The Dual Elevator Pushrod System (DEPS)

The basic DEPS layout includes two (2) solid core Carbon Fiber rods running the length of the fuselage to each elevator.   They’re 0.070” diameter or the same size as a 2-56 pushrod, so they’re pretty small. These rods are 48” long and come with the kit.

The DEPS kit also comes with fittings, and two (2) sleeves similar to a Nyrod housing. A 5/32” hollow pushrod is included for use in connecting the two solid core rods to the servo arm. This makes for a perfect pushrod setup for 2m birds.

The 0.070” Carbon Fiber rods are pretty stiff but will flex and can’t be run unsupported for the length of the fuse. In this system they’re supported the entire length of their travel inside the fuse. Using the sleeves as guides, they’re attached to light ¼” sq. balsa sticks. This can be the lightest you can find because it’ll become very stiff when assembled in the structure. Don’t just pick a piece of bass or maple that says its balsa. 

Ok, getting started, you wrap sewing thread around the balsa stick and the sleeve (or guide). See photo #1 below for the layout.

Central found the perfect sized guides made of a stiffer plastic. On previous versions of this setup I used a Teflon Sleeve. The problem was getting the sewing thread on tight enough to secure the guide sleeve without crushing it — causing friction on the rods. This problem has been solved in the new DEPS Kit.

Attach each pushrod guide to its own ¼” sq. balsa stick. The wrap is done like a fishing pole with close-together wraps for about an inch or two, then looser for 2-3 inches, then tighter wraps, then looser. You always want to keep just enough tension in the thread to hold the pushrod guide snug against the balsa stick.

Once the wrapping is done you hit the sewing thread with some thin CA glue. The balsa will soak up the CA like mad and will stiffen. That’s why a softer piece of balsa will work. You don’t need to soak the whole stick.  Just make sure that the thread and the pushrod sleeve are not moving on the balsa stick, and there is no way for it to come off. These sticks won’t move once they’re glued into the fuse as the support guides for the sleeves holding the CF rods.

Now here’s where I vary from the original designer’s idea a little bit.  I measure the length required to build a ladder from the front mounted elevator servo to the exit holes in the fuse.  I build a ladder type structure attaching the two pushrod assemblies to each other. This is done in a big “V” with the guides on the outside of the “V”.   See the photo #1 view of the inside.

DEPS   Photo #1: "Ladder" built and glued inside the fuselage.

The horizontal balsa former you see above the ladder (at the rear of the fuse) is part of the stab install. You should have your stab installed already before you install this pushrod setup.

I leave the tail post open so I can get in there and work.  But the stab is 100% installed. I use removable stabs, but glued-in solid stabs are fine also.   The pushrod doesn’t care.  The vertical former with the hole in the middle is located in the fuse ahead of the stab slightly, and keeps the fuselage from twisting in front of the stab. This former also keeps the fuse sides from flexing ahead of the stab, and causes the fin to be much stiffer.