as well as the tail, in order to get them ready for each
other. First, in order to mount
the mechanics to the mounting plate, I made up some aluminum blocks and
tapped them so they could be mounted to the plate.
The KDE Direct aluminum
base for the Trex 700 is perfect for this, as it gives me a really solid
mounting. Now, I can reassemble the mechanism on top of the plate.
The tail boom gets a
bearing-holder end cap, just like on the mechanism. Here is my
trusty lathe turning it out of Delrin:
This mounting, I planned
way ahead, and had already milled channels in the tail for the wiring
and the gearbox bearing. The tail skid is not scale, but it is
very, very strong, has a 90 degree bend inside the tail fin, which is
filled with epoxy for strength. I wanted a tail skid that could
actually handle the energy of a heavy, tail-first touchdown without
When I designed the gear
mechanics, I made them so that they would absolutely, positively lock in
the "Down" position! With the fragile and detailed ADF
Pod underneath, I wanted to take no chances. What I discovered
while working on it, is that it was possible to "hyper-extend"
them past the "down" position. To prevent this, I
machined an arm that locks onto the keyed shaft, and limited with a Delrin
I also needed to make the
rudder control rod about an inch shorter. This was an opportunity
to correct something we saw during the flight trials: The rod was
vibrating (just a bit). I switched from a
carbon-over-brass-over-stainless rod to a
brass-over-carbon-over-brass-over-stainless combination. This is
incredibly stiff and should eliminate the problem completely.
The horizontal fins are
really attached well (I drilled holes in both the body and the fin so the
excess epoxy would form "Rivets"). Unfortunately, the
body of the tail actually flexes, so I did not get the rigidity I was
looking for. I ended up drilling a 6mm hole through the fins, and
inserting a 6mm carbon rod (actually a Trex 700 Tail boom brace) all the
way through the body from the tip of one fin to the other. The
high placement of the tail tube in the tail section allowed this rod to
pass under it.
Now, with solid horizontal
fins to mount to, I filled the vertical fins with epoxy, then milled out
recesses for screws. The vertical fins were then attached with BVM
Aeropoxy (god, I really love that stuff) and screws.
After all the prep,
attaching the tail was rather anticlimactic. I taped
everything up, drilled holes for screws, then added epoxy, and set the
Some clamps and a prop
under the tail skid hold everything together while the epoxy cures.....
And it's starting to look
more like a Helicopter!
Here is the join from the
inside, after some touching up with an airbrush for the interior
color. I am doing this as I go, as the paint shop will never be
able to get complete coverage after other parts are added.