X8 morphs to S9TWL: Case of a Tail

April 1, 2014

Nick Roberts and Sai Ravela

Over the last year or so, we have been working up on various mods on the standard airframe including:

  1. Kevlar reinforced wings for high stress environments.
  2. Motor mount w/ damping and spar coupling for improved resilience.
  3. Vertical control surfaces for yaw control.
  4. Wings extension to 3m wingspan for increased lift with flaps/air brakes.
  5. Launch points for catapult launches.
  6. Nose redesign for sensing.

These mods are disclosed on this blog and freely available. Here we document the twin tail system with synchronized rudder control is developed using NACA-1414 airfoil and  Hitec Servos. The tail surfaces are made from Spyder Surfboard foam. This foam was selected because of its' high stiffness and ease of modification and shaping. The detailed specifications for the tail are included at the end of this entry.

Here's one view of the mounted tails.

The surfaces are mounted on a tail mounting rib, see below, which slides over the two main wing spars and screws to the body through several counter-sunk holes. The forward assembly provides various trigger and mount points for automated launch and the aft assembly inserts into slots the foam tail. The slots were put into the tail using a hot knife and simple stencil to match the prongs in the tail mounting rib.  The tail is slid onto the prongs and then glued in place using epoxy or other adhesive. Additional adhesive can be added in between the tail surface and the upper surface of the wing to provide additional stability.


The shot below shows the final mounting of the tail.



Tail Section Specifications:

Airfoil: NACA-1414

Material: Surfboard Spyder Foam

Length: 11.5 inches

Root Cord: 8 inches

Tip Cord: 5 inches

Tip Setback: 4 inches


For all the aviation hobbyists, please feel free to use this design but be kind enough to acknowledge this source. Watch this space for more updated detail on the T!