The design report

Empennage structure 4.1.3
Preliminary and detail design (Empennage):
Horizontal tail:
Figure 4.1.301 shows the horizontal tail and the elevator assembly in CATIA
As discussed earlier, the horizontal tail was to sit on the fuselage. We had to make sure
there was no angle of incidence for the horizontal. A major issue while designing the tail
was its assembly with the fuselage. Details on how this problem was fixed are discussed
later.
The internal structure of the horizontal tail was similar to that of the wing. From the
calculations done during conceptual design phase, the chord length was set to 180 mm.
The entire horizontal tail was 763 mm long. Due to its size; all ribs were made of 2 mm
ply to provide enough strength.
The structure consisted of 11 ribs, 3 spars, 1 web spar, webbings, a servo plate and two
blocks at the sides.
Ribs:
The 4 mm ribs on the ends were given flat bottom to avoid any angle of incidence. The
ribs in the middle had slots so that the servo plate could sit on it. The distance between
each rib was 100 mm except the sides where the distance was 30 mm and in the middle
where the distance was 50 mm. This was done to evenly distribute the spacing between
the ribs. The rear end of the ribs in the middle had a 35 degree cut which gave enough
space for the elevator deflection. Holes were cut in the ribs in order to save space and
to connect wires to the battery.
Spars:
The structure consisted of 3 spars (one in the front, the other two at 25% of the chord).
The spars were made of 6x6 mm pine rods.
Web spar:
This part did functions of both, the spar and the webbing. This part was at the rear side
of the horizontal tail structure. The web spar was made of 3 mm ply. It had slots in it so
that the ribs and the end plates could easily slide in. The main purpose of these slots
was to avoid as much glue as possible and eliminate errors during fabrication.
Webbing:
3 mm balsa was used as webbing just to add more support to the structure.