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Installing Tail-Mounted Servos

Installing Tail-Mounted Servos

When it comes to fitting out a high performance aerobatic airplane, saving weight and making sturdy linkages adds a lot to your airplane’s response. You can do this easily enough by installing your servos close the control surfaces they are moving.

For my Florio Flyer 60 fun fly plane I used Savox servos as they are mid-size servos with coreless and brushless motors driving metal gears for precise control and excellent centering.

Florio Flyer 60 Build-along  Florio Flyer 60 Build-along

To install the elevator and rudder servos in the tail you first mark the areas in the fuselage to form the recessed wells for the servos to set in. I also added some 1/8 inch sheeting to extend the side doublers in the servo attachment areas.

Florio Flyer 60 Build-along  Florio Flyer 60 Build-along

I used 3/8 inch square hardwood servo mounting rails glued to the inside of the fuselage. This makes the wells 1/4 inch deep so the servo mount tabs are more or less flush with the outside of the fuselage.

Florio Flyer 60 Build-along  Florio Flyer 60 Build-along

Here you see the recessed treatment of the servo while still being completely exposed for easy linkage setup and adjustment. This top view shows how you have to stagger the servo up and down the vertical so they do not touch each other inside the fuselage. Once this is all installed, you can finish the top and bottom fuselage cross-grain sheeting to seal up the structure.

Florio Flyer 60 Build-along  Florio Flyer 60 Build-along

With the servos in place, you can now install the tail feathers! Here the horizontal stabilizer has been slide into place and aligned with the centerline of the fuselage.

Florio Flyer 60 Build-along Tail   Florio Flyer 60 Build-along Tail

Once you square up the vertical fin and glue it in place, you can complete the aft fuselage sheeting on the top and bottom. The servo leads require 12 inch extensions to reach the receiver. Be sure to secure the connections with some tape or heat shrink tubing.

Use good quality hardware when you assemble you linkages. I use heavy duty 4-40 size clevises and pushrod wire.

To make your linkage the correct length you need to center the the control surfaces and lock them in place. I clamp a piece of wood across the hinge line to do this.

Install the servo and assemble the linkage and install it so you can solder the clevis to the pushrod wire.

Run the servo leads back under the wing into the radio compartment and connect them top to the receiver. You have to activate your servos so the transmitter will center the servo before you add the solder.

With the control surface and the servo centered, carefully solder the clevis to the pushrod.

Here’s the completed linkage for the elevator. Do the same thing for the rudder then you are ready to cover your model. Note the length of fuel tubing over the clevis. It acts as a keeper to prevent it from opening while the model is in the air. Also the lock nut is an important part to lock the clevis in place and remove any slop in the linkage.

My 60-size Florio Flyer is a great flying airplane. With the tail servo setup it has excellent response to control inputs!

Updated: September 25, 2018 — 4:24 PM
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6 Comments

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  1. The geometey on the rudder servo is horrible and the servo is at the wrong location. Also the pushrod is too long and not supported. it needs to be thicker or sleved with brass tube. The better option would have been an aluminum arrow shaft pushrod and supported half way along the fuse or closed loop on the rudder.

    1. Mr. Bathie, Do you believe the pushrod will flex, considering the forces involved? It appears to be a 4-40 rod, about 6-8 inches long, in a linear application. No doubt the arrow shaft would be stiffer, but to what gain? I would also think the arrow shaft and it’s end fitments would out weigh the 4-40 rod. Especially with the arrows midway support. But the really important thing here is that the author states it has “excellent response to control inputs” which leads me to believe he is satisfied and that is what really counts in a hobby.

  2. @Ross if this was a larger plane I’d agree, but its only 60 size so I cant see there being any issues PLUS the camera may make the rod look longer then it really is. I like how the server was flush fit to the fuse, need to do that one mine from now, cant believe I never thought of that!

  3. The first paragraph of the article says to put the servo as close to the control surface as possible…which is appropriate advice…!

    Why not put the servo’s output shaft toward the control surface… thus shorting the servo’s distance to the control surface…! The author doesn’t follow his own advice…!

    1. Larry, you will note that the servos are positioned so the servo wires are exiting the servo toward the front of the airplane. If you were to flip the servo as you suggest the servo wires would be directed toward the tail and would have to make a 180 and cross over or behind the servos. No where near as clean of an install that way, plus that 3/4 of an inch difference in distance to the spline output of the servo wouldn’t make that much of a difference.

  4. Hmmmm. Looks fine to me. Thanks for sharing. Mine is similar, but smaller scale.

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