Building a UAV for photo mapping - Kit Mods

First I must thank Jeffrey Johnson who posted a set of images of the Cularis he is building for photo mapping. He has made a really neat modification by moving the rudder and elevator servos from the stock position in the cockpit, to tail mounting in the fuselage. Not only does this free up space in the cockpit area, which will make it easier to enlarge to take the camera, but it also moves some 35gm of weight to the rear. This should greatly help in balancing the plane without adding too much lead.

I have also now read some 670 posts in the Cularis building thread on the rcgroups forum. There is a wealth of good stuff there, including a number of modifications to the stock kit to improve performance and ease of use. Specifically, I now plan to do the following.

  • Extend the travel of the flaps by reversing the control horns, thus allowing for slower landings
  • Reverse the direction of one of the flap servos so that if can be connected to the other flap servo with a simple Y lead.
  • Remove some 30% of the hinge material from the ailerons and flaps to reduce the load on the wing servos.
  • Cut away the stock mountings for the mating connectors in the wing roots and run the cables through to connect by hand. This seems to be a major cause of poor reliability as if the wing moves a little in flight, the connectors can cease to make contact, leading to loss of control in the wing.
  • Replace the side canopy latches with a single magnetic mount on the rear bulkhead. This also makes it easier to enlarge the cockpit area to take the camera.
  • Move the servos for rudder and elevator to the rear.
  • Sand the trailing edges of the rear stabilizers a little to reduce drag.

There is one other modification that I am in two minds about and that is a secondary means of fixing the wings. In the stock kit, the wings are held in place with plastic catches. These are design to open in the event of a heavy landing so that the wings break away. If would seem, however, that some have opened in flight leading to spectacular crashes. Jeffrey has a a similar modification to several shown in the thread that involve using a secondary pin through the wing root. While this will certainly keep the wings solidly in place, I am not sure if it is better or worse in the case of a bad landing.

Building a UAV for phot mapping - Previous Posts

  1. The Goal
  2. Camera Selection
  3. Packing it all in
  4. Autopilot
  5. Kit Mods

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